U.S. patent application number 11/673256 was filed with the patent office on 2008-08-14 for method and apparatus for removing ice from outdoor housing for an environmental conditioning unit.
This patent application is currently assigned to Lennox Manufacturing., Inc. a Corporation of Delaware. Invention is credited to Eric Berg, Paul Buckley, Peter Denboer, Richard Giallombardo, Kevin Keoppel.
Application Number | 20080190131 11/673256 |
Document ID | / |
Family ID | 39684681 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080190131 |
Kind Code |
A1 |
Giallombardo; Richard ; et
al. |
August 14, 2008 |
METHOD AND APPARATUS FOR REMOVING ICE FROM OUTDOOR HOUSING FOR AN
ENVIRONMENTAL CONDITIONING UNIT
Abstract
A method for removing ice from an outdoor housing for an
environmental conditioning unit that includes the housing
surrounding a coil and a fan for moving air past the coil includes
the steps of: (a) operating the fan at a first speed in a first
direction to move air in a first flow past the coil while the
conditioning unit is in a heating mode; (b) disengaging the fan
when the conditioning unit is in a defrost mode; (c) operating the
fan at a second speed in a second direction to move air in a second
flow past the coil when an operational parameter attains a first
value; and (d) operating the fan in the first direction at the
first speed to move air in the first flow when the operational
parameter attains a second value.
Inventors: |
Giallombardo; Richard;
(Madison, WI) ; Keoppel; Kevin; (Frisco, TX)
; Berg; Eric; (The Colony, TX) ; Buckley;
Paul; (Carrollton, TX) ; Denboer; Peter; (The
Colony, TX) |
Correspondence
Address: |
LAW OFFICE OF DONALD D. MONDUL
3060 Bonsai Drive
Plano
TX
75093
US
|
Assignee: |
Lennox Manufacturing., Inc. a
Corporation of Delaware
Richardson
TX
|
Family ID: |
39684681 |
Appl. No.: |
11/673256 |
Filed: |
February 9, 2007 |
Current U.S.
Class: |
62/324.5 ;
62/150 |
Current CPC
Class: |
F24F 1/48 20130101; F24F
13/22 20130101; F25D 21/002 20130101; F25B 2313/0294 20130101; F25B
13/00 20130101; F24F 1/50 20130101; F25B 2313/02741 20130101; F25D
2323/00283 20130101; F24F 11/42 20180101 |
Class at
Publication: |
62/324.5 ;
62/150 |
International
Class: |
F25B 13/00 20060101
F25B013/00; F25D 21/00 20060101 F25D021/00 |
Claims
1. A method for effecting ice removal from an outdoor housing for
an environmental conditioning unit; said environmental conditioning
unit including a coil structure and a fan configured for moving air
past said coil structure; said housing substantially surrounding
said coil; the method comprising the steps of: (a) operating said
fan at a first speed in a first direction to move air in a first
flow past said coil structure while said environmental conditioning
unit is in a heating operational mode; (b) disengaging said fan for
at least a portion of a time when said environmental conditioning
unit is in a defrost operation mode; (c) operating said fan at a
second speed in a second direction to move air in a second flow
past said coil structure when at least one selected operational
parameter substantially attains a selected first predetermined
value; and (d) operating said fan in said first direction at said
first speed to move air in said first flow when said at least one
selected operational parameter substantially attains a selected
second predetermined value.
2. A method for effecting ice removal from an outdoor housing for
an environmental conditioning unit as recited in claim 1 wherein
said coil flowingly contains a fluid and wherein said at least one
operational parameter is temperature of said fluid as said fluid
exits said coil.
3. A method for effecting ice removal from an outdoor housing for
an environmental conditioning unit as recited in claim 1 wherein
said first speed and said second speed are substantially equal.
4. A method for effecting ice removal from an outdoor housing for
an environmental conditioning unit as recited in claim 1 wherein
said at least one first predetermined value said at least one
second predetermined value are selected appropriately to assure
that said environmental conditioning unit is in said defrost
operation mode when said at least one first predetermined value
said at least one second predetermined value are attained.
5. A method for effecting ice removal from an outdoor housing for
an environmental conditioning unit as recited in claim 2 wherein
said first speed and said second speed are substantially equal.
