507762-01
Issue 1907
Page 42 of 46
Gas Pressure Adjustment
Gas Flow (Approximate)
Unit
Seconds for One Revolution
Natural
1 cu ft Dial
2 cu ft Dial
-040
90
180
-060
60
120
-080
45
90
-100
36
72
Natural-1000 btu/cu ft
Table 11. Gas Meter Clocking Chart
Furnace should operate at least 5 minutes before checking
gas flow. Determine time in seconds for two revolutions of
gas through the meter. Two revolutions assures a more
accurate time. Divide by two and compare to time in Table
11. If manifold pressure matches Table 12 and rate is
incorrect, check gas orifices for proper size and restriction.
Remove temporary gas meter if installed.
NOTE:
To obtain accurate reading, shut off all other gas
appliances connected to meter.
Supply Pressure Measurement
A threaded plug on the inlet side of the gas valve provides
access to the supply pressure tap. Remove the threaded
plug, install a field-provided barbed fitting and connect a
manometer to measure supply pressure.
On multiple unit installations, each unit should be checked
separately, with and without units operating. Supply
pressure must fall within range listed in Table 12.
Check Manifold Pressure
To correctly measure manifold pressure, follow the steps
below.
1. Remove the threaded plug from the outlet side of the
gas valve and install a field-provided barbed fitting.
Connect measuring device “+” connection to barbed
fitting to measure manifold pressure.
2. Start unit and allow 5 minutes for unit to reach steady
state.
3. After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in
4. Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to
remove barbed fitting and replace threaded plug.
5. Start unit and perform leak check. Seal leaks if found.
For safety, connect a shut-off valve between the
manometer and the gas tap to permit shut off of gas
pressure to the manometer.
IMPORTANT
Unit
Fuel
Manifold
Pressure
Line
Pressure
All
Nat
3.5
4.5 - 10.5
Table 12. Supply Line and Manifold Pressure
(inches w.c.)
Proper Combustion
Furnace should operate minimum 15 minutes with correct
manifold pressure and gas flow rate before checking
combustion. Take combustion sample beyond the flue
outlet and compare to Table 13.
Model
CO
2
% for Nat
-040
6.3 - 7.8
-060
6.5 - 8.2
-080
7.2 - 8.4
-100
7.3 - 8.5
The maximum carbon monoxide reading should not exceed
100 ppm.
Table 13.
High Altitude Information
Units are NOT approved for installations over 4500 ft.
Содержание 95G1UH040BE12X
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