Page No 24 of 56 Reznor, RHC21 4000 Installation EN May 2021 D301334 Issue 0
1 - Offset adjustment
2 - Inlet pressure measuring point
3 - CO
2
adjustment point (throttle)
4 - Offset pressure measuring point
Figure 7: Gas valve adjustment. Note
that there are two valves on the modular
heaters (RHC21 4125M15 and 4150M18)
Model RHC21 4100-12
To adjust the throttle use a 4mm hex key on the
screw located on the venturi. Rotate clockwise
to increase %CO
2
. Rotate counter 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.
1 - Offset adjustment
2 - Inlet pressure measuring point
3 - CO
2
adjustment point (throttle)
4 - Offset pressure measuring point
Figure 8: Gas valve adjustment model
RHC21 4100-12
5.8 Gas conversion
RHC21 4000 heaters are designed to operate
on natural gas types G20, G25 and G25.3.To
modify for use on an alternative listed gas
type, follow the commissioning guide and refer
to the Combustion Data table adjacent for
approximate throttle turns from G20 setup.
The data label needs to be updated after
conversion. Using permanent ink place an 'X'
in the box above the relevant gas type column
to indicate the new gas setting. Obscure any
previous indication.
Upon completion of conversion recommission
the heater. Refer to the commissioning section
for more details.
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2
3
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