6. A method for effecting ice removal from an outdoor housing for
an environmental conditioning unit as recited in claim 2 wherein
said at least one first predetermined value said at least one
second predetermined value are selected appropriately to assure
that said environmental conditioning unit is in said defrost
operation mode when said at least one first predetermined value
said at least one second predetermined value are attained.
7. A method for effecting ice removal from an outdoor housing for
an environmental conditioning unit as recited in claim 3 wherein
said at least one first predetermined value said at least one
second predetermined value are selected appropriately to assure
that said environmental conditioning unit is in said defrost
operation mode when said at least one first predetermined value
said at least one second predetermined value are attained.
8. A method for effecting ice removal from an outdoor housing for
an environmental conditioning unit as recited in claim 5 wherein
said at least one first predetermined value said at least one
second predetermined value are selected appropriately to assure
that said environmental conditioning unit is in said defrost
operation mode when said at least one first predetermined value
said at least one second predetermined value are attained.
9. A method for effecting ice removal from an outdoor housing for a
heat pump environmental conditioning unit; said heat pump unit
including a coil structure, a reversing valve and a fan configured
for moving air past said coil structure; said housing substantially
surrounding said coil; said heat pump unit operating in a heating
mode when said reversing valve unit is in a first orientation; said
heat pump unit operating in a cooling mode when said reversing
valve is in a second orientation; the method comprising the steps
of: (a) operating said fan at a first speed in a first direction to
move air in a first flow about said coil structure while said heat
pump unit is in said heating mode; (b) disengaging said fan and
orienting said reversing valve in said second orientation when said
heat pump unit substantially attains a predetermined first
operating condition to place said heat pump unit in a defrost mode;
(c) operating said fan at a second speed in a second direction to
move air in a second flow past said coil structure when said heat
pump unit is in said defrost mode and said heat pump unit
substantially attains a predetermined second operating condition;
and (d) engaging said fan and orienting said reversing valve in
said first orientation when said heat pump unit substantially
attains a predetermined third operating condition to place said
heat pump unit in said heating mode.
10. A method for effecting ice removal from an outdoor housing for
a heat pump environmental conditioning unit as recited in claim 9
wherein said coil flowingly contains a fluid between a first coil
end and a second coil end, and wherein at least one of said first
operating condition, said second operating condition and said third
operating condition is related to temperature of said fluid
substantially adjacent one of said first coil end and said second
coil end.
11. A method for effecting ice removal from an outdoor housing for
a heat pump environmental conditioning unit as recited in claim 9
wherein said first speed and said second speed are substantially
equal.
12. A method for effecting ice removal from an outdoor housing for
a heat pump environmental conditioning unit as recited in claim 1
wherein said first operating condition and said second operating
condition are selected appropriately to assure that said heat pump
unit is in said defrost mode when said second operating condition
is attained.
13. A method for effecting ice removal from an outdoor housing for
a heat pump environmental conditioning unit as recited in claim 10
wherein said first speed and said second speed are substantially
equal.
14. A method for effecting ice removal from an outdoor housing for
a heat pump environmental conditioning unit as recited in claim 10
wherein said first operating condition and said second operating
condition are selected appropriately to assure that said heat pump
unit is in said defrost mode when said second operating condition
is attained.
15. A method for effecting ice removal from an outdoor housing for
an environmental conditioning unit as recited in claim 11 wherein
said first operating condition and said second operating condition
are selected appropriately to assure that said heat pump unit is in
said defrost mode when said second operating condition is
attained.
16. A method for effecting ice removal from an outdoor housing for
an environmental conditioning unit as recited in claim 13 wherein
said first operating condition and said second operating condition
are selected appropriately to assure that said heat pump unit is in
said defrost mode when said second operating condition is
attained.
