U.S. patent application number 12/839522 was filed with the patent office on 2012-01-26 for load management aware fan control.
Invention is credited to Kevin C. Allmaras, James A. Coffel, Roger W. Rognli, Brock M. Simonson.
Application Number | 20120017611 12/839522 |
Document ID | / |
Family ID | 45492434 |
Filed Date | 2012-01-26 |
United States Patent
Application |
20120017611 |
Kind Code |
A1 |
Coffel; James A. ; et
al. |
January 26, 2012 |
LOAD MANAGEMENT AWARE FAN CONTROL
Abstract
A fan-control device for overriding normal operation of a
circulation fan delivering conditioned air through ductwork in an
unconditioned space. The fan-control device includes a detection
circuit and a fan relay. The detection circuit is configured to
detect a cooling system control voltage and a cooling system
control current and to output a fan control override signal when
the cooling system control voltage is detected and the cooling
system control current is absent.
Inventors: |
Coffel; James A.; (Shakopee,
MN) ; Rognli; Roger W.; (Otsego, MN) ;
Allmaras; Kevin C.; (Carrington, ND) ; Simonson;
Brock M.; (Carrington, ND) |
Family ID: |
45492434 |
Appl. No.: |
12/839522 |
Filed: |
July 20, 2010 |
Current U.S.
Class: |
62/89 ;
62/186 |
Current CPC
Class: |
F24F 2140/50 20180101;
F24F 2140/60 20180101; F24F 11/77 20180101 |
Class at
Publication: |
62/89 ;
62/186 |
International
Class: |
F25D 17/06 20060101
F25D017/06; F25D 17/04 20060101 F25D017/04 |
Claims
1. A load-management-aware fan-control device for overriding normal
operation of a circulation fan delivering conditioned air through
ductwork that is normally controlled by a thermostat that includes
a load management device, the load-management-aware fan-control
device comprising: a detection circuit configured to detect a HVAC
system control voltage and a HVAC system control current and to
output a fan control override signal when the HVAC system control
voltage is detected and the HVAC system control current is absent,
the control voltage being detected by the detection circuit when
the HVAC system requests that a load under control of a
load-management device be powered, and the control current being
detected as absent when the HVAC system requests that the load be
powered and the load-management device is activated such that the
load is not powered; and a fan relay configured to receive the fan
control override signal from the detection circuit and to break an
electrical connection between a thermostat of the HVAC system and
the fan in response to the fan control override signal, thereby
overriding normal control of the fan by the thermostat and
preventing operation of the fan and circulation of unconditioned
air when the load-management device is activated.
2. The device of claim 1, wherein the detection circuit further
includes a current-sensing coil configured to detect the HVAC
system control current.
3. The device of claim 2, wherein the current-sensing coil is a
snap-on current transformer.
4. The device of claim 1, wherein the fan relay is a
normally-closed relay.
5. The device of claim 1, wherein the detection circuit is further
configured to detect the HVAC system control voltage at a terminal
of a forced-air unit of the HVAC system and the thermostat.
6. The device of claim 1, wherein the HVAC system control voltage
is a 24VAC control voltage.
7. The device of claim 1, further including a time delay device in
electrical communication with the detection circuit and the fan
relay, the time delay device configured to delay the break of the
electrical connection between the thermostat of the HVAC system and
the fan for a predetermined time period after the detection of a
HVAC system control voltage and the detection of the absence of the
HVAC system control current.
8. The device of claim 7, wherein the predetermined time period is
an amount of time required to force substantially all of a volume
of conditioned air remaining in the ductwork after the detection
circuit has detected the HVAC system control voltage and the
absence of the HVAC system control current, and before the fan
relay breaks the electrical connection between the thermostat of
the HVAC system and the fan.
9. The device of claim 1, further including a timer device in
electrical communication with the detection circuit and the fan
relay, the timer device configured to signal the fan relay to make
an electrical connection between the thermostat of the HVAC system
and the fan after a predetermined time period, the predetermined
time period measured from the break of the electrical connection
between the thermostat and the fan.
10. The device of claim 1, wherein the detection circuit includes:
a first detection circuit relay configured to be in an open
position in the absence of the HVAC system control current; a
second detection circuit relay in electrical communication with the
first detection circuit relay and the fan relay, and configured to
be in a closed position when the first circuit relay is in an open
position, such that in the presence of the HVAC system control
voltage, the HVAC system control voltage is applied to a coil of
the fan relay, the fan relay thereby receiving the fan control
override signal.
11. A method of controlling a circulation fan of an HVAC system
having ductwork located in an unconditioned space and a
load-management device controlling an electrical load, the method
of controlling the circulation fan comprising: detecting an HVAC
system control voltage when the HVAC system requests an electrical
load under control of a load-management device be powered;
detecting an absence of an HVAC system control current when the
HVAC system requests the electrical load be powered and when the
load-management device is activated such that the electrical load
is not powered; in response to detecting the HVAC system control
voltage and detecting the absence of the HVAC system control
current, generating a fan control override signal for overriding a
fan control signal of a thermostat requesting operation of a
circulation fan; and breaking an electrical connection between the
thermostat and the circulation fan by receiving the fan control
override signal at the fan relay and causing the fan relay to open,
thereby overriding the fan control signal of the thermostat and
preventing operation of the circulation fan.
12. The method of claim 11, wherein the HVAC system is a cooling
system and the electrical load is a compressor, such that detecting
an HVAC system control voltage when the HVAC system requests an
electrical load under control of a load-management device be
powered comprises: detecting a cooling system control voltage when
the cooling system requests an electrical load under control of a
load-management device be powered; detecting an absence of an HVAC
system control current when the HVAC system requests the electrical
load be powered and when the load-management device is activated
such that the electrical load is not powered comprises detecting an
absence of a cooling system control current when the cooling system
requests the compressor be powered and when the load-management
device is activated such that the compressor is not powered; and
detecting the HVAC system control voltage and detecting the absence
of the HVAC system control current comprises detecting the cooling
system control voltage and detecting the absence of the cooling
system control current.
13. The method of claim 11, further comprising activating the
load-management device to interrupt power to the electrical
load.
14. The method of claim 13, wherein activating the load-management
device to interrupt power to the electrical load comprises
receiving a load-management command at the load-management device
and activating a relay of the load-management device, thereby
breaking a power connection of the electrical load.
15. The method of claim 11, wherein detecting an HVAC system
control voltage when the HVAC system requests an electrical load
under control of a load-management device be powered comprises
detecting a 24VAC HVAC system control voltage.
16. The method of claim 11, further comprising delaying the
breaking of the electrical connection between the thermostat and
the circulation fan for a predetermined time period after the
detecting of the HVAC system control voltage and the detection of
the absence of the HVAC system control current.
