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Weil Mclain Again or Burnham Revolution

Kirk_3 Member Posts: 1
I currently have a 9 year old Weil McLain GV 6 running my home radiant and DHW. I have had two service calls and both service men have told me that this particular model of Weil's is prone to problems with some type of plugged mixing valve and this problem creates a white powdery substance in the vent. It is also causing the boiler flame to constantly run for 10 seconds and then turn off, and run again..thus it takes hours to bring the DHW temp up 15 degrees.
Has anyone heard of this issue with these Weil GV units? If so, has Weil ever sent a tech bulletin out regarding the fix? According to the last service person, Weil suggested getting rid of the mixing valve in the boiler and replacing it with two pumps???

My options are to 1. buy a new Weil CGi non condensing boiler or 2. purchase another boiler from a different manufacturer...the Burnham revolution was mentioned as a good replacement.

I would appreciate your thoughts


  • Darrell
    Darrell Member Posts: 303

    The GV is a great boiler...but like any higher efficiency equipment it has a few quirks:

    The GV must be checked with a digital combustion analyzer and a digital differential manometer or your tech is just guessing and replacing parts. No test equipment...not a tech.

    Nine years old is NOT an old GV! It is NOT ready for the junk yard as long as it was installed properly and the off board controls applied correctly.

    The first thing the tech should do is replace the ignitor as a matter of course...eliminates a source of frutration...just do it.

    If your boiler is limiting at 180 plus but not sending the heat to the zones...then the thermostatic mixing valve has failed and needs to be replaced...not common but not unheard of. The 1-1/4 plug in the top of the mixer is so tight that I usually cut the nipples with my handy Makita cordless hacksaw and put it in a vice...faster to rebuild and repipe with unions and less blood letting.

    If the boiler never comes up to temp or limits, then it might be recycling on "flame failure". Easy to fix...pull the burner assembly and clean the flame cone...it may be burned out and need replacing. The flame rectification circuit must have a clean ground, and the burner cone is part of that circuit. Don't forget to put anti-seize on the studs when you re-assemble. A combustion test will show an elevated CO level if the cone is burned out or dirty.

    It is also possible that the pressure switch is dropping out as the burn goes on...a tech needs to confirm that there is enough air moving through the boiler. Several things can get in the way of that; a dirty induction blower, a dirty flame cone, dirty sections, dirty flue passage, dirty flue pipe, dirty flue termination. A differential digital manometer is required to watch the game. If the pressure is high enough and steady but the switch drops out...replace the switch...very common. A combustion test will also show strange numbers for some of these situations.

    One other common problem is the original control board gets "stupid" after awhile and gives you nuisance lockouts...the newer board will retrofit to the older series and everything you need is in the kit. This is common enough that all my customers have the newer board.

    The two-pump idea is found on the newer GV's and retrofitting a prior series would be a pain, expensive and unnecessary. I don't remember that WMC ever suggested modifying the prior series of GV boilers.

    One thing to check while your tech is poking around is to make sure the silicone that seals the sections together has not burned out underneath the boiler...you'll be venting flue gass directly into the house but it WILL NOT CAUSE A FAULT OR LOCKOUT. WMC will cover that under warranty with a new boiler...no labor though.

    Call WMC and they will put you in touch with a good service tech. Ot check the find a pro section of this site. Remember...no test equipment...not a tech.

    Figure on 2-3 hours of service time.

    Someones trying to sell you a new boiler...

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • hot_rod
    hot_rod Member Posts: 16,863
    ahead of it's timei

    that GV is a solid performing boiler. Fairly simple, easy to work on and dependable. the sections should last 20 years or more. not bad efficiency either.

    if the 3 way mixer is giving you problems check the water conditions inside the system. Rebuild it and maybe flush the system with a hydronic cleaner and add a treatment like Rhomar.

    Be sure it is not taking on fresh fill water due to a small leak somewhere, or undersized expansion tank.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • tim smith
    tim smith Member Posts: 2,465
    Weil Mclain GV boiler

    There is a tech bulleting out on deleting the thermostatic bypass valve. Pretty simplt, If I remember right you take the guts out of mixer and press in a 1/2" copper cap in bottom port of mixer body. There is not much more than that. Look at tech bulleting. Another very likely problem is this boiler was prone to scale build up inside flue passages and would shut off on pressure proving switch. A pain to clean but we have done several. have to order section gasket kits, $$ and dismantle whole boiler and separate block, descale completeley along with some worn away pins. Install new gaskets and bolt together and reassemble. Makes a world of difference. This will take all day for a man + a little help from someone else to lift block off and back on to dismantle. Good luck, Tim
    When finished, depending on operating temps, you will want to verify return temps so they are not too low. Usually the internal blending pumps will cover this but check.
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