17. An apparatus for effecting ice removal from an outdoor housing
for an environmental conditioning unit; said environmental
conditioning unit including a coil structure, a reversing valve and
a fan configured for moving air past said coil structure; said
environmental conditioning unit operating in a heating mode when
said reversing valve unit is in a first orientation; said
environmental conditioning unit operating in a cooling mode when
said reversing valve is in a second orientation; said housing
substantially surrounding said coil; the apparatus comprising: (a)
a control unit coupled with said fan; (b) at least one sensor unit
coupled with said control unit and coupled with said coil structure
for sensing at least one predetermined operating parameter
associated with said fluid; (c) said control unit cooperating with
said at least one sensor unit to effect operating said fan at a
first speed in a first direction to move air in a first flow past
said coil structure while said environmental conditioning unit is
in said heating mode; (e) said control unit cooperating with said
at least one sensor unit to effect disengaging said fan and
orienting said reversing valve in said second orientation when said
environmental conditioning unit substantially attains a
predetermined first operating condition to place said environmental
conditioning unit in a defrost mode; (f) said control unit
cooperating with said at least one sensor unit to effect operating
said fan at a second speed in a second direction to move air in a
second flow past said coil structure when said environmental
conditioning unit is in said defrost mode and said environmental
conditioning unit substantially attains a predetermined second
operating condition; and (g) said control unit cooperating with
said at least one sensor unit to effect operating said fan in said
first direction at said first speed to move air in said first flow
when said environmental conditioning unit substantially attains a
predetermined third operating condition.
18. An apparatus for effecting ice removal from an outdoor housing
for an environmental conditioning unit as recited in claim 17
wherein said coil flowingly contains a fluid between a first coil
end and a second coil end, and wherein at least one of said first
operating condition, said second operating condition and said third
operating condition is related to temperature of said fluid
substantially adjacent one of said first coil end and said second
coil end.
19. An apparatus for effecting ice removal from an outdoor housing
for an environmental conditioning unit as recited in claim 17
wherein said first speed and said second speed are substantially
equal.
20. An apparatus for effecting ice removal from an outdoor housing
for an environmental conditioning unit as recited in claim 19
wherein said first operating condition and said second operating
condition are selected appropriately to assure that said heat pump
unit is in said defrost mode when said second operating condition
is attained.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention is directed to environmental
conditioning systems, and especially to environmental conditioning
systems employing heat pump technology and operated in cold
environments tending to ice up outdoor units of the systems.
[0002] Environmental conditioning systems, such as heat pump
systems, typically include indoor components arranged within a
space to be conditioned and outdoor components situated outside the
space to be conditioned. Environmental conditioning in the context
of this description includes air conditioning of an interior space,
such as heating and cooling of the interior space.
[0003] In cold climate areas, housing structures, such as louvered
housings, surrounding an outside coil of an environmental
conditioning system may become iced over. Such icing over reduces
air flow available for drawing over the outside coil and reduces
efficiency and effectiveness of the environmental conditioning
system.
[0004] There is a need for a method and apparatus for effecting
removal of ice from a housing for an environmental conditioning
unit.
[0005] In particular, there is a need for a method and apparatus
for effecting removal of ice from a housing for an outdoor
component for a heat pump system.
SUMMARY OF THE INVENTION
[0006] A method for removing ice from an outdoor housing for an
environmental conditioning unit that includes the housing
surrounding a coil and a fan for moving air past the coil includes
the steps of: (a) operating the fan at a first speed in a first
direction to move air in a first flow past the coil while the
conditioning unit is in a heating mode; (b) disengaging the fan
when the conditioning unit is in a defrost mode; (c) operating the
fan at a second speed in a second direction to move air in a second
flow past the coil when an operational parameter attains a first
value; and (d) operating the fan in the first direction at the
first speed to move air in the first flow when the operational
parameter attains a second value.
[0007] An apparatus for effecting ice removal from an outdoor
housing for an environmental conditioning unit that includes a coil
structure substantially surrounded by the housing, a reversing
valve and a fan configured for moving air past the coil structure
operates in a heating mode when the reversing valve unit is in a
first orientation and operates in a cooling mode when the reversing
valve is in a second orientation includes: (a) a control unit
coupled with the fan; (b) at least one sensor unit coupled with the
control unit and coupled with the coil structure for sensing at
least one predetermined operating parameter associated with the
fluid. The control unit cooperates with the at least one sensor
unit to effect operating the fan at a first speed in a first
direction to move air in a first flow past the coil structure while
the environmental conditioning unit is in the heating mode. The
control unit cooperates with the at least one sensor unit to effect
disengaging the fan and orienting the reversing valve in the second
orientation when the environmental conditioning unit substantially
attains a predetermined first operating condition to place the
environmental conditioning unit in a defrost mode. The control unit
cooperates with the at least one sensor unit to effect operating
the fan at a second speed in a second direction to move air in a
second flow past the coil structure when the environmental
conditioning unit is in the defrost mode and the environmental
conditioning unit substantially attains a predetermined second
operating condition. The control unit cooperates with the at least
one sensor unit to effect operating the fan in the first direction
at the first speed to move air in the first flow when the
environmental conditioning unit substantially attains a
predetermined third operating condition.
