NG to LP Conversion Guide
Form CP-UD-GC, P/N 197209R11, page 5
Instructions for
Changing
the
Pressure
Switch
1. In the control com-
partment, locate the
pressure switch.
2. Mark and disconnect
the two wires attached
to the pressure switch.
3. Disconnect the sensing
tube(s) from the
pressure switch.
4. Locate the two screws
holding the switch
mounting bracket.
Remove the screws
(save screws) and the
pressure switch.
5. Using the same
screws, install the
correct pressure switch.
Attach the sensing
tube(s) and wires.
5. Check for high altitude.
If the installation location is above 6000 ft (1830M), verify that the altitude on the
rating plate or high altitude label is above 6000 ft (1830M). If the rating plate or
label does not indicate an altitude above 6000 ft (1830M), order and install the
appropriate high pressure switch kit.
Or, if the heater is equipped for above 6000 ft (1830M) elevation and is being
installed at a lower elevation, order the appropriate switch and install it (see
instructions on the left).
Contact your distributor to select the factory-authorized replacement part.
6. Turn on the electric and the gas. Relight, following the instructions on the
heater. Check for gas leaks using a commercial leak detecting uid or a rich soap
and water solution. Leaks are indicated by the presence of bubbles. Check all
connections. If a leak cannot be stopped by tightening, replace the part.
7. Adjust the manifold pressure. Follow requirements and instructions in 1)
through 7) below to adjust manifold gas pressure.
1) The correct pressure adjustment depends on the area of the country in terms of
elevation. If you don’t know the elevation, check with your local gas company.
2) See TABLE 2 and determine the required manifold pressure.
WARNING
If the heater will be operated above 6000 ft (1830M), a high altitude
pressure switch must be used.
Manifold Pressure Settings by Altitude for the UNITED STATES
Altitude Natural Gas (inches w.c.) Propane (inches w.c.)
Feet Meters
Single Stage and
Two Stage High Fire
Two Stage
Low Fire
Single Stage and
Two Stage High Fire
Two Stage
Low Fire
0-2000 0-610 3.5 1.8 10.0 5.0
2001-3000 611-915 3.1 1.6 8.8 4.4
3001-4000 916-1220 3.0 1.5 8.5 4.2
4001-5000 1221-1525 2.8 1.5 8.1 4.1
5001-6000 1526-1830 2.7 1.4 7.7 3.9
6001-7000 1831-2135 2.6 1.3 7.4 3.7
7001-8000 2136-2440 2.5 1.3 7.1 3.5
8001-9000 2441-2745 2.4 1.2 6.7 3.4
9001-10000 2746-3045 2.3 1.2 6.7 3.4
Manifold Pressure Settings by Altitude for CANADA
Altitude Natural Gas (inches w.c.) Propane Gas (inches w.c.)
Feet Meters
Single Stage and
Two Stage High Fire
Two Stage
Low Fire
Single Stage and
Two Stage High Fire
Two Stage
Low Fire
0-2000 0-610 3.5 1.8 10.0 5.0
2001-4500 611-1373 2.8 1.5 8.1 4.1
TABLE 2 - Manifold
Pressures by Altitude
WARNING
Manifold gas pressure must never exceed 3.5” w.c. for natural
gas or 10” w.c. for propane.
3) See FIGURE 4 and locate the 1/8” outlet pressure tap on the valve. Turn the
knob or switch on the top of the valve to “OFF”. Connect a manometer to the
1/8” pipe outlet pressure tap in the valve. Use a water column manometer that
is readable to the nearest tenth of an inch. (NOTE: A manometer (uid-lled
gauge) is recommended rather than a spring type gauge due to the difculty of
maintaining calibration of a spring type gauge.)