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Is this a common piping configuration

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EastonM
EastonM Member Posts: 2
in Domestic Hot Water

Hello,

This is my first post on this forum and I apologize if this is so simple that I could have found it with a search, but I wasn't sure how to phrase the search so that it didn't pull up a thousand responses…

In the attached picture, what is the purpose of (what seems like) the unusual piping shown?

The pipes going to the left feed a wall mounted heating unit with the feed coming from the right. (I'll attach a photo of the wall unit and the piping)

What I'm wondering is, is there hot water always circulating in the piping going to the heater? Because those pipes running to left that feed it, run through an unheated crawl space and I wonder if they need to be insulated to prevent freezing. We wouldn't mind having that little bit of heat in that area that the pipes would give off if it was safe to not have them insulated.

Thanks!

PXL_20260611_161651480.jpg PXL_20260602_184312223.jpg

Thanks

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 20,469

    The unit shown must have its own water circulator in it. You have a primary secondary circuit. We would need to see the ends of both sets of pipes to see exactly what is going on. I am assuming the pipes on the left in the second photo go to the wall unit.

  • 109A_5
    109A_5 Member Posts: 4,204
    edited June 18

    Looks like two MonoFlo Tees to me.

    image.png image.png image.png image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    HydronicMike
  • mattmia2
    mattmia2 Member Posts: 17,462

    the unit heater's coil is likely always hot when the boiler is on and it regulates temp by turning the blower on and off. monoflo needs to have constant flow in the main loop and the branch to keep flow in all the other branches.

  • EastonM
    EastonM Member Posts: 2

    Okay so if there is in fact constant flow in the circuit going to the wall unit (yes those are the ones on the left) am I safe to assume there is little chance that they could freeze in a non heated crawl space that is partially open to the basement?

  • hot_rod
    hot_rod Member Posts: 27,824
    https://forum.heatinghelp.com/discussion/comment/1898870#Comment_1898870

    If there is an infiltration, drafts in the crawlspace, that tends to freeze pipes quickly.

    Always good to seal a crawlspace, especially the rim joist connection to the foundation.

    If it is below freezing, generally the heat is flowing and pipes are safe.

    The biggest concern is extended power outage in sub freezing weather.

    But if the crawlspace is below freezing,invest in insulation, the gift that keeps on giving.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream

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