[0008] It is, therefore, an object of the present invention to
provide a method and apparatus for effecting removal of ice from a
housing for an environmental conditioning unit.
[0009] It is a further object of the present invention to provide a
method and apparatus for effecting removal of ice from a housing
for an outdoor component for a heat pump system.
[0010] Further objects and features of the present invention will
be apparent from the following specification and claims when
considered in connection with the accompanying drawings, in which
like elements are labeled using like reference numerals in the
various figures, illustrating the preferred embodiments of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic diagram of a heat pump environmental
conditioning system.
[0012] FIG. 2 is a schematic diagram of air flow about an outdoor
coil unit for a heat pump environmental conditioning system
operating in a heating mode.
[0013] FIG. 3 is a schematic diagram of air flow about an outdoor
coil unit for a heat pump environmental conditioning system
operating in an ice removing mode according to the present
invention.
[0014] FIG. 4 is a graphic representation of operation of a heat
pump environmental conditioning system employing the present
invention for ice removal.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] FIG. 1 is a schematic diagram of a heat pump environmental
conditioning system. In FIG. 1, a heat pump system 10 is installed
for conditioning an interior or inside space 12. A compressor 14 is
situated in an exterior or outside space 16 outside a wall 18. An
interior or inside coil 20 is situated in interior space 12.
Interior coil 20 is in fluid communication with an exterior or
outside coil 22 and with compressor 14 in a fluid network involving
a reversing valve 24, an expansion valve 21 and an expansion valve
23. Exterior coil 22 and reversing valve 24 are situated in
exterior space 16. A blower unit 26 urges air across interior coil
20 in a direction indicated by an arrow 28. A blower unit 30 urges
air across exterior coil 22 in a direction indicated by an arrow
32. Exterior coil 22 may be substantially enclosed within a housing
50. Housing 50 may include louvers 52 or other access structures
for permitting air flow from outside space 16 about exterior coil
22 in response to blower unit 30.
[0016] Heat pump system 10 also includes a thermostat unit 34 and a
defrost unit 36 coupled with a control unit 38. Control unit 38 is
also coupled with compressor 14 and with reversing valve 24. Some
heat pump systems embody defrost unit 36 and control unit 38 in a
single circuit board unit.
[0017] Reversing valve 24 has a common input port 40, a common
output port 42 and bidirectional ports 44, 46. A directing element
48 is situated inside reversing valve 24. Directing element 48 may
be situated in a first position spanning common output port 42 and
bidirectional port 44 (indicated by a solid line) or in a second
position spanning common output port 42 and bidirectional port 46
(indicated by a dotted line). Details regarding how directing
element 48 is moved are not illustrated in FIG. 1.
[0018] Heat pump system 10 may also include thermostats T.sub.1,
T.sub.2. Thermostats T.sub.1, T.sub.2 may be situated in any of
several loci within heat pump system 10. Preferably thermostats
T.sub.1, T.sub.2 are situated between expansion valve 21 and
exterior coil 22. Most preferably thermostats T.sub.1, T.sub.2 are
situated between expansion valve 21 and exterior coil 22, and
substantially nearer to expansion valve 21 than exterior coil 22.
Thermostats T.sub.1, T.sub.2 participate in employing the present
invention for controlling a defrost cycle for heat pump system 10,
as will be described in greater detail hereinafter in connection
with FIG. 4.
[0019] During cooling operations when heat pump system 10 operates
to cool interior space 12, directing element 48 is in its
right-hand (dotted line) position in FIG. 1. In this configuration,
refrigerant is exhausted from compressor exhaust 13 and enters
reversing valve 24 at common input port 40. Because directing
element 48 is in its right-hand position bidirectional port 44 is
left unmasked and refrigerant exits reversing valve 24 via port 44.
