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Low pressure in boiler but zone 1 worked still worked while zone 2 did not?

danitheplumberdanitheplumber Member Posts: 31
I came to a house for a no heat call. It was a Larrs Endurance boiler. Some how the first floor got heat but the basement was not. In the end it was just low pressure issue, about 10 psi at the time. I would have thought both zones would not work if there was not enough pressure so I was looking for something wrong after the boiler with in the basement zone line. How is possible for one zone to work and not the other with low pressure?


  • There must be

    another reason. Ten pounds pressure is plenty for a 2-story house.

    I'd say there's a pump or zone valve not working, air in the line, bad thermostat............
    Often wrong, never in doubt.
  • billtwocasebilltwocase Member Posts: 2,385
    ditto Alan

    How is it zoned? 1 circ with zone valves, 2 circs? Basement mono-flo? Sticking flowcheck? Close to zero pressure would heat the same level or lower as the boiler
  • danitheplumberdanitheplumber Member Posts: 31
    Low pressure in boiler but zone 1 worked still worked while zone 2 did not?

    Its a Larrs Endurance which has a Grundfos pump built into it. The first floor would get heat but basement wouldn't and the boiler is in the basement so I would think the basement would get hot first and 1st floor wouldn't get hot but the opposite happened. I also thought 10 was enough being some boilers run at 12-15 psi but I guess it needed 20 psi
  • danitheplumberdanitheplumber Member Posts: 31
    Low pressure in boiler but zone 1 worked still worked while zone 2 did not?

    no air... both thermostat worked just basement wouldn't get heat but i could feel water circulating and zone valves worked just seem to not be enough pressure but how it dropped is also an issue. Didn't find any leaks.
  • icesailoricesailor Member Posts: 7,265
    Internal pump?

    You have an internal pump? Does it need to be piped as a P?S system? Is it piped as the Installation manual?

    Where did the pressure go (10#)? The pressure should rise as the water is heated and it expands. If the fill valve is on (is it?), the pressure should read between 12#/15#. Is the expansion device big enough for the volume of water in the system? Open the fast fill by-pass on the fill valve and get the pressure to 20# and see what happens.

    Post some photos of the boiler and the piping.
  • danitheplumberdanitheplumber Member Posts: 31
    Added pressure and all up and running. Could be a small kink that 10 psi wasnt enough but 20 was. We'll see this winter.
  • GordyGordy Member Posts: 7,106
    I think the pressure had nothing to do with it. If it did the higher elevation zone would not have heat. Unless there is some funky piping that goes higher than the basement zone and main floor zone then back down to feed basement zone.
  • danitheplumberdanitheplumber Member Posts: 31
    Could be a piping issue but didnt look like it. Most likely it was put in by unlicensed plumber based on the neiberhood which is a problem in itself.
  • icesailoricesailor Member Posts: 7,265
    Did you try a "trusted" pressure gauge to check to see what you actually had in the system?

    I never saw a pressure gauge that I trusted until I checked it with a known quantity.
  • 4Johnpipe4Johnpipe Member Posts: 475
    I'm not familiar with that boiler but the condition is familiar. Ive seen it many times the system will almost gravity feed and the second floor always benefits from this condition. Once you get flow from the warmer water rising the return side will also be pulling on the water. With a little help from the circulator it will actually work to some extent. The basement floor doesn't get the momentum to flow.
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  • icesailoricesailor Member Posts: 7,265
    If the system is tight on the second floor, and air can't get in, and the piping is such that air can't get to the second floor, the second floor can work and others can't. It only takes a small amount of air to stop flow.

    The system should never be at 10# unless there is a reason. Just the higher pressure will help squish and absorb air. Is the expansion tank big enough for the application? If it is a #15, it's probably way too small for the expansion in the system. A #30 might be fine. A #60 might be even better. Or another #30, somewhere. If you get a gauge like I described, you can see what is happening pressure wise in an operating system. If it goes from 10# to 25# or higher, the expansion tank has failed, the pre-charge is wrong or it is just plain too small for the amount of water in the system.

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