Set Temperature Rise - Bryant 352MAV Installation, Start-Up, And Operating Instructions Manual

EXAMPLE: (0-2000 ft altitude)
Furnace input from rating plate is 100,000 Btuh.
Btu heating input = Btu/cu ft X cu ft/hr
Heating value of gas = 975 Btu/cu ft
Time for 1 revolution of 2-cu ft dial = 70 sec
Gas rate = 103 cu ft/hr (from Table 11)
Btu heating input = 103 X 975 = 100,425 Btuh. In this
example, the orifice size and manifold pressure adjustment
is within ±2 percent of the furnace input rate.
NOTE: Measured gas inputs (high-heat and low-heat) must be
within ±2 percent of that stated on furnace rating plate when
installed at sea level or derated per that stated above when installed
at higher altitudes.
n. Remove jumper across R, W/W1, and W2 thermostat
connections to terminate call for heat.
B. Set Temperature Rise
CAUTION: Temperature rise must be within limits
specified on unit rating plate. Recommended operation is
at midpoint of rise or above. Failure to follow this caution
may result in overheating the heat exchangers or condens-
ing flue gases in heat exchanger areas not designed for
condensate.
Place SW-1 in ON position. Jumper R to W/W1 and W2 to check
high-gas-heat temperature rise. To check low-gas-heat temperature
rise, remove jumper to W2. Determine air temperature rise for both
high and low gas heat. Do not exceed temperature rise ranges
specified on unit rating plate for high and low gas heat.
This furnace must operate within the temperature rise ranges
specified on the furnace rating plate. Determine the air temperature
as follows:
a. Place duct thermometers in return and supply ducts as
close to furnace as possible. Be sure thermometers do not
'see' heat exchangers so that radiant heat does not affect
thermometer readings. This is particularly important
with straight run ducts.
b. When thermometer readings stabilize, subtract return-air
temperature from supply-air temperature to determine
temperature rise.
If the temperature rise is outside this range, check the following:
a. Gas input for low- and high gas heat operation.
b. Derate for altitude if applicable.
c. Return and supply ducts for excessive restrictions caus-
ing static pressures greater than 0.50-in. wc.
d. Adjust temperature rise by adjusting blower speed.
Increase blower speed to reduce temperature rise. De-
crease blower speed to increase temperature rise.
For high-heat, the following connections can be made at HI
-HEAT on control:
a. Med-high (Yellow)
b. Med (Orange) -Available only on 5-speed motors. Fac-
tory setting for these motors.
c. Med-Low (Blue) - Do NOT use for HI GAS-HEAT on
80K & 120K Btuh input models. Factory setting for
4-speed motors.
CAUTION: To avoid operation outside the rated rise
range:
1. NEVER connect Low Speed (Red) wire to "HI
-HEAT".
2. Do NOT connect Medium Low Speed (Blue) wire to
"HI-HEAT" on 80,000 Btuh and 120,000 Btuh input
model sizes.
For low-heat, the following connections can be made at LO
-HEAT on control:
a. Med (Orange) -Available only on 5-speed motors
b. Med-Low (Blue)
c. Low (RED) - Factory setting.
WARNING: Disconnect 115-v electrical power before
changing speed tap. Failure to follow this warning could
result in personal injury.
To change blower motor speed selections for heating mode,
remove blower motor lead from control HI-HEAT terminal. (See
Fig. 32.) Select desired blower motor speed lead from one of the
other terminals and relocate it to HI-HEAT terminal. See Table 13
for lead color identification. Reconnect original lead on SPARE
terminal. Follow this same procedure for proper selection of
LO-HEAT and COOL speed selection.
→
Set Blower Off Delay
a. Remove Blower Access Door if installed.
b. Turn Dip switch 2 and 3 ON or OFF for desired blower
off delay. See Table 9A and B or Fig. 31 and 32.
TABLE 13–SPEED SELECTION
COLOR
White
Black
Yellow
Orange†
Blue
Red
* Continuous blower speed
† Available on 5-speed blowers only
C. Adjust Blower Off Delay (Heat Mode)
If desired, the main blower off time delay period may be
lengthened or shortened when operating in the heating mode to
provide greater comfort. See Table 9 for position of switches and
Fig. 31 or 32 for location of switches on control center.
D. Set Thermostat Heat Anticipator
When using a nonelectronic thermostat, the thermostat heat-
anticipator must be set to match the amp draw of the electrical
components in R-W/W1 circuit. Accurate amp draw readings can
be obtained at thermostat subbase terminals R and W.
Fig. 56 illustrates an easy method of obtaining actual amp draw.
The amp reading should be taken after blower motor has Started
and furnace is operating in low heat. To operate furnace in
low-heat, first move SW-1 to ON position, then connect ammeter
wires as shown in Fig. 56. The thermostat anticipator should NOT
be in the circuit while measuring current. If thermostat has no
subbase, the thermostat must be disconnected from R and W/W1
wires during current measurement Return SW-1 to final desired
location after completing the reading.
See thermostat manufacturer's instructions for adjusting heat
anticipator and for varying heating cycle length.
—45—
SPEED AS SHIPPED
Common C
OM
High Cool
Med-High SPARE
Med High-Gas Heat
Med-Low Spare/High-Gas Heat
Low* Low-Gas Heat