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Fig. 35: Operating Control
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. 36: Low Water Cut-Off
High and Low Gas Pressure Switches
The low gas pressure switch (standard) connection
mounts upstream of the gas valve to ensure that suffi-
cient gas pressure is present for proper regulator
performance. The low gas pressure switch automati-
cally shuts down the heater if gas supply drops below
the factory setting of 5.0 in. WC for natural gas, and
10.0 in. WC for propane gas.
The high gas pressure switch (optional) connection
mounts down-stream of the stage-1 gas valve. If the
gas pressure regulator fails, the high gas pressure
switch automatically shuts down the burner. The high
sheets supplied with your heater paperwork. See the
General Safety Section for safety precautions con-
cerning domestic hot water applications.
Fig. 37: High/Low Gas Pressure Switch
Fig. 38: Fan-Proving Switch
Fig. 39: Blocked Vent Switch
gas pressure switch automatically shuts down the
heater if gas manifold pressure rises above the recom-
mended setting of 5.0 in. WC for natural gas, and 11.5
in. WC for propane gas.