Patent application title: Heat pump defrost control
Reynold Kenneth Lawson, Sr. (Cullman, AL, US)
IPC8 Class: AF25D2106FI
Class name: Preventing, removing or handling atmospheric condensate defrosting including time or program actuator
Publication date: 2011-09-01
Patent application number: 20110209489
An electronic defrost system consisting of a circuit board designed to
implement defrost cycle of an air source heat pump outdoor coil during
the off-cycle period. off-cycle is when the house thermostat is
satisfied, heat pump is timed off for two minutes and then reactivated in
regular defrost cycle if defrost sensor is calling for defrost. (Temp/off
cycle). When sensor opens, heat pump will shut off for two minutes to
allow pressure equalization.
The automatic emergency heat is an option that can be selected. The
automatic setting will activate the same circuit as the manual switch at
the indoor house thermostat.
Defrost control board designed to activate all heat strips during defrost
cycle if desired.
1. A defrost control apparatus designed to activate defrost cycle during
off-cycle period, A. The circuit board is designed to defrost the outdoor
coil every time the heat pump shuts down if defrost sensor is closed,
This is a temp/off cycle mode, The unit will have a frost-free coil on
start-up, B. Another board design function is if ambient temperature is
too cold for house thermostat to satisfy, a selector switch set on 30/60
minutes will force the unit off on time/temp, and perform the same
off-cycle defrost as the temp,/off cycle.
2. An automatic emergency heat circuit will energize all heat strip relays or sequencers if balance-point stays approximately two degrees below indoor thermostat set-point for thirty minutes. Compressor and outdoor fan motor will be off during this time.
3. As in prior art defrost cycles, the auxiliary heat (normally one heat strip) energizes. The present invention will give owner an option to energize all heat strips for entire defrost cycle, A. This will eliminate cold-blow for an acceptable temperature.
INCORPORATION BY REFERENCE
 Title: Defrost system and method for heat pumps
 Inventor: Shaw, David N.
 Date: Mar. 10, 2009
 Application Ser. No. 12/401,136
 Specific reference: Paragraph -
 The description goes into great detail how a heat pump defrost system operates.
SCHEMATIC AND CONNECTION LEGEND
 12--Heat pump defrost control circuit board drawing  13--Split unit connection drawing  14--K-1 Defrost relay coil--24 volts  16--K1-1 Energizes main contactor on heat pump  18--K1-2 Energizes auxiliary heat during defrost cycle  20--K1-3 Activates blower motor relay  22--k1-4 Shifts reversing valve to cool mode for defrosting outdoor coil  24--K1-5 Interlocks K-2 during defrost cycle  26--K1-6 Interlocks Y-2  28--K1-7 Energizes TD-4  30--K1-8 Prevents voltage feedback in running mode  31--K1-9 Activates all heat strips  32--K-2 Normal running mode coil--24 volts  34--K2-1 Interlocks defrost coil K-1  36--K2-2 Interlocks K-3 to prevent K3-1 from opening during defrost cycle  37--K2-3 Energizes Y-1 in normal running mode (heat or cool)  38--K-3 Emergency Heat relay coil--24 Volts  40--K3-1 De energizes compressor and outdoor fan motor when emergency heat activates automatically or manually  42--K3-2 Prevents voltage feedback  44--K-4 Outdoor fan motor relay coil--24 volts/10 amps  46--K4-1 Stops outdoor fan motor during defrost cycle  48--SW-1 Overrides K3-1 if heat strips are inoperable, or not installed, enabling switch to run heat pump while automatic emergency heat is on  50--SW-2 Disables off cycle defrost  52--SW-3 Disables automatic emergency heat  54--SW-4 Disables thirty-minute defrost circuit. By placing switch on, it will put secondary defrost circuit in thirty-minute time-on. Place switch in off position for sixty-minute time-on  55--SW-5 Selector switch for energizing all heat strip sequencers  56--TD-1 Thirty-minutes on-make timer for automatic emergency heat. Activates when House thermostat is approximately two degrees below setting.  58--TD-2 Two-minute on-make timer for pressure equalization  60--TD-3 Thirty-minute on-make timer time/temp. secondary defrost circuit  62--TD-4 Two-minute off-timer reversing valve holding circuit for pressure equalization  64--TD-5 Three-second on-make timer resets TD-2  66--TD-6 Time delay-on two-minute timer. Holding circuit for pressure equalization  68--TD-7 Sixty-minute on-make defrost timer time/temp. secondary circuit  70--TD-8 Ten-minute off-break timer--terminates defrost cycle if ambient temperature too cold for adequate defrost
  72--NOTE: LVJB-Low voltage junction box  74--G--Connect to green wire in LVJB  76--Y-1 Connect to CC coil (main contactor on heat pump)  78--Y-2 Connect series with yellow wire in LVJB  80--O-R--24V--Connect parallel to red wire in LVJB  82--O Reversing valve--Connect parallel to orange wire from house thermostat in LVJB  84--W1 Auxiliary heat--Connect parallel to white wire in LVJB  86--E Emergency heat--Connect brown wire parallel in LVJB  88--DFT Defrost sensor--Connect to DET on circuit board  90--T1 Disconnect from defrosts relay N.C. contacts input side, connect to T1 on defrost control board  92--DR Defrost relay--Connect to DR N.C. contacts input side that connects to outdoor fan motor.  94--C Common--Connect parallel to blue wire in LVJB (blue on most models)
FIELD OF INVENTION
 This invention relates to the field of heat pumps, more particularly, this Invention presents a unique defrost method for air source heat pumps.
