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Thread: Weil-McLain GV-5 Series 1 gas boiler lockout

  1. #1
    DIY Junior Member daling58's Avatar
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    Default Weil-McLain GV-5 Series 1 gas boiler lockout

    My Weil-McLain GV-5 Series 1 gas boiler stopped working last night. The green power light is on, all other lights are off, no flashing lights. The circulator is really hot.

    I reset it by powering it off and on, it tried the whole cycle once and went back into lockout. The light sequence is: 1. purge on, 2. purge off and ignitor on. 3. igintor off and valve on. 4. valve and flame both on for about a minute. 5. valve and flame both off. 6. purge on for a few seconds. 6. Purge off and all red lights off, only green power light stayed on. What could be the problem?
    Last edited by daling58; 01-23-2013 at 06:39 AM.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Sounds like the flame sensor is not detecting the flame is actually on.
    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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    DIY Junior Member daling58's Avatar
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    Thanks for the reply. This boiler is an old model and it does not have a flame sensor. Today I replaced the pressure switch, but it didn't help. After reset, it went through the normal sequence, and fired up for about a minute and shut off itself. What else should I try?

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    It will have something that detects whether the flame actually turned on. On some systems, the igniter performs both functions. If you have the manual, it will describe the sequence.
    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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    DIY Junior Member daling58's Avatar
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    Thanks again. A service tech came and replaced both ignitor and circulator. Now it does not lock out anymore, but it has very short cycles. Once it fires up, only lasts 1 minute and then shuts off, waits another 5 minutes and starts again. I have all 4 themostat calling for heat, should it restart immediately? I am suspecting the new circulator lacks power - because it only has 1/25 HP, my old one has 1/12 HP. What do you think?

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    Look at the temperature gauges...if it reaches the high-point and then shuts down when the house is still cold, it may be the circulator is not moving the water well. Now, that may be because you have an air lock (or more than one). Air locks are not uncommon after you've opened the system (which I assume was done as he replaced a circulator). Without knowing the head requirements of your system, it's impossible to say whether the new circulator is sufficient - it might be, it might not be. If the older one had higher head capability, it may have forced the water through the air locks, and the new one can't. That's not totally a bad thing, but it just means you must get the air out of the system manually, rather than the air extractor doing all of it for you. Most air extractors are only designed to extract dissolved air, not handle large quantities. Well, it doesn't take all that much to create an air lock situation. Bleed the radiators and see if this helps. First, see how far the heat is actually traveling. My guess is not all that far and that is why the thing is shutting down - to prevent it from boiling in the heat exchanger because the water is not moving properly. Many boilers have a time-delay that prevents them from restarting quickly. My last boiler used the igniter as the flame sensor - so, it makes sense that may be why that solved your initial problem.
    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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    DIY Junior Member daling58's Avatar
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    Thanks Jim, you were right about the igniter, it has the built-in flame sensor, and replacing it fixed the lockout problem. The short cycle problem was caused by the defective circulator, it didn't work well. After replacing it again with a good one, and bleeding the radiators like what you described, the whole system works very well now. This is a very useful forum, I've learned a lot here, thanks everyone who has posted and answered questions here.

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