Bryant 355CAV Adjustments, Set Gas Input Rate, Redundant Automatic Gas Valve

NOTE: Reference Fig. 52-59:

1.Heat pump MUST have a high pressure switch for dual fuel applications.

2.Refer to outdoor equipment Installation Instructions for additional information and setup procedure.

3.Select the “ZONE” position on the two-speed heat pump control.

4.Outdoor Air Temperature Sensor must be attached in all dual fuel applications.

5.Dip switch No.1 on Thermidistat should be set in OFF position for air conditioner installations. This is factory default.

6.Dip switch No. 1 on Thermidistat should be set in ON position for heat pump installations.

7.Dip switch No. 2 on Thermidistat should be set in OFF position for single-speed compressor operation. This is factory default.

8.Dip switch No. 2 on Thermidistat should be set in ON position for two-speed compressor operation.

9.Configuration Option No. 10 “Dual Fuel Selection” must be turned ON in all dual fuel applications.

10.NO connection should be made to the furnace HUM terminal when using a Thermidistat.

11.Optional connection. If wire is connected to W2 on furnace control board, either dip switch SW1-2 or SW4-2 on furnace control should be set in ON position to allow Thermidistat/Thermostat to control furnace at 2 stages Low/High or Medium/High.

12.Optional connection. If wire is connected, ACRDJ jumper on furnace control should be removed to allow Thermidistat/Thermostat to control outdoor unit staging.

13.Furnace must control its own staging operation via furnace control algorithm. This is factory default.

14.The RVS Sensing terminal “L” should not be connected. This is internally used to sense defrost operation.

15.DO NOT SELECT the “FURNACE INTERFACE” or “BALANCE POINT” option on the two-speed heat pump control board. This is controlled internally by the Thermidistat/Dual Fuel Thermostat.

16.Dip switch D on Dual Fuel Thermostat should be set in OFF position for single-speed compressor operation. This is factory default.

17.Dip switch D on Dual Fuel Thermostat should be set in ON position for two-speed compressor operation.

Step 4 — Adjustments

Set Gas Input Rate

Furnace gas input rate on rating plate is for installations at altitudes up to 2000 ft.

In the U.S.A., the input rating for altitudes above 2000 ft must be reduced by 2 percent for each 1000 ft above sea level.

In Canada, the input rating must be derated by 5 percent for altitudes of 2000 ft to 4500 ft above sea level.

Adjust manifold pressure to obtain input rate.

Furnace input rate must be within +2 percent of input rate on furnace rating plate.

1.Determine natural gas orifice size and manifold pressure for correct input.

a.Obtain average heat value (at installed altitude) from local gas supplier.

b.Obtain average specific gravity from local gas supplier.

c.Verify furnace model. Table 10 can only be used for model 355CAV Furnaces.

d.Find installation altitude in Table 10.

NOTE: For Canadian altitudes of 2000 to 4500 ft, use U.S.A. altitudes of 2001 to 3000 ft in Table 10.

e.Find closest natural gas heat value and specific gravity in Table 10.

f.Follow heat value and specific gravity lines to point of intersection to find orifice size and low-, medium-, and high-heat manifold pressure settings for proper operation.

EXAMPLE: (0 - 2000 ft altitude) Heating value = 1050 Btu/cu ft Specific gravity = 0.62 Therefore: Orifice No. 45

Manifold pressure: 3.8-in. wc for high heat 1.6-in. wc for medium heat 0.6-in. wc for low heat

*Furnace is shipped with No. 45 orifices. In this example, all main burner orifices are the correct size and do not need to be changed to obtain proper input rate.

g.Check and verify burner orifice size in furnace. NEVER ASSUME ORIFICE SIZE; ALWAYS CHECK AND VERIFY.

2.Adjust manifold pressure to obtain input rate.

		HIGH-HEAT
	ON/OFF	ADJUSTMENT
		(UNDER CAP)
	SWITCH
		BURNER
		ENCLOSURE
INLET		REFFERENCE
		TAP
PRESSURE
TAP

MEDIUM-HEAT

ADJUSTMENT

(UNDER CAP)

LOW-HEAT

ADJUSTMENT

(UNDER CAP) MANIFOLD PRESSURE

TAP

A07280

Fig. 60 - Redundant Automatic Gas Valve

a. Remove burner enclosure front.

NOTE: Manifold pressure MUST always be measured with the burner box cover REMOVED.

b. Remove regulator seal caps that conceal adjustment screws for medium- and high-heat gas valve regulators. (See Fig. 60.)

c. Move setup switch SW4-2 on control center to ON position. (See Fig. 33.) This keeps furnace locked in medium-heat operation.

d.Jumper R and W/W1 thermostat connections on control to start furnace.

e.Turn medium-heat adjusting screw counterclockwise (out) to decrease manifold pressure or clockwise (in) to increase manifold pressure.

355CAV

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