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Triangle tube prestige excellence 110 combi radiant piping

I am in the process of installing a new 110 combi along with a basement remodel. The existing system is a natural gas 140,000 btu 30 year old Lennox boiler supplying 140' of baseboard, with a standard 40 gallon water heater for domestic. We live in Colorado so our altitude is right around 5200 so the btu's take a little hit. Split level stick built late 60's, 4 bedroom, 3 bath with cathedral ceilings 3000 sq. ft. with 900 sq. ft. basement. The rest of the house is over crawl space. 400 sq.ft. of double pane glass in the house. I tore the basement floor up to install a perimeter drain so new concrete floor with 2" of foam underneath and 1/2" pex in the floor. I'm installing 1/2" floor trax underneath the rest of the house for the radiant so no more

Back in the 80's I worked for a Lennox dealer as an installer, so I am familiar installing the system I'm tearing out. I understand that system. I realized the radiant systems are more complex, I'm realizing now just how much more. Originally I was just having a company install the system and found out just how much that can understandably cost due to the amount of labor. After talking to my boiler guy he was confident I could do the grunt work and he would consult for the system. So I purchased the boiler from him and have the top of the boiler plumbing installed ( domestic hot water recirculation, expansion tanks, make-up water) along with the gas line.

Now I'm looking at the radiant side and this is where my problem has become apparent and I'm not as confident my boiler guy has the experience. I would "like" a zone system with 6 thermostats. The original plan was for 6 taco 006 zone circulator pumps that the thermostats would control. Each pump would be piped to a wisbro radiant manifold to balance the individual zone, each of the manifolds will have 2-7 loops depending on the zone. A couple of the zones are fairly small, (300 sq. ft.) but have 110 sq. ft. of glass. The manifold supplying the pumps would be 1 inch coming out of the boiler and 1 inch going out of the pumps to the radiant manifolds. I have a couple of concerns and maybe I'm crazy but here it goes. Number one, I'm not sure the boiler pump or the manifold can handle the 6 pumps, I'm afraid the pumps are going to have cavitation issues but that may be the least of my worries. Second and more important I believe the boiler is going to short cycle to its untimely death. Possibly a 30-40 gallon buffer tank? I'm in deep now so this is what I have to work with......definitely looking for advice and really apriciate all the options.


  • Ironman
    Ironman Member Posts: 6,400
    You're absolutely correct about the zoning causing short cycling. And, you probably don't need more than two or three zones.

    A radiant slab will usually require a lower water temp than the staple up floor. So, you may need two or three different water temp zones, depending upon if you're keeping any of the BBs.

    Some initial considerations:
    1. Have you done an accurate, detailed heat loss calc? That's crucial and its the foundation for designing and sizing everything.
    2. You'll need to use extruded aluminum heat transfer plates on the staple up floor. Not the cheap beer can plates, extruded ones. Rehau has a nice double track one that's very easy to use and gives optimal heat transfer. Without these, you're probably gonna get less than 7 btus per square foot output. With them, you'll get 19 + btus per square foot.
    3. If the radiant slab is of any significant size, the water temp to it needs to be controlled by a SMART mixing system that uses outdoor reset or the floor will overheat. Go to Tekmar's site and lookup their essay on variable speed injection mixing for a detailed explanation.

    That's enough to get you started and get your gears turning. Like you said, it's a lot more complicated than what folks realize.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Zman
    Zman Member Posts: 6,712
    Where are you exactly?
    There are quite a few folks on here from Colorado.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • justken
    justken Member Posts: 2
    I live in the front range Zman

    Thanks ironman! I had checked out the Rehau transfer plates...without having one in my hand they appear to be roll-formed out of .032 aluminum, the joist trak we are using is a extruded aluminum (like you have suggested) with a very tight connection to the tubing allowing a great transfer rate.

    Sounds like we are going to cut the zones down to 3-4. 6 would have been nice but a couple are just to small of a room to be practical without some sort of storage buffer. I'm working on a room by room heat calc before we get much further.

    Thanks again for the advice.