Bryant 355CAV Checklist, Check Safety Controls, Check Primary Limit Control

355CAV

the R-W/W1 circuit. Accurate amp draw measurements can be obtained only at the thermostat subbase terminals R and W.

The thermostat and anticipator should NOT be in the circuit while measuring current. If thermostat has no subbase, the thermostat must be disconnected from R and W/W1 wires during current measurement.

Fig. 63 illustrates an easy method of obtaining thermostat amp draw measurements. The amp reading should be taken after blower motor has started and furnace is operating in low-heat.

1.To operate furnace in low-heat, turn setup switch SW1-2 to ON position (See Fig. 33) and connect ammeter leads across thermostat subbase R-W.

2.See thermostat manufacturer’s instructions for adjusting the heat anticipator and for varying heating cycle length.

NOTE: When using an electronic thermostat, set cycle rate for 3 cycles per hr.

3.Return setup switch SW1-2 to OFF position and replace thermostat on subbase.

Check Safety Controls

This section covers the safety controls that must be checked before the installation is complete. The flame sensor, gas valve, and pressure switches were all checked in the Start-up procedure section as part of normal operation.

Check Primary Limit Control

This control shuts off the gas control system and energizes the air-circulating blower motor if furnace overheats.

1.The recommended method of checking this limit control is to gradually block off return air after furnace has been op- erating for a period of at least 5 minutes.

2.As soon as limit control has shut off burners, a status code 33 will appear on furnace control.

3.The return-air opening should be unblocked to permit normal air circulation.

By using this method to check the limit control, it can be established that the limit is functioning properly and the furnace

will operate safely if there is a restricted return-air duct or motor failure. If the limit control does not function during this test, the cause must be determined and corrected.

Check Pressure Switches

This control proves operation of the draft inducer. Check switch operation as follows:

1.Turn off 115-v power to furnace.

2.Remove control access door and disconnect inducer motor 12-pin wire harness at inducer motor.

3.Turn on 115-v power to furnace.

4.Set thermostat to “call for heat.” When pressure switches are functioning properly, status code 42 will flash on fur- nace control approximately 20 sec after thermostat switch is closed. If either a status code 31 or 32 is flashed when inducer motor is disconnected, the furnace will shut itself down immediately. Determine the reason pressure switches did not function properly and correct the condi- tion.

5.Turn off 115-v power to furnace.

6.Reconnect inducer motor wire harness. Reinstall furnace access door.

7.Turn on 115-v power to furnace.

8.Reset thermostat to desired temperature.

CHECKLIST

1.Put away tools and instruments. Clean up debris.

2.Verify flame rollout manual reset switch has continuity.

3.Verify that blower and main access doors are properly in- stalled.

4.Cycle test furnace with room thermostat.

5.Check operation of accessories per manufacturer’s instruc- tions.

6.Review User’s Manual with owner.

7.Leave literature packet near furnace.

THERMOSTAT SUBBASE TERMINALS WITH THERMOSTAT REMOVED (ANITICIPATOR, CLOCK, ETC.,

MUST BE OUT OF CIRCUIT.)

HOOK-AROUND AMMETER

R Y W G

10 TURNS

FROM UNIT 24-V

CONTROL TERMINALS

EXAMPLE:	5.0 AMPS ON AMMETER	=	0.5 AMPS FOR THERMOSTAT
	10 TURNS AROUND JAWS		ANTICIPATOR SETTING

A96316

Fig. 63 - Amp Draw with Ammeter

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