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New Boiler Return Connection

Albie Member Posts: 6
Hi to all,
I have an old hot water heating system consisting of a 1-1/4" supply and return loop with diverting tees with 1/2" supply/return to/from each heater. I want to install a new Buderus boiler but noticed the return connection on the boiler is only 1". Q. any problem with reducing the size of my return connection at the boiler?. A little background about myself, I'm an old geezer from the UK and was a Plumber for many years and have installed a few boilers in my time but I can't wrap my head around this little conundrum. Seems like there would be a bottle neck.
Thank you for any help.


  • hot_rod
    hot_rod Member Posts: 15,014
    The quick answer...the size of the pipe determines how much heat energy you can flow. What size boiler?

    Typically a 1" pipe will carry 12 gpm, so 120,000 BTU/hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    HVACNUT Member Posts: 4,188
    edited August 2017
    I presume the boiler is the G115.
    That "bottleneck" is there to prevent thermal shock.
    You're fine in that application, just reduce it at the boiler. Don't use a bushing. Use a reducer coupling.

    Sounds like it's a mono flo piping system, so DON'T reverse the supply and return.

    Are you going to use the 2107 Logamatic?

    You didn't say where your located (still the U.K.?), but most states in the northeast require a low water cutoff, if you didn't already know.
  • Albie
    Albie Member Posts: 6
    Thanks for your answers. And yes it's the G115 boiler I'm looking at the heat load is only about 50,000 btu with a indirect water heater. I'm in the USA now and am aware of the low water cut off. Not sure if I'm going to use the logamatic yet still researching it, pretty expensive.
    HVACNUT Member Posts: 4,188
    It certainly isn't cheap, but we'll worth it IMO.
  • newagedawn
    newagedawn Member Posts: 586
    im not a fan of the logimatic, i use a honeywell l7224u
    "The bitter taste of a poor install lasts far longer than the JOY of the lowest price"
  • Albie
    Albie Member Posts: 6
    All your comments have been a great help and as they say in Aussie land "Good on ya Mates"