Thread: Boiler Leaking
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      10-24-2019, 11:59 AM   #10
byroncheung
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Quote:
Originally Posted by ToddBlack88 View Post
Does it stay at that pressure for a bit after it stops firing and the pump shuts off, before dropping back down, or does it drop as soon as the pump shuts down?

I ask because i have found most tankless setups pump into the boiler, and with the large pressure drop design of a tankless system for efficiency, the pressure spikes within the boiler. So thaTs pretty normal.

If the pressure slowly drops back down between firings, then most likely the air charge of the expansion tank is low. I like to set the air charge at about 90% of the static , at operating temperature, system pressure. So if you have a 3 story house with the boiler in the basement, you need a system pressure of about 20psi read off the boiler gauge, when the lines are all up to temperature. Set your air charge to about 18psi.

Every system is different as some may run auxiliary heat exchangers to save the boiler if there is various plastic pipes like poly b in the system, or if the boiler does both heating and domestic generation, as well as the pressure maximum design of the exchanger in the boiler.
i *think* it drops pretty quickly. i don't think i have observe it long enough to see it drop when the unit on - but i def have noticed when i shut it down down and restart it, the starting pressure will be the 13-14psi right away.

i only read the psi from the display of the boiler, there is no pressure gauge in the my pipes. i'm going to buy one of those trouble shooting pressure gauge so i can read the pressure inside the pipes as well.

but from what you said sounds like it is normal. thanks for your input!!!
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