Boiler Low Water Cut-Off Mounting

Questions have been asked about the proper mounting of a Low Water Cutoff on a steam boiler.

Notice: The measurements given in this article will be close to the measurements necessary for the installation and may not be the same as the recommended measurements by the boiler manufacturer or the manufacture of the Low Water Cutoff.  Care MUST be taken to follow installation measurements supplied by the manufacture of the boiler and control.

The first issue to answer is…Is this installation for a primary or secondary LWCO?  The Primary LWCO is the operating LWCO and the Secondary LWCO usually incorporates a manual reset and is used for a safety backup for the primary.

Note: on a steam boiler please make sure you have a set of water gauge cocks in the installation. The “center line” of the visible glass should correspond with the boiler’s COLD WATER LINE.

The next issue for the service person to identify is the location of the COLD WATER LINE on the boiler. This is the “normal” cold water fill line as established by the boiler manufacturer. After the boiler’s cold water line is located, look at the LWCO and locate the level mark on the body of the LWCO. With these two marks established installation can now begin.

Primary LWCO Installation:

As a primary LWCO the level mark of the LWCO should be placed for mounting between 1 3/8” to 1 ½” below the boiler’s cold water line which will establish the boiler’s normal operating range.

½” to 3/8” below the LWCO’s level mark will be the burner’s “cut-off level”

Secondary Safety LWCO:

As a secondary safety LWCO the level mark of the control should be placed for mounting between the 1” to 1 ½”area below the primary LWCO’s burner cut-off level. Careful attention MUST be made not to let the float drop below the lowest visible level of the site glass.

Before commissioning the boiler for final usage PLEASE test the Primary and Seconday LWCO levels and make adjustments as needed for proper levels.

I would like to thank Peerless Boilers for their help with information and drawings supplied in this article.