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Thread: What is the proper way to lay down 1/2" Radiant Heat pipe? - Looking for perfection

  1. #1
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Default What is the proper way to lay down 1/2" Radiant Heat pipe? - Looking for perfection

    I'm helping a client out in New York design his new master en-suite. This on suite will have heated floors and his contractor is going to remove the old radiator and replace it with a floor heating system. The piping will be 1/2" and the question is what is the best design for the install.

    We have had a chance to chat with Richard (Noble Company) and we understand what thickness levels of mortar to use but the real question is what is the best way to run the heating loops. With cable heat or electric heat some manufactures recommend no straight runs longer than 10'. I believe this is do to stress or thermal changes on the wire.

    Is there a similar logic with the heating pipe when the heat source is hot water?

    We have always used electric heat but since there is access the home's hot water system we are going that route.

    The prep we we have designed is to have 3/4" plywood over the floor joist. Then set down 1/2" Hardy board with KeraBond/Keralastic. Next the heating pipes go in and after this a screed mortar layer of dry pack.

    My gut tells me that we should keep the loops to 10'. What say ye Plumbers?

    Thanks Men. JW
    Last edited by johnfrwhipple; 05-30-2013 at 06:39 AM.


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    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Default Longest Radiant Heat Loop Length - 250' or less unless designed by an engineer

    I have been working the phone and calling suppliers this morning to get a larger sampling of opinions and this is what I found out.

    I called VanGuard Pipe and Fittings and spoke with Ken who told me that the longest loop can be no more than 300' with a 1/2" pipe.

    I called Bow and got an answering machine - they never did call back all day.

    I called Watts and spoke with Shawn who told me that no home run should be more than 280'

    And to get a third opinion called Heat Link and spoke with Rea who told me no run should be more than 250'. I asked Rea why the others said 280' and 300' and he told me that an engineer can asses the install and approve longer runs but without an engineer the runs should be keep to 250' or less.

    I asked each man directly about the length of the run before looping (i.e. no more than 10'-20' before looping) and was told there is no restrictions other than the max loop length.

    What other points should we consider in this design? Do any of you guys work in an extra bleeder location? I have seen these installs rough'd in where there is couplings used and spoken with other plumbers who swear they should never be used. I would imagine any coupling would make removing the air from the zone a little harder.

    JW
    Last edited by johnfrwhipple; 05-30-2013 at 06:40 AM.


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    Retired Defense Industry Engineer jadnashua's Avatar
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    Getting the air out of a second story pex loop can be a pain. OFten, you may need to run the feed pressure up (with the boiler isolated so you don't dump it out of the safety valve) so it can flow everywhere just like it would in a potable water situation. THen, once you have the air out and reopen the boiler isolation valves, things should be okay. The air extraction system should be able to then purge any entrained air in the fresh water you've introduced. If there are any exterior walls, run the loop around them first before doing the interior of the room, otherwise, it really doesn't make a lot of difference. Make nice rounded loops and ensure you don't get any kinks, as it will severely impact the flow. Assuming that this is part of other radiant zones, you often will need a balancing valve to get the flow proper. If the rest of the house is using radiators or convectors, you'll also need to temper the water in this loop so you don't have the potential to make the floor too hot for safety or comfort. IOW, you don't want to circulate 180-degree water through your floor heat when it is embedded in mortar!
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member DougB's Avatar
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    I don't do this for a living, but my grandfather was a heat transfer engineer, and I picked up some 'stuff' from working on jobs (40 yrs ago).

    The heated area is a seperate zone, with it's own circulator pump. You install a manifold that supplies the 'loops' with hot water. The flow of water is balanced with the valves on the manifold. There were no 'bleeders' - get the air out of the system by using a pump at 30 lbs (block off the pressure relief) to purge the air
    If a hammer won't fix it, it's an electrical problem.

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    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Default 1/2" Pex Heating Pipe - coverage of screed mortar.

    Thanks men.

    So no worries about running the loops in 15' - 20' lengths? If this was your own home what would be the maximum length of pipe you would run before making a loop back?

    I had a great chat with Mapei's tech Darryl today and he confirmed that the Mapecem 102 was a good fit for the covering of the heating pipe. I have always liked the Mapecem Pre-Mix Fast Setting and both could be used. Darryl felt that perhaps the 102 would be a little easier to trowel and I like the fact that it is used for both inside and outside applications.

    The question now is do we use a slurry coat of KeraBond/Kerlastic or a slurry coat of Mapecem 102 with possible Planicrete??? Placed another call in to technical and waiting for a call back.
    Last edited by johnfrwhipple; 05-30-2013 at 06:40 AM.


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    Retired Defense Industry Engineer jadnashua's Avatar
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    When you say loops, I'm assuming you mean straight lengths before turns? As I understand it, it is not a factor, and they can be nearly any length as long as the entire heating loop is within specs (200' or so, depending on who you ask). Note, that distance is from the manifold back to the manifold. I have four loops in my place - three under wood, and one embedded in SLC...I have never heard expansion/contraction noises from any of them in the 8-years they've been in place. The big thing it to get the spacing proper so you can get even heating plus the desired heat output for the area in question. Had you looked at Bekotec http://www.schluter.com/1460.aspx ? It might simplify the installation considerably.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Thanks Jim. I'll look closer into this. Just got back off the phone with Darryl and I'm glad I doubled checked the slurry coat becuase he did not like the introduction of Hardi Board at all into the mix in such a large space. He mentioned we should omit the hardy all together and go with a 1.5" 4-1 mix with the ad-mix & wire reinforcement over a slip joint. I'm going to call back Richard and Noble and get a second opinion on this but I have know Darryl for years and trust his gut read on this.

    I'll bring up the Bekotec system as well.

    It never ends - It's like we are training to be NASA pilots here!!! JW
    Last edited by johnfrwhipple; 05-30-2013 at 06:41 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

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    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Default Schluter - Bekotec with 1/2" radiant heating pipe

    So I left a message with my local Schluter rep just now and earlier had a chance to call back Noble. I spoke to Richard from Noble Company and he does not have any issues of following Darryl's recommendation but asked about the weight rating of the floor. HMMM. Another thing to check.

    I read the Bekotec PDF and it tells me it lowers the weight by about 20% in this 1.25" build up scenario. Lowers it by 50% if a 2" lift was necessary.

    Now the larger the room you need to include the wire mesh so we have a few more things to double check. Man I thought this would be two calls and it's turning into an epic investigation. My brain hurts - I think it's growing!!! lol

    I better call New York and chat with my client before it gets to late and bring him up to speed on the research so far.

    Maybe we can stick with the original plan of 3/4" subfloor. 1/2" Hardy. Then Bekotec. Then Noble Seal TS or Ditra.

    Is there any performance gain or loss with using Bekotec? With less mortar to warm I wonder if the floor warms up faster? I wonder if it cools down faster? Who would have done these studies. Maybe