17. A method of optimizing cooling efficiency when managing
multiple electrical loads of cooling systems of buildings included
in a load-management program, at least some of the cooling systems
including above-ground ductwork, the method comprising: providing a
load-management device to each of a plurality of buildings having
cooling systems, each of the load-management devices configured to
cause power to a compressor of the cooling system to be interrupted
in response to a load-management command, and at least one of the
plurality of buildings including a cooling system having
above-ground ductwork for distributing conditioned air; providing a
fan control device to the at least one of the plurality of
buildings including the cooling system having above-ground
ductwork, the fan control device configured to communicate with the
load-management device provided to the building and to prevent
operation of a circulation fan when power to the compressor is
interrupted; and transmitting a load-management command to the
plurality of load-management devices, the command causing each of
the load-management devices to interrupt power to the compressor,
the interruption of power to the compressor of any building of the
plurality of buildings having above-ground ductwork causing the fan
control device to prevent operation of the circulation fan, thereby
preventing unconditioned air from being distributed through the
above-ground ductwork in that building.
18. The method of claim 17, wherein providing a load-management
device to each of a plurality of buildings having cooling systems
includes providing a load-management device to a plurality of
residential home-owners as part of a load-management program for a
specified geographic region.
19. The method of claim 17, wherein providing a load-management
device to each of a plurality of buildings having cooling systems
includes providing a load-control receiver having an internal relay
configured to open a set of contacts when activated.
20. The method of claim 17, wherein providing a fan control device
to the at least one of the plurality of buildings includes
providing a fan control device having a detection circuit and a fan
relay, the detection circuit and the fan relay in electrical
communication with a thermostat and the circulation fan.
21. The method of claim 20, further including: the detection
circuit being configured to detect the presence of a cooling system
control voltage and the absence of a cooling system control
current; and the fan relay configured to break a connection between
a thermostat and the circulation fan in response to the detection
circuit detecting the presence of a cooling system control voltage
and the absence of a cooling system control current.
22. The method of claim 17, wherein transmitting a load-management
command to the plurality of load-management devices includes
transmitting a load-management command over a wireless
communication network.
23. The method of claim 22, wherein transmitting a load-management
command over a wireless communication network includes transmitting
a radio-frequency load-management command.
24. The method of claim 17, wherein transmitting a load-management
command to the plurality of load-management devices includes
transmitting a load-management command over a wired communication
network.
25. The method of claim 24, wherein the wired communication network
is selected from a group consisting of a power line communication
network, a telephone service network and an interne service
network.
26. A load-management-aware fan-control device for overriding
normal operation of a circulation fan delivering conditioned air
through an above-ground ductwork that is normally controlled by a
thermostat of a cooling system that includes a load management
device controlling a compressor of the system, the
load-management-aware fan-control device comprising: means for
detecting a cooling system control voltage and a cooling system
control current and to output a fan control override signal when
the cooling system control voltage is detected and the cooling
system control current is absent, the control voltage being
detected when the cooling system requests that a compressor under
control of a load-management device be powered, and the control
current being detected as absent when the cooling system requests
that the compressor be powered and the load-management device is
activated such that the compressor is not powered; and means for
receiving the fan control override signal and breaking an
electrical connection between a thermostat of the cooling system
and the fan in response to the fan control override signal, thereby
overriding normal control of the fan by the thermostat and
preventing operation of the fan and circulation of uncooled air
when the load-management device is activated.
27. The device of claim 26, further comprising means for delaying
the break of the electrical connection between the thermostat of
the cooling system and the fan for a predetermined time period
after the detection of a cooling system control voltage and the
detection of the absence of the cooling system control current.
28. The device of claim 26, further comprising means for activating
the load-management device such that the compressor is not
powered.
29. A load-management-aware fan-control device for overriding
normal operation of a circulation fan delivering conditioned air
through ductwork in an unconditioned space, the circulation fan
being normally controlled by a thermostat, the
load-management-aware fan-control device comprising: a detection
circuit configured to detect a cooling system control voltage and a
cooling system control current and to output a fan control override
signal when the cooling system control voltage is detected and the
cooling system control current is absent, the control voltage being
detected by the detection circuit when the cooling system requests
that a compressor under control of a load-management device be
powered, and the control current being detected as absent when the
cooling system requests that the compressor be powered and the
load-management device is activated such that the compressor is not
powered; and a fan relay configured to receive the fan control
override signal from the detection circuit and to break an
electrical connection between a thermostat of the cooling system
and the fan in response to the fan control override signal, thereby
overriding normal control of the fan by the thermostat and
preventing operation of the fan and circulation of unconditioned
air when the load-management device is activated.
30. The load-management-aware fan-control device of claim 29,
wherein the ductwork located in an unconditioned space comprises
ductwork located above ground.
31. The load-management-aware fan-control device of claim 29,
wherein the ductwork located above ground comprises ductwork
located in an attic space.
32. The device of claim 29, wherein the detection circuit further
includes an external current-sensing coil configured to detect the
cooling system control current.
33. The device of claim 29, wherein the detection circuit further
includes internal current-sensing circuitry.
34. The device of claim 29, wherein the cooling system comprises a
portion of an HVAC system that also includes a heating system.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to management of
electrical loads. More particularly, the present invention relates
to control of circulation fans in a load-managed system for
conditioning air.
BACKGROUND OF THE INVENTION
[0002] To manage electricity usage during times of peak demand,
utility companies enroll consumers in load management, or
load-shedding, programs. Participants of load-management programs
agree to allow utility companies to reduce their power consumption
by controlling operation of high-energy usage appliances such as
air conditioners, hot water heaters, pool heaters and so on.
Control of such appliances may be accomplished through the use of a
controller integrated into, or cooperating with, a utility meter,
thermostat, load-control device, or other such device.
[0003] One of the most common high-energy-consuming appliances
targeted for load control is a compressor of an air-conditioner. In
a traditional forced-air heating and cooling system, air is heated
or cooled and forced through a network of air ducts by a
circulation fan. Based upon a temperature set point, a thermostat
calls for heating or cooling, and in the case of cooling, causes
the compressor to turn on, and the circulation fan to circulate
cooled air through the ductwork to various points about the
structure, such as rooms in a residence, or offices in a commercial
building.
[0004] When a load management system is introduced to the
forced-air HVAC system, a load-management controller or device may
take control of the thermostat or the appliances themselves in
order to regulate operation of the HVAC system and reduce energy
consumption. In some load management systems, the temperature set
point may be modified, for example, by being slowly ramped up so as
to not call for cooling. In some systems, power to the
energy-consuming appliances may be cycled on and off by means of a
relay switch located between the appliance and its power
source.
[0005] One such relay switch is described in U.S. Pat. No.
7,355,301 (the '301 patent), commonly assigned to the owners of the
present application, and incorporated herein by reference. In the
'301 patent, a load control receiver (LCR) responds to remote
commands and detected power line parameters to remove power to
selected appliances.