BACKGROUND OF THE INVENTION
 There are patent applications that is referenced that describe an inherent problem with the prior art defrost system.
SUMMARY OF INVENTION
 The present invention has timers incorporated so as to alleviate system shock by idling heat pump for a period of time and then initiate defrost cycle. At completion of defrost, it holds reversing valve in cool mode for a short time to allow pressure equalization.
 The higher SEER rated heat pumps that has been mandated uses a higher pressure refrigerant which could wear more on the reversing valve on systems where the compressor continues to run during defrost cycle. Even a small blow-by leak can reduce the efficiency of a heat pump considerably.
 Some heat pump manufacturers have designed their units with just the basic parts necessary. This gives the heat pump an increased reliability and less service call-outs. Switching to a defrost board that adds additional functions could be viewed as counter to what they have accomplished, but by utilizing the Off-Cycle Defrost System presented in the claims section, I believe it would increase reliability for the reversing valve and the entire system. A reversing valve is one of the more expensive repairs to make when leaks occur.
 The biggest advantage to using the off-cycle system is it will have a clean coil on start-up, in addition, it is heating the entire time. It does the defrost after the thermostat has satisfied.
 The automatic emergency heat circuit will save the homeowner from manually switching to emergency heat when temperature is too low to be efficient.
 Supplemental heat stage one sequencer energizes when defrost initiated as in most prior art units. What's different about this system is the entire strip heat unit can be turned on during the entire defrost cycle if desired.
 The circuit board as shown on the schematic is drafted with conventional parts for better understanding of the invention. The manufacturer will use logic circuits such as USASI, some magnetic relays, timers designed with hexadecimal counters. Microprocessor chips could also be used at the manufacturer's discretion.
 The invention has been reduced to practice in the most basic form with board hard-wired (no etching), using relays and timers. No claim to an earlier filing date, only the provisional filing date is claimed.
 Safety precautions will be printed for installers concerning using all heat strips with unit running during defrost without first checking breaker size, ampacity of conductors, also check register temperature if fibrous ducts installed. (max.125*)
 To simulate defrost cycle when troubleshooting, unplug outdoor fan motor, check for 24 volts AC between DFT and common, turn thermostat down until heat pump shuts off.
 The system that is presented is a basic modification from the prior art systems that is used in most heat pumps, but after reducing it to practice in a limited way, the present invention is much quieter during change-over, and it eliminates the sudden pressure/temperature change.
BRIEF DESCRIPTION OF DRAWINGS
 FIG. 1 consist of one off-cycle defrost schematic shown front view with all parts numbered and legends explained. This drawing is a simplified Formal Draft and is not the best mode. Reference paragraph  for best mode.
 FIG. 2 is a Connection diagram for split system heat pumps, illustrating that the connections are the same for split units as it is for a package unit.
 The Off-Cycle Defrost Board will replace most existing PC boards in use, primarily the more basic boards used in residential package units and split systems.
 The PCB will operate in heat or cool mode, defrost in off-cycle when temperature around forty degrees or below when system shuts down, either on normal off-cycle or forced off-cycle.
