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Low Water Cut Off (Optional)
The 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 prevents
premature lockout due to temporary conditions such
as power fluctuations or air pockets.
Fig. 27: Flow Switch
Fig. 29: Low Water Cut Off
Flow Switch
Dual-purpose control shuts off heater in case of pump
failure or low water flow. Mounted and wired in series
with the main gas valve.
NOTE: Flow switch will not operate if flow is less
than 12 gpm.
High and Low Gas Pressure
Switches (Optional)
The low gas pressure switch (optional) connection
mounts upstream of the gas valve to ensure that suffi-
Fig. 26: High Limit — Auto Reset (Optional)
cient gas pressure is present for proper regulator per-
formance. The low gas pressure switch automatically
shuts down the heater if gas supply drops below the
recommended setting of 4.0 in. WC for natural gas,
and 9.0 in. WC for propane gas.
T
he high gas pressure switch (optional) connection
mounts down-stream of the gas valve. If the gas pres-
sure regulator fails, the high gas pressure switch
automatically shuts down the burner. The high gas
pressure switch automatically shuts down the heater if
gas manifold pressure rises above the recommended
setting of 4.0 in. WC for natural gas, and 10.5 in. WC
for propane gas.
Fig. 28: Gas Pressure Switch
The optional adjustable auto reset high limit is located
behind the front panel (see Fig. 3). Adjust the setting
to approx. 20°F (10°C) above desired outlet tempera-
ture.