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What should a boiler expansion tank be set at?
For most installations, the expansion tank pre-charge setting should be the same as the boiler’s cold pressure setting. That’s why the manufacturer ships the expansion tank pre-charged to 12 psi. That’s the same default feed pressure found on hydronic boiler water feeders.
How much water should be in an expansion tank?
Going bigger is fine — going smaller is not. Most water heaters that are 50 gallons or smaller should use a 2 gallon expansion tank, such as an Amtrol ST-5 or a Watts PLT-5.
How much pressure should be in a boiler expansion tank?
Most expansion tanks require a PSI reading of about 12 PSI; check your manual for the precise rating for your expansion tank. If the pressure is less than 12 PSI, you will need to add some air.
How does an expansion tank in a hot water system work?
The hot water expansion tank is a two-gallon tank that hangs off of your hot water system or your boiler. It is used to absorb excess water pressure. When water is heated or a hot water faucet is turned off abruptly, pressure builds from expanding water molecules.
What kind of pump has an expansion tank?
An expansion tank is for pumps that pulse (especially piston pumps). The difference is in the design: The liquid-steam interface is where expansion typically occurs. The water is given enough thermal energy to expand up the water tubes.
How can you tell if an expansion tank is working?
It should be hollow about half way up. If you hear a thud sound instead of a hollow sound it probably means your tanks diaphragm is damaged. Check the temperature by feeling the top and bottom of the tank. The tank should be warm on the bottom and cool on the top if it is working properly. Use an air gauge to check the pressure inside the tank.
Why do you need an expansion tank for a diaphragm?
An expansion tank works how you describe, but they are mainly for pumps, such as diaphragm or piston pumps. ( Source ). The idea is to allow the pressure of the pump to stabilize against the compressed air, rather than deal with the jerky motion of the single piston compressing the liquid.