A trend has developed in some states regarding the installation of residential boilers. Previously accepted codes, such as BOCA, are now being phased out and replaced by the International Mechanical Code (IMC).

Some states, including New York and New Jersey, have already adopted the new code, while others have set future effective dates and still others have yet to institute a change.

As far as boiler installations are concerned, the major difference between the IMC and the current codes is the requirement of a low water cutoff (LWCO) in every residential installation, be it steam or hot water.

While steam boilers are factory-equipped with LWCOs and therefore already comply with the IMC, hot water boilers that are not factory equipped with LWCOs must be addressed.

Who Is Responsible?

The IMC is a building code, and, as with any building code, the builder or equipment installer is responsible for compliance. As time goes by with some states adopting the IMC, you might find that manufacturers offer water boilers equipped with LWCOs. Until that time, the LWCO must be added at the time of the boiler installation.

LWCOs being used in the installation of water boilers are "probe-type" electronic cutoffs. As the name suggests, a probe is used to sense the presence of water. As long as water is in contact with the probe, the probe provides a closed circuit for the electrical power and allows the boiler to operate. In the absence of water, the probe creates an open circuit, preventing the electrical power from continuing beyond the LWCO, rendering the boiler inoperable.

There are several LWCOs available from various manufacturers. Most manufacturers offer the option of line voltage (120 V) or low voltage (24 V) models. A 24-V or 120-V model can be used with any Utica gas-fired boiler; only the 120-V models are recommended for use with Utica oil-fired boilers.

Regardless of the type of cutoff you use, it is recommended that it be installed in the supply piping, as close to the outlet of the boiler as possible. This is frequently above the boiler's aquastat.

When using a 120-V cutoff, it acts as a junction box of sorts. The line voltage feed for the boiler is simply wired to the LWCO first, then to the boiler's aquastat directly below it. This requires basic wiring and results in an application that is neat in appearance.

A 24-V LWCO is located in the same place in the boiler piping as the 120-V models. Because the 24-V LWCOs work off low voltage, they must be wired into the 24-V wiring on the boiler. This requires the installer to splice into the boiler wiring or control circuitry. This can pose some difficulty in wiring and might not be as neat in appearance as the 120-V LWCO application.

Always check with your local codes enforcement agency for the applicable code in your area. Remember too, that despite your geographical location, a LWCO is required on all water boiler installations where the boiler is higher or at the same level as the radiation.

Author Peter Desens is technical service manager for ECR International Products, Utica, N.Y. This article is reprinted with permission from ECR International Products.

Publication date: 11/10/2003