26
For satisfactory operation, propane gas pressure must be
10” WC at the furnace manifold with all gas appli ances in
operation. Maintaining proper gas pressure depends on
three main factors:
1. Vaporization rate, depending on temperature of the
liquid, and “wetted surface” area of the con tainer or
containers.
2. Proper pressure regulation. (Two-stage regulation is
recommended for both cost and efficiency).
3. Pressure drop in lines between regulators, and
between second stage regulator and the appliance.
Pipe size will depend on length of pipe run and total
load of all appliances.
Complete information regarding tank sizing for vaporiza-
tion, recommended regulator settings, and pipe sizing is
available from most regulator manufacturers and propane
gas suppliers.
Always use a pipe thread sealant approved for all gases.
DUCT WORK
Duct systems and register sizes must be properly designed
for the CFM and external static pressure rat ing of the
furnace. Design the ductwork in accor dance with the
recommended methods of “Air Conditioning Contractors of
America” Manual D.
Install the duct system in accordance with Standards of
the National Board of Fire Underwriters for the Installation
of Air Conditioning, Warm Air Heating and Ventilating
Systems. Pamphlets No. 90A and 90B.
A closed return duct system must be used, with the return
duct connected to the furnace.
NOTE:
Ductwork must
never be attached to the back of the furnace.
For upflow
installations requiring 1800 CFM or more, use either two
side returns or bottom return or a combination of side /
bottom. Flexible joints may be used for supply and return
con nections to reduce noise transmission. To prevent the
blower from inter fering with combustion air or draft when a
central return is used, a connecting duct must be installed
between the unit and the utility room wall. Never use a
room, closet, or alcove as a return air chamber.
When furnace duct(s) supply air outside the space
containing the furnace, a return air duct must terminate in
the same space as the supply duct and be sealed to the
furnace casing.
NOTE: Never exceed specified pressures for
testing. Higher pressure may damage the gas valve
and cause subsequent overfiring, resulting in heat
exchanger failure.
Disconnect this unit and shutoff valve from the gas supply
piping system before pressure testing the supply piping
system with pressures in excess of 1/2 psig (3.48 kPa).
Isolate this unit from the gas supply piping system by
closing its external manual gas shutoff valve before
pressure testing supply piping system with test pressures
equal to or less than 1/2 psig (3.48 kPA).
Propane Gas Tanks and Piping
WARNING
If the gas furnace is installed in a basement, an
excavated area or confined space, it is strongly
recommended to contact a propane supplier to
install a gas detecting warning device in case of
a gas leak.
• Since propane gas is heavier than air, any
leaking gas can settle in any low areas or
confined spaces.
• Propane gas odorant may fade, making gas
undetectable except with a warning device.
200 PSIG
Maximum
5 to 15 PSIG
(20 PSIG Max.)
Continuous
11" W.C.
Second Stage
Regulator
First Stage
Regulator
Propane Gas Installation (Typ.)
Figure 36
A gas detecting warning system is the only reliable way
to detect a propane gas leak. Rust can reduce the level
of odorant in propane gas. Do not rely on your sense
of smell. Contact a local propane gas supplier about
installing a gas detecting warning system. If the presence
of gas is suspected, follow the instructions listed in the
Safety Considerations
section of this manual.
All propane gas equipment must conform to the safety
standards of the National Board of Fire Underwriters,
NBFU Manual 58.
CANADA: National Standard of Canada, Natural Gas and
Propane Installation Code (NSCNGPIC) CAN/CSA B149.1-
15.
