Proper pressure for a boiler?

Don Dada_2

1psi for every 2.3 feet above the boiler.DD

Larry McCoy

Proper pressure for boiler

I have a question regarding the proper water pressure for my Slantfin boiler. Last year my system ran with pressure from 10 to 15 lbs. After cleaning and replacing the air purge control the system works much better. But after refilling and purging the system it runs at about 30 lbs if I can believe the gauge. The pressure relief valve is 32 lbs. That seems pretty close to popping off? Should I draw some water off. The system works perfect in regard to noise etc. This is a two loop zoned system with a second floor requiring a lift of about 15 feet from the boiler located in the basement. What kind of pressure would be best on this small system? Thanks for any advice that may be available.
Larry.

Unknown

Normally, the system is filled to 12-15 PSI cold, and as it heats up water expands into the expansion tank (precharged to the same pressure as the fill valve).

This compresses the air, and if the tank is sized big enough, the pressure should rise to around 20PSI hot.

I think your expansion tank needs attention.

Noel

Unknown

I agree

Check the air pressure on your expansion tank. It should match the fill PSI of the system to use all of it's expansion capacity. Bring system pressure down to zero before checking air side of tank. 12-15 is good.

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Dale

Pressure cold

If the cold pressure is near 30 and it doesn't go up much when the boiler is hot and doesn't weep at the relief valve I think your auto fill valve needs to be replaced. I don't have much luck adjusting old ones. To check this manually shut off the water fill line (and what the other posts said ) and draw off water until the 12 pound mark is reached then fire the boiler. If the gauge goes up to 15 or 18 all is well and my guess is correct. If it quickly goes to 30 or so then the other posts had it right and you need to replace or drain the expansion tank depending on what type it is.

Larry McCoy

Thanks for the help

Thanks for the help. That was the information I was looking for. It all now makes sense.

Larry

David_6

PSI issue also

I just had a simliar issue. I cranked up my Peerless 1 pipe system the other evening to take the chill out of the house and after about 5 min started checking radiators for heat. All was well and then I checked on the boiler again and noticed the psi at 30. Never have seen this in the 10 yrs of living here. Usually it is between 5-10psi. I've seen it hit 10-12 and cycle off. Nstar came this morning and said that the gauge is welded inside and can't be easily replaced. He said it would go to 30 and drop back and I must have not noticed before. Of course I wasn't home to deal with these issues and grill him. I've never seen this and I've watched that system for full cycles. He said there are a few safety features that would prevent it from ever getting that high and my basement would be a steam bath if it did. I do know there is a releif valve on the boiler. So my question is do I ignore the gauge now and just go by past knowledge on how the system is working or get an independant to come out and look? Nstar was a no charge call. My wife said he was there for 40 min and they did crank the heat and all was fine. I'll have to watch this tonight and see what registers on the psi gauge during a cycle. Yesterday morning I put it on and within 10 min it was at 30psi which I thought was nuts and suspected the gauge bonkers but with little kids in the house I didn't want to experiment and had to get to work.

Thanks for your thoughts.

Dale

Gauges are good

I never heard of a welded in gauge but if it we me I would just shut off the fill and open the boiler drain and watch what the gauge does, if it goes to whatever water height is above the gauge, about 1/2 pound per foot then the gauge is fine, if you have an auto fill see if it fills and stops filling, with 30 pounds on the gauge and the relief not even weeping I would manually open the relief to be sure it's not blocked, then if ok I would add water to 35 or so and the relief better open ( assuming you have standard residential boiler tagged for 30PSI) you can easily confirm your gauge by buying a gauge that screws to the boiler drain, one with a memory hand, open the boiler drain and see if both gauges are close. If you do need a new gauge it can go just about anywhere on the boiler or piping and will read static pressure when the pump is off. I think you have a bad gauge or expansion tank in need of draining or replacement. All are guesses from a distance.