Boiler heat water system - water pressure too stable ?

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Old 12-09-18, 03:12 PM
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Post Boiler heat water system - water pressure too stable ?

Hello,

I have a heat water system at home and for the last 2 years (when I bought the house) the pressure (psi) rise each time the system was heating the house : cold/warm around 13 psi and when it is heating hard it could go up to 25/27 psi. I read that it should not go more than 30 psi so I was not worried.

Today I changed one radiator valve, so I drained all the water from the pipes : lot of water came black and dirty.
I changed the valve and put water again in the system at 15psi : I have a 3 story house.
When the boiler is running until 160F, now the pressure doesn't move at all !!!! and it stays all the time around 15psi... I am not used to this... so I don't know it is normal or if there is an issue ?

Thank you for your help, I wrote other posts for my boiler and always had good replies here !!!

Best

Alex
 
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Old 12-09-18, 04:17 PM
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Pictures of your system would help. We need to see what type of expansion tank you have, etc. Is this a warm-start or cold-start boiler - i.e., when there not a call for heat, is the boiler temp maintained or does it eventually cool of to room temp?

Don't worry about the black water - it is harmless and inevitable.
 
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Old 12-09-18, 04:53 PM
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Thank you

I uploaded pictures to help. When the boiler is not working for heat, the pipes can be very cold. So there is no system to keep the water warm. It is an old boiler, like 30 years old.

Alex
 
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Old 12-09-18, 05:32 PM
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One more thing, when it is cold/warm, it goes back to around 12/13 psi. I just checked.

Alex
 
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Old 12-09-18, 08:13 PM
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You have a cold start boiler.
Looks like it's going to be a joy servicing that pressure tank now that's it's sheetrocked in.

Question...... does the heat get to the third floor now ?
It usually takes high pressure..... +25-30psi to bleed a three story building.
 
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Old 12-09-18, 09:27 PM
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On the third floor it is hard to remove air from one of the radiator. I have to bleed it each time the boiler is working... I believe it will take some time but Indeed my main concern now is to get enough pressure for the 3rd floor. Looks like the tank pressure is setup for 12psi.
​What will happen if I add more water in the system until 20 psi for example ?

Alex
 
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Old 12-09-18, 09:37 PM
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You may need to add up to 25psi to bleed the third floor. The boiler is not usually firing when bleeding the air out. The circulator can run. After bleeding you can remove water to lower the pressure.
 
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Old 12-10-18, 04:38 AM
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To get the minimum cold system pressure needed for your heating system, measure from the highest radiator or the highest point in the system to the pressure gauge on the boiler. Multiply this measurement in feet by .433 to get the minimum pressure setting. For example; if the measurement is 35 feet, then the minimum pressure setting should be 15.2 psi. (35 X .433= 15.2) then add 2 to 3 psi to that setting and get a cold setting of 17 to18 psig. Then turn off the boiler and the circulating pump and bleed all radiation starting at the bottom and working up to the 3rd. flood. Bleed all radiation twice, bottom to top.
 
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Old 12-12-18, 06:51 PM
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Hello,

Thank you four your help guys. I added water to go to 25 psi and bleed air from all radiators.

I went back to 18 and now when the system is super hot it goes to 24/25 max.

No air anymore in the system.

Thank you again!

Alex
 
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