Sears 9MPD - Manual (Page 38)

Figuro 40 Condensate Line Raised by Base
8. Checks and Adjustments
Startup
NOTE: Refer to the start-up procedures in the "User's Informa­
tion Manual' or to the "Operating Instructions Label' on the fur­
nace.
CAUTION
If any sparks, odors or unusual noises occur, immediately
shut OFF power to furnace. Check for wiring errors or
obstruction to blower.
Gas Supply Pressure
Gas supply pressure should be within minimum and maximum
values listed on rating plate. Pressures are usually set by gas sup­
pliers.
Manifold Gas Pressure Adjustment
NOTE: Make adjustment to manifold pressure with burners oper­
ating.
FIRE OR EXPLOSION HAZARD
Failure to turn OFF gas at shut off before connecting
manometer can result in death, personal injury and/or
property damage.
Turn OFF gas at shut off before connecting manometer.
1. Remove the burner compartment door.
2. With gas OFF, connect manometer to tapped opening on
gas valve. Use manometer with a 0 to 15" water column
range.
3. Turn gas ON and remove adjustment screw cover on gas
valve. Turn counterclockwise to decrease pressure and
clockwise to increase.
4. For altitudes up to 2000', set pressure to value shown in
Table 6, + 0.3" {
8
mm) water column. For altitudes of 2000'
to 8000', see Section 5 for correct pressure setting.
Adjust Pilot Burner
The furnace has a pilot flame to light the main burner. The flame
should surround ^/g" to V
2
" of the flame sensor. See Figure 41 . To
adjust, remove cap from pilot adjusting screw on gas valve. Turn
screw counterclockwise to increase or clockwise to decrease
flame as required. Replace adjusting screw cap.____________
Main Burner Flame Check
Allow the furnace to run approximately 10 minutes then inspect
the main burner and pilot flames. See
Figure 42.
Check for the following (Figure 42):
• Stable and blue flames. Dust may cause orange tips or
wisps of yellow, but flames MUST NOT have solid, yel­
low tips.
• Flames extending directly from burner into heat ex­
changer.
• Flames do NOT touch sides of heaf exchanger.
If any problems with main burner flames are noted, it may be nec­
essary to adjust gas pressures, or check for drafts.
Temperature Rise Check
The blower speed MUST be set to give the correct air temperature
rise through the furnace as marked on the rating plate. Tempera­
ture rise is the difference between supply and return air tempera­
tures.
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