Bryant Comprehensive Guide to the Communicating Thermostat for Optimal Heat Pump Performance
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Defrost Thermostat

Defrost thermostat signals heat pump that conditions are right for defrost or that conditions have changed to terminate defrost. It is a thermally actuated switch clamped to outdoor coil to sense its temperature. Normal temperature range is closed at 30_ ± 3_F and open at 65_ ± 5_F. Defrost thermostats are used in Legacy RNC and Legacy Line models, a coil temperature thermistor is used in Preferred and Evolution series units.

FEEDER TUBE

STUB TUBE

DEFROST

THERMOSTAT

A97517

Fig. 8 – Defrost Thermostat Location

Check Defrost Thermostat

There is a liquid header with a brass distributor and feeder tube going into outdoor coil. At the end of 1 of the feeder tubes, there is a 3/8-in. OD stub tube approximately 3 in. long. (See Fig. 8.) The defrost thermostat should be located on stub tube. Note that there is only 1 stub tube used with a liquid header, and on most units it is the bottom circuit.

Heating Sequence of Operation

On a call for heating, thermostat makes R-Y, and R-G. Circuit R-Y sends low voltage through the safeties and energizes the contactor, which starts the compressor and energizes the T1 terminal on the circuit board. The T1 terminal energizes the defrost logic. This will energize the OF2 fan relay start the outdoor motor. The T1 terminal must be energized for defrost to function.

When the cycle is complete, R-Y is turned off and the compressor and outdoor fan should stop. There is no compressor delay built into this control.

Defrost Sequence (HK32EA001)

The defrost control is a time/temperature control that has field selectable settings of 30, 60, and 90 minutes. These represent the amount of time that must pass after closure of the defrost thermostat before the defrost sequence begins.

The defrost thermostat senses coil temperature throughout the heating cycle. When the coil temperature reaches the defrost thermostat setting of approximately 32ºF, it will close, which energizes the DFT terminal and begins the defrost timing sequence. When the DTF has been energized for the selected time, the defrost cycle begins, and the control shifts the reversing valve into cooling position, and turns the outdoor fan off. This shifts hot gas flow into the outdoor coil which melts the frost from the coil. The defrost cycle is terminated when defrost thermostat opens at approximately 65_F, or automatically after 10 minutes.

NOTE: The defrost thermostat must be located on the liquid side of the outdoor coil on the bottom circuit and as close to the coil as possible.

Defrost Control Board

Troubleshooting defrost control involves a series of simple steps that indicate whether or not board is defective.

NOTE: This procedure allows the service technician to check control board and defrost thermostat for defects. First, troubleshoot to make sure unit operates properly in heating and cooling modes. This ensures operational problems are not attributed to the defrost control board.

HK32EA001 Defrost Control

The HK32EA001 defrost control is used in all Legacy RNC Line heat pump models 213ANA and 213ANC. Its features include selectable defrost intervals of 30, 60, 90 minutes, and standard defrost speed up capability. This section describes the sequence of operation and trouble shooting methods for this control.

Cooling Sequence of Operation

On a call for cooling, thermostat makes R-O, R-Y, and R-G. Circuit R-O energizes reversing valve switching it to cooling

T1 - ENABLES DEFROST

TIMER. MUST BE

ENERGIZED FOR

DEFROST TIMER TO START

C - COMMON

O - REVERSING VALVE

OUTDOOR FAN

RELAY

DEFROST THERMOSTAT

HK32EA001

 

MUST BE CLOSED BEFORE

 

DEFROST TIMER BEGINS

 

Y OUTPUT TO PRESSURE

SWITCHES AND CONTACTOR

SPEEDUP

position. Circuit R-Y sends low voltage through the safeties and energizes the contactor, which starts the compressor and energizes the T1 terminal on the circuit board. This will energize the OF2 fan relay which starts the outdoor fan motor.

When the cycle is complete, R-Y is turned off and compressor and outdoor fan should stop. With Bryant thermostats, the O terminal remains energized in the cooling mode. If the mode is switched to heat or Off, the valve is de-energized. There is no compressor delay built into this control.