[0006] In many known systems having a thermostat controlling a
forced air unit, when power to a controlled appliance, such as an
air-conditioning compressor, is interrupted by use of an LCR or
other such load-management device, the thermostat typically
continues to call for cool air from the forced air unit. A
circulation fan of the forced air unit continues to run,
circulating air throughout the building or structure, despite the
lack of power to the compressor, and despite an effective cooling
effect.
[0007] If the conditioned air circulating throughout the space
warms at a relatively low rate, which is most often the case for
structures having air ducts located in basements, and between first
and second floors of multi-story buildings, the continued
recirculation of air throughout the space while the compressor
remains unpowered does not result in a significant temperature rise
given the generally short time that the compressor is cycled off.
However, in those buildings having air ducts located primarily in
uncooled attic spaces, the continued operation of the circulation
fan may cause the temperature of the space to be cooled to rise
relatively quickly, especially in very hot weather conditions. This
relatively fast rise in temperature is a result of recirculated air
continually passing through the higher-temperature attic space and
warming the residential space. This accelerated warming effect is
especially problematic in high-temperature climates, such as those
in the southern and western parts of the United States.
[0008] One method to address the accelerated warming effect is to
install a local area network, such as a home area network or other
localized control system that centrally controls all of the
power-consuming appliances in a residence. A local area network may
be configured to communicate directly with a circulation fan,
turning the circulation fan at the same time it turns off the
compressor.
[0009] In one example of a such a home area network, U.S. Pat. No.
7,010,363, entitled "Electrical Appliance Energy Consumption
Control Methods and Electrical Energy Consumption Systems"
describes a system of microprocessor-controlled relays and software
that controls not only high-energy usage appliances such as an
air-conditioning compressor, but also directly controls power to
the circulation fan.
[0010] In another example, known "smart" thermostats, utility
meters, or other such controllers may be introduced to the building
to establish a local network. The circulation fan may be modified
to receive communications from the controller as part of a local
network, such as a Zigbee.RTM. network.
[0011] While installing such relatively extensive and complex
networks into a building to directly control all appliances,
including a circulation fan, may be one way to avoid the
accelerated warming effect described above, this option remains
relatively expensive and often impractical.
SUMMARY OF THE INVENTION
[0012] In one embodiment, the invention comprises a
load-management-aware fan-control device for overriding normal
operation of a circulation fan delivering conditioned air through
ductwork in an unconditioned space. The circulation fan is normally
controlled by a thermostat of an HVAC system that includes a load
management device controlling an electrical load of the system. The
load-management-aware fan-control device includes a detection
circuit and a fan relay. The detection circuit is configured to
detect an HVAC system control voltage and an HVAC system control
current and to output a fan control override signal when the HVAC
system control voltage is detected and the HVAC system control
current is absent. The control voltage is detected by the detection
circuit when the HVAC system requests that a load under control of
a load-management device be powered, and the control current is
detected as absent when the HVAC system requests that the load be
powered and the load-management device is activated such that the
load is not powered.
[0013] In some embodiments, the fan relay is configured to receive
the fan control override signal from the detection circuit and to
break an electrical connection between a thermostat of the HVAC
system and the fan in response to the fan control override signal,
thereby overriding normal control of the fan by the thermostat and
preventing operation of the fan and circulation of unconditioned
air when the load-management device is activated.
[0014] In another embodiment, the invention comprises a method of
controlling a circulation fan of an HVAC system, the HVAC system
having ductwork located in an unconditioned space and a
load-management device controlling a compressor. The method of
controlling the circulation fan includes detecting an HVAC system
control voltage when the HVAC system requests an electrical load
under control of a load-management device be powered, and detecting
an absence of an HVAC system control current when the HVAC system
requests the load be powered and when the load-management device is
activated such that the load is not powered. The method also
includes generating a fan control override signal for overriding a
fan control signal of a thermostat requesting operation of a
circulation fan, breaking an electrical connection between the
thermostat and the circulation fan by receiving the fan control
override signal at the fan relay and causing the fan relay to open,
thereby overriding the fan control signal of the thermostat and
preventing operation of the circulation fan.
[0015] In yet another embodiment, the present invention comprises a
method of optimizing cooling efficiency when managing multiple
electrical loads of cooling systems of buildings included in a
load-management program, at least some of the cooling systems
including above-ground ductwork. The method includes providing a
load-management device to each of a plurality of buildings having
cooling systems, providing a fan control device to the at least one
of the plurality of buildings including the cooling system having
above-ground ductwork, and transmitting a load-management command
to the plurality of load-management devices, the command causing
each of the load-management devices to interrupt power to the
compressor and unconditioned air from being distributed through the
above-ground ductwork in that building.
[0016] Each of the load-management devices of this method is
configured to cause power to a compressor of the cooling system to
be interrupted in response to a load-management command, and at
least one of the plurality of buildings includes a cooling system
having above-ground ductwork for distributing conditioned air.
Further, the fan control device is configured to communicate with
the load-management device provided to the building and to prevent
operation of a circulation fan when power to the compressor is
interrupted.
BRIEF DESCRIPTION OF DRAWINGS
[0017] The invention may be more completely understood in
consideration of the following detailed description of various
embodiments of the invention in connection with the accompanying
drawings, in which:
[0018] FIG. 1 is an illustration of a building with an HVAC system
that includes above-ground ductwork;
[0019] FIG. 2 is a block diagram of a fan control system according
to an embodiment of the present invention;
[0020] FIG. 3 is a block diagram of a fan control system according
to another embodiment of the present invention;
[0021] FIG. 4 is a circuit diagram of a fan control device
according to an embodiment of the present invention;
[0022] FIG. 5 is a block diagram of a dual-relay fan control system
according to an embodiment of the present invention;
[0023] FIG. 6 is a block diagram of the dual-relay fan control
system of FIG. 5 enclosed in a common housing;
[0024] FIG. 7 is a diagram depicting a load-management command
being transmitted to a plurality of buildings, some of which
include cooling systems having above-ground ductwork.
[0025] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to the particular embodiments described. On the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims.
DETAILED DESCRIPTION
[0026] Referring to FIG. 1, a cross-section of a building 10 with
an HVAC system 20 that includes ductwork 30 located in an
unconditioned space, is depicted. Building 10, though depicted as a
residential building or home, may also be a commercial building,
industrial building, or any such building or structure having an
interior space 40 requiring heating or cooling, and an attic or
similar such space 50 located above space 40, and not receiving
conditioned air. Though the term "HVAC" is generally understood to
mean "heating, ventilating, and air conditioning", it will be
understood that HVAC system 20 may comprise heating and cooling
capability, just cooling capability, or just heating capability. As
such, when specific reference is made to a cooling configuration
and operation, it will be understood that the same configuration
and operation may exist and operate as a heating configuration and
operation.
