High Heat Temperature Rise Too Low - Carrier PG9UAA Troubleshooting Manual

AIR CONDITIONING TONS
(12,000 BTU/HR)
1---1/2
2
2---1/2
3
3---1/2
4
5
6
HIGH HEAT TEMPERATURE RISE TOO LOW - - Generally, this indicates the HI solenoid
in gas valve GV has failed or the furnace is extremely underfired.
STEP
1. Remove the blower access panel. Disconnect the R thermostat lead from the furnace con-
trol board. If setup switch SW1- -2 is ON then set it 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 low heat, clock the low heat gas rate. You have 16 minutes
on this first call for heat before unit switches to high heat. On propane installations check
the manifold pressure.
5. When the furnace is running in high heat, clock the high heat gas rate. On propane installa-
tions check the manifold pressure.
6. Is the high heat rate approximately the same as the low heat rate?
7. Do you have 24 vac across gas valve terminals HI and C
ing high heat?
8. 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.
9. Go to the page number indicated in Index for the CLEANUP AND STARTUP INSTRUC-
TIONS.
10. Replace the gas valve.
11. Is the high heat rate within 2% of that specified on the rating plate?
Table 2 – Cooling Tonnage vs. Airflow (CFM)
AIRFLOW (CFM)
525
700
875
1050
1225
1400
1750
2100
BASED ON 350 CFM/TON (SETUP SWITCH SW1-5 OFF)
SETUP SWITCH SW2/SW3 POSITIONS
MODEL
SIZE
040, 060, 3T-080 DEF. 525
5T-080, 100 DEF. 700
120 DEF. 700
BASED ON 400 CFM/TON (SETUP SWITCH SW1-5 ON)
SETUP SWITCH SW2/SW3 POSITIONS
MODEL
SIZE
040, 060, 3T-080 DEF. 600
5T-080, 100 DEF. 800
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
Air Conditioning or Continuous Fan Airflow Selection Chart
ACTION
040, 060, &
3T ---080 MODEL
X
X
X
X
X
700 875 1050 1225
2 1
875 1050 1225 1400
2
875 1050 1225 1400
2
800 1000 1200 1400
2 1
1000 1200 1400 1600
2
1000 1200 1400 1600
2
V on 2- -stage gas valve dur-
OM- - 24
11
5T ---080 & 100
120 MODEL
MODEL
X
X
X
X
X
X
1225 1225
1750 1750
1
1750 2100
1
1400 1400
2000 2000
1
2000 2100
1
YES NO
7
10
13
X
X
X
X
X
X
X
A10472
GO TO
2
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6
11
8
9
INDEX
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12