Reznor CAUA Unit Installation Manual - Manual (Page 8)

Form I-CAUA, P/N 164771 R8, Page 8
6.2 Venting and Combustion Air
WARNING
The vent must be installed in accordance with national and local regulations. Failure to provide
proper venting could result in death, serious injury and/or property damage. This unit must be
installed with a vent to the outside of the building. Safe operation of any power-vented, gas-fired
equipment requires a properly operating vent system, correct provision for combustion air, and
regular maintenance and inspection.
WARNING
Units installed in multiples require individual vent pipe runs and vent caps. Manifolding of
vent runs is not permitted due to possible recirculation of combustion products into the
building and back pressure effects on the combustion air proving switch.
Instructions on How
to Check Valve Outlet
(Manifold) Pressure
(can only be done when
heater is operating):
WARNING
Manifold gas pressure
must never exceed
3.5" w.c. for natural
gas or 10" w.c. for
propane.
6.1 Gas Piping
and Pressures
(cont'd)
6.0 Mechanical
(cont'd)
Manifold or Orifice Pressure Settings
Measuring manifold gas pressure cannot be done until the heater is in operation. It is
included in the steps of the "Check-Test-Start" procedure in Paragraph 9. The following
warnings and instructions apply.
For Natural Gas: When the heater leaves the factory, the combination gas 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
pressure to the valve for natural gas must be a minimum of 5" w.c. or as noted on the
rating plate and a maximum of 14" w.c.
For Propane: When the heater leaves the factory, the combination gas 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 10" w.c. Low fire on a two-stage valve is set to 5.0" w.c. Inlet supply pres-
sure to the valve for propane must be a minimum of 11" w.c. and a maximum of 14" w.c.
Before attempting to measure or adjust valve outlet (manifold) gas pressure, the inlet
supply pressure must be within the specified range 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. If natural gas supply pressure is too high, install a
regulator in the supply line before it reaches the heater. If natural gas supply pressure
is too low, contact your gas supplier.
1) With the manual 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 outlet pressure of the gas
valve. To measure low stage pressure on units equipped with a two-stage valve,
disconnect 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
adjustment is necessary, remove the cap from the adjustment screw(s). Set pressure
to correct settings by turning the regulator screw IN (clockwise) to increase pressure.
Turn regulator screw OUT (counterclockwise) to decrease pressure.
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.
Venting must be in accordance with the National Fuel Gas Code Z223.1 or CSA B149.1
and B149.2, Installation Code for Gas Burning Appliances and Equipment, and all local
codes. Local requirements supersede national requirements. Combustion air for this
heater may be either taken from the space or may be ducted from the outside using the
concentric adapter combustion air/vent system. Flue products must always be vented
to the outdoors.