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Radiant heat manifolds and zone controls

CJO Member Posts: 3
I bought a home last year that has in floor radiant heat and have fixed /repaired quite a bit of stuff.

Replaced Polaris water heater/boiler "Seeping Tank" , recirculation pump "Failed", re plumbed with all brass and stainless flexible lines and also took apart and rebuilt Manifold assembly "Basically just a bunch of orings". My question is I don’t really trust the Manifold as it is showing signs of cracks and seepage and want to replace it. When searching for new manifolds it seems a quality brass one is the best option but I would like to keep my current configuration pretty much the same and the new manifolds put actuators on the return side "Cold side" and my system has them on the inlet side or "Hot feed" line. Apparently one or the older designs, I’ve included pictures for you to laugh at.

Also the actuators are of a 4 wire design to turn on a recirculation pump. "There is only one for the whole system" and helps circulate the water to the 6 zones.

Will my system still work the same if I use the new manifolds and put actuators on the return side and be able to still be able to balance the flow rate correctly? I have also been told I can use 2 wire actuators but don’t you need the 4 wire design with an end switch to turn on recirculation pump.

Thanks Craig


  • zacmobile
    zacmobile Member Posts: 211

    Depending on the manufacturer & model modern heating manifolds can have the actuators on the supply (hot) side or the return (cold) side, it doesn't make any difference to the system performance. If you are using a zone control as indicated in the picture then it should have a built in end switch to tell the pump to turn on and hence make 4 wire actuators redundant.

    Another thing: it looks as though you may have non-oxygen barrier PEX pipe, if that is the case then you are on the right track replacing steel fittings & pipe with brass & stainless, you should also make sure the pump is bronze or stainless as well. Also you may want to look at an anti corrosion chemical treatment for the system fluid.
  • CJO
    CJO Member Posts: 3

    Thanks for the help when you say redundant so you mean 4 wire version is not needed and I can use 2 wire sensors like others have said?

    As for  anti corrsion chemicals I use the boiler for both Radiant heat and Domestic hot water is there a chemical that is safe for this.

    Thanks again
  • Ironman
    Ironman Member Posts: 7,343
    edited January 2013

    The manifolds are not a big problem. Using the same tank for domestic and space heating is. Apart from the system issues that can develop with an open system, the larger issue is that such a system is a legionella breeding farm. 10 + years ago, these systems were popular in the U.S. because of the lack of knowledge and education in the plumbing and hydronic trades. And, they were a cheap way to get hot water for space heating. "Why buy a boiler when you can use a water heater for both"? Now, we're better educated as to "why".

    The water that stays in the floor during summer months breeds legionella and then dumps it back into the hot water tank when the heat is turned on. If the aquastat on the polaris is not set to a minimum of 140*, the bacteria continues to breed in the tank. It's then vaporized through your shower head and inhaled into your lungs. If you have a healthy immune system, it will probably ward off the disease. But the young, the elderly or those whose immune system is weakened, are prime targets for contracting what could be fatal.

    You need to have the space heating separated from the domestic through a heat exchanger with the proper controls or use a boiler. A combi boiler could handle both and replace the polaris which will probably go sooner than later.

    For the moment, I would recommend that you turn the polaris up to at least 150* and have a mixing valve on the domestic to temper the water down to 125*. You may also need a mixing valve on the floor if you don't already have one. This is not a permanent solution, but it will make the system much safer regarding legionella.

    Oh, Manifolds. Look at using European made: Caleffi, Rehau, Uponor. Don't use the chinese, they're junk.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • CJO
    CJO Member Posts: 3

    Well thanks for the info as for the polaris it is already set to 155

    I dont have any mixing valves but might add one.

    As for manifolds im thinking a Caleffi in going to be the one of choice.

    As for seperating the system I Just bought the Polaris that does both so will live with that as is for now.

    I am still looking for an answer on the actuators my control system panel has to use what appears to be a 4 wire version with end switch unless you can use a jumper to run the circulation pump with 2 wire actuators in place of the 3rd and 4th wire. This does  show on a schematic as a possibility.

    Thanks again all
  • zacmobile
    zacmobile Member Posts: 211
    edited January 2013

    Yes you probably only need the 2 wire actuators (no end switch) I was under the impression that the Polaris tank had a built-in heat exchanger for the radiant side? If it does in fact share the same water between the radiant & domestic that should be corrected ASAP as Ironman says, you would need to add a heat exchanger & a pump & an expansion tank to the radiant side.

    Edit: http://www.americanwaterheaternews.com/media/lit/polaris/Polaris_Installation_Manual.pdf Actually it doesn't appear to. Yeah, you need to change that.
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