Bryant 355CAV installation instructions Burner Orifice

355CAV

NOTE: DO NOT set medium-heat manifold pressure less than 1.3- in. wc or more than 1.7-in. wc for natural gas.

!CAUTION

UNIT DAMAGE HAZARD

Failure to follow this caution may result in reduced furnace life.

DO NOT bottom out gas valve regulator adjusting screws. This can result in unregulated manifold pressure and result in excess overfire and heat exchanger failures.

NOTE: If orifice hole appears damaged or it is suspected to have been redrilled, check orifice hole with a numbered drill bit of correct size. Never redrill an orifice. A burr-free and squarely aligned orifice hole is essential for proper flame characteristics. (See Fig. 61.)

f. Move setup switch SW4-2 to OFF position after completing medium-heat adjustment.

g.Jumper R and W/W1 and W2 thermostat connections on furnace control. (See Fig. 33.) This keeps furnace locked in high-heat operation.

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

NOTE: DO NOT set high-heat manifold pressure less than 3.2-in. wc or more than 3.8-in. wc for natural gas.

i.Remove jumpers R to W/W1 and R to W2.

j.Wait for blower off-delay to finish then reset 115-v power to furnace.

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

l.Wait for the blower to turn ON then check low-heat manifold pressure. It should be between .5 to .6-in. wc. This setting should not require adjustment but if it does remove the low-heat adjustment cap (See Fig. 60) and turn the low-heat adjusting screw clockwise (in) to decrease manifold pressure or counterclockwise (out) to increase manifold pressure. You will only have 15 minutes to make an adjustment if needed. If you need more time then move setup switch SW1-2 on control center to ON position (See Fig. 33).

NOTE: DO NOT set low-heat manifold pressure before setting medium-heat manifold pressure. DO NOT set low-heat manifold pressure less than .5-in. wc or more than .6-in. wc for natural gas.

m. When correct manifold pressures are obtained, replace caps that conceal gas valve adjustment screws. Main burner flame should be clear blue, almost transparent. (See Fig. 62.)

n.Remove jumper across R and W/W1. If necessary move setup switch SW1-2 to the OFF position.

3.Verify natural gas input rate by clocking gas meter.

NOTE: Be sure all pressure tubing, combustion-air and vent pipes, and burner enclosure front are in place when checking input by clocking gas meter.

a.Calculate high-altitude adjustment (if required).

UNITED STATES

At altitudes above 2000 ft, this furnace has been approved for 2 percent derate for each 1000 ft above sea level. See Table 11 for derate multiplier factor and example.

CANADA

At installation altitudes from 2000 to 4500 ft, this furnace must be derated 5 percent by an authorized Gas Conversion Station or Dealer. To determine correct input rate for altitude, see example and use 0.95 as derate multiplier factor.

EXAMPLE: 80,000 BTUH HIGH-HEAT INPUT FURNACE INSTALLED AT 4,300 FT

Furnace Input Rate at Sea Level X Derate Multiplier Factor = Furnace Input Rate at Installation Altitude 80,000 X 0.91 = 72,800

b.Reinstall burner box cover.

NOTE: Clocking gas input rate MUST always be performed with the burner box cover INSTALLED.

c. Check that gas valve adjustment caps are in place for proper input to be clocked.

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

NOTE: Be sure heating value of gas used for calculations is correct for your altitude. Consult local gas utility for altitude adjustment of gas heating value.

e. Check and verify orifice size in furnace. NEVER ASSUME THE ORIFICE SIZE. ALWAYS CHECK AND VERIFY.

f.Turn off all other gas appliances and pilots.

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

BURNER

ORIFICE

A93059

Fig. 61 - Burner Orifice

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