[0027] Ductwork 30 is connected to HVAC system 20, with portions of
ductwork 30 located in attic space 50 of building 10. As indicated
by the arrows in FIG. 1, conditioned air from HVAC system 20 flows
through attic space 50 of building 10 via ductwork 30 and is
distributed into an interior space of building 10, thereby
conditioning space 40. A portion of the conditioned air, along with
a portion of fresh air, is drawn back into forced air unit (FAU)
102 of HVAC system 20, and the cycle repeated.
[0028] Referring also to FIG. 2, load-management-aware (LMA) fan
control system 100 of HVAC system 20 in the depicted embodiment
includes FAU 102, thermostat 104, contactor 106, load 107,
load-management device 108, and LMA fan control device 110 with
current-sensing coil 112.
[0029] FAU 102 includes circulation fan 114, and electrical control
circuitry having several electrical terminals, including common
terminal COMMON, and terminal FAN'. FAU 102 may be any of several
known types of forced air units used to condition and circulate
air. FAU 102 may also include heating and cooling elements,
filters, dampers, and other related HVAC equipment not depicted.
FAU 102 and circulation fan 114 are connected to ductwork 30 for
distributing the conditioned air throughout space 40 of building 10
to be conditioned.
[0030] Thermostat 104 may be any of known thermostats used for
regulating a temperature within a space, such as one or more rooms
of a residence or other building. As such, thermostat 104 may be
programmable, non-programmable, digital, mechanical, communicative,
and so on. Thermostat 104 may operate on 24VAC, line voltage, or
another voltage as needed. As depicted, and as described in further
detail below, thermostat 104 includes terminal FAN which provides
an electrical signal requesting circulation fan 114 to be turned on
or off. Thermostat 104 also includes terminals COOL and HEAT (not
shown), used to call for cooling and heating of the conditioned
space, respectively.
[0031] Contactor 106 may be one of many known contactors or other
known controlling devices for switching the power of load 107,
wherein load 107 may be an air-conditioning compressor, heat pump,
or other such generally high-current-load device of a heating or
cooling circuit. Contactor 106 may operate on alternating current
(AC) or direct current (DC), and at a control circuit voltage
appropriate for the particular control circuit. In one embodiment,
a control voltage for contactor 106 may be 24VAC.
[0032] Contactor 106 is in electrical communication with FAU 102
through load-management device 108 via control lines 118, 120, and
122. As depicted, terminal 124 of contactor 106 is electrically
connected to terminal 128 of load-management device 108 via control
line 118. Terminal 130 of load-management device 108 is
electrically connected to terminal COOL of thermostat 104 via
control line 120. Terminal 126 of contactor 106 is electrically
connected to terminal COMMON of FAU 102.
[0033] Contactor 106 is connected to Line Voltage which, which
unlike the control voltage at lines 118 and 122, is typically a
higher voltage alternating voltage source. In one embodiment, Line
Voltage is 240VAC. In another embodiment, Line Voltage is 120VAC.
It will be understood that Line Voltage may comprise any voltage,
current, and frequency appropriate for operating load 107.
Contactor 106 is in electrical communication with load 107 through
one or more switches, providing power to load 107 via power lines
133 and 134.
[0034] In one embodiment, system 100 operates on a 24VAC control
voltage, such that contactor 106 is a 24VAC contactor, and the
voltage potential across terminals 124 and 126, and control lines
120/118 and 122 is also 24VAC. In other embodiments, other AC or DC
voltages may be used.
[0035] In other embodiments, rather than a contactor 106, another
form of switching device, such as a relay, for a load such as a
compressor, or other electrical load of system 100 may be used. In
yet another embodiment, system 100 may not include contactor 106,
and load-management device 108 and FAU 102 may be in direct
electrical communication with a load 107, such as a compressor or
other electrical load of system 100.
[0036] Load-management device 108 as depicted includes terminals
128 and 130, and a switching device, such as relay 132.
Load-management device 108 may also include other control and
communication circuits adapted to interface and communicate with
other portions of system 100, including meters, gateways, and other
devices forming part of a local wired or wireless network.
[0037] Generally, load-management device 108 functions as an on-off
switch for a control line. Load-management device 108 may be
controlled by a local internal or external control circuit that
monitors and senses conditions and parameters relating to system
100. Such conditions and parameters may include monitoring of
voltage and frequency of power lines providing power to system 100
and its components. An example of one such load-management device
108 is a load-control receiver (LCR) as described in U.S. Pat. No.
7,355,301 (the '301 patent). The LCR of the '301 patent may be
locally controlled, and switches a load-management device/LCR 108
off, thereby interrupting power to a load 107 when voltages and
frequencies fall below a detected threshold level. Such conditions
often occur during times of peak electrical consumption.
[0038] Load-management device 108 may also be controlled by a
device or a network as part of a greater load management, or demand
response system, as known to those skilled in the art. A local
controller such as a thermostat, meter, or other communicative
device, may communicate with, and control operation of,
load-management device 108. In such a load-management system,
load-management device 108 will be used to interrupt power to an
intended load, thereby cycling the load on and off for
energy-saving purposes. As discussed further below, and with
respect to FIG. 7, electric utility companies may broadcast
commands to a controller of load-management device 108, or directly
to a load-management device 108, thereby providing operational
instructions on managing load 107.
[0039] As depicted, system 100 includes a single load management
device 108 coupled to a single load 107. However, in alternate
embodiments, system 100 may include a second load management device
108b connected to a second load 107b. In such an embodiment, the
first load 107 may be a cooling load, and the second load 107 may
be a heating load.
[0040] LMA fan control device 110 as depicted in FIG. 2 includes,
in addition to current-sensing coil 112, detection circuit 140, and
normally-closed fan relay 142, enclosed in housing 144. In the
embodiment depicted, current-sensing coil 112 is a device separate
from LMA fan control device 110, though in other embodiments, as
discussed further below with respect to FIG. 3, current sensing
coil 112 may be an integral part of LMA fan control device 110. In
some embodiments, LMA fan control device 110 may also include time
delay devices 143 and 145.
[0041] LMA fan control device 110 is electrically coupled to
thermostat 104 via control line 146 and to FAU 102 at control line
148, such that terminal FAN of thermostat 104 is in electrical
communication with terminal FAN of FAU 102 through fan relay
142.
[0042] Detection circuit 140 of LMA fan control device 110 is
electrically coupled to terminal COOL of thermostat 104 via sensing
line 150 and control line 120, and to terminal COMMON of FAU 102
via sensing line 152 and control line 122. Detection circuit 140 is
also electrically connected to switch or relay 142. Current sensing
coil 112 is in electrical communication with control line 122, and
detects current flow in control line 122.
