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Will this radiant setup work?

themow Member Posts: 11
I recently replaced the 1st floor floors in my 3 story Philadelphia row home. I removed my cheap baseboard heaters on floor 1 intending on using cast iron radiators I have in storage to replace them. I am currently using a mini split heat pump to heat the first floor which works well to about 30 degrees out door temp then the room is not as comfortable.

The boiler is in the basement and I have access to the floor joists from there. 3 zones, one per floor. 3 valves, one pump
The boiler is a 140000btu unit with the temp set to 180
floor is 3/4 pine tongue and groove with pergo over it. There is sound deadening foam under the pergo.

I have 275 feet of joist bay. Bays are spaced 18-20"

I would like to use radiant to heat this zone. I know its advised to have lower temps than 180 but I do not want to install a mixing valve and separate pump for this zone.

I was thinking 2 275ft circuits of 1/2 pex. Or maybe one of 3/4? Can I get away without the heat diffusers? Any cheaper alternative.

The baseboard that was in the room was 12000btu and I felt it was a little low for the room. The room is 424sqft



  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    You MUST do a heat loss calculation first. (FREE on line)

    Ultrafin is your only possible solution based on your not wanting to do it right (mixing valve and extruded aluminum heat transmission plates, not diffusers or reflectors). Almost sounds like you've discovered one of those internet radiant peddlars, and honestly, they do not have your best interests in mind.

    You can do it wrong the first time, and suffer the monetary loss and loss of comfort, or do it right, and enjoy the benefits of a good radiant floor heating system. We know all too well about systems done wrong. Those people come here AFTER they make the mistakes and come here for help. At least you came here BEFORE you make any bad decisions.

    Best to buck up and do it right, once.

    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.
  • Rich_49
    Rich_49 Member Posts: 2,762
    edited January 2016
    Do it right or not at all . Why would you even imagine someone here might tell you how to do it wrong or validate what you know to be wrong ? Do you realize where you are ?
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • hot_rod
    hot_rod Member Posts: 20,725
    Suspended tube systems can often times run at the same temperature as the baseboards, and as high as 180F, so no mixing would be required.

    Uponor still shows suspended tube as an option in their design manual for floor warming as you describe. They offer small area "kits" for installing suspended tube.

    UltraFin is another option for increasing the transfer from bare tube systems.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • themow
    themow Member Posts: 11
    I have been remodeling houses for 15 years so i know a few things.
    There is more than one way to skin a cat.
    I also have been in many homes that have radiant installed stapled up that were not diy jobs.

    I guess if I don't take the most expensive route, then I won't get any love on this board

    I rerouted some 3/4 pex under my second floor boards when remodeling. There was no intent to heat the floor.
    When zone two is pumping, those floor boards are a comfy 80 degrees. So I know it will heat but I don't know how to calculate the btu

  • Gordy
    Gordy Member Posts: 9,537
    There are several ways to skin a cat, but one way is the best.

    Your experience with unintentional floor warming is but a smaller section of pipe. When you refer to expensive which way? Pay now, or later? Installation cost, or operational cost? The later goes on for the life of the system.

  • Gordy
    Gordy Member Posts: 9,537
    If the floor,radiant will be your only emitter at 420 SF, and 35 btus a SF the highest you could possibly achieve done right. Would yield 13700 btus. You said you had 12000 of emitter before, and thought it was undersized for the space.

    You will never achieve 35 btus a SF doing what you want to do.