Page No 22 of 52 Reznor, RHC21 8000 Installation EN May 2021 D301319 Issue 0
• Check ignition controller program key
matches the resistance value as shown in
Combustion data table for the heater model.
• Check that no combustibles are near to the
unit. Requirements are in the location and
installation section of this manual.
• Check vent system to be sure that it is
installed according to the combustion air
supply instructions given in the installation
section of this manual.
• Press LC3 thermostat reset button to ensure
it is not in lockout.
5.4 Start-up
For your safety, follow the
instructions exactly otherwise
damage or injury could occur!
During start up all gas services (up
to the gas meter) must be checked
again for gas soundness to ensure
no leaks are present.
1. Turn on the gas supply and check for gas
leaks. Ensure that all pressure test points are
closed and gas tight.
2. Switch on the electrical supply.
3. Set the room thermostat to call for heat at
high fire (10V).
4. If the red light next to the lockout reset
switch is illuminated, press and hold it for 3
seconds, then release. If the light does not
go off see Fault Finding section.
5. From initial power up there can be a delay
of up to 2 minutes before the heater will
respond to a heat demand. During this
time, the ignition controller performs a self
diagnostic routine.
6. The combustion fan will now run and the
burner will automatically light after about 35
seconds.
7. If the installation is new, three start-up
cycles may be necessary due to air still being
present in the gas pipe. Should the air heater
still not light, refer to Fault Finding section.
8. The gas pressure must correspond to the
data in table 3 on page 9. If the gas pressure
is higher than 50mbar, a pressure regulator
must be installed. If the gas pressure is lower
than the minimum as shown on the data
plate, check the supply pipework to ensure
it is correctly sized. Gas pressure should
be checked with the appliance running at
maximum heat load.
When overheating occurs, shut the manual gas
tap before turning off the electric power.
5.5 Air / gas ratio controls
RHC21 8000 appliances are fitted with air-gas
ratio control devices with two adjustments -
throttle and offset.
Throttle is adjusted at high fire.
Offset is adjusted at low fire.
5.6 Modular Heaters
For modular models (RHC21 8125M15,
8150M18, 8175M21, 8200M24), the gas valves
should be individually adjusted / commissioned.
M series products have a Master and Slave
burner arrangement. Each burner has its own
individual air-gas ratio control.
Throttle is adjusted at high fire.
Offset is adjusted at low fire.
5.7 Gas valve adjustment
All units are set before leaving the factory. Any
modification must be carried out by a suitably
qualified technician.
Models RHC21 8045-09, 8060-12, 8075-
09, 8125M15 (2 off), 8150M18 (2 off)
and 8175M21 (1 off)
To adjust the throttle use a 4mm hex key on the
screw located on the venturi. Rotate counter
clockwise to increase %CO
2
. Rotate clockwise to
decrease %CO
2
.
To adjust the offset, use a T40 Torx key to
remove the protection cap on the gas valve.
Rotate counter clockwise to decrease pressure /
%CO
2
and rotate clockwise to increase pressure
/ %CO
2
. Refit cap after adjustment.