[0043] In operation, when load 107 is not being managed by
load-management device 108, relay 132 of load-management device 108
is closed. As will be explained further below, relay 142 of LMA fan
control device 110, is also closed. FAU 102 in conjunction with
thermostat 104 operates normally to heat or cool air so as to
maintain a relatively constant air temperature in the conditioned
space. A temperature set point of thermostat 104 may be set
manually by a user, automatically by a programmed thermostat 104,
or by an external controller in communication with thermostat 104.
Thermostat 104 senses the space temperature of building 10, and as
cool air is needed to lower or maintain a temperature, thermostat
104 signals circulation fan 114 via terminal COOL to operate, and
for cool air to be delivered by FAU 102. Similarly, in heating
mode, thermostat 104 signals FAU 102 via terminal HEAT to operate,
and for heated air to be delivered by FAU 102. For the purposes of
explanation operation of system 100, it will be assumed that system
100 is operating in a cooling mode, though it will be understood
that system 100 may alternatively operate in a heating mode,
utilizing terminal HEAT, Iheat, I cool, and so on.
[0044] In the embodiment depicted, when thermostat 104 requests
cool air, terminals COOL and FAN of thermostat 104 switch logic
states, typically to a positive 24VAC control voltage. As discussed
further below, when load 107 is not being managed by
load-management device 108, relay 142 remains closed, such that a
voltage at terminal FAN' of FAU 102 becomes the same as a voltage
at terminal FAN.
[0045] A fan signal from thermostat 104 at terminals FAN and FAN'
turns on circulation fan 114, and air is forced through ductwork 30
connected to FAU 102 to the space to be cooled. Thermostat 104 has
called for load 107 to be powered by causing a cooling system
control voltage Vcool to be across terminals COOL and COMMON. In
one embodiment, control voltage Vcool may be 24VAC, or another
voltage appropriate for switching contactor 106. In the depicted
embodiment, when control voltage Vcool exists across terminals COOL
and COMMON, cooling system control current Icool flows through the
current path formed of control line 120, relay 132, control line
118, contactor 106 and control line 122. It will be understood that
although control voltage Vcool is depicted with a positive or "+"
symbol at line 120 and a corresponding negative, or "-" symbol, and
control current Icool is depicted as current flow in a particular
direction, the actual polarity of control voltage Vcool and
direction of control voltage Icool will alternate when an AC
current is used. This will also be understood to be true of other
references to positive and negative voltages or directional current
flow, throughout this description, unless otherwise indicated.
[0046] Under these conditions, control voltage Vcool is also at
contactor 106 terminals 124 and 126, switching power on to load
107. When load 107 is a cooling device such as a compressor, the
compressor operates and cools the air forced into the ductwork by
FAU 102 for circulation throughout the building space.
[0047] Detection circuit 140 of LMA fan control device 110 is
electrically connected to terminals COOL and COMMON, and thereby
monitors and detects voltage potential Vcool. Detection circuit 140
also detects control current Icool flowing through control line
122, via current-sensing coil 112. In other embodiments, current
Icool is detected elsewhere in the circuit, such as at any of lines
107, 118, 120, 133, 134, or other such locations that would
indicate current flowing to contactor 106. As long as control
voltage Vcool and control current Icool both remain above a
threshold value, relay 142 remains closed such that terminals FAN
and FAN' remain electrically connected, such that thermostat 104
remains in control of circulation fan 114, and LMA fan control
device 110 does not override thermostat 104.
[0048] When the building 10 space reaches the desired temperature,
thermostat 104 removes the logic signal from terminals CCOL and
FAN, turning off circulation fan 114, and removing control voltage
Vcool from terminals COOL and COMMON. Without control voltage Vcool
between terminals 124 and 126, contactor 106 switches power to load
107 off, and load 107 powers down.
[0049] As long as load-management device 108 is not activated, the
heating and cooling cycle described above continues, with
thermostat 104 controlling operation of circulation fan 114.
[0050] However, when a load management situation occurs, and
load-management device 108 is activated, operation of system 100
changes. For example, when load 107 is managed, relay 132 of
load-management device 108 makes or breaks, thereby cycling power
to load 107 on and off. During this load management mode, with
relay 132 of load-management device 108 open, terminal 124 of
contactor 106 floats, the previously-described current path is
broken, and control current Icool is zero, regardless of the
voltage potential across control lines 120 and 122.
[0051] In system 100, load-management device 108 is generally
controlled independent of the operation of thermostat 104 and FAU
102. Therefore, thermostat 104 and FAU 102 will attempt to control
the space temperature regardless of the status of load-management
device 108.
[0052] Consequently, when load 107 is being controlled, such that
relay 132 is open, and when the desired air temperature rises above
the desired set point, thermostat 104 and FAU 102 will attempt to
operate normally.
[0053] In previously-known load-managed HVAC systems not including
LMA fan control device 110, when an LCR relay opens to remove power
to a load, and the space temperature is above the desired set
point, the thermostat continues to call for cool, and the
circulation fan operates continuously. As discussed above, the
circulation fan forces air through the ductwork into the building
space, then draws return air from the space back to the FAU for
conditioning. If heat is transferred to the circulated air in the
ductwork as it passes an unconditioned space, such as an attic, the
circulated air temperature rises. As this cycle of constant fan
with no cooling mechanism continues, the space temperature may rise
rapidly.
[0054] However, unlike such previously-known cooling systems,
system 100 employing LMA fan control device 110 controls operation
of circulation fan 114 during those times that LCR 132 is open such
that circulation fan 114 generally does not run, and a rapid rise
in space temperature is avoided, reduced or delayed.
[0055] More specifically, and still referring to FIG. 2, under this
managed-load condition, where load-management device 108 is
activated, and thermostat 104 calls for cool due to a space
temperature rising above a set point, thermostat 104 provides a
control voltage at line 146, requesting that circulation fan 114
turn on. The call for cool causes a control voltage Vcool to appear
across terminals COOL and COMMON. However, control current Icool is
zero because relay 132 is open and the current path of control
current Icool is broken. Detection circuit 140 monitoring voltage
Vcool and current Icool detects the presence of control voltage
Vcool, and detects the absence of control current Icool.
[0056] To avoid the accelerated heating effect that occurs when
circulation fan 114 operates during a managed-load condition,
detection circuit 140 sends a fan control override signal to fan
relay 142 causing relay 142 to open. Doing so breaks the electrical
connection between terminals FAN and FAN'. Under these conditions,
circulation fan 114 will not be turned on by thermostat 104, even
though thermostat 104 calls for circulation fan 114 to be
operated.
[0057] In some embodiments, LMA fan control device 110 may include
time delay devices 143 and/or 145, in electrical communication with
detection circuit 140 and fan relay 142. In such an embodiment,
time delay device 143 may delay the break of the electrical
connection between the thermostat 104 of the cooling system and the
fan 114 for a predetermined time period after the detection of a
cooling system control voltage and the detection of the absence of
the cooling system control current. Allowing circulation fan 114 to
operate for a relatively short period of time after load-management
device 108 is activated provides the benefit of allowing fan 114 to
force conditioned air already located in ductwork 30, into space
40, rather than allowing such conditioned air to be warmed in
ductwork 30 while awaiting fan 114 to restart.
