16
5.5.1. Appliance Categories
Heaters are divided into four categories based on the
pressure produced in the exhaust and the likelihood of
condensate production in the vent.
Category I – A heater which operates with a non-positive
vent static pressure and with a vent gas temperature that
avoids excessive condensate production in the vent.
Category II – A heater which operates with a non-positive
vent static pressure and with a vent gas temperature that
may cause excessive condensate production in the vent.
Category III – A heater which operates with a positive
vent pressure and with a vent gas temperature that avoids
excessive condensate production in the vent.
Category IV – A heater which operates with a positive
vent pressure and with a vent gas temperature that may
cause excessive condensate production in the vent.
5.6. Gas Supply Connections
GAS INLET
HEATER JACKET
MANUAL SHUT-OFF VALVE
(Field supplied)
GAS VALVE
FINISH FLANGE
UNION
(Field supplied)
SEDIMENT TRAP
(Field supplied)
Figure 13. Gas Supply Plumbing
Gas piping must have a sediment trap ahead of the heater
gas controls, and a manual shut-off valve located outside
the heater jacket. All gas piping should be tested after
installation in accordance with local codes.
A
A
CAUTION:
The heater and its manual shut-off valve
must be disconnected from the gas supply during any
pressure testing of that system at test pressures in excess
of 1/2 psi (3.45 kPa). Dissipate test pressure in the gas
supply line before reconnecting the heater and its manual
shut off valve to gas supply line. FAILURE TO FOLLOW
THIS PROCEDURE MAY DAMAGE THE GAS VALVE.
OVER PRESSURIZED GAS VALVES ARE NOT COVERED
BY WARRANTY. The heater and its gas connections shall
be leak tested before placing the appliance in operation.
Use soapy water for leak test. DO NOT use open flame.
5.6.1. Supply Pressure
A
A
CAUTION:
Only sealant tape or a pipe compound rated
for use with natural and propane gases is recommended.
Apply sparingly only on male pipe ends, leaving the two
end threads bare.
A minimum of 6 in. WC and a maximum of 14 in. WC
upstream pressure under load and no-load conditions
must be provided for natural gas. A minimum of 12 in. WC
and a maximum of 14 in. WC are required for propane gas
under load and no-load conditions.
5.6.2. Gas Pressure Regulator
The gas pressure regulator is preset at 4.0 in. WC
throughout for natural gas, and 10.5 in. WC. for propane
gas. The pressure at the gas valve, taken with a manometer,
should be about 4.0 in. WC natural gas and 10.5 in. WC
propane gas. If an adjustment is needed, remove seal and
turn adjustment screw clockwise to increase pressure or
counter-clockwise to decrease pressure.
MANOMETER
MANUAL
SHUT-OFF
VALVE
UNION
Figure 14. Manual Shut-Off Valve Installation
5.6.3. Gas Pressure Adjustment Locations
Gas Pressure Adjustment
Figure 15. Robertshaw 7000 BDER (Heater Model 268)
