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Viega design?

jonny88 Member Posts: 1,139
Hi,I always kept my loops to a max of 250'.I am now working on a radiant job designed by Viega,under a slab they are showing two loops with piping more than 300'.one loop is 323 and the other is 316.Is this ok as I dont want to deviate from their plan.The customer specified he wanted a viega design .1/2 "pipe under slab.Do you think i will run into trouble????


  • unclejohn
    unclejohn Member Posts: 1,833
    I reckon

    You could do 1000' if it was all sized up good.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Follow manufacturers recommendations...

    Viega is a European company, and they do things a LOT differently than we do on this side of the pond. We ran into some minor issues when we were developing the hydronics code, and they convinced us to change the recommendations to follow the manufacturers recommendations. They do know what they are doing. If all information provided to them was correct, then their design is correct. GIGO applies her. If you put garbage in to the equation, you will get garbage out.

    But you WON"T see them calling for a 1000 foot loop. Unless they are also allowed to spec a cat pump and a 4 way reversing valve (just kidding).

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • hot_rod
    hot_rod Member Posts: 22,142
    What the pump spec

    And the rest of the design show, delta t, pressure drop? I think the RPA RadPad shows 300 foot loop length for 1/2". Sometimes the lengths are odd so they work out of a 1000 foot coil?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Snowmelt
    Snowmelt Member Posts: 1,415
    3 loops

    You could have it like you mentioned 2 loops at 300 and 20 ish


    3 loops a 215 ish,

    Just be a 3 zone manifold instead of 2.

    But I like yours better that's how I do it sometimes I lose a job because it's more material but that's how I roll.

    I did a snow melt where I was allowed 400 but I went 275 foot per loop.

    Like the post above said it will lower your pump head. Therefor smaller pump.
  • Dave H_2
    Dave H_2 Member Posts: 556
    Its all about the math!

    Loop length's by manufacturers install guide guide are just that, a guide. Rule of thumb. Guesstimates.

    Doing the math will reveal on each project what the loop lengths will need to be. I am just finishing up my house and with working the math right, I have over 300 foot loops in my house. With 3/8" pex!

    It made sense, heat loads were low, flow rates, head loss and off the shelf circs.

    I ended up with a 6 loop manifold upstairs. If i followed "max loop length recommendations", this manifold would have been a 10 looper. Adds material cost, labor costs and space (10 loop manifolds don't fit to well in a linen closet)

    Trust the math, if you do it, you can never, ever be wrong!

    Dave H
    Dave H