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Fig. 59—Example of Setup Switch in OFF Position
Step 3—Prime Condensate Trap With Water
Condensate trap must be PRIMED or proper draining may not
occur. The condensate trap has 2 internal chambers which can
ONLY be primed by pouring water into the inducer drain side
of condensate trap.
1. Remove upper inducer housing drain connection cap. (See
Fig. 60.)
2. Connect field-supplied 1/2-in. ID tube to upper inducer
housing drain connection.
3. Insert field-supplied funnel into tube.
4. Pour 1 quart of water into funnel/tube. Water should run
through inducer housing, overfill condensate trap, and flow
into open field drain. (See Fig. 61.)
5. Remove funnel and tube from inducer housing and replace
drain connection cap and clamp.
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 test
for gas leaks with an open flame. Use a commercially
available soap solution made specifically for the detection of
leaks to check all connections. 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.
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Adjust manifold pressure to obtain input rate.
Furnace input rate must be within ±2 percent of input rate on
furnace rating plate.
1. Determine natural gas orifice size and manifold pressure for
correct input.
a. Obtain average heat value (at installed altitude) from local
gas supplier.
b. Obtain average specific gravity from local gas supplier.
All manuals and user guides at all-guides.com
1
OFF
A95198
c. Verify furnace model. Table 11 can only be used for model
58MVP Furnaces.
d. Find installation altitude in Table 11.
NOTE: For Canadian altitudes of 2000 to 4500 ft, use U.S.A.
altitudes of 2001 to 3000 ft in Table 11.
e. Find closest natural gas heat value and specific gravity in
Table 11.
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.
EXAMPLE: (0—2000 ft altitude)
Heating value = 1050 Btu/cu ft
Specific gravity = 0.62
Therefore: Orifice No. 45
Manifold pressure: 3.8-in. wc for high heat
* Furnace is shipped with No. 45 orifices. In this example,
all main burner orifices are the correct size and do not need
to be changed to obtain proper input rate.
g. Check and verify burner orifice size in furnace. NEVER
ASSUME ORIFICE SIZE; ALWAYS CHECK AND
VERIFY.
2. Adjust manifold pressure to obtain input rate.
a. Remove burner enclosure front.
NOTE: Manifold pressure MUST always be measured with the
burner box cover REMOVED.
b. Remove regulator seal caps that conceal adjustment screws
for low- and high-heat gas valve regulators. (See Fig. 62.)
c. Move setup switch SW1-2 on control center to ON posi-
tion. (See Fig. 32.) This keeps furnace locked in low-heat
operation.
d. Jumper R and W/W1 thermostat connections on control to
start furnace.
e. Turn low-heat adjusting screw (3/32) hex Allen wrench)
counterclockwise (out) to decrease input rate or clockwise
(in) to increase input rate.
NOTE: DO NOT set low-heat manifold pressure less than 1.3-in.
wc or more than 1.7-in. wc for natural gas. If manifold pressure is
outside this range, change main burner orifices to obtain manifold
pressure in this range.
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.
NOTE: If orifice hole appears damaged or it is suspected to have
been redrilled, check orifice hole with a numbered drill bit of
correct size. Never redrill an orifice. A burr-free and squarely
aligned orifice hole is essential for proper flame characteristics.
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f. Move setup switch SW1-2 to OFF position after completing
low-heat adjustment.
→
g. Jumper R and W/W1 and W2 thermostat connections on
furnace control. (See Fig. 32.) This keeps furnace locked in
high-heat operation.
h. Turn high-heat adjusting screw (5/64 hex Allen wrench)
counterclockwise (out) to decrease input rate or clockwise
(in) to increase rate.
41
1.6-in. wc for low heat
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