[0058] The period of delay may be adjustable, and may be calculated
to be the amount of time required to displace conditioned air with
unconditioned air in ductwork 30. In one embodiment, the timer
period of delay ranges from 30 seconds to 3 minutes.
[0059] Another optional delay may be utilized via time delay device
145. Time delay device 145, in electrical communication with
detection circuit 140 and fan relay 142, may be configured to
restart fan 114 after a predetermined period of time has passed in
order to ensure a minimum amount of fresh air continues to be drawn
into building 10. More specifically, time delay device 145 begins a
countdown starting from the activation of load-management device
108. After a predetermined time period, if circulation fan 114
continues to be overridden by fan control device 110, time delay
device 145 may override fan relay 142, thereby causing fan 114 to
operate for a brief period of time. The specific time interval may
be dependent on a minimum desired air exchange rate.
[0060] Referring to non-delayed operation again, when
load-management device 108 is no longer activated, and load 107 is
no longer in a managed state, relay 132 closes or makes. Assuming
the space temperature remains above the desired setpoint,
thermostat 104 continues to call for cool, and detection circuit
140 continues to detect control voltage Vcool. Further, with the
closing of relay 132, control current Icool begins to flow, and is
also detected by detection circuit 140. Under these conditions,
relay 142 closes, terminals FAN and FAN' become electrically
connected again, such that the control voltage at terminal FAN is
also at FAN', and circulation fan 114 is turned on, thereby
circulating cooled air.
[0061] When load-management device 108 is later activated to open
relay 132, the cycle repeats.
[0062] Table 1 below summarizes the operation of system 100:
TABLE-US-00001 TABLE 1 Voltage Current Fan Relay Vcool Icool 142
Fan 114 System 100 State Present? Present? Position On/Off 1
Calling for cool, load- Yes Yes Closed On management device 108 not
activated 2 Calling for cool, load- Yes No Open Off management
device 108 activated 3 Not calling for cool, load- No No Closed Off
management device 108 not activated 4 Not calling for cool, load-
No No Open Off management device 108 activated
[0063] Referring to system 100 state 1, "calling for cool,
load-management device 108, not activated", during this state,
system 100 operates normally such that LMA fan control device 110
does not interfere with the call for cool. Control voltage Vcool is
present at terminals COOL and COMMON, and detected by detection
circuit 140. Current Icool is present flowing through closed relay
132 and current sensing coil 112, and detected by detection circuit
140. Fan relay 142 of LMA fan control device 110 is closed, and
thermostat 104 signals fan 114 to be turned on.
[0064] Referring to system 100, state 2, "calling for cool,
load-management device 108 activated", during this managed-load
state, load-management device 108 relay 132 is open, thereby
interrupting power to load 107. Voltage Vcool is present at
terminals COOL and COMMON and detected by detection circuit 140.
Current Icool is not present, or does not flow, as relay 132 is
open. The lack of current Icool is detected by detection circuit
140, and relay 142 is open. With relay 142 open, terminals FAN and
FAN' are not electrically connected. Although thermostat 104 is
calling for circulation fan 114 to be turned on by causing a
control voltage to appear at terminal FAN, the control signal does
not appear at terminal FAN', and circulation fan 114 is not
automatically turned on.
[0065] Referring to system 100, state 3, "not calling for cool,
load-management device 108 not activated", load-management device
108 is not activated, such that relay 132 is closed. FAU 102 and
thermostat 104 are not calling for cool, and thus, neither control
voltage Vcool nor control current Icool are present. Therefore,
although relay 142 is closed, circulation fan 114 is not turned on,
and air is not circulated.
[0066] Referring to system 100, state 4, "not calling for cool,
load-management device 108 activated", similar to state 3 discussed
above, system 100 is not calling for cool, such that cooling system
control voltage Vcool and cooling system control current Icool are
not present, and circulation fan 114 is not turned on.
[0067] Referring also to FIG. 3, in another embodiment, system 100
operates essentially the same as described in the embodiment of
FIG. 2, but in the embodiment of FIG. 3, system 100 does not
include external current-sensing coil 112. Rather, current-sensing
capability is internal to detection circuit 160.
[0068] When LMA fan control device 110 is installed on an existing
HVAC system, it may be more convenient to install external
current-sensing coil 112, as is the case of system 100 of FIG. 2.
In such a retrofit application, minimal rewiring may be required to
add LMA fan control device 110 to the HVAC system as
current-sensing coil 112 may not require breaking or disconnecting
control line 122 in order to sense current Icool in line 122.
[0069] Referring to FIG. 3, in other applications, whether new
installations, or retrofit situations, LMA fan control device 110
includes detection circuit 160. As depicted in FIG. 3, detection
circuit 160 does not include external current-sensing coil 112.
Rather, detection circuit 160 includes internal current-sensing
circuitry enclosed within housing 144. In such an embodiment, LMA
fan control device 110 may be a unitary, modular device easily
integrated into a new or existing HVAC system.
[0070] When installed, control line 122 is broken such that a first
portion line 122a electrically connects terminal COMMON of FAU 102
to detection circuit 160. Second portion, line 122b, electrically
connects detection circuit 160 to terminal 126 of contactor 106.
Consequently, Icool flows through detection circuit 160.
[0071] Referring to FIG. 4, a circuit diagram 162 of an embodiment
of LMA fan control device 110 is depicted. Circuit 162 includes
detection circuit 160 as described above with respect to FIG. 3,
and fan relay 142. As also described above with respect to FIG. 3,
relay 142 is electrically connected to terminals FAN of thermostat
104, and terminal FAN' of FAU 102. Detection circuit 160 is
electrically connected to FAU 102 terminals COOL and COMMON, and
terminal 126 of cooling contactor 126.
[0072] Under the conditions described above with respect to FIGS. 1
and 2, control voltage Vcool appears across terminals COOL and
COMMON, and control current Icool flows through a circuit path that
includes terminal 126 and terminal COMMON. It will be understood
that although control voltage Vcool and control current Icool are
depicted with a particular polarity and direction, respectively,
the polarity and direction will alternate when system 100 uses an
AC voltage, for example, when control voltage Vcool is 24VAC.
[0073] In the embodiment depicted, detection circuit 160 includes a
pair of diodes D1 and D2, transformer T, full-wave rectifier FWR,
current-limiting resistor R, capacitor C, relay 164, and relay
166.
[0074] Diodes D1 and D1 are located in parallel across terminals
126 and COMMON and in parallel to the inputs to transformer T. The
anode of diode D1 is electrically connected to terminals COMMON and
to terminals 182 and 186 of relay 166. The cathode of diode D1 is
electrically connected to diode D2 and to terminal COMMON. The
anode of diode D2 is electrically connected to terminal 126 and the
cathode of diode D2, while the cathode of diode D2 is electrically
connected to terminal COMMON and terminals 182 and 186 of relay
166.
