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Thread: In floor heat not working

  1. #1
    DIY Junior Member brewdog's Avatar
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    Default In floor heat not working

    I have a Bradford White Model M2CTW75T10CN12 with an Armstrong Astro 30 pump and I am not getting any heat. I went to the system and heard the pump vibrating. The pump appears to be installed on the feed side of the hot water heater. On the "hot" side of the hot water heater is a gauge with both temp. and pressure on it. It reads 0 pressure. I tapped the pump and it quit making noise and then I think I felt movement through the system (holding on to the pipes). But I waited 5 minutes and the pump was hot but there was no heat in the pipes to the system which if it was actually pumping I would have expected some in a few minutes. Any help would be appreciated. I have several specific questions. How do you depressurize the system? Which way is the water moving through the tank? How do I test the pump? Could it be the Sparco mixing valve that is clogged? Thanks for any information.

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    In the Trades Tom Sawyer's Avatar
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    well for one thing you need more pressure on the system than that. Around 15lbs. is normal
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    Moderator & Master Plumber hj's Avatar
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    Bradford does not list that model, but from your description it mush have a separate heating coil inside the tank and it has lost its pressure. That is why the pump is vibrating, (it is cavitating), and there is no circulation.
    Licensed residential and commercial plumber

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    DIY Junior Member brewdog's Avatar
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    I appreciate your response. How do I get pressure up. Could the system need bleeding? If so how do I do that. Again, I appreciate your time. Thanks

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    Retired Defense Industry Engineer jadnashua's Avatar
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    The system should have a pressure gauge on it for reference. There must be someplace with a way to add water to the system and that's where you'd add enough under pressure to get the internal system pressure high enough to make things work. It should also have an expansion tank to account for the variations in the water volume that occur when the temperature changes. Without seeing it, it's hard to tell.
    Jim DeBruycker
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    General Engineering Contractor ballvalve's Avatar
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    grunfos at least has a end port - slottted screw - to let the water out of the wetted Rotor. And so you can spin the unit to get it free after a summer of rest. Usually get a bit of rust & grit out and it runs fine again.

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    DIY Junior Member brewdog's Avatar
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    I do have an Amtol Extrol expansion tank. It sits directly under my Sparco powervent. My gauge reads zero pressure and I was wandering if I may have an air bubble in the system and if opening my relief valve and starting the pump may help or does an Astro 30 pump need priming?
    Last edited by brewdog; 10-27-2011 at 04:12 PM.

  8. #8
    DIY Junior Member brewdog's Avatar
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    The Astro 30 pump has a slotted screw in it. Do I just turn the screw? My pump looks just like a Grunfos UPS series 100. Do I need to disconnect the power to it prior? Thanks again.

  9. #9
    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by brewdog View Post
    I do have an Amtol Extrol expansion tank. It sits directly under my Sparco powervent. My gauge reads zero pressure and I was wandering if I may have an air bubble in the system and if opening my relief valve and starting the pump may help or does an Astro 30 pump need priming?
    Closed hydronic heating systems get their pressure from the house's water supply. The tank itself should have a pre-charge, but to set that, it must have room for the bladder to expand while adding air (i.e., the water must have an open path to prevent the bladder from trying to push against a closed water column). Then, you'd add enough water to bring the pressure in the system to around 15# or so. If you have an autofeed valve, it would do it all by itself. Otherwise, you'd have a valve from the house's water supply and a pressure gauge and add enough water to bring the pressure up.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Moderator & Master Plumber hj's Avatar
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    You CANNOT have an "air bubble" until you create enough water pressure to form one.
    Licensed residential and commercial plumber

  11. #11
    General Engineering Contractor ballvalve's Avatar
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    These wetted rotor motors are impedence protected: the rotor can be full stopped with no breaker pop. Open the screw and you should get rust and crud and usually the motor end has another slot to get the motor turning again. Leave it open as it runs and let it leak for a few minutes.

    The screw has an o ring on it and I often open mine while running.

    If its not a wet rotor its a magnetic drive.

    Radiants have air bubbles all over until the water absorbs it. hopefully your pump is at the LOW end of the sys.
    Last edited by ballvalve; 10-28-2011 at 10:35 AM.

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