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weil mclain 68 questions, help please

Mack82 Member Posts: 1
Hi everyone,

New to the site and I've got a few issues with my furnace.

It's an old 768. Previous owner had it plumbed so that it would preheat an electric hot water heater. I want to disconnect those pipes coming out of the boiler so that the hot water heater is working by itself.

Are the pipes I'm disconnecting just able to be capped off?

Will this affect the heating portion of the furnace?


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505

    How is it preheating the domestic tank?  If it's boiler water (doubt it, but you never know), then you'll have to valve it off or drain it, cut/cap pipes, re-bleed system, remove controls,etc.

    Most likely it's from the domestic coil.  You can close off the domestic water supply on hot and cold, cut and cap it.  But there is still a control issue to figure out.  A triple aquastat or an aquastat in the hot water heater was controlling this somehow.

    Post a few pictures, just to make sure.

    BTW, if you gonna start cutting pipes on a 768, I'd be thinking about a new, triple pass (if oil) boiler, a modern gas boiler. and an indirect

    There was an error rendering this rich post.

  • icesailor
    icesailor Member Posts: 7,265
    Old boilers:

    The Weil-McLain series 68 boilers were manufactured between April 1987 to April 1995. Your boiler was installed some time after April 1987. It is surviving because it was left and ran as a "warm start" when someone added the water heater. There are much better ways to do what is done. But from experience, that boiler is really long in the tooth and probably leaks air and isn't very efficient. Are the tankless cover plate bolts all rusted? If they are, it is sort of a death knell for the boiler because it is such a project to repair it. And the cleanout covers on the top.

    If you chose to move on with the boiler as is, I would properly connect the water heater with the potable hot water connections on the boiler, install a pump, and let the boiler water heat the coil and you get the hot water from there. If you disconnect the tankless heater like you propose, and then do what many will propose, turning the boiler into a "Cold Start", the boiler will probably fail within 5 years from an accumulation of Kibbles & Bits and major expansion and contraction of the boiler block. And when someone tries to get through them with a soot saw, they will break out through insulating putty between the sections and it is ready for a trip to the scrap yard. 768. Nice mud mooring for a boat.