Step 2—Start-Up Procedures
FIRE AND EXPLOSION HAZARD
Failure to follow this warning could result in personal injury,
death and or property damage.
Never purge a gas line into a combustion chamber. Never use
matches, candles, flame, or other sources of ignition for the
purpose of checking leakage. Use a soap-and-water solution
to check for leakage.
1. Purge gas lines after all connections have been made.
2. Check gas lines for leaks.
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury,
or death.
Blower access door switch opens 115-v power to control. No
component operation can occur unless switch is closed.
Caution must be taken when manually closing this switch for
service purposes.
3. To Begin Component Self-Test:
Remove blower access door. Disconnect the thermostat R lead
from the furnace control board. Manually close the blower
door switch. Short (jumper) the C
OM-24v terminal on control
to the TEST/TWIN 3/16-inch quick connect terminal on
control until LED goes out (approximately 2 sec). Gas valve
and humidifier will not be turned on. (See Fig. 24.)
NOTE: The furnace control allows all components, except the gas
valve, to be run for short period of time. This feature helps
diagnose a system problem in case of a component failure.
Component test feature will not operate if any thermostat signal is
present at the control.
Component test sequence is as follows:
Refer to service label attached to furnace or see Fig. 49.
a. LED will display previous status code 4 times.
b. Inducer motor starts and continues to run until Step f of
component test sequence.
c. Hot surface igniter is energized for 15 sec., then off.
d. Blower motor operates on HEAT speed for 10 sec.
e. Blower motor operates on COOL speed for 10 sec.
f. Inducer motor stops.
g. Reconnect R lead to furnace control board, release blower
door switch and re-install blower door.
4. Operate furnace per instruction on door.
5. Verify furnace shut down by lowering thermostat setting
below room temperature.
6. Verify furnace restarts by raising thermostat setting above
room temperature.
Step 3—Adjustments
FIRE HAZARD
Failure to follow this warning could result in injury, death
and/or property damage.
DO NOT bottom out gas valve regulator adjusting screw.
This can result in unregulated manifold pressure and result in
excess overfire and heat exchanger failures.
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in reduced furnace
life.
DO NOT redrill orifices. Improper drilling (burrs, out-of-
round holes, etc.) can cause excessive burner noise and
misdirection of burner flames. This can result in flame
impingement of heat exchangers, causing failures. (See Fig.
47.)
Furnace gas input rate on rating plate is for installations at altitudes
up to 2000 ft. Furnace input rate must be within ±2 percent of
furnace rating plate input.
1. Determine the correct gas input rate.
In the U.S.A.:
The input rating for altitudes above 2,000 ft. must be reduced
by 4 percent for each 1,000 ft. above sea level. For installa-
tions below 2000 ft., refer to the unit rating plate. For
installations above 2000 ft., multiply the input on the rating
plate by the de-rate multiplier in Table 8 for the correct input
rate.
In Canada:
The input rating must be derated by 10 percent for altitudes of
2,000 ft. to 4,500 ft. above sea level by an authorized Gas
Conversion Station or Dealer. To determine correct input rate
for altitude, see example 1 and use 0.90 as derate multiplier
factor.
2. Determine the correct orifice and manifold pressure adjust-
ment. There are two different orifice and manifold adjustment
tables. All models in all positions, except Low NOx models in
downflow or horizontal positions, use Table 12 (22,000
Btuh/Burner).
Low NOx models in the downflow or horizontal positions
must use Table 13 (21,000 Btuh/Burner). See input listed on
rating plate.
a. Obtain average yearly gas heat value (at installed altitude)
from local gas supplier.
b. Obtain average yearly gas specific gravity from local gas
supplier.
c. Find installation altitude in Table 12 or 13.
Table 8–Altitude Derate Multipler for U.S.A.
ALTITUDE
(FT)
PERCENT
OF DERATE
DERATE MULTIPLIER
FACTOR*
0–2000 0 1.00
2001–3000 8–12 0.90
3001–4000 12–16 0.86
4001–5000 16–20 0.82
5001–6000 20–24 0.78
6001–7000 24–28 0.74
7001–8000 28–32 0.70
8001–9000 32–36 0.66
9001–10,000 36–40 0.62
* Derate multiplier factors are based on midpoint altitude for altitude range.
EXAMPLE 1:
88,000 BTUH INPUT FURNACE INSTALLED AT 4300 FT.
Derate Furnace Input Rate
Furnace Input Rate X Multiplier = at Installation
at Sea Level Factor Altitude
88,000 X 0.90 = 79,200
31
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