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Capped diverter tees in tight crawl space

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here_to_learn
here_to_learn Member Posts: 21
I am planning a retrofit of my old 1952 boiler, which is a one-pipe diverter tees system with 1-1/2” steel main loop and diverter tees going to 3/4" copper to cast iron baseboard. (If interested in other parts of this conversation or more details, see first post of forum #1746414.) The overall goal is to replace this with a mod con boiler and indirect tank for DHW.

In a previous kitchen remodel, two cast iron baseboard sections were taken out (11 ft total) and the diverter tees were capped. The kitchen was terribly air leaky, and that has significantly been improved. It is my understanding now that those diverter tees should not have been capped, since the restriction in the diverter tee will reduce the flow in the supply loop and there is no relief going through the removed CI rads. Unfortunately, there is no space in this kitchen to reconnect the CI rads.

To get to these diverter tees that are capped, you must work in a small crawl space. The space is now air sealed and fully insulated with rigid foam (floor and outside walls) and encapsulated with plastic. Yet, the crawl space is only about 18” tall with the 1-1/2” supply hanging below the joists. Rather than trying to remove these diverter tees, I was pondering some other possibilities. Note these capped diverter tees are at the end of the supply loop.

At the least to make it easier, I see the option to connect the branches with 3/4” copper tubing. Do any other options come to mind? What concerns are there to consider with connecting something else to those diverter tees and keeping it in the crawl space to add some heat in there?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,445
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    I wouldn't count on the piping giving you much significant heat in there. I'd just short the section of pipe which contains them with a bypass, which I think if what you are suggesting -- and either abandon that length of pipe completely or just leave it for some future person to puzzle over.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    mattmia2here_to_learn
  • mattmia2
    mattmia2 Member Posts: 9,748
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    Can you cut it and connect it together before it goes in to/exits the crawlspace or does it serve something else in there? Eliminating that section of the loop is the easiest way. Which I think @Jamie Hall is suggesting.

    The other option if that section of loop still servers other emitters is to screw right angle pex adapters in to the diverter tees and use a piece of pex in place of the missing emitters. Propex is particularly good in that you can expand the end out in the open than shove it on a fitting back in a dark corner to contract if you can borrow or rent the tool.
  • here_to_learn
    here_to_learn Member Posts: 21
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    I cannot cut it, since this section of the loop serves 2 other emitters. By bypass, I thought @Jamie Hall was suggesting to remove the caps and install (for example 3/4" copper) pipe from cap to cap. I'm visualizing this would just be the way the CI rads are run, except there is no CI rad in the middle.

    @mattmia2, your ideas sounds similar. The pex idea is nice. I might have access to that. I could get access to a propress and use copper.

    I suppose I'm left wondering if there is any way to use those diverter tees to add more heat in the space, since 11 ft of CI baseboard was removed and only 7 ft of CI baseboard remains.
  • mattmia2
    mattmia2 Member Posts: 9,748
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    You could put other emitters in that space off of the diverter tees but you would have to delve in to the engineering the original installers did to make sure you selected something that would get enough flow and it would have to be relatively high mass to balance with the rest of the system.

    A better idea would be to run a second zone to the boiler that is only for the kitchen. That would eliminate the issues with balancing it with the existing system and would allow it to have a separate thermostat so it can stay off if someone is cooking and generating a lot of heat in the kitchen.

    Since pex is flexible it makes it a lot easier to run it in a space with limited access, you don't have to cut and fit a number of pieces and fittings like you do with copper, you just find a place to run it, cut it to length, and make up the 2 ends.
    here_to_learn
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,629
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    You can run from cap to cap with 1/2 copper. If I am not mistaken that is what @DanHolohan recommends.
    bburd
  • Big Ed_4
    Big Ed_4 Member Posts: 2,806
    edited May 2023
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    Crawl spaces suck ,,, Yes the capped rises need to reconnected as a bypass . Just capping without removing the Venturi would affect the system . I would use heat Pex , no need to get fancy. Shorter the better for air removal .. Mixing fin tube base board with radiators sucks too . Any room for panel radiator ? Then use the capped tees . You would need to pitch the risers up into the radiators to remove the air. If your adding baseboard , best off zoning the baseboard. .. Radiators and fin tube are different animals . Different heating characteristics ...

    There was an error rendering this rich post.

    here_to_learn
  • here_to_learn
    here_to_learn Member Posts: 21
    edited May 2023
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    @Big Ed_4 there is probably not enough room for panel radiators. I agree that crawl spaces suck.

    This is a strange crawl space. I've had a couple ideas. Both of these sound strange and might not be worth the effort. I'm only considering this, since the heat load and Btu/hr output of the system wind up really close to condensing temperatures. I'm just trying to ensure higher efficiency with a mod con and that the kitchen space is warm. (Maybe I just need a nudge to say just do the bypass :smile:.)

    1.) What about putting the original 6' and 5' sections of cast iron baseboards in the crawl space? Maybe they could be suspended from the floor joists. The space is fully sealed and insulated--floor, outside walls, and rim joists.

    2.) I'd be thinking radiant floor heat in an extra zone would be nice, but the subfloor in kitchen area has long nails/staples protruding 1-2" from the subfloor everywhere. So, the use of aluminum radiant heat plates against the bottom of the subfloor would not be possible. Has anyone installed something like ultra-fin plates on the joists?

    Maybe the best option would be to bypass the diverter tees. Install the mod con system. If additional heat is needed, then consider adding option 2).
  • Big Ed_4
    Big Ed_4 Member Posts: 2,806
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    No space for panel radiators , radiant walls or ceilings are not a option . Or knock off the nails with a dye grinder for plates . Been there but heat is comfort .

    There was an error rendering this rich post.

    here_to_learn