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motor failure. If the limit control does not function during
this test, the cause must be determined and corrected.
a. Run furnace for at least 5 minutes.
b. Gradually block off return air with a piece of cardboard or
sheet metal until the limit trips.
c. Unblock return air to permit normal circulation.
d. Burners will re- -light when furnace cools down.
2. Check Pressure Switch(es)
This control proves operation of the draft inducer blower.
a. Turn off 115- -v power to furnace.
b. Disconnect inducer motor lead wires from wire harness.
c. Turn on 115- -v power to furnace.
d. Set thermostat to "call for heat" and wait 1 minute. When
low pressure switch is functioning properly, hot surface
igniter should NOT glow and control diagnostic light
flashes a status code 3. If hot surface igniter glows when
inducer motor is disconnected, shut down furnace immedi-
ately.
e. Determine reason low pressure switch did not function
properly and correct condition.
f. Turn off 115- -v power to furnace.
g. Reconnect inducer motor wires, replace door, and turn on
115- -v power.
h. Blower will run for 90 sec before beginning the call for
heat again.
i. Furnace should ignite normally.
Checklist
1. Put away tools and instruments. Clean up debris.
2. Verify that the jumper is removed from the TEST/TWIN
terminal. Verify that there is nothing plugged into the PLT
440 01 4541 00
3. Verify that the Blower/Heat Off Delay jumpers are set as
4. Verify that the blower (lower door in upflow position) and
5. Verify that the Status LED heartbeat (bright- -dim). If not,
6. Cycle test furnace with room thermostat to be sure that it
7. Check
8. Review Owner's Manual with owner.
9. Attach entire literature packet to furnace.
0–2000
2001–3000
3001–4000
4001–5000
5001–6000
6001–7000
7001–8000
8001–9000
9001–10,000
*Derate multiplier factors are based on midpoint altitude for altitude range.
Specifications subject to change without notice.
connector. (Note: If there is a jumper connector plugged
into PLT, remove it and discard.) See Fig. 37.
desired. See Fig. 37 and 71.
control ("Main" or upper door in upflow position) doors are
properly installed.
check that the power supply is energized and that the blower
door is secure. See Fig. 64 to interpret diagnostic codes.
operates properly with the room thermostat. Check all
modes including Heat, Cool and Fan.
operation
of accessories
instructions.
Table 19 – Altitude Derate Multiplier for U.S.A.
PERCENT
ALTITUDE
FT.
M
0--- 610
610--- 914
914--- 1219
1219--- 1524
1524--- 1829
1829--- 2134
2134--- 2438
2438--- 2743
2743--- 3048
per manufacturer's
DERATE
OF
MULTIPLIER
DERATE
FACTOR*
0
1.00
4--- 6
0.95
6--- 8
0.93
8--- 10
0.91
10--- 12
0.89
12--- 14
0.87
14--- 16
0.85
16--- 18
0.83
18--- 20
0.81
69
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