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Furnace pressure

MARK_21
MARK_21 Member Posts: 19
in THE MAIN WALL
Just wondering what would cause the system pressure to exceed 30LBS of pressure? I changed the expan tank-and drained a pail of water from the system-but as soon as the burner kicks on-when the water temp reaches 170 to 180--the pressure goes past 30BS and you guessed it--The press rel valve starts to let water out! BTW--The PRES REL VALVE IS NEW!
Low limit is set to 160 high limit set to 175.......

Its a 2 zone system and everything else seems to working fine---heat in all rooms work fine.. Thanks!!!

Comments

  • Ted_9
    Ted_9 Member Posts: 1,718
    feeder?

    did you check the water feeder? try shutting the water supply and see if the pressure goes up. thats the next basic step.
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    Things to check...

    What does the water pressure start out at? It usually starts out around 12 PSI. Your pressure reducing valve could be sticking.

    Is there a DHW coil attached to the boiler? If yes, try shutting off its supply and see if the pressure stablizes.

    Did you check the air charge on the new expansion tank? It should be around 12 psi with 0 pressure on the water side.

    Is the expansion tank properly sized? If the old tank had a volume of 30 gallons, and you replaced it with a # 30 tank, you should be OK.

    I have seen the diaphrams on new tanks stick to the walls of the tank, limiting its ability to accept expansing water.

    ME
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