508107-01
Issue 2041
Page 47 of 58
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
15. If manifold pressure matches Table 17 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 located on the gas valve to facilitate test gauge
connection. See Figure 53. 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 17.
Manifold Pressure Measurement
Follow the steps below and use Figure 55 as a reference.
Gas manifold Kit 10L34 provides additional components if
needed.
1.
Connect the test gauge positive side “+“ to manifold
pressure tap on gas valve.
2.
Tee into the gas valve regulator vent hose and connect
to test gauge negative “-”.
3. Start unit and let run for 5 minutes to allow for steady
state conditions.
4.
After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in
5.
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.
6.
Start unit and perform leak check. Seal leaks if found.
(+)
(−)
Gas Valve Regulator
Vent Hose
(to burner box)
2” Long Square Tubing
(remove for manifold adjustment)
Tee
10” Long
Square
Tubing
Measuring Device
Barbed Fitting
Manifold Pressure Outlet
Negative Barbed Fitting
(remove for manifold adjustment)
Figure 55.
