Reznor SC Duct Furnace Unit Installation Manual - Manual (Page 9)

Form I-SC, P/N 207696 R11, Page 9
WARNING
Manifold gas pressure
must never exceed
3.5" w.c. for natural
gas and 10" w.c. for
propane.
CAUTION: DO NOT
bottom out the gas
valve regulator
adjusting screw.
This can result
in unregulated
manifold pressure
causing excess
overfire and heat
exchanger failure.
6.3 Venting and
Combustion Air
All separated combustion, power vented units MUST BE equipped with both combus-
tion air and exhaust piping to the outdoors. The unique concentric adapter assembly
designed for use with this heater allows for both combustion air and exhaust piping
with only one horizontal or vertical penetration hole in the building.
These instructions apply to installation and use of the concentric adapter and vent/
combustion air kit (Option CC2 or CC6) designed for use with all Reznor ® separated-
combustion products. The systems illustrated in this manual are the only venting/com-
bustion air systems approved for these separated combustion units. Do not use this
concentric adapter box with any other products.
WARNING
Do not use an existing venting system. This heater requires installation
of the combustion air/vent system ordered with the unit (either Option
CC2 or Option CC6).
Installation should be done by a qualified agency in accordance with these instructions.
The qualified service agency installing this separated-combustion system is responsible
for the installation.
WARNING
SC Series separated combustion units are not designed or approved
for use in atmospheres containing flammable vapors or atmospheres
highly laden with chlorinated vapors. See Hazard Levels, page 2, and
Hazards of Chlorine in Paragraph 2.0.
For Natural Gas: When the heater leaves the factory, the combination valve is set so
that the outlet gas pressure of a single-stage valve or high fire of a two-stage valve is
regulated to 3.5" w.c. Low fire on a two-stage valve is set to 1.8" w.c. Inlet supply pres-
sure to the valve must be a minimum of 5" w.c. or as noted on the rating plate and a
maximum of 14" w.c. NOTE: Always check the rating plate for minimum gas sup-
ply pressure. Minimum supply pressure requirements vary based on size of burner
and the gas control option. Most units require a minimum of 5" w.c. of natural gas as
stated above, but Sizes 350 and 400 with electronic modulation require a minimum of
6" w.c. natural gas supply pressure.
For Propane: When the heater leaves the factory, the combination valve is set so that
the outlet gas pressure of a single-stage valve or high fire of a two-stage valve is 10"
w.c. Low fire on a two-stage valve is set to 5" w.c. Inlet pressure to the valve must be
a minimum of 11" w.c. and a maximum of 14" w.c.
Before attempting to measure or adjust manifold gas pressure, the inlet (supply) pres-
sure must be within the specified range for the gas being used both when the heater is
in operation and on standby. Incorrect inlet pressure could cause excessive manifold
gas pressure immediately or at some future time.
Instructions to Check Valve Outlet (Manifold) Pressure:
1) With the manual valve (on the combination valve) positioned to prevent flow to the
main burners, connect a manometer to the 1/8" pipe outlet pressure tap in the valve.
NOTE: A manometer (fluid-filled gauge) is recommended rather than a spring type
gauge due to the difficulty of maintaining calibration of a spring type gauge.
2) Open the valve and operate the heater. Measure the gas pressure to the manifold.
To measure the low stage pressure on units equipped with a two-stage valve, discon-
nect the wire from the "HI" terminal on the valve. (Be sure to reconnect the wire.)
Normally adjustments should not be necessary to the factory preset regulator. If adjust-
ment is necessary, set pressure to correct settings by turning the regulator screw IN
(clockwise) to increase pressure. Turn regulator screw OUT (counterclockwise) to
decrease pressure. Consult the valve manufacturer's literature provided with the fur-
nace for more detailed information.
Specific Venting
Requirements
1) Type of Pipe
All pipe is field supplied. Requirements are listed for both the vent pipe and the com-
bustion air inlet pipe.