Payne PG96VAT Installation, Start-Up, Operating And Service And Maintenance Instructions page 67

f. Refer to Table 20 for cubic ft. of gas per hr.
g. Multiply gas rate cu ft./hr by heating value (Btuh/cu ft.) to
obtain input rate.
h. If clocked rate does not match required input from Step 1,
increase manifold pressure to increase input or decrease
manifold pressure to decrease input. Repeat steps b through
e until correct low- -heat input is achieved. Re- -install low
heat regulator seal cap on gas valve.
i. Jumper R to W/W1, and W2. This keeps furnace locked
in high- -heat operation when both W/W1 and W2 are ener-
gized.
j. Repeat items d through h for high- -heat operation, repeat-
ing Step 2 and adjusting the high- -heat regulator screw as
required.
2. Restore furnace to normal operating condition.
a. Turn gas valve ON/OFF switch to OFF.
b. Remove water column manometer or similar device from
manifold pressure tap (if still connected).
WARNING
!
FIRE HAZARD
Failure to follow this warning could result in personal
injury, death, and/or property damage.
Manifold pressure tap set screw must be tightened and
1/8- -in. NPT pipe plug must be installed to prevent gas
leaks.
c. Tighten set screw on manifold tower pressure tap with
3/32- -in. hex wrench, or if
apply pipe dope sparingly to end of plug and re- -install in
the gas valve.
d. Turn gas valve ON/OFF switch to ON.
e. Move setup SW1- -2 on furnace control to position required
for attached thermostat (OFF for single-stage thermostats,
ON for two-stage thermostats).
f. Check for gas leaks and verify furnace operation.
Adjust Temperature Rise
NOTE: Blower door must be installed when taking temperature
rise reading. Leaving blower door off will result in incorrect
temperature measurements, due to possible changes in duct static
pressure and airflow.
CAUTION
!
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in:
S Overheating the heat exchangers or condensing flue gases
in heat exchanger areas not designed for condensate.
S Shortened furnace life
S Component damage.
Temperature rise must be within limits specified on furnace
rating plate. Recommended operation is at midpoint of rise
range or slightly above.
When setup switch SW1- -4 is ON, operation will be near the high
end of the rise range for improved comfort.
Determine air temperature rise as follows:
1. Place thermometers in return and supply ducts as near
furnace as possible. Be sure thermometers do not see heat
exchanger so that radiant heat does not affect readings. This
practice is particularly important with straight- -run ducts.
⅛
- -in. NPT plug was removed,
2. When thermometer readings stabilize, subtract return- -air
temperature from supply- -air temperature to determine air
temperature rise.
NOTE: Temperature rise can be determined for low- -heat and
high- -heat operation by locking the furnace in each mode of
operation. The mode of operation is based on the position of Setup
Switch SW1- -2 on the furnace control board.
3. This furnace is capable of automatically providing proper
airflow to maintain the temperature rise within the range
specified on furnace rating plate. If temperature rise is
outside this range, proceed as follows:
a. Check gas input for low- - and high- -heat operation.
b. Check derate for altitude, if applicable.
c. Check all return and supply ducts for excessive restrictions
causing static pressure greater than 0.5- -In. W.C.
d. Ensure Low Heat Rise Adjust switch SW1- -3 on furnace
control is in ON position when a bypass humidifier is used.
See Fig. 39 for switch location.
e. Verify correct model plug is installed.
To lock the furnace in low heat:
1. Turn SW1- -2 ON at the furnace control.
2. Connect a jumper across R and W/W1 at the thermostat
terminals at the furnace control.
3. Allow the burners to ignite and the blower to turn on.
4. Allow the supply temperature to stabilize and verify the
proper rise range.
If the temperature rise is too high or too low in low heat:
1. Remove jumpers from R and W/W1.
2. Wait until the blower off delay is completed.
3. Turn 115 VAC power off.
4. Check the position of setup switch SW1- -3. When set to
ON, airflow is raised 18% for low heat. Factory default
position is OFF.
5. Turn 115 VAC power on.
6. Re- -check low heat temperature rise.
To lock the furnace in high heat:
1. Connect a jumper across R and W/W1 and W2 at the
thermostat terminals at the furnace control.
2. Allow the burners to ignite and the blower to turn on.
3. Allow the supply temperature to stabilize and verify the
proper rise range.
If the temperature rise is too high or too low in high heat:
1. Remove jumpers from R and W/W1 and W2.
2. Wait until the blower off delay is completed.
3. Turn 115 VAC power off.
4. Check the position of setup switch SW1- -4. When set to
OFF and SW1- -3 is set to OFF, airflow is raised 7% for low
Heat, and 10% for high heat. Factory default position is
ON. If SW1- -3 is ON and SW1- -4 is OFF, airflow is raised
18% for low heat and 10% for high heat.
5. Turn 115 VAC power on.
6. Re- -check high heat temperature rise.
After the temperature rise has been verified:
1. Remove jumpers from thermostat terminals.
2. Allow the blower off delay to complete.
3. Turn setup switches SW1- -2 to the OFF position unless
two- -stage thermostat operation is desired. See Fig. 66.
4. Proceed to "Adjust Blower Off Delay" or install blower
door if complete.
Adjust Blower Off Delay (Heat Mode)
a. Remove blower door if installed.
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