Water boiler pressure

[mnicholet]

I inspected a Lennox propane water boiler

The pressure gauge read about 28 PSI

and the temperature gauge read about 165 F

I thought the pressure should be around 12-15 PSI when it reaches its steady state.

What is your recommendation? Thank you.

[Michael Larson]

Not enough info.

It may be high unless this unit is in the basement and its there ore two stories above it.

It is based on the distance to the highest point in the system.

[Scott Gilligan, CMI]

Water pressure is determined by how high of a water column the water has to travel to supply heat to the highest radiator. 12-15 lbs is good for a single story home with a basement. 15-18 is bare minimum for a 2 story house with basement. 18-22 would be appropriate for a 3 story house. The general rule of thumb for figuring out the required pressure is to measure or estimate the water column hight and multiply it by 0.45 to get a general idea of the required pressure for the system.

So...if your highest radiator is 40 feet above the circulator pump (Typical for a 3 story house here in Philly), multiply 40 by 0.45 and that gives you 18. So, 18 lbs would be the absolute minimum that the system should be maintained at in order to circulate heat to the highest radiators. It is a good idea to set the system a little higher than the bare minimum because some systems will loose a little water here and there. Make up water supplies also let in a lot of air into the system. When the air reaches an automatic bleed valve or air scoop and is released, the pressure will drop slightly, which is why it is important to have the system set above the minimum pressure required.

Hope this helps.

[Scott Gilligan, CMI]

Mark...after looking at the pictures closely, I am noticing a lot of other defects in that system. I am seeing evidence of previous leaks at joints, a PVC discharge line on the temperature relief valve, looks to be copper gas supply line in the picture, abandoned plumbing that is not perminantly capped, possible clearance issue, just to name a few things I can see from the pictures.

[David A. Andersen]

Lennox propane water boiler

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