Refrigerant exits via port 44 and enters exterior coil 22 in a
compressed high-pressure, high-temperature vapor state. In the
cooling operation, exterior coil 22 operates as a condenser and
interior coil 20 operates as an evaporator so that as refrigerant
passes from compressor exhaust 13 via reversing valve 24 and
traverses exterior coil 22 the refrigerant is cooled and condenses
to a liquid. Air flowing over exterior coil 22 in response to
blower unit 30 removes heat from refrigerant in exterior coil 22.
Refrigerant therefore arrives at expansion valve 23 in a
high-pressure, high-temperature liquid state. Expansion valve 23
operates to present a low-pressure, low-temperature liquid state
refrigerant to interior coil 20. Liquid refrigerant enters interior
coil 20 where it is heated by air forced over interior coil 20 by
blower unit 26. In this manner refrigerant in interior coil 20
picks up heat from interior space 12, thereby cooling interior
space 12. Refrigerant exits interior coil 20 in a vapor state and
enters reversing valve 24 via bidirectional port 46. Because
directional element 48 is in a position spanning bidirectional port
46 and output port 42, refrigerant entering reversing valve 24 via
bidirectional port 46 is directed to exit reversing valve 24 via
output port 42. Thereafter refrigerant in its vapor state returns
to compressor 14 via an intake port 15.
[0020] During heating operations when heat pump system 10 operates
to heat interior space 12, directing element 48 is in its left-hand
(solid line) position in FIG. 1. In this configuration, refrigerant
is exhausted from compressor exhaust 13 and enters reversing valve
at common input port 40. Because directing element 48 is in its
left-hand position bidirectional port 46 is left unmasked and
refrigerant exits reversing valve 24 via port 46. Refrigerant exits
reversing valve 24 via port 46 and enters interior coil 20 in a
compressed vapor state. In the heating operation, interior coil 20
operates as a condenser and exterior coil 22 operates as an
evaporator so that as refrigerant traverses interior coil 20 it is
cooled and condenses to a liquid. Air flowing over interior coil 20
because of blower unit 26 picks up heat given up by refrigerant in
interior coil 20 as the refrigerant condenses and cools. It is this
heat that warms interior space 12. Refrigerant therefore arrives at
expansion valve 21 in a high-pressure, high-temperature liquid
state. Expansion valve 21 operates to present a low-pressure,
low-temperature liquid state refrigerant to exterior coil 22. In
exterior coil 22 refrigerant is heated by air forced over exterior
coil 22 by blower unit 30. In this manner refrigerant in exterior
coil 22 picks up heat from exterior space 16 thereby returning
refrigerant in exterior coil 22 to a vapor state. Refrigerant exits
exterior coil 22 in a vapor state and enters reversing valve 24 via
bidirectional port 44. Because directional element 48 is in a
position spanning bidirectional port 44 and output port 42,
refrigerant entering reversing valve 24 via bidirectional port 44
is directed to exit reversing valve 24 via output port 42.
Thereafter refrigerant in its vapor state returns to compressor 14
via an intake port 15.
[0021] One may observe that there are characteristic loci within
heat pump system 10 that exhibit temperatures related to the
operation being performed by heat pump system 10. That is, when
heat pump system 10 is performing a cooling operation, temperatures
at certain loci in heat pump system 10 will be relatively cool and
other loci in heat pump system 10 will be relatively warm.
Providing a temperature sensing device such as, by way of example
and not by way of limitation, a thermostat device at one or more
such characteristic loci permits one to check whether heat pump
system 10 is actually performing a cooling operation or a heating
operation. As mentioned earlier herein, thermostats T.sub.1,
T.sub.2 may be situated in any of several loci within heat pump
system 10. Preferably thermostats T.sub.1, T.sub.2 are situated
between expansion valve 21 and exterior coil 22. Most preferably
thermostats T.sub.1, T.sub.2 are situated between expansion valve
21 and exterior coil 22, and substantially nearer to expansion
valve 21 than exterior coil 22. Thermostats T.sub.1, T.sub.2 are
preferably coupled with at least one of control unit 38 and defrost
unit 36 to participate in employing the present invention for
controlling a defrost cycle for heat pump system 10.
