What are the Different Methods of Hot Water Control?

Judith Smith Sullivan
Judith Smith Sullivan
A person washing his hands in hot water.
A person washing his hands in hot water.

Hot water control refers to operation of a boiler. There are a broad range of mechanisms that are part of a boiler system. Whether it is a hot water boiler or a steam boiler, there are many components that determine the type of hot water controls. Typically, there are mechanical or electronic controls to regulate the fuel and water level in a boiler.

Water level is very important to the operation of a boiler. Both hot water and steam boilers must have adequate water to avoid overheating. Some water escapes through evaporation since boilers are open systems, but excessive amounts of water can escape if there are dirty valves or leaky seams. The type of hot water control used to prevent overheating is called a low water shut-off.

There are two types of low water shut-offs—probe and float. A probe is an electronic shut-off. A wand—the probe—sits directly below the the water line. The electrical circuit controlling the burner is completed using the water as a path to ground. If the water falls below the probe, the electrical circuit is broken and the boiler shuts down.

The float type of low water shut-off sits inside the boiler. It floats at the water line and has a link connecting it to the burner switch. If the water line falls too low, the switch is tripped and the burner shuts off. It is an electro-mechanical system and similar to the float system in a tank toilet, which shuts off when the water has reached the appropriate level.

An additional hot water control can be attached to the low water shut-off. It is called a feeder component. A feeder adds the additional water needed to maintain proper water level while the shut-off mechanism prevents overheating. When enough water reenters the boiler chamber, the sensor recognizes that the water level is at a normal level and turns the burners back on.

Burners normally use a gas fuel for power. Occasionally, electricity is used when no other fuel is available, but it is expensive. Modulating controls, or air/fuel loss-limiting controls, control the amount of air allowed in the combustion of fuel, which maximizes the fuel efficiency. The demand on the boiler changes throughout the year and the fuel consumption is adjusted accordingly.

Valves are another method of hot water control. They are used to control pressure in the boiler and rid the chamber of foreign particles. Release valves ensure that the pressure of the steam inside the boiler does not exceed the capacity of the vessel. Bottom blow-down valves are used to eliminate mineral deposits which accumulate in the boiler chamber.

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Discussion Comments


My electronic water shutoff is operating erratically. With a spoonful of water fed in, the boiler tries to fire, then stops and tries again. When fed manually, boiler operates normally, shutoff's satisfied. however when it reaches that level again where it requires a new feed, it goes erratic again. what's a good solution?

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      A person washing his hands in hot water.