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Radiator Repipe with pex

Mbyrnes92
Mbyrnes92 Member Posts: 16
in THE MAIN WALL
Looking to repipe my house with pex al pex with my original radiators. Should I pipe it in a 2 pipe reverse return? I drew out a diagram on what I think I should do as far as a reverse return, if anyone can give me some tips I would appreciate it greatly. 

Comments

  • Ironman
    Ironman Member Posts: 7,375
    Diagram?

    More info about the type of system, radiators, size of boiler, present piping, etc.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Mbyrnes92
    Mbyrnes92 Member Posts: 16
    edited October 2020
    Forced hot water, Had steel piping with iron fittings, not too sure of size of boiler...the rads are about 4’ Long  3’ tall 1.5’ wide
  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    That should be OK -- provided you can do two things: first, keep the temperature of you water below the recommended maximum for PEX of 180 F. (The actual rated maximum temperature for PEX is 200 F, but it shouldn't be used above 180). Second, PEX expands and sags like crazy when it's heated, so be sure to give it full support -- either very closely spaced hangers or, better, in a trough, and with plenty of provision for expansion.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    1Johnny
  • Ironman
    Ironman Member Posts: 7,375
    edited October 2020
    Jamie,
    He's proposing the use of pex-al-pex which has about the same expansion rate as copper due to the aluminum core.

    Hangers about every six feet should be adequate.

    The problem is that we need to know the btu output of the boiler (it's on the tag) and the EDR of the rad's to know what SIZE pex-al-pex is required.

    Special pressing tools are also required as well as special fittings.

    Here’s an EDR table:


    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Mbyrnes92
    Mbyrnes92 Member Posts: 16
    155000 btu/hour 
  • Mbyrnes92
    Mbyrnes92 Member Posts: 16
    And also I want to add In trvs and is it necessary to use diverted tees or just reg tees?
  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    Regular Ts. Diverter Ts are for monoflow systems. If you're going to throw in TRVs, it would be best if the pump were set up for delta P operation.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Mbyrnes92
  • Mbyrnes92
    Mbyrnes92 Member Posts: 16
    Thank you. Any suggestion on pipe size? And the 2 pipe system of definitely the way to go over a regular 1 pipe system 
  • hot_rod
    hot_rod Member Posts: 22,120
    Also, once you know what radiators you have see how they match the room by room heat load. In some cases you can run lower supply temperatures for much, maybe most of the year.

    This journal has some ideas and formulas for that.
    https://www.caleffi.com/sites/default/files/file/idronics_25_na.pdf

    Viessmann talks about the 3:1 rule. For every 3° you lower the SWT, 1% lower fuel consumption.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Mbyrnes92
  • Mbyrnes92
    Mbyrnes92 Member Posts: 16
    Tthis is my boiler set up, going to relocate it and use a manifold with 2 zones 1 for upstairs and 1 for downstairs. Pump is on supply, can I run this set up with the same pump and just reconnect all lines? 
  • Mbyrnes92
    Mbyrnes92 Member Posts: 16

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