507276-04B
Page 46 of 56
Issue 1904
3. After a 15 second pre-purge, the hot surface ignitor
energizes.
4. After a 20 second ignitor warm-up period, the gas
valve solenoid opens. A 4-second “Trial for Ignition”
period begins.
5. Gas is ignited, flame sensor proves the flame, and the
combustion process continues.
6. If flame is not detected after first ignition trial, the
ignition control will repeat steps 3 and 4 four more
times before locking out the gas valve. The ignition
control will then automatically repeat steps 1 through
6 after 60 minutes. To interrupt the 60 minute period,
move thermostat from “Heat” to “OFF” then back to
“Heat”. Heating sequence then restarts at step 1.
Gas Pressure Adjustment
Gas Flow (Approximate)
Gas Meter Clocking Chart
Capacity
Seconds for One Revolution
Natural
LP
1 cu ft
Dial
2 cu ft
Dial
1 cu ft
Dial
2 cu ft
Dial
-45
80
160
200
400
-70
55
110
136
272
-90
41
82
102
204
-110
33
66
82
164
Natural-1000 btu/cu ft LP-2500 btu/cu ft
Table 9. 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 Figure 68. If manifold pressure matches Table 11 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
When testing supply gas pressure, use the 1/8” N.P.T.
plugged tap or pressure post located on the gas valve to
facilitate test gauge connection. See Figure 69. Check
gas line pressure with unit firing at maximum rate. Low
pressure may result in erratic operation or underfire. High
pressure can result in permanent damage to gas valve or
overfire.
On multiple unit installations, each unit should be checked
separately, with and without other units operating. Supply
pressure must fall within range listed in Table 11.
Manifold Pressure Measurement
1. Remove the threaded plug from the outlet side of
the gas valve and install a field provided barbed
fitting. Connect to a manometer to measure manifold
pressure.
2. Start unit and allow 5 minutes for unit to reach steady
state.
3. While waiting for the unit to stabilize, observe the
flame. Flame should be stable and should not lift from
burner. Natural gas should burn blue.
4. After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in
NOTE:
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.
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 the tables below.
Table 10.
Capacity
CO
2
% for Nat
CO
2
% for L.P.
All
7.2 - 7.9
8.6 - 9.3
The maximum carbon monoxide reading should not exceed
100 ppm.
Table 11.
Manifold and Supply Line Pressure 0-10,000 ft.
Capacity
Gas
Manifold Pressure in. w.g.
Supply Line Pressure
in. w.g.
0-10,000 ft.
0-4500 ft.
4501-5500 ft.
5501-6500 ft.
6501-7500 ft. 7501-10000 ft.
All Sizes
Natural
3.5
3.3
3.2
3.1
3.5
4.5
13.0
LP /
Propane
10.0
9.4
9.1
8.9
10.0
11.0
13.0
NOTE
: A natural to LP propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation
instruction for the conversion procedure.
Summary of Contents for BG951UHE
Page 3: ...507276 04B Page 3 of 56 Issue 1904 Figure 1 Parts Arrangement ...
Page 22: ...507276 04B Page 22 of 56 Issue 1904 Figure 25 Figure 26 ...
Page 37: ...507276 04B Page 37 of 56 Issue 1904 Figure 59 Trap Drain Assembly Using 1 2 PVC or 3 4 PVC ...
Page 43: ...507276 04B Page 43 of 56 Issue 1904 Figure 67 Typical Wiring Diagram ...