THERMOSTAT INPUTS

A05332

Fig. 9 – HK32EA001 Defrost Control

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Contents Application Guideline Table of ContentsSerial Number Nomenclature Table of Contents TWO Stage NON-COMMUNICATINGTWO Stage Communicating AIR Conditioner and Heat Pump Model Number NomenclatureSafety Considerations Installation GuidelineIntroduction Accessories Required Field-Installed Accessories for Air ConditionersRequired Field-Installed Accessories for Heat Pumps Accessory Descriptions LOW-AMBIENT Cooling Guideline Base / Mid-Tier / Deluxe 4-sided Baffle AssemblyDeluxe 3-sided Baffle Assembly and Dimensions Cabinet Assembly Long Line GuidelineBasic Cabinet Designs Access Compressor Or Other Internal Cabinet Components Legacy RNC and Legacy Line Control Box Identification Figure Labels LabelingCapacitor Aluminum WireElectrical ContactorTime-Delay Relay Crankcase HeaterCycle Protector Personal Injury Hazard Pressure SwitchesDefrost Control Board Defrost ThermostatIf defrost thermostat is stuck open Troubleshooting HK32EA001 If outdoor unit will not runDefrost Speedup If defrost thermostat is stuck closedHeating Five-Minute Compressor DelayQuiet Shift CoolingLow-Voltage Terminals Troubleshooting HK32EA003Fan Motor Compressor PlugRuns, Does Not Pump Compressor FailuresMechanical Failures Locked RotorSplit Post Grommet part number KA75UG100 Noisy CompressorSingle-Phase Motors Electrical FailuresUnit Personal Injury Hazard Refrigeration System RefrigerantCompressor Oil Oil Charging Synthetic Roof Precautionary ProcedureServicing Systems on Roofs With Synthetic Materials BrazingService Valves and Pumpdown Pumpdown ProcedurePersonal Injury and Unit Damage Hazard AccuRaterr Components Used in R-22 Heat Pumps Heating Piston AccuRaterr Heat Pumps OnlyReversing Valve Heating Mode, Solenoid De-Energized Reversing ValveInstall Liquid-line Filter Drier Indoor AC Liquid Line Filter DrierSuction Line Filter Drier Accumulator AccumulatorUnit Operation Hazard Install TXVThermostatic Expansion Valve TXV TXV OperationPersonal Injury and Environmental Hazard Make Piping ConnectionsReplacing TXV on an Indoor Coil pre-2006 Replacing TXV on Indoor Coil post-2006Fire Hazard Refrigeration System RepairLeak Detection Coil RemovalSystem Clean-Up After Burnout Compressor Removal and ReplacementCheck Charge EvacuationDeep Vacuum Method Low Superheat with High Suction Pressure Troubleshooting with SuperheatBasic Diagnostics Low Superheat with Normal or Low Suction PressureHigh Superheat with Normal or High Suction Pressure Hunting SuperheatPseudo Evaporator Superheat Instructions Example Puron System Suction Pressure Drop22 System Suction Pressure Drop Psig PuronrRefrigerant Pressure Temperature ChartPsig 22 Refrigerant Pressure Temperature RelationshipLiquid Line Temperature F Liq Press Subcooling F Psig Puron Subcooling ChartSuperheat F Psig Puron Superheat ChartLiquid Line Temperature F PT F Subcooling F Pres Psig 22 Subcooling Chart22 Superheat Chart Model Plug Information TWO-STAGEApplication Guidelines Model PlugAirflow Selection for 315AAV/355AAV Furnaces General InformationLow Ambient Cooling DefrostAll 286A units must be charged in high stage only Liquid-Line Solenoid AccessoryDefrost Hold Forced DefrostCompressor Operation on 286ANA/187ANA Models One Minute Stage Change Time Delay on 286ANA/187ANA ModelsCooling and Heating Operation Utility Interface With Evolution ControlOutdoor Fan Motor Operation ECM Fan Motor TroubleshootingTime Delays Muffler, Accumulator, Reversing Valve RVSThermistors Control BOX Troubleshooting Contactor Shorted Detection 230V Line Power Disconnect Detection230v Brown-Out Protection Defeated Compressor Voltage SensingThermistor Sensor Comparison Unloader Test ProcedureTemperature Thermistors Failed Thermistor Default OperationStatus Codes TroubleshootingEdge Thermidistat Models T6-PRH-01 or T6-NRH-01 TWO-STAGE 286B/289B/180B/187B General Information All 286B units must be charged in high stage only Heating Check Chart ProcedureCompressor Operation on 289B/180B Models Low Stage High Stage Low & High Model Contactor And Capacitor Incoming PowerTroubleshooting 187B & 286B Start Circuit Control BoxTroubleshooting HK38EA015 circuit board 289B Compressor Thermal Cutout 286B Models Compressor Thermal CutoutOutdoor Coil Thermistor OCT Attachment Status Codes Single Stage Furnace with 2-Stage Air Conditioner Airflow Selection for FV4C Fan Coils non-communicating TWO Stage NON-COMMUNICATING 127A/226AOperating Ambient Airflow Selections ECM FurnacesSystem Function and Sequence of Operation Compressor OperationDefrost Speedup Check Charge TWO Stage Communicating 167A/266A Airflow Selections for ECM Furnaces non communicatingIndoor Thermostat Control Options Defrost Hold Evolution Controlled Low Ambient CoolingMajor Components Communication and Status Function Lights Outdoor Fan Motor OperationFor Evolution Control only, Green communications Comm Light 2230V Brown-Out Protection Defeated Thermistor Curve No 230V at Compressor ContactorOutdoor Coil Thermistor OCT Attachment Status Codes 167A / 266A TroubleshootingCare and Maintenance Puronr R-410A Refrigerant Quick Reference Guide Final Check-OutAIR Conditioner Troubleshooting Chart Heat Pump Troubleshooting Heating Cycle Heat Pump Troubleshooting Cooling Cycle TWO-STAGE 286B/288B 180B/187B Index of TablesDescription Table # TWO-STAGE 286A/288A 180A/187ACatalog No. SM01---6
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R-22 specifications

