IO137 13
inability to maintain the proper pressure range will require reorificing. After reorificing, repeat
the above steps to insure that the furnace input is adjusted properly.
• Turn off gas and electrical supply, remove manometers and replace any plugs that were re-
moved. Use a pipe joint compound that is suitable for use with LP gas.
• Restore any other appliances affected to their normal operating mode.
METER TIME IN MINUTES AND SECONDS FOR NORMAL INPUT RATING OF FURNACES
EQUIPPED FOR USE WITH NAT. GAS AT 0 - 2,000 FEET ALTITUDE.
INPUT
Btu/hr
METER
SIZE
FT
3
HEAT
VALUE
900
MIN. SEC.
HEAT
VALUE
1,000
MIN. SEC.
HEAT
VALUE
1040
MIN. SEC.
HEAT
VALUE
1,100
MIN. SEC.
45,000 1
10
1 12
12 00
1 20
13 20
1 23
13 50
1 28
14 40
75,000 1
10
0 43
7 12
0 48
8 00
0 50
8 19
0 53
8 48
100,000 1
10
0 32
5 24
0 36
6 00
0 37
6 14
0 40
6 36
125,000
1
10
0 26
4 19
0 29
4 48
0 30
5 00
0 32
5 17
150,000 1
10
0 22
3 16
0 24
4 00
0 25
4 10
0 26
4 24
MAIN BURNER ADJUSTMENT
The main burners should not need adjustment in most instances. However, burner air shutters are
provided should adjustment be necessary. After the furnace has been in operation for at least five
(5) minutes loosen the air shutter locking screws and close the shutter until yellow tipped flames
appear. Now slowly open the shutter until the yellow disappears. Retighten the locking screw.
SAFETY CONTROL FUNCTIONS AND CHECK-OUT PROCEDURE
GENERAL
In most cases the safety controls are wired is series with the “W” leg. It is imperative that these
switches remain in the circuit. Never jumper, relocate or bypass any control. The safety controls
must be checked for proper operation at the time of start-up of the furnace.
WARNING
SHOULD ANY SAFETY CONTROL BE ALTERED, JUMPERED OR BYPASSED, A
HAZARDOUS CONDITION SUCH AS FIRE OR THE POSSIBILITY OF CARBON MONOXIDE
ENTERING THE BUILDING MAY OCCUR.
MAIN LIMIT SWITCH
The main limit switch is a 1/2” disc designed to shut off the burner gas should the supply air tem-
perature exceed the maximum design temperature. This switch is not adjustable. To check the
operation, block the return air flow through the unit temporarily. The limit switch should function
and shut the burner gas off within a few minutes. Remove the blockage and allow the switch to
cool sufficiently before reestablishing burner flames.
VENT PRESSURE SWITCH
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