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LAARS system Ghost heating during summer

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Robert_H
Robert_H Member Posts: 330
in Gas Heating

Customer in small home with a single loop system is getting heat to the baseboard during the summer. She reported the it was random, but almost daily. Also the owner moved in this past December so we don't know if this problem occurred during previous summers.

This is a LAARS EPB-110 with domestic hot water.

What I found todays is that it happens when the boiler is responding to a domestic hot water demand. To prove it to my self I flushed the single loop to get it cold. With the boiler sill warm there was no drift up the return or supply.

Then I ran hot water long enough to get the boiler running and heat started moving out the supply line at least as far as the first few baseboards. The heating circulator was not running, I verified there was no power to it.

EPB flow.gif

Boiler internal diagram

heat flow.gif

Heating diagram from manual. Piped exactly like this excpt no bypass and single zone, no zone valves.

Any help will be apprciated

Robert

Comments

  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,812
    edited June 25

    Add a check valve after the pump to stop ghost flow. A check valve on the return as well.

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    Robert_H
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 20,507

    You may need Flow check valve but,

    How is the priority valve controlled? If DHW is the priority the valve in the heating return should be closed on a DHW call.

    109A_5Robert_H
  • 109A_5
    109A_5 Member Posts: 4,213

    Hmmm… Space heat water flow during a DHW Call ? I'd be very curious how the 'Priority Valve' works and its integrity. Looks like the 'Priority Valve' may also called an 'Anti-Condense Valve', it looks like it has an End Switch for external circulator control.

    image.png image.png image.png image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    Robert_H
  • Robert_H
    Robert_H Member Posts: 330
    https://forum.heatinghelp.com/discussion/comment/1899147#Comment_1899147

    The symptoms I'm seeing make it seem like that valve is either stuck open or being opened when it shouldn't be.

    Thank you for the thorough reply!

  • 109A_5
    109A_5 Member Posts: 4,213

    I would think the valve would be leaking or stuck partially open.

    If the valve was being fully opened 'electrically' "at least as far as the first few baseboards" may be much worse. There would be power to the valve. Depending on how the overall external circulator control is wired the circulator may be running, however you stated it was not running. Even if the valve's End Switch is not used you could check to see if the End Switch is closing, or stuck closed, indicating the valve is stuck all the way open.

    Also if the valve is stuck all the way open the flow may be partially restricted by the external circulator that is not active, limiting the space heat.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    Robert_H

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