The Bryant R-22 stands out in the landscape of residential heating and cooling systems with its combination of efficiency, durability, and modern technology. Designed primarily for homeowners seeking comfortable climate control solutions, the R-22 model delivers consistent performance throughout varying seasonal extremes.

One of the main features of the Bryant R-22 is its high energy efficiency. Rated with a SEER (Seasonal Energy Efficiency Ratio) that meets or exceeds industry standards, this air conditioning unit is designed to reduce energy consumption while providing optimal cooling. This not only helps in lowering monthly utility bills but also promotes environmentally responsible usage.

Another notable characteristic is the unit's durability. Constructed with a robust cabinet and high-quality components, the R-22 is built to withstand the rigors of daily use, with protective features that enhance its longevity. The cabinet comes with a powder-coated finish that resists corrosion and harsh weather conditions, ensuring that the unit stays functional and aesthetically pleasing for years.

The Bryant R-22 also incorporates advanced technology to improve user experience. One such innovation is the SmartSet technology, which allows homeowners to program their unit to optimize comfort levels according to their specific needs. This programmable capability enhances energy savings and ensures that the home remains at the desired temperature when residents are present.

Moreover, the unit features a Quiet Operating System that significantly reduces noise levels, making it suitable for residential areas where noise might be a concern. The design minimizes vibrations and optimizes airflow, creating a comfortable environment without disruptive sounds.

For added convenience, the Bryant R-22 is compatible with various thermostat options, including Wi-Fi-enabled models. This allows users to control their home's climate from anywhere using a smartphone app, facilitating effortless adjustments and monitoring of energy usage.

Finally, the Bryant R-22 is backed by a solid warranty, providing peace of mind for homeowners. This commitment to quality and customer satisfaction is a testament to Bryant’s dedication to producing reliable and efficient HVAC solutions. Overall, the Bryant R-22 is an exemplary choice for those looking to enhance their home comfort with the latest in HVAC technology.
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