[0022] Most heat pump systems have an installed defrost control
unit, such as defrost unit 36. Defrost units are typically
configured for deciding when to cease compressor operation in
response to predetermined system conditions. The system conditions
that may occasion a compressor shut down vary from system to
system. Defrost units also typically include a defrost timer (not
shown in detail in FIG. 1) that times out after a predetermined
defrost period to limit defrost operations to a duration no greater
than the predetermined defrost period. The present invention
enables an alternative employment of a defrost operation to effect
ice removal from housing 50 during heating operations by heat pump
system 10.
[0023] FIG. 2 is a schematic diagram of air flow about an outdoor
coil unit for a heat pump environmental conditioning system
operating in a heating mode. In FIG. 2, a housing 50 substantially
surrounding an exterior coil 22 presents louvers 52 for permitting
air flow from outside space 16 about exterior coil 22 in response
to a blower unit 30. Blower unit 30 may be substantially contained
within housing 50 and may include a blower motor 33 driving a fan
blade structure 35. When blower motor 33 drives fan blade structure
35 in a first direction 37, air is moved in a first flow F.sub.1
from outside space 16 through louvers 52 past exterior coil 22 and
blower unit 30.
[0024] FIG. 3 is a schematic diagram of air flow about an outdoor
coil unit for a heat pump environmental conditioning system
operating in an ice removing mode according to the present
invention. In FIG. 3, housing 50 substantially surrounds exterior
coil 22 and presents louvers 52 for permitting air flow from
outside space 16 about exterior coil 22 in response to blower unit
30. In the outdoor coil unit illustrated in FIG. 3, blower unit 30
is substantially contained within housing 50 and includes blower
motor 33 driving fan blade structure 35. When blower motor 33
drives fan blade structure 35 in a second direction 39, air is
moved in a first flow F.sub.2 past blower unit 30 and exterior coil
22 through louvers 52 to outside space 16. Preferably, rotation
directions 37, 39 are substantially opposite each other and flows
F.sub.1, F.sub.2 are substantially equal and opposite each
other.
[0025] Reversing direction of air flow during a defrost operation
for a heat pump is disclosed in U.S. Pat. No. 5,095,711 to Marris
et al. for "Method and Apparatus for Enhancement of Heat Pump
Defrost", issued Mar. 17, 1992 (hereinafter referred to as
"Marris"). Marris describes a heat pump with a reversible fan motor
in its outdoor coil and, after a delay period following initiation
of the defrost cycle, the fan is caused to operate in a reverse
direction to thereby cause the surrounding air to flow through the
outdoor coil in a direction opposite to that in which it flows
during the heating mode operation. During this time, according to
Marris, the fan is operated at a relatively slow speed to thereby
prevent the convective flow of heat upwardly, while at the same
time causing little, if any, flow of ambient air downwardly into
the coil.
[0026] Marris pointedly limits the flow of air in the reverse
direction. As a result, no clearing of an air-flow-accommodating
structure such as louvers is effected using Marris' method. The
problem of icing over of air-flow-accommodating structure and
consequent restriction of air flow past the outdoor coil remains a
problem when using Marris' method.
[0027] FIG. 4 is a graphic representation of operation of a heat
pump environmental conditioning system employing the present
invention for ice removal. In FIG. 4, a graphic plot 70 illustrates
temperature of refrigerant displayed as a function of time. As
mentioned earlier herein, heat pump system 10 (FIG. 1) may include
thermostats T.sub.1, T.sub.2. Thermostats T.sub.1, T.sub.2 may be
situated in any of several loci within heat pump system 10.
Preferably thermostats T.sub.1, T.sub.2 are situated between
expansion valve 21 and exterior coil 22. Most preferably
thermostats T.sub.1, T.sub.2 are situated between expansion valve
21 and exterior coil 22, and substantially nearer to expansion
valve 21 than exterior coil 22. Thermostats T.sub.1, T.sub.2
participate in employing the present invention for controlling a
defrost cycle for heat pump system 10.