[0075] Diodes D1 and D2 may have typical forward bias voltages in
the 0.7 to 1.0V range, with relatively high breakdown voltages, for
example, 520V. In other embodiments, the forward and reverse
voltages may be higher or lower, depending on the particular
requirements of system 100.
[0076] Transformer T as depicted is electrically connected in
parallel to diodes D1 and D2. In one embodiment, transformer T is a
step-up transformer, stepping up the forward bias voltage of diodes
D1 and D2 to a higher voltage output. In one embodiment,
transformer T is a 1:13 step-up transformer. The winding ratio of
transformer T may vary in other embodiments, dependent in part on
the characteristics of relays 164 and 166.
[0077] Full-wave rectifier FWR is electrically connected to the
output terminals of transformer for rectification of the output of
transformer T. Full-wave rectifier FWR is any of those known to
those skilled-in-the art, and although is depicted as a known
arrangement of four diodes, may comprise other configurations.
[0078] Current-limiting resistor R and capacitor C electrically
connect full-wave rectifier FWR to relay 164. In one embodiment,
current-limiting resistor R is a 1.5 k-ohm resistor, and capacitor
C is a 22 microfarad capacitor with a 50V rating. It will be
understood that R and C are not limited to these particular values
in this embodiment, and that in other embodiments, the values of R
and C may vary.
[0079] Relay 164 as depicted is a solid state relay electrically
connected to the output transformer T via full-wave rectifier FWR,
resistor R, and capacitor C, at input terminals 170 and 172. Relay
164 also includes switch terminals 174 and 176. Switch terminal 174
is electrically connected to coil terminal 180 of relay 166, and
switch terminal 176 is electrically connected to a terminal COOL
and to coil terminal 192 of relay 142.
[0080] Relay 166 as depicted is a single-pole, double-throw relay,
though in other embodiments, may be single-pole, single-throw, or
double-pole double-throw, as needed. Relay 166 includes coil
terminals 180 and 182, and switch terminals 184 and 186. In one
embodiment, relay 166 is a normally closed relay, such that when no
voltage potential is applied to coil terminals 180 and 182, switch
terminals 184 and 186 are made, forming an electrical connection.
When a voltage potential exists across coil terminals 180 and 182,
relay 166 opens, such that terminals 184 and 186 are not
electrically connected.
[0081] Coil terminal 180 is electrically connected to terminal 176
of relay 164; terminal 182 is electrically connected to terminal
COMMON; switch terminal 184 is electrically connected to coil
terminal 190 of relay 142; and switch terminal 186 is electrically
connected to terminal COOL.
[0082] Relay 142 as depicted is essentially the same relay as relay
166, a normally-closed, single-pole, double-throw relay having coil
terminals 190 and 192, and switch terminals 194 and 196. When a
voltage potential is at coil terminals 190 and 192, relay 142 opens
such that switch terminals 194 and 196 are not electrically
connected.
[0083] Coil terminal 190 is electrically connected to switch
terminal 184 of relay 166; coil terminal 192 is electrically
connected to terminal COOL and terminal 176 of relay 164; switch
194 is electrically connected to terminal FAN; and switch terminal
196 is electrically connected to terminal FAN'.
[0084] In operation, detection circuit 160 in conjunction with
relay 142 operates generally as described above with reference to
FIG. 3 and Table 1. Table 2 below shows additional details of the
operation of circuit 162 as part of system 100, and will be used to
describe the more detailed operation of circuit 162:
TABLE-US-00002 TABLE 2 Voltage Vcool Current Icool Relay 164 Relay
166 Fan Relay Fan 114 System 100 State Present? Present? Position
Position 142 Position On/Off 1 Calling for cool, load- Yes Yes
Closed Open Closed On management device 108 not activated (relay
closed) 2 Calling for cool, load- Yes No Open Closed Open Off
management device 108 activated (relay open) 3 Not calling for
cool, load- No No Open Closed Closed Off management device 108 not
activated (relay closed) 4 Not calling for cool, load- No No Open
Closed Closed Off management device 108 activated (relay open)
[0085] Referring to Table 2, system state 1, system 100 is calling
for cool and fan, and load-management device 108 is not activated
(relay 132 is closed). In this system state, control voltage Vcool
is present across terminals COOL and COMMON, and control current
Icool flows, or is "present".
[0086] Under these circumstances, and assuming the embodiment
employing an AC control voltage, current Icool is an AC current,
and diodes D1 and D2 alternatingly conduct such that transformer T
receives an AC voltage signal at its input terminals, the AC
voltage signal having a peak voltage substantially equal to the
bias voltage of diodes D1 and D2.
[0087] Referring again to FIG. 4, transformer T steps up the
received voltage signal with the output signal of transformer T
being rectified by full-wave rectifier FWR, while capacitor C
smoothes the rectified signal. Current-limiting resistor R reduces
the current to relay 164, and a voltage potential exists across
terminals 170 and 172 of relay 164.
[0088] In the depicted embodiment, relay 164 is a solid-state
relay, and in one embodiment is an opto-isolator. In operation, a
voltage potential across terminals 170 and 172 causes relay 164 to
make, such that terminals 174 and 176 are electrically
connected.
[0089] At the same time, a voltage potential occurs at terminals
180 and 182 of relay 166, such that it opens, and switch terminals
184 and 186 are not electrically connected. Further, current does
not flow through coil terminals 190 and 192, and fan relay 142
maintains its closed position with switch terminals 194 and 196 in
electrical contact.
[0090] With relay 142 closed, terminals FAN and FAN' are connected,
and thermostat 104 turns on circulation fan 114.
[0091] Referring to Table 2, system state 2, system 100 is calling
for cool and fan, and load-management device 108 is activated
(relay 132 is open). In this state, control voltage Vcool exists
across terminals COOL and COMMON, but control current Icool does
not flow, or is not present, because load-management device 108 is
activated and relay 132 open.
[0092] Under this system state, neither diodes D1 or D2 conduct, no
potential across terminals 170 and 172 exists at relay 164, such
that relay 164 is open. In turn, no current flows through coil
terminals 180 and 182 such that relay 166 remains closed. With
relay 166 closed, voltage Vcool is across terminals 190 and 192,
causing relay 166 to open, thereby overriding the signal from
thermostat 104 to turn on circulation fan 114.
[0093] Consequently, under system state 2, even though system 100
is calling for cool and thermostat 104 requests circulation fan 114
to run, relay 142 opens, preventing circulation fan 114 from
circulating increasingly hot air throughout the building space.
[0094] Referring to Table 2, system state 3, system 100 is not
calling for cool, and load-management device 108 is not activated.
