Raypak 302-902 Installation And Operating Instructions Manual page 48

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 3 second
time delay prevents premature lockout due to temporary conditions
such as power fluctuations or air pockets.
HIGH AND LOW GAS PRESSURE SWITCHES
The low gas pressure switch (optional) mounts upstream of the gas valve
to ensure that sufficient gas pressure is present for proper regulator
performance. The low gas pressure switch automatically shuts down the
boiler if gas supply drops below the factory setting of 5" W.C. for Natural
gas, and 10" W.C. for Propane gas.
The high gas pressure switch (optional) mounts down-stream of the gas
valve. If the gas pressure regulator fails, the high gas pressure switch
automatically shuts down the burner.
Drw. #8996
LOW WATER CUTOFF
Drw. #8236
GAS PRESSURE SWITCH
48
Fig.# J-5
Fig.# J-6