Bryant R-22 Control Box, Thermistor Curve, Muffler, Accumulator, Reversing Valve RVS, Thermistors

Muffler, Accumulator, Reversing Valve (RVS)

The Puronr two-stage air conditioners and heat pumps have a compressor discharge line muffler, to dampen sound pressure pulsations.

The Puronr two-stage heat pumps have a specifically designed reversing valve, for Puronr application and an accumulator for storing excess liquid refrigerant during the heating mode to prevent damaging flood-back.

Thermistors

Outdoor Ambient Thermistor

The Puronr two-speed air conditioner and heat pump units have an outdoor ambient air thermistor. The control board must know the outdoor air temperature so it can activate various functions. These functions include:

SActivating the compressor crankcase heater when ever the outdoor unit is in the off cycle.

SThe fan motor speed changes for both air conditioner and heat pump on the ECM equipped units.

Outdoor Coil Thermistor(OCT)

The coil or defrost thermistor is the same thermistor used to monitor outdoor air temperature. The control board must know the coil temperature so it can activate various functions. These functions include:

SFrost sensing on heat pumps

SCoil-vs-Ambient temperature relationship

SLow ambient cooling operation

Thermistor Curve

The resistance vs. temperature chart enables the service technicians to check thermistor resistance, regardless of the temperature.

For example, at a 60_F temperature, thermistor resistance should be around 16,000 Ohms. (See Fig. 43.)

We will talk about the thermistor in more detail when we review the control board fault codes.

THERMISTOR CURVE

	90
(KOHMS)	80
	70
	60
RESISTANCE	50
	20
	40
	30
	10
	0

0	20	40	60	80	100	120
(-17.77)	(-6.67)	(4.44)	(15.56)	(26.67)	(37.78)	(48.89)
		TEMPERATURE °F (°C)

A08054

Fig. 43 – Resistance Values Versus Temperature

Control Box

Contactor And Capacitor

Removal of the information plate exposes the control components. Both air conditioner and heat pump control boxes will appear to be nearly identical. There are two contactors, two capacitors, a control board and a compressor start assist. The contactors are identical to those used in the standard single speed units. One controls low capacity operation and the second controls high speed. The capacitors also are similar to those used in standard single speed units. You have a fan capacitor for the outdoor fan motor, and a run capacitor for the compressor motor. The control board, start capacitor, and start relay control the starting of the compressor.

Always replace these devices with the Factory Approved Components.

Incoming Power

Incoming power is attached to the two power wire stripped leads. A ground lug is also provided. Outdoor unit should always be grounded through the ground lug to the unit disconnect and from the disconnect to the electrical fuse box. Failure to do so can cause serious injury or death.

Start Circuit Sequence of Operation - 187B & 286B

On a call for high- or low-stage compressor operation, the start relay is closed by the control board through the Vs, Vr, and L2 terminals. This puts the start capacitor in the circuit. Compressor voltage is sensed on the VR and VS terminals throughout the process. As the compressor comes up to speed, the control board senses the change in voltage across VR and VS, and opens the start relay at the appropriate voltage. The control is programmed with the parameters for opening the start circuit. The voltage will be different for high- and low-stage, and for different unit sizes.

Since the same control board is used in all 2-stage units, the model plug determines the start circuit voltage.

Troubleshooting 187B & 286B Start Circuit:

If starting problems are encountered, the control board will flash fault codes to help indicate where the problem was encountered. See Table 21 for appropriate actions by active fault code.

SFirst check that the model plug is correct for the unit model and size, and that it is installed properly

START CAPACITOR

MOUNTING HOLES

START RELAY

MOUNTING HOLE

TAB ON BOTTOM OF

START RELAY TO BE

PLACED IN THIS CORNER

A10157

Fig. 44 – Start Relay and Capacitor Mounting Locations

Evolution / Evolution in Cube Cabinet

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