Medium And/Or High Heat Temperature Rise Too Low - Bryant 355CAV A Series Troubleshooting Manual

AIR CONDITIONING TONS
(12,000 BTU/HR)
1-1/2
2-1/2
3-1/2
MEDIUM AND/OR HIGH HEAT TEMPERATURE RISE TOO LOW - Generally, this indicates the
HI solenoid in gas valve GV has failed, the throttling valve TV has failed, the furnace is
extremely underfired, or the gas valve GV is miswired.
STEP
1. Remove the blower access panel. Disconnect User Interface ABCD connector (if used) or the
R thermostat lead (if used) from the furnace control board. If setup switches SW1-2 or SW4-2
are ON then set them to OFF.
2. Depress the door switch. Use piece of tape to hold it closed.
3. Jumper R and W/W1 thermostat terminals.
4. When the furnace is running in medium heat, clock the medium heat gas rate. On propane
installations check the manifold pressure.
5. Jumper R and W2 thermostat terminals. When the furnace is running in high heat, clock the
high heat gas rate. On propane installations check the manifold pressure.
6. Is the high heat rate approximately the same as the medium heat rate?
7. Do you have 24-vac across terminals HI and C on gas valve GV during high heat?
8. Are the BLUE and GREEN/YELLOW wires on the gas valve GV reversed? The BLUE wire
should be connected to the M terminal and the GREEN/YELLOW wire should be connected
to the C terminal.
9. Is 24-vac across BROWN wire on the high heat pressure switch HPS and C
variable speed furnace control?
10. You have an open wire or bad terminal on the BROWN wire from the high heat pressure
switch HPS to the gas valve GV. Repair it or replace the harness.
Table 2 – Cooling Tonnage vs. Airflow (CFM)
AIRFLOW
(CFM)
525
2 700
875
3 1050
1225
4 1400
1750
5
6 2100
AIR CONDITIONING (A/C) OR CONTINUOUS-FAN (CF)
AIRFLOW SELECTION CHART
BASED ON 350 CFM/TON (SETUP SWITCH SW1-5 OFF)
SETUP SWITCH SW3 POSITIONS
MODEL
SIZE
060, 3T-080 DEF. 525
2
5T-080, 100 DEF. 700
2
120 DEF. 700
BASED ON 400 CFM/TON (SETUP SWITCH SW1-5 ON)
SETUP SWITCH SW3 POSITIONS
MODEL
SIZE
060, 3T-080 DEF. 600
2
5T-080, 100 DEF. 800
2
120 DEF. 800
1. DEFAULT A/C AIRFLOW WHEN A/C SWITCHES ARE IN OFF POSITION
2. DEFAULT CONT. FAN AIRFLOW WHEN CF SWITCHES ARE IN OFF POSITION
3. SWITCH POSITIONS ARE ALSO SHOWN ON FURNACE WIRING DIAGRAM
ACTION
060, & 3T-080
MODEL
X
X
X
X
X
700 875 1050 1225
1
875 1050 1225 1400
875 1050 1225 1400
2
800 1000 1200 1400
1
1000 1200 1400 1600
1000 1200 1400 1600
2
OM
- 13 -
5T-080 & 100 120 MODEL
MODEL
X X
X X
X X
X X
X X
X X
X
1225 1225
1750 1750
1
1750 2100
1
1400 1400
2000 2000
1
2000 2100
1
YES
7
12
18
-24V on 10
NO GO TO
2
19
4
5
6
13
8
9
35
11