508034-02
Issue 2135
Page 39 of 49
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
16. 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
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. Replace the
threaded plug after measurements have been taken. See
Table 17 for supply line pressure.
On multiple unit installations, each unit should be checked
separately, with and without units operating.
Manifold Pressure Measurement
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 on low heat and allow 15 minutes for unit to
reach steady state.
3. After allowing unit to stabilize for 15 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.
Altitude
Unit
Natural
LP / Propane
Manifold
Supply
Manifold
Supply
0 - 4,500 ft.
040
3.5
4.5 - 10.5
n/a
n/a
060
3.6
11.0 - 13.0
080
100
n/a
n/a
4,501 - 7,500 ft.
040
3.2
4.5 - 10.5
n/a
n/a
060
2.3
2.5
11.0 - 13.0
080
2.4
2.8
100
2.3
n/a
n/a
Table 17. 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 18.
Model
CO
2
% for Nat
CO
2
% for LP
-040
6.3 - 7.8
-
-060
6.5 - 8.2
8.4 - 9.9
-080
7.2 - 8.4
9.0 - 10.4
-100
7.3 - 8.5
-
The maximum carbon monoxide reading should not exceed
100 ppm.
Table 18.
High Altitude
Units may be installed at altitudes up to 7,500 ft. above sea
level. See Table 17 for de-rate manifold values.
Model
0 - 7,500 ft.
(0 - 2286m)
-040
-
-060
19U44
-080
19U45
Table 19. Propane Conversion Kit
