Low Water Cutoffs:
Definition: Each cutoff device shall be installed to prevent startup and to cut off the boiler fuel or
energy supply automatically, prior to the fall of the water level below the lowest visible part of the
gauge glass.
Standard low water cutoff is Fulton level probes. Alternate cutoffs are MM-63, MM-150, MM-157,
MM-193-7b, etc. All cutoffs are tested in the same manner as described below.
When testing the low water cutoff devices, it is important that the boiler feed pump is turned off to
allow for proper draining. Remember to turn the pumps back on when level cutoff testing is
complete.
Testing of Low Water Cutoff Controls:
Your Fulton steam boiler is equipped with two automatic Low-Water Cut-Off (LWCO) controls. Each
LWCO will prevent startup and cut off the boiler fuel or energy supply automatically when the surface
of the water falls to a level not lower than the lowest visible part of the gage glass. One control is set to
function ahead of the other. The standard Fulton LWCO control utilizes a water level probe and
incorporates a 3 seconds time delay to prevent short cycling. Optional float type LWCO controls may
also be used on the boiler.
The LWCO controls can be tested by lowering the water in the boiler. The test should be done with zero
steam pressure in the boiler, or not more than 10 PSI.
Shut off the make-up water supply to the boiler.
Open the blow-down valve at the back of the boiler to allow the water level to slowly drop until ¾” and
1” of water level is visible sight glass and close the blow down valve. The first LWCO control will drop
out within 3 seconds and cut off the boiler fuel or energy supply. This LWCO control is typically
configured to automatically reset when the adequate water level in the boiler is restored. Some local
jurisdictions require this LWCO control to be a manual reset.
Open the blow-down valve at the back of the boiler to allow the water level to slowly drop until 1/8” to
1/4” of water level is visible sight glass and close the blow down valve. The second LWCO control will
drop out within 3 seconds and cut off the boiler fuel or energy supply. This LWCO control is
configured for manual reset. When the adequate water level in the boiler is restored you have to
momentarily press the LWCO manual reset button to enable operation of the boiler.
Air Switch:
To test the air switch, first turn the boiler to the off position.
Once the boiler is off, remove the air supply from the air switch and turn on the boiler. Once the
boiler is in the purge process, the safety interlock should appear and shut down the burner.
Turn the burner off and reattach the air switch air supply.
Reset the flame programmer.
Cycle the boiler multiple times to be sure that no nuisance faults occur.
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