Why would my boiler expel steam when it's set at 180F
I will give this a try.

Physics says that water can not make steam, at sea level pressure under 212 degrees F. 

It is also why steam pipes and automobile systems are under pressure, you can hold more heat, when water is under pressure and not have it boil. Pressure cookers cook food faster for the same reason.

The only way to make steam, from water, at 180 F, is to do it under partial vacuum.

To get water to boil at 180 F, you need to reduce the air pressure to about 7.5 psi.

7.5 psi is a column of water about 15' tall.

If a boiler tank, had a 15' tall pipe, filled with water, and caught between a drain trap and the return to the boiler, it would make steam at 180 F.

I have a physics background, and I am not a stationary engineer, well not a train engineer either, to be honest.

Hopefully someone who has actually worked on a boiler system can take this and run with it.


Note, never pay someone to work on a boiler that thinks the temperature of the water should be below the boiling point of water.


You are better off hiring a competent plumber to work on a storage water heater. You get the same result with fewer parts, faster, and for less money.