[0028] Refrigerant temperature is illustrated in FIG. 4 as
declining during a time interval t.sub.0-t.sub.1. At time t.sub.1,
refrigerant temperature, as measured by one of thermostats T.sub.1,
T.sub.2 (FIG. 1) is at a level TEMP.sub.1. Temperature TEMP.sub.1
may be a set point for a defrost operation for heat pump system 10
so that at time t.sub.1 defrost unit 36 may operate as a defrost
control unit to start a timer for a defrost delay. By way of
example and not by way of limitation, thermostat T.sub.1 may be
configured to electrically close at set point temperature
TEMP.sub.1 to effect detection of refrigerant attaining temperature
TEMP.sub.1. By way of example and not by way of limitation,
TEMP.sub.1 may be established substantially at 42.degree. F.
Defrost delays are sometimes settable by a field selectable pin on
a defrost board or similar unit and may, by way of example and not
by way of limitation, be preset for setting at 30, 60 or 90
minutes.
[0029] Once the selected defrost delay elapses, defrost control
unit 36 may initiate a defrost mode of operation by orienting
reversing valve 24 for cooling operation and disengaging outdoor
fan motor 33 (FIGS. 2 and 3). This operational mode change is
indicated in FIG. 4 as being effected at a time t.sub.2.
Refrigerant in heat pump system 10 warms during defrost mode
operation and may equal set point temperature TEMP.sub.1 at a time
t.sub.3. While heat pump system 10 is in the defrost mode exterior
coil 22 warms up, ice that has accumulated on exterior coil 22 may
melt and refrigerant temperature may increase. In a normal prior
art defrost operation, thermostat T.sub.1 may be set to
electrically open at a second set point temperature TEMP.sub.3 to
terminate defrost operation by re-engaging fan motor 33 and
configuring reversing valve 24 for heating mode operations by heat
pump system 10. Second set point temperature TEMP.sub.3 is attained
at a time t.sub.5 in a normal prior art defrost operation, as
indicated in FIG. 4.
[0030] However, when employing the present invention a second
thermostat T.sub.2 is preferably configured to sense attainment of
an interim set point temperature TEMP.sub.2. Interim set point
temperature TEMP.sub.2 is attained at a time t.sub.4 in FIG. 4.
When interim set point temperature TEMP.sub.2 is detected as
behaving been attained, thermostat T.sub.2 electrically closes and
an enhanced defrost routine is initiated by which fan motor 33 is
re-energized and run in a reverse rotational direction (e.g.,
direction 39; FIG. 3) at substantially the same speed at which fan
motor 33 is operated during a heating mode of operation by heat
pump system 10. The enhanced defrost routine may be initiated at
any time after first temperature set point TEMP.sub.1 is attained.
However, delaying commencement of the enhanced defrost routine may
be advantageous; after having no fan rotation during a defrost
interval such as substantially from time t.sub.2 to substantially
time t.sub.4, external coil 22 may build up heat so that relatively
warm air is extant about external coil 22. The warm air accumulated
or built up about external coil 22 may therefore be available for
movement toward housing 50 in an enhanced defrost operation during
time interval t.sub.4-t.sub.5 or longer. When fan rotation is
reversed, refrigerant temperature may tend to warm at a slower
rate, as indicated by a line segment 80 during times following time
t.sub.4 in FIG. 4. In such conditions when fan rotation is
reversed, refrigerant temperature may not reach second set point
temperature TEMP.sub.3 to occasion termination of an extant defrost
operation until time t.sub.7. Defrost timer limits may terminate
defrost operation at a predetermined defrost period ending at a
time t.sub.6 earlier than time t.sub.7. Experiments by the
inventors have demonstrated that warm air and increased air
velocity impinging a louvered housing structure during an enhanced
defrost operation as described herein significantly reduces ice
accumulation on the louvered housing structure, even when defrost
operations are terminated according to a defrost timer
predetermined defrost period.
[0031] It is to be understood that, while the detailed drawings and
specific examples given describe preferred embodiments of the
invention, they are for the purpose of illustration only, that the
apparatus and method of the invention are not limited to the
precise details and conditions disclosed and that various changes
may be made therein without departing from the spirit of the
invention which is defined by the following claims:
* * * * *