Cooling Mode - Bryant 352MAV Installation, Start-Up, And Operating Instructions Manual

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 HEAT speed five seconds after
the R to W2 circuit opens.
C. Cooling Mode
The thermostat "calls for cooling"
1. Single-Speed Cooling
(See Fig. 27 or 28 and 50A, C, or E 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 electronic 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
cooling off -delay to 5 seconds.
2. Two-Speed Cooling and Single-Stage Thermostat
(Adaptive Mode)
(See Fig. 27 and 50H 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. 31.) 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 HEAT).
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 shut down for 1 minute while the
BLWM continues to run at low-cool speed (same speed as
LO-HEAT) 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. 32.)
3. Two-Speed Cooling and Two-Stage Thermostat
(See Fig. 28 and Fig. 50B, D, G, and F for thermostat
connections.)
NOTE: The ACRDJ must be disconnected to allow thermostat
control of the outdoor unit staging. (See Fig. 31.)
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 HEAT). 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. 31.)
D. Thermidistat Mode
See Fig. 50A-D 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.
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 HEAT).
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 HEAT 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 HEAT
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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