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APPENDIX A: LOW WATER CUT OFF (LWCO) ON HOT WATER BOILERS
(continued)
How to Test
Shut off fuel supply. Close shut-off valves in system
supply and return piping located in near boiler piping
above LWCO as shown in Figure A1. Open drain valve
to lower water level until water is below the LWCO
probe. It may be necessary to open relief valve seat to
allow air into system for the water to drain, close drain
valve and relief valve once completed. Generate a
boiler demand by turning up thermostat. Boiler should
not attempt to operate. Open fill valve to increase the
water level by filling the system. It may be necessary
to open relief valve to allow air to escape during filling
process. The boiler should attempt to operate once the
water level is above the LWCO.
