The More You Know: What Is a Low Water Cut Off And Why Is It Critical for Your Boiler?

If you provide heat and hot water as a landlord for a New York City property, you likely have a low water cut off for the boiler as part of your system. This is an essential element, but it often goes overlooked until there are problems with it. Here is some vital information about your boiler low water cut off valve and how you can keep it functioning properly.

What Is a Low Water Cut Off?

Safety for your boiler

Low water in a boiler refers to any level that the manufacturer has deemed unsafe for operation. If a boiler continues to run without adequate water, eventually, there will only be steam in the system. As a result, the metal tank can overheat and fail.

Therefore, many boilers are outfitted with a low water cut off valve (sometimes abbreviated LWCO). These devices have been around since the 1920s, although the technology has improved considerably in recent decades.

A mechanical float or electronic sensor monitors the amount of water in the tank (see below). If the water level reaches dangerously low levels, the low water cut off valve shuts off the heat source for the system. Continuing to operate without sufficient water levels is known as “dry firing” and should be avoided at all costs. With few exceptions, a dry fired boiler will need to be immediately replaced.

What’s the Difference Between the Two Types of LWCOs?

Float-type or mechanical device

This type of device is used in a variety of different boilers, including those in residential, commercial, and institutional buildings. You might compare the older mechanical versions of this device to the float arm in a toilet tank.

A float is connected to an electrical switch, which, in turn, is tied to the boiler burner circuit. If the float drops due to a low water level, the circuit is broken, and the burner shuts off, cutting heat to the boiler.

Electronic sensor

With this type of device, an electrode tip remains immersed in the boiler tank to the desired level. If the electrode becomes dry due to the water being too low, it no longer conducts, cutting the circuit and stopping the heating process.

Is a Low Water Cut Off Required on Your Boiler?

NYC requirements

Because of the safety implications of running dry, low water cut offs are required by multiple entities. The New York City Construction Code states that:

“All steam and hot water boilers shall be protected with dual low water cut-off control.”

The only exception is boilers that only supply the individual dwelling unit in which they’re located, and they must have a total heat input of less than 350,000 Btu/h (1025 kW). These boilers are permitted to have only one low water cut off control, versus dual controls.

Other groups or publications that require low water cut off devices for boilers in their protocols include the American Society of Mechanical Engineers and the Internal Mechanical Code.

Do Low Water Cut Offs Malfunction?

Dangerous situation

Low water cut off valves do sometimes fail, which creates a high-risk situation, since this is a safety device. There are multiple factors that can cause a low water cut off to malfunction:

• Condensates, hard water deposits, scale, mineral encrustation, etc.
• Buildup of rust, dirt, or sediment
• Poor maintenance, such as improper or lack of flushing
• Aging, which can, in turn, result in worn parts, leaks, and shorts
• Loss of water over time
• Jumper wires left in place permanently after being used in tests to bypass circuits

Every year in the United States, there are thousands of accidents reported due to low water cut off control failure.

How Can You Keep Your Low Water Cut Off Working Properly?

Maintenance musts

Fortunately, low water cut off devices are typically not very complicated, which means that it’s largely within your control as a property owner or manager to keep yours working properly.

The first thing you can do as part of your own maintenance program is to check for obvious problems, such as:

• Leaks
• Buildup of undesirable materials
• Corrosion
• Electrical connection wear and tear
• Breaker tripping repeatedly
• Failure to activate when you know the water level is low

Second, older low water cut off valves or detectors should be replaced. If yours is nearing the end of its expected lifespan, it’s wise not to wait for it to fail before replacing it. Instead, be proactive, and arrange for the installation of a new device early. You’ll appreciate the peace of mind it gives you, and it’s well worth the cost.

If you have a float-type device, you want to make sure scale buildup on the inside wall of the tank doesn’t cause it to stick rather than floating free. You also want to check to see that it’s not waterlogged and sinking when it shouldn’t. One sign of this is the boiler cutting out even though the water level is fine. If you need assistance with these checks, we’re happy to do them for you, and they are part of our routine boiler maintenance program.

Electronic low water cut off devices can also fail due to scale buildup. The electrode may continue to “think” it’s in water when it’s not because it’s tricked by the mineral deposits. It can still conduct in many instances, so the system doesn’t shut off even when the water level drops to hazardously low levels.

Of course, thorough and professional maintenance of your boiler, including the low water cut off, is essential. We check everything with your low water cut off and perform proper flushing to get rid of anything that could cause malfunction.

If your boiler has not been looked over in a while, it’s time to call in the experts. You can reach Calray Boilers at 212-722-5506, or make an appointment using our online form. Don’t wait until you have a boiler emergency to call! Get in touch today.