Payne PG8MVA Installation Instructions Manual page 39

b. When thermometer readings stabilize, subtract return- -
air temperature from supply- -air temperature to determ-
ine air temperature rise.
NOTE: Temperature rise can be determined for low- -heat
operation by placing setup switch SW1- -2 on furnace control in
ON position. For high- -heat operation, place setup switch SW1- -2
in OFF position and jumper R- -W2 on furnace control. DO NOT
forget to return setup switch to OFF position and remove R- -W2
jumper upon completion of testing.
c. This furnace is capable of automatically providing
proper airflow to maintain the temperature rise within
the range specified on furnace rating plate. If temperat-
ure rise is outside this range, proceed as follows:
(1.) Check gas input for low- - and high- -heat opera-
tion.
(2.) Check derate for altitude if applicable.
(3.) Check all return and supply ducts for excessive
restrictions causing static pressure greater than
0.5- -In. W.C..
(4.) Ensure Low Heat Rise Adjust switch SW1- -3 on
furnace control is in ON position when a bypass
humidifier is used. (See Fig. 26 for switch loca-
tion.)
(5.) Make sure proper model plug is installed.
d. Remove thermostat jumpers and release blower access
door switch.
e. Repeat Steps a through c as required to adjust for high
heat temperature rise.
f. When correct high heat input rate and temperature rise
is achieved, turn gas valve ON/OFF switch to OFF.
g. Release blower access door switch.
h. Remove manometer or similar device from gas valve.
i. Re- -install manifold pressure tap plug in gas valve.
(See Fig. 49.)
WARNING
!
FIRE HAZARD
Failure to follow this warning could result in personal
injury, death, and/or property damage.
Reinstall manifold pressure tap plug in gas valve to prevent
gas leak.
j. Remove thermostat jumper wire from furnace control
board.
k. Turn gas valve ON/OFF switch to ON.
CAUTION
!
FURNACE OVERHEATING HAZARD
Failure to follow this caution may result in reduced furnace
life.
Recheck temperature rise. It must be within limits specified
on the rating plate. Recommended operation is at the
mid- -point of rise range or slightly above.
l. Proceed to Step 6, "Set Blower Off Delay" before in-
stalling blower access door.
7. Set Blower Off Delay
a. Remove blower access door if installed.
b. Turn Dip switch SW- -7 or SW- -8 ON or OFF for de-
sired blower off delay. (See Fig. 26, 52 and 54.)
8. Set thermostat heat anticipator.
a. Mechanical thermostat. Set thermostat heat anticipator
to match the amp. draw of the electrical components in
the R- -W/W1 circuit. Accurate amp. draw readings can
be obtained at the wires normally connected to ther-
mostat subbase terminals, R and W. The thermostat
anticipator should NOT be in the circuit while measur-
ing current.
(1.) Set SW1- -2 switch on furnace control board to
ON.
(2.) Remove thermostat from subbase or from wall.
(3.) Connect an amp. meter as shown in Fig. 51.
across the R and W subbase terminals or R and
W wires at wall.
(4.) Record amp. draw across terminals when furnace
is in low heat and after blower starts.
(5.) Set heat anticipator on thermostat per thermostat
instructions and install on subbase or wall.
(6.) Turn SW1- -2 switch OFF.
(7.) Install blower access door.
b. Electronic thermostat: Set cycle rate for 3 cycles per
hr.
9. Set Airflow for Air Conditioning - -Single Stage and High
Stage Cooling
The ECM blower can be adjusted for a range of airflow
for Low Speed or High Speed cooling. See Table 4- -Air
Delivery - - CFM (With Filter ). Depending on the model
size, the cooling airflow can be adjusted from 1. tons nom-
inal cooling to 3 ., to 4 or to 6 tons of nominal cooling
based on 350 cfm ton.
The cooling airflow is adjusted by turning Setup switches
SW2- -1, SW2- -2 and SW2- -3 either ON or OFF. Select the
required airflow from Fig. 58. Fig. 58 is based on 350
CFM per ton. For airflow at 400 CFM per ton, turn Setup
SW1- -5 ON (See Fig. 26 and 52.)
NOTE: 6 ton airflow will truncate at 2200 cfm on applicable
models. For a complete explanation of cooling airflow, refer to
the section titled "Sequence of Operation."
10. Set Airflow For Continuous Fan/Low Speed Cooling Air-
flow The ECM blower motor can be adjusted for continu-
ous fan speeds different than heating or cooling fan speed.
See Table 4 - - Air Delivery - - CFM (With Filter). Select the
required continuous fan airflow from Fig. 58.
The continuous fan speed is also the fan speed for low
speed cooling when furnace is used with a 2- -speed cool-
ing unit. Adjust the Continuous Fan CFM to match the
airflow required for low speed cooling. Select the required
airflow from Fig. 56. For airflow at 400 CFM per ton, turn
Setup SW1- -5 ON (See Fig. 58.) The airflow selected for
low speed cooling will also be the airflow used for con-
tinuous fan.
The continuous fan speed can be further adjusted at the
thermostat using the "Comfort Fan" select function.
Changing the continuous fan speed at the thermostat
DOES NOT change the low speed cooling airflow selec-
ted at the control board.
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