In this state, neither voltage Vcool nor current Icool are present.
Diodes D1 and D2 don't conduct; relay 164 is open, relay 166
closed, and relay 142 is closed. Circulation fan 114 is not turned
on because thermostat 104 is not calling for cool.
[0095] Referring to Table 2, system state 4, system 100 is not
calling for cool, and load-management device 108 is activated. In
this state, neither control voltage Vcool nor control current Icool
are present, so circuit 162 operates the same as under system state
3. Diodes D1 and D2 don't conduct; relay 164 is open, relay 166
closed, and relay 142 is closed. Circulation fan 114 is not turned
on because thermostat 104 is not calling for cool.
[0096] Referring to FIG. 5, in an alternate embodiment, system 200
includes multiple load-management devices 108 to prevent the
accelerated heating situation caused by circulation fan 114
operating during the time that a load is being managed. System 200
includes FAU 102, thermostat 104, contactor 106, load 107, a first
load-management device 108a enclosed in housing 202a, and a second
load-management device 108b enclosed in housing 202b. In one
embodiment, load-management device 108a may be located conveniently
near contactor 106 and load 107, which is often outdoors.
[0097] Similar to the embodiments described above with respect to
FIGS. 1-3, relay 132a of load-management device 108a is
electrically connected between terminal COOL of thermostat 104 and
terminal 124 of contactor 106. Terminal COOMON of FAU 102 is
electrically connected to terminal 126 of contactor 106. When
thermostat 104 calls for cool, voltage Vcool is applied across
terminals COOL and COMMON. When load-management device 108a is not
activated, current Icool flows, and cooling contact 106 maintains
power to load 107.
[0098] Unlike the embodiments of FIGS. 1-3 described above, rather
than including an LMA fan control device, system 200 includes
second load-management device 108b to make or break the connection
between FAN and FAN', thereby preventing circulation fan 114 from
operating when system 200 calls for cool, but load-management
device 108a is activated.
[0099] In the depicted embodiment, terminal 128b of load-management
device 108b is electrically connected to terminal FAN of thermostat
104, and terminal 130b is electrically connected to terminal FAN'
of FAU 102. Load-management device 108b may be located near
load-management device 108a to facilitate optimal communications
from a controller of load-management device 108a and
load-management device 108b, but alternatively, may be located at a
location separate from load-management device 108a for ease of
wiring and accessibility.
[0100] Regardless of location, load-management device 108a and
load-management device 108b operate in tandem, such that they both
operate substantially at the same time. When relay 132a is open,
relay 132b is open, and vice versa, load-management device 108a and
load-management device 108b may be operated by a common controller
and common control signal, such that when load-management device
108a is activated to remove power to load 107, LCR 108b is also
activated to remove power to circulation fan 114. In other
embodiments, load-management device 108a and 108b may operate in a
master-slave relationship such that anytime load-management device
108a is activated, such activation causes load-management device
108b to also be activated.
[0101] Referring to FIG. 6, system 300 is substantially the same as
system 200 of FIG. 5, with the exception that load-management
device 108a and load-management device 108b are enclosed in the
same housing 202. By enclosing both load-management device 108a and
load-management device 108b into a single housing 202, the
installation of the two LCRs 108 may be somewhat simplified as
compared to the installation of the two separate LCRs 108 of the
embodiment of FIG. 5.
[0102] Referring to FIG. 7, transmission of a load-management
command to a plurality of buildings, some of which include cooling
systems having above-ground ductwork, is depicted. A transmission
network 220 transmits load-management command to buildings 10, 12,
and 14. Reference letter "A" indicates a building with above-ground
ductwork, and reference letter "B" indicates a building with
below-ground ductwork. Buildings 10, as described above, include
above-ground ductwork 30, and are enrolled in a load-management
program administered by an electrical utility provider. Buildings
12 have below-ground ductwork and are also enrolled in a
load-management program. Buildings 14 are not enrolled in a
load-management program and may have either below-ground or
above-ground ductwork.
[0103] Buildings 10, 12, and 14 may be grouped geographically such
that all buildings in a particular geographic area include
above-ground ductwork, such as buildings 10 and 14 in geographic
area 222. Other geographic areas, such as geographic area 224, may
include buildings 10 having above-ground and buildings 12 having
below-ground ductwork.
[0104] Transmission network 220 as depicted is a wireless
transmission network transmitting a wireless signal that includes
load-management commands to buildings 10 and 12. In one embodiment,
transmission network 220 broadcasts an RF signal, though other
wireless signals, and a variety of protocols, may be employed. The
wireless network may include a long-haul wireless network as is
commonly used by utility providers, but may also include a
short-haul, or local wireless network, such as a Zigbee,
Bluetooth.RTM., Z-Wave.RTM., or other such local wireless
network.
[0105] Although depicted as a wireless network in FIG. 7,
transmission network 220 may also be a wired network, transmitting
load-management commands over a power line communication network, a
telephone service network, an internet service network, or another
similar wired network.
[0106] A utility provider may offer one or more load-management
programs to building owners, occupants, managers, and so on. When
enrolled in such a program, a utility provider may provide
load-management device 108, such as a load-control receiver, relay,
or similar device, for installation at buildings 10 or 12. As
described above, load-management device 108 receives
load-management commands, some of which activate the
load-management device 108, causing device 108 to interrupt or
remove power to a load 107, which may be a compressor.
Load-management device 108 may receive commands directly from
transmission network 220, or through a controller of a local
network.
[0107] For buildings 10 enrolled in the load-management program,
frequently cycling the power to compressor 107 on and off as part
of the load-management program may cause the accelerated heating
effect described above. Shortening the length of time that
load-management device 108 is activated, and increasing the
frequency of on-off cycling, otherwise known as short-cycling the
compressor, may alleviate the heating effect somewhat. However,
continual short-cycling of compressors significantly decreases the
life of the compressor such that short-cycling is generally
undesirable.
[0108] Therefore, a utility provider may also provide a
load-management aware fan control device 110 with instructions for
use to one or more buildings 10 having above-ground ductwork 30 for
the purposes of controlling a circulation fan 114 and avoiding the
accelerated heating effect described above. In such an instance,
the electrical utility provider may transmit a uniform set of
load-management commands to be received at buildings 10 and 12
without concern that the commands received by buildings 10 will
create the accelerated heating effect.
[0109] Although the present invention has been described with
respect to the various embodiments, it will be understood that
numerous insubstantial changes in configuration, arrangement or
appearance of the elements of the present invention can be made
without departing from the intended scope of the present invention.
Accordingly, it is intended that the scope of the present invention
be determined by the claims as set forth.
[0110] For purposes of interpreting the claims for the present
invention, it is expressly intended that the provisions of Section
112, sixth paragraph of 35 U.S.C. are not to be invoked unless the
specific terms "means for" or "step for" are recited in a
claim.
* * * * *