Step 4—Purge Gas Lines
If not previously done, purge the lines after all connections have
been made and check for leaks.
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. Failure to follow this warning could
result in fire, explosion, personal injury, or death.
Step 5—Adjustments
SET GAS INPUT RATE
Furnace gas input rate on rating plate is for installations at altitudes
up to 2000 ft.
In the U.S.A., the input rating for altitudes above 2000 ft must be
reduced by 2 percent for each 1000 ft above sea level.
In Canada, the input rating must be derated by 5 percent for
altitudes of 2000 ft to 4500 ft above sea level.
Furnace input rate must be within
±
2 percent of input on furnace
rating plate.
1. Determine natural gas orifice size and manifold pressure for
correct input.
a. Obtain yearly heat value average (at installed altitude) from
local gas supplier.
b. Obtain yearly specific gravity average from local gas
supplier.
c. Verify furnace model. Table 12 can only be used for model
58MVP Furnaces.
d. Find installation altitude in Table 12.
NOTE:
For Canada altitudes of 2000 to 4500 ft, use U.S.A.
altitudes of 2001 to 3000 ft in Table 12.
e. Find closest natural gas heat value and specific gravity in
Table 12.
f. Follow heat value and specific gravity lines to point of
intersection to find orifice size and low- and high-heat
manifold pressure settings for proper operation.
Table 9—Continuous Fan (CF) Airflow Setup Switch Position
CONTINUOUS
FAN (CFM)
CF SETUP
SWITCH POSITION
ALLOWABLE FURNACE MODEL SETUP
CF-1
CF-2
CF-3
040-14
060-14
080-14
080-20
100-20
120-20
Default
OFF
OFF
OFF
565*
515*
690*
690*
860*
1035*
600
ON
OFF
OFF
X
X
X
—
—
—
800
OFF
ON
OFF
X
X
X
X
X
X
1000
ON
ON
OFF
X
X
X
X
X
X
1200
OFF
OFF
ON
X
X
X
X
X
X
1400
ON
OFF
ON
X
X
X
X
X
X
1600
OFF
ON
ON
—
—
—
X
X
X
2000
ON
ON
ON
—
—
—
X
X
X
* Add 15% additional CFM when Bypass Humidifier switch SW-3 on control board is used.
X—Indicates allowable selection.
Table 10—Setup Switch Description
SETUP
SWITCH NO.
NORMAL
POSITION
DESCRIPTION OF USE
SW-1
(FLT)
OFF
Turn switch to ON for fault history display. No thermostat signal can be
present for fault history display.
SW-2
(LOW)
OFF
Turn switch to ON to lock furnace in low-heat mode only or when using a
2-stage thermostat with R-W/W1 and R-W2 signals.
SW-3
(BPH)
OFF
Turn switch to ON when a bypass humidifier is used. This compensates
for higher return-air temperature and provides 15 percent more airflow in
low-heat mode only.
SW-4
(EMER HEAT)
OFF
Turn switch to ON to bypass microprocessor control. Furnace will oper-
ate at high heat only with main blower and inducer motor operating at
maximum RPM. NO safeties are bypassed.
SW-5
(MZ)
OFF
Turn switch to ON when modulating dampers are used. In this mode,
main blower speed is recalculated once every minute while furnace is in
low-heat or continuous fan mode.
SW-6
(COMP TEST)
OFF
Turn switch to ON to initiate component test. Furnace will operate in-
ducer motor for 20 sec at low speed, operate inducer motor for 20 sec at
high speed, energize HSI for 15 sec, operate blower for 20 sec at low
speed, and operate blower for 20 sec at high speed. SW-1 must be in
OFF position. No thermostat signal can be present for component test to
be initiated.
SW-7 and -8
(Blower Off Delay)
See Table 11
Adjust switches to provide desired heating mode blower off delay time,
90, 135, 180, or 225 sec.
Table 11—Blower Off Delay Setup Switch
Position
DESIRED HEATING
MODE BLOWER
OFF DELAY (SEC)
SETUP SWITCH (SW-7 AND -8) POSITION
SW-7
SW-8
90
OFF
OFF
135
ON
OFF
180
OFF
ON
225
ON
ON
38
