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Correct plumbing

I am renovating an old house and installing  floor radiant heat to replace a hot air system.  I'm afraid I didn't do enough front end research when I bought into a system design by Mr. Seton from the Radiant Design institute.  I've attached a diagram of the Indirect system w/ DHW he provided.  I have purchased all the materials he listed to complete the system.

I've finished installing the pex tubing; four loops of staple-up and three loops in concrete in the addition.   I'm ready to plumb the manifold/heat exchanger/heater and thought I would model it on the 'Thermal Transfer Station'  and 'Manifold Assemblies' he sells. (,  

After noting that his HX is not plumbed for counter-flow as recommended, I began to do more research and am worried about the effectiveness of the system as designed.

So, some specific questions on plumbing

On the manifold side, is the Expansion Tank plumbed right:- am I pumping away from it if the HX is between it and the pump, and shouldn't it come off an Air Eliminator?

On the heater side, am I pumping away from the check valve?

Will I need to add mixing valve(s) for DHW and the different pex loops (Fred never indicated or answered my question about the design temp for the loops)

Is a check valve needed where the cold supply meets the return from the HX and tees to the heater inlet?

Do the Taco 008 pumps have or require check valves?

I've done irrigation and house plumbing, and the radiant heating  seemed straightforward until I started looking at it in more depth.  Any advice or suggestions on additional components needed for finishing this system correctly would be greatly appreciated.


  • RichRich Member Posts: 2,224

    is pretty convincing isn't he ? First do away with the DBPV , second order a 008 VDT , third add a backflow preventer where the pressure reducer is , fourth purchase and install a Spirovent or Caleffi vertical air separator and locate it under the FPHX , you can leave the expansion tank where it is . plumb the HX counter flow as you have suggested .  Oh the hell with it , see if you can get your money back from Fred and send him his garbage back and design a real system with a little HELP from your friends . 
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • RobGRobG Member Posts: 1,850
    First things

    Before you insulate and close in the home you really need to answer some questions.

    Was there a heat-loss done on the home? Did you use plates on the tube? Did you insulate under the slab. if so, with what? Did you use barrier PEX? What are your floor coverings? Do you need supplemental heat? Etc........ And as Rich said, can you return any materials?

  • SnowmeltSnowmelt Member Posts: 750

    I use a takagi to do snow melt for my driveway . Your missing air separators, servicing valves. I would be using a 009 or 11 on the boiler side. And a bumble bee on secoundary side. You need servicing valves. What temp are you running the water at? What model unit are you using?
  • AlemonAlemon Member Posts: 2
    More questions

    Thanks to all for the input. 

    I should say I bought materials from outside sources, based on Fred’s

    material list.

    RobG, for what it’s worth, I did a heat loss calc on the

    Warmly Yours website.  Total house came

    to just shy of 33k btu.  I’m  most concerned with heating the new addition

    as it accounts for over a third of the loss-(high ceiling, lots of

    windows).  The slab is insulated underneath

    and the foundation is Logix block forms. 

    I think the three embedded loops of 1/2'” pex, are O2 barrier, I know

    the staple up loops are. We are keeping the woodstove currently used for heat

    on the first floor, and prefer cooler bedrooms upstairs  Floor covering is to be tile or engineered hardwood.

    Rich and Snowmelt, I’ve attached a sketch based on

    suggestions.  I doubt I can return what I

    have, so I’ll get a Taco VDT and chalk up the Iron 008 and bypass valve (and

    Fred’s design) as costly lesson learned. 

    Thanks for the servicing valve suggestion.  Are my placements OK?,  I assume I would need to isolate the pumps and HX.  How about a drain and fill assembly between

    the manifold and air eliminator?  As for

    system temp, that concern and possible need of mixing valves prompted my

    original post.  Can it be determined by

    heat loss and tube lengths? 
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