Payne PG9MXA Installation, Start-Up, And Operating Instructions Manual page 50

2. Switching From High-To Low-Heat - - If the thermostat R
to W2 circuit opens, and the R to W1 circuit remains
closed, the furnace control CPU will switch the inducer
motor IDM speed from high to low. The high-heat
pressure switch relay HPSR is energized to open the NC
contact and de-energize the high-heat gas valve solenoid
GV-HI. When the inducer motor IDM reduces pressure
sufficiently, the high-heat pressure switch HPS will open.
The gas valve solenoid GV-M will remain energized as
long as the low-heat pressure switch LPS remains closed.
The blower motor BLWM will switch to LO HT speed five
seconds after the R to W2 circuit opens.
COOLING MODE
The thermostat "calls for cooling".
1. Single-Speed Cooling
(See Fig. 31, 50, 52, or 54 for thermostat connections.) The
thermostat closes R-to-G-and-Y circuits. The R-to-Y circuit
starts the outdoor unit, and R-to-G-and-Y/Y2 circuits start
the furnace blower motor BLWM on COOL speed. The elec-
tronic air cleaner terminal EAC-1 is energized with 115-v
when blower motor BLWM is operating.
When the thermostat is satisfied, the R-to-G-and-Y circuits
are opened. The outdoor unit will stop, and furnace blower
motor BLWM will continue operating on COOL speed for an
additional 90 sec. Jumper Y/Y2 to DHUM to reduce the cool-
ing off-delay to 5 seconds. (See Fig. 37.)
2. Two-Speed Cooling and Single-Stage Thermostat
(Adaptive Mode)
(See Fig. 31 and 50- -57 for thermostat connections.)
This furnace can operate a two-speed cooling unit with a
single-stage thermostat because the furnace control CPU
includes a programmed adaptive sequence of controlled
operation, which selects low-cooling or high-cooling
operation. This selection is based upon the stored history of
the length of previous cooling period of the single-stage
thermostat.
NOTE: The air conditioning relay disable jumper ACRDJ must
be connected to enable the adaptive cooling mode in response to
a call for cooling. (See Fig. 37.) When in place the furnace
control CPU can turn on the air conditioning relay ACR to
energize the Y/Y2 terminal and switch the outdoor unit to
high-cooling.
The furnace control CPU can start up the cooling unit in
either low-or high-cooling. If starting up in low-cooling,
the furnace control CPU determines the low-cooling
on-time (from 0 to 20 minutes) which is permitted before
switching to high-cooling.
If the power is interrupted, the stored history is erased and
the furnace control CPU will select low-cooling for up to
20 minutes and then energize the air conditioning relay
ACR to energize the Y/Y2 terminal and switch the outdoor
unit to high-cooling, as long as the thermostat continues to
call for cooling. Subsequent selection is based on stored
history of the thermostat cycle times.
The wall thermostat "calls for cooling", closing the R to
G-and-Y circuits. The R to Y1 circuit starts the outdoor
unit on low-cooling speed, and the R to G-and-Y1 circuits
starts the furnace blower motor BLWM at low-cool speed
(same speed as LO HT).
If the furnace control CPU switches from low-cooling to
high-cooling, the furnace control CPU will energize the air
conditioning relay ACR. When the air conditioning relay
ACR is energized the R to Y1-and-Y2 circuits switch the
outdoor unit to high-cooling speed, and the R to
G-and-Y1-and-Y/Y2 circuits switch the furnace blower
motor BLWM to COOL speed.
NOTE: When transitioning from low-cooling to high-cooling the
outdoor unit compressor will shutdown for 1 minute while the
BLWM continues to run at low-cool speed (same speed as
LO-HT) until the outdoor unit compressor comes back on at high
speed.
The electronic air cleaner terminal EAC-1 is energized
with 115 vac whenever the blower motor BLWM is
operating. When the thermostat is satisfied, the R to
G-and-Y circuit are opened. The outdoor unit stops, and
the furnace blower BLWM and electronic air cleaner
terminal EAC-1 will remain energized for an additional 90
seconds. Jumper Y1 to DHUM to reduce the cooling
off-delay to 5 seconds. (See Fig. 37.)
3. Two-Speed Cooling and Two-Stage Thermostat
(See Fig. 32 and Fig. 50- -57 for thermostat connections)
NOTE: The ACRDJ must be disconnected to allow thermostat
control of the outdoor unit staging. (See Fig. 37.)
The thermostat closes the R to G-and-Y1 circuits for low-
cooling or closes the R to G-and-Y1-and-Y2 circuits for
high-cooling. The R to Y1 circuit starts the outdoor unit on
low-cooling speed, and the R to G-and-Y1 circuit starts the
furnace blower motor BLWM on low-cool speed (same
speed as LO-HT).
The R-to-Y1-and-Y2 circuits start the outdoor unit on
high-cooling speed, and the R to G-and-Y/Y2 circuits start the
furnace blower motor BLWM on COOL speed.
The electronic air cleaner terminal EAC-1 is energized with
115 vac whenever the blower motor BLWM is operating.
When the thermostat is satisfied, the R-to-G-and-Y1 or R-to
G-and-Y1-and-Y2 circuits are opened. The outdoor unit stops,
and the furnace blower BLWM and electronic air cleaner terminal
EAC-1 will remain energized for an additional 90 seconds.
Jumper Y1 to DHUM to reduce the cooling off-delay to 5
seconds. (See Fig. 37.)
THERMIDISTAT MODE
(See Fig. 50- -53 for Thermidistat connections.)
The dehumidification output, DHUM on the Thermidistat should
be connected to the furnace control thermostat terminal DHUM.
When there is a dehumidify demand, the DHUM input is
activated, which means 24 vac signal is removed from the
DHUM input terminal. In other words, the DHUM input logic is
reversed. The DHUM input is turned ON when no dehumidify
demand exists. Once 24 vac is detected by the furnace control on
the DHUM input, the furnace control operates in Thermidistat
mode. If the DHUM input is low or OFF for more than 48 hours,
the furnace control reverts back to non-Thermidistat mode.
The cooling operation described above also applies to operation
with a Thermidistat. The exceptions are listed below:
a. When the R to G-and-Y1 circuit is closed and there is
a demand for dehumidification, the furnace blower
motor BLWM will continue running at low-cool speed
(same speed as LO HT).
b. When the R to G-and Y/Y2 circuit is closed and there
is a demand for dehumidification, the furnace blower
motor BLWM will drop the blower speed from COOL
to HI HT for a maximum of 10 minutes before
reverting back to COOL speed. If there is still a
demand for dehumidification after 20 minutes, the
furnace control CPU will drop the blower speed back
to HI HT speed. This alternating 10-minute cycle will
continue as long as there is a call for cooling.
c. When the "call for cooling" is satisfied and there is a
demand for dehumidification, the cooling blower-off
delay is decreased from 90 seconds to 5 seconds.
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