 During defrost cycle a selector switch can activate all heat strips. (Optional)
 In extremely cold weather the heat pump will automatically shut down and energize emergency heat which will be the same operation as manual emergency heat.
Description Of Prior Art
 The reverse cycle Hot--Gas defrost system for heat pumps has been the preferred method by manufacturer's for many years. There has been many patents granted concerning defrost of heat pump coils that, for the most part, have been unsucessful for varying reasons. Many patents in the defrost field have been abandoned.
Prior Art References Follow:
 A. Shaw, David N.  application Ser. No. 12/401,136  Filed: March 2009  Title: Defrost system and method for heat pumps
 B. Maths, Derick A.  U.S. Pat. No. 5,332,028  Filed: July 1994  Ref: Claims 1-14
 C. Shuster, Don A.  U.S. Pat. No. 5,758,507  Filed: June 1998  Title: Heat Pump Defrost control  Ref.: Abstract Background of Invention Summary
 Reference US Class: 62/3; 62/81; 62/151; 62/259.1
Description of the Preferred Embodiment
 Referring to the drawing FIG. 1, a schematic diagram is shown front view of an off-cycle heat pump defrost control 12 embodying the present invention with circuits to be etched and parts mounted on a PCB to be installed in the junction box of a package or split unit (outdoor condenser) with connections 74 through 94 made
 In reference to connection diagram 13 FIG. 2 for split heat pump units, the defrost control board connections 13 are the same as the package units 12. The defrost board section 13 is the only relevant part to the present invention. 13 has the the same reference numbers as 12. The remainder of drawing 13 which includes the thermostat, air handler, and the outdoor low voltage junction box, is shown for Illustration purposes.
 To further clarify the connections and the purpose of the circuits in FIGS. 1 and 2 referenced by identification numbers as follow:  G-74--Controls blower motor paralleled with existing green conductor in LVJB 72.  Y1-76--Connects to main contactor (CC) mounted inside heat pump and controls outdoor fan and compressor.  Y2-78--Connects series with yellow wire from house thermostat in LVJB 72. Conductor controls many functions on the defrost board to effect defrost.  R-80--24 Volts AC power source from secondary side of 240/24V transformer. Connects parallel to red wire in LVJB 72 in heat pump.  O-82--Reversing valve--Connects parallel to orange wire from house thermostat in LVJB 72. Circuits will energize REV 82 when unit is off and DFT 88 is calling for defrost. The valve 82 shifts to cooling mode until defrost thermostat opens.  W1-84--Auxiliary heat--Connects parallel to white wire in LVJB 72. When unit goes into defrost, one stage of the heat strips 84 will be energized unless SW-5/55 is closed during installation or by the owner. Closed position will activate all heat strips 86 during defrost cycle, including a two-minute time delay-on between shut-down and defrost start-up 66.  E-86--Emergency heat-Brown wire connects parallel in LVJB 72. EM HT 86 has two functions, one to furnish extra heat while in defrost, or to shut down compressor and outdoor fan 76 automatically during extremely cold weather when thermostat approximately two degrees below balance--point for thirty minutes 56. Closing SW-3/52 will activate EM HT 86 and is an option that the owner and installer can choose.  DFT-88--Defrost thermostat--Connects to defrost thermostat output side to DFT 88 on circuit boards 12/13. DET t'stat is located on refrigerant line to monitor for frost and ice build-up. DFT 88 is the primary circuit that puts most other circuits in operation to accomplish the defrost cycle.  T1-90--Connects to T1 on CC (main contactor) located in heat pump and feeds medium voltage to T1 terminal on circuit board. T1-90 runs the outdoor fan through DR 92. K4-1 Normally closed contacts 46 opens and will stop outdoor fan while in defrost mode.  DR-92--Defrost relay contacts control OFM (outdoor fan motor) during defrost cycle. These N.C. contacts could be eliminated if the present invention is used. Connect DR 92 on defrost board to DR N.C. contacts input side going to OFM.  C-94--Common-Neutral side of the 24 volt AC power source 80. Connect common to blue conductor (blue on most models) parallel in LVJB 72.
 Since certain changes may be necessary in the foregoing disclosure without departing from the scope and spirit of the invention herein involved, it is intended that all matter contained in the above description and depicted in the accompanying schematic draft be construed in an illustrative way and not in a limiting sense.
Patent applications in class Including time or program actuator
Patent applications in all subclasses Including time or program actuator