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Unwanted Heat

Jim100FlowerJim100Flower Member Posts: 77
Sometimes when the Master Bedroom (MBR) zone thermostat is not calling for heat, the zone gets heat anyway. It does not get as hot as it would if the thermostat were calling, but it is warmer than I would like. I think the MBR zone is passively drawing heat when other zones are running. Is that possible? What is the cause and remedy?

For example, if all zones are not calling and then I turn up the basement zone, the basement pipes will get hot (increase > 30+F) and the MBR pipes will slowly creep up maybe 5-6F. As best I can tell by listening with a screwdriver in this case, the MBR pump is not running and the basement pump is.

I believe the thermostat is wired correctly because it will turn on the zone when the setting calls for it. There has been no change to the thermostat wiring in 6 years.

I don’t know when this problem started but I have lived here for 7 years and there have been lots of years when the MBR zone worked correctly. Last year was the first year of service for a new boiler.

My home was built in 1986 and has 6 zones of forced hot water baseboard heating running off a gas-fired Laars Minitherm boiler.

Comments

  • ch4manch4man Member Posts: 165
    edited December 1
    well, how long ago did you have your ONIX tubing installed and how long after that did your system gunked up?.

    now that the system is cleaned up youve awoke a sleeping giant
  • Jamie HallJamie Hall Member Posts: 11,432
    It's called ghost flow. Basically gravity flow through the off circulator and around and back. Are there any check valves on your system?
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Jolly BodgerJolly Bodger Member Posts: 132
    I agree with Jamie Hall. You have a check valve sticking open. it may be a separate valve above the MBR pump or integrated in the pump. The Grundfos UP15-58 has a check valve in the discharge flange. Some Isolation flanges can damage this check valve if the pump is running when it gets closed.
  • Jim100FlowerJim100Flower Member Posts: 77
    The 6 pumps are Taco 007-F5. I don't think they have a valve.
    Photos show what I think are the check valves. Am I right?
    Can a check valve be cleaned or does it just get replaced?
    It looks like it would be straightforward to unscrew the valve from the housing. Would the system need to be drained?

  • Jim100FlowerJim100Flower Member Posts: 77
    Is it time to replace them all?
  • EdTheHeaterManEdTheHeaterMan Member Posts: 248
    You are correct. The actual name of the valves are FlowCheck. designed to open when the circulator operates and prevent reverse flow from other circulator zones if a zone is not operating. This is described on page 9 column 2 of Zoning Made Easy. A text published by ITT the B&G circulator guys. The Ghost Flow that @Jamie Hall is referring to is described starting on page 11 at the bottom of the second column and continues on page 12.
    here is a link where you might find the text: http://media.blueridgecompany.com/documents/ZoningMadeEasy.pdf
    ALSO the one valve closest to the camera when the picture was taken... may not be all the way closed to Automatic. If partially lifted... that can be the source of gravity or ghost flow. Those valves last forever on most systems, no maintenance required unless they fail...

    To be sure: Get the boiler up to temperature with no circulators operating. the pipe on the boiler side of the flow check valve should be hot... the pipe on the other side of the flow check should be much cooler. If any pipes are hot on both sides of the valve ... that valve is not closing completely. If you cant turn the screw down more to stop the flow. Replace it!


  • Jim100FlowerJim100Flower Member Posts: 77
    @EdTheHeaterMan the check valve is as tight down as it goes. So I guess it is time to replace it. Does that require the system to be drained? If so, I'll wait until spring.
    In the mean time, there is a ball valve near the check valve. I've turned this about half off. I think it could reduce the flow and let the MBR cool down more.
    Thanks a lot for the booklet - I read what you pointed out and will probably read more.
    I wasn't sure how to do the test you proposed. The only way I know to bring the boiler up to temperature is to turn up a thermostat and that starts the circulator.
  • Jim100FlowerJim100Flower Member Posts: 77
    My cutoff valve adjustment worked and the MBR was pleasantly cool last night.
    I am guessing that replacing the check valve will require draining the system and for that reason will wait until the spring.
  • EdTheHeaterManEdTheHeaterMan Member Posts: 248
    Yes, replacing the Flo-Check will require draining boiler
  • EdTheHeaterManEdTheHeaterMan Member Posts: 248
    To do the test... turn off the boiler and let it cool down for several hours. Set all the thermostats below the room temperature. Turn on the boiler and allow only one zone to operate the boiler (not the problem zone) when the boiler reaches 140° or higher, feel the pipe temperature on both sides of the Flo-Check on the problem zone. (and all the other zones that are not operating). If the pipe is hot on both sides, then the valve is not closed and needs to be replaced. If the valve is holding back the temperature, you have a different problem.
  • Jim100FlowerJim100Flower Member Posts: 77
    @EdTheHeaterMan Warm day today, good day for boiler testing.
    Cooled system down to 64F. Turned on Basement zone. Measured temp on boiler side (BS) and far side (FS) of check valves using laser thermometer.

    Boiler at 140F BS/FS temp
    Foyer 152/81 FS warm to touch
    Bsmt 83/89 FS warm to touch
    MBR 120/80 FS slightly warm to touch
    Kit 121/88 FS warm to touch
    Beds 68/64 FS cool to touch
    LivRm 88/66 FS warm to touch

    Boiler at 160F BS/FS temp
    Foyer 128/106
    Bsmt 106/113
    MBR 136/80
    Kit 115/104
    Beds 82/70
    LivRm 92/67

    Looks to me that there may be three bad check valves: MBR, Foyer, and Kit. I have noticed unwanted heat in MBR (original topic of this post) and also in Foyer. I have not noticed it in the kitchen which is a very large (600 SF) zone that often seems to be working hard to reach temperature.

    I'll do a different test to see if the Basement check valve holds back the temperature.

    I'm not surprised that half the check valves are faulty. If you look at my earlier posts you will see that the system was cleaned last year and before that the boiler water was black gunk. I don't know how a check valve is constructed but it seems like the kind of thing that could be clogged, either by the original gunk or by something that broke free in the cleaning.

    What do you think? Replace 3 valves?
  • Jim100FlowerJim100Flower Member Posts: 77
    When replacing a check valve does the central portion get swapped out or does the whole "T" have to be soldered in?
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