Furnace Expansion Tank Pressure

If youre considering converting an old non captive type expansion tank to a captive air expansion tank an easy rule of thumb is to replace the existing tank with the model that is equal to the existing tanks volume.

Furnace expansion tank pressure.

Air molecules entrained in water inside the heating boiler itself as well as in the heating system piping baseboards or radiators expand and thus cause an initial pressure increase in the heating system. A detailed procedure for sizing diaphragm type expansion tanks is given in reference 1 as well as several other industry publications. Pricing is largely dependent on the size of the tank. When water is heated or a hot water faucet is turned off abruptly pressure builds from expanding water molecules.

Since the air side of the expansion tank is charged according to the fill pressure plus 4 p s i. The key concepts are. It is used to absorb excess water pressure. The boiler expansion tank absorbs the expanding water by allowing the air in the expansion tank to compress this prevents the pressure from building and allows the boiler to heat and cool without too mush pressure building up.

An expansion tank or expansion vessel is a small tank used to protect closed not open to atmospheric pressure water heating systems and domestic hot water systems from excessive pressure. Having an expansion tank helps prevent dripping faucets and running toilets by keeping the extra built up pressure in the system from reaching the fixtures and prematurely damaging them. The tank is partially filled with air whose compressibility cushions shock caused by water hammer and absorbs excess water pressure caused by thermal expansion. Heating boiler bladder type expansion tank compression tank pressure adjustment.

Pressurizing the air side of the tank to equal the static pressure of the water at the expansion tank location and before adding water to the system. Fill pressure heating system expansion tanks. Heating boiler expansion tanks are metal tanks of varying sizes that are installed to absorb the initial pressure increase that occurs when the heating boiler system warms up. Steam boilers are simpler systems that lack several components found in hot water boiler systems such as the circulating pump expansion tank and regulators for water pressure and temperature.

Water heater expansion tank prices start at around 40 and range up to nearly 200. Then the pressure reducing valve prv is set to the same pressure as the bladder expansion tank air side pressure. For most installations the factory set air pre charge in an expansion tank is correct and should be left alone. But there are some circumstances in which an adjustment to the pre charge may be needed.

An expansion tank is not found in steam boiler systems which create heat by circulating hot vapor rather than hot water through the pipes and radiators.