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Flow Switch
This standard, dual-purpose control, mounted and
wired in series with the main gas valve, shuts off the
boiler in case of pump failure or low water flow.
Fig. 27: Flow Switch
Fig. 28: Low Water Cut-Off
Low Water Cut-Off (Optional)
The optional low water cut-off automatically shuts
down the burner whenever water level drops below the
level of the sensing probe. A 5-second time delay pre-
vents premature lockout due to temporary conditions
such as power fluctuations or air pockets.
High & Low Gas Pressure Switches
(Optional)
The optional low gas pressure switch connection
mounts upstream of the gas valve (on the inlet flange
to the gas valve) and is accessible through the remov-
able access panels on the rear of the boiler to reset the
gas pressure switch, as necessary. It is used to
ensure that sufficient gas pressure is present for prop-
er valve/regulator performance. The low gas pressure
switch automatically shuts down the boiler if the gas
supply drops below the factory setting of 3.0 in. WC for
natural gas or propane gas.
T
he optional high gas pressure switch connection
mounts down-stream of the gas valve. Special ports
are located on the backside of the gas valve and
accessible from the front of the boiler (to reset the gas
p
ressure switch), as necessary. If the gas pressure
regulator in the valve fails, the high gas pressure
s
witch automatically shuts down the burner.
Operation of either the High or Low Gas Pressure
Switch will turn on an LED inside the switch housing.
Push the top of the plastic switch housing as shown in
Fig. 29 to reset a tripped pressure switch. The LED will
go out when the switch is reset.
Fig. 29: High/Low Gas Pressure Switch
Blocked Vent Switch
This heater is equipped with a blocked vent pressure
switch to prevent the operation of the boiler when too
much of the vent is blocked. This switch is located on
the left side of the heater near the left rear corner.
Fig. 30: Blocked Vent Switch