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Thread: Radiant in floor system never has worked well...time to replace?

  1. #1
    DIY Junior Member donl1150's Avatar
    Join Date
    Mar 2013

    Default Radiant in floor system never has worked well...time to replace?

    I currently have a radiant hot water in floor heating system that really has never worked very well. The house and system is only 9 years old. We are the second owners but the builder is our neighbor and he tells me there are plenty of coils in the floor. The original homeowner installed the heating system since the wife was employed by Wirsbo and thus got discounted pricing on the materials. The builder reluctantly agreed to the situation.

    The heat source is a Bradford White combo unit that also serves as the domestic water heater. Propane is the fuel source. We recently added on and provided a separate in floor system powered by an electric boiler in that space. That system works great!

    I am considering options to replace the existing heating system since it is aging, I am sure not fuel efficient and really doesn't work well anyway. One option is to separate the domestic water heater and radiant floor system but we are limited on space in the utility room. I assume other options exist as well but I am really not familiar with them. I read a bit about a boiler coupled with an indirect water heater. I would greatly appreciate any advice with regard to the pluses/minuses of any available options. Are there systems I should absolutely avoid?

    Thanks in advance


  2. #2
    In the trades Dana's Avatar
    Join Date
    Jan 2009


    It's important on a re-design to figure out why the current system isn't working correctly, or you could easily drop ten grand into it and end up pretty much where you are today. The problem may or may not be related to the B-W combi- it could easily be the pumping or the capacity of the heat exchange on the tubing. Hopefully it has extruded aluminum heat transfer plates between the tubing and the floor? If not, that alone might be the solution, but that depends on how difficult it is to retrofit them.

    Every good heating design starts with a careful room-by-room heat load calculation, from which all else flows. A decent radiant designer would be able to zero in on the most cost-effective solution, but it's probably not something reliably resolvable in a "design-by-web-forum" approach.

    At the current price of propane something with a condensing burner will pay for itself well within the anticipated lifecycle of the unit. But whether that burner is a customized combi based on something like an A.O.Smith Vertex or a Polaris water heater vs. a modulating condensing boiler operating on outdoor reset control depends on your water temp and BTU/hour requirements at your design-condition heat load. Calculate the heat load first, then based on your radiant floor design, the design-day peak water temps can be derived. Without those fundamentals as a starting point it's all just a big WAG, and the last thing you want to be doing is another round of "install first, design later", as it appears the original installation was. It's important to do the math before diving in. (And that's the REAL math, not 10 minutes of lipstick-on-mirror or crayon-on-napkin hackery.)

    There is at least one competent MN radiant pro posting on this forum who may be able to take this on directly, or at least steer you to someone local to who can. (Paging Morgan Audetat...) Simply flipping through the yellow pages isn't gonna cut it.

  3. #3
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
    Join Date
    Mar 2011


    Thanks Dana.

    We are a Bradford White certified contractor and naturally work on many CombiCor water heaters as about half the houses here in Eden Prairie use one to heat the basement and domestic. We replace a few under warranty and quite a few that simply were specified by mistake e.g. too small to fill the big tub on the coldest day of the year.

    All of your advice is well made, as usual.

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