A hot water boiler is an enclosed container that allows heat to be transmitted into water till the time it becomes heated water. The hot water is then effectively utilized for transferring the heat to where it is needed. A hot water boiler is filled with water, unlike the steam boiler.

However, like the steam boiler, hot water boilers have many add-ons to function effectively. The presence of aquastat serves a two-fold objective. It monitors the temperature in which the boiler runs, and offers a low-voltage transformer and relay to control the circulator.

A majority of commercial buildings, manufacturers and businesses employ hot water boilers. Water is heated to dispersing temperatures, characteristically 140-180F, and generally put back about 20F lower.

These structures are called "closed loop," with nominal fresh water make-up. Hot water boilers are favored since they generally do not call for operators or complex water chemistry. As they function at lower temperatures, hot water boilers can perform at greater fuel-conversion efficiencies than steam boilers.

Some of the characteristic features of a hot water boiler include low water fuel cutoff and a safety valve. Low water fuel cutoff dries up the supply of fuel to the burner during low water conditions in the boiler. The low water fuel cut ff is positioned 2" to 6" beneath the boiler water level.

Low water fuel discontinues operations using an electric probe or a float sensor. When the sensor displays a low water state, a contact to the main burner control circuit unlocks and blocks the fuel.

Low water fuel cutoffs should be checked regularly based on usage or necessities. If a low water condition is not correctly gauged there are chances for the boiler to overheat. Under these circumstances boilers are likely to be damaged for good. Safety valves are the most significant devices on a boiler. They unbolt to vent pressure that climbs over the maximum boiler operating pressure.