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GUD MANIFOLD PRESSURE
WARNING
To prevent death or personal injury due to
carbon monoxide, all hoses must be
connected as shown in Figure 28. Failure
to connect the hose between the burner
box and the pressure switch will result in
excessive levels of carbon monoxide if the
air inlet is blocked.
Figure 28
Measuring Inlet Gas Pressure
(Alternate Method)
A Cap over adjustment screw must be in place when furnace is
operating.
To measure manifold pressure connect manometer between B and C.
B Hose between gas valve and air box (tee supplied by servicer).
C Tapped opening in manifold (hose barb supplied by servicer).
Measuring Manifold Pressure
CHECK GAS INPUT (NATURAL GAS ONLY)
To measure the gas input using the gas meter proceed as
follows:
1. Turn off gas supply to all other appliances except the
furnace.
2. With the furnace operating, time the smallest dial on
the meter for one complete revolution. If this is a 2
cubic foot dial, divide the seconds by 2; if it is a 1 cubic
foot dial, use the seconds as is. This gives the seconds
per cubic foot of gas being delivered to the furnace.
3. INPUT = GAS HTG VALUE x 3600 SEC. PER CUBIC
FOOT (3600 is a conversion factor: 3600 seconds =
one hour)
Example: Natural gas with a heating value of 1000
BTU per cubic foot and 34 seconds per cubic foot as
determined by Step 2, then:
Input
= 1000 x 3600 ÷ 34
= 106,000 BTU per Hour
Note: BTU content of the gas should be obtained from
the gas supplier.
This measured input must not be greater than the input
indicated on the rating plate of the furnace.
4. Relight all other appliances turned off in Step 1. Be
sure all pilot burners are operating.
CHECK MAIN BURNER FLAMES
Flames should be stable, soft and blue, (dust may cause
orange tips but they must not be yellow). They should
extend directly outward from the burner without curling,
floating or lifting off (Figure 30).
24
Figure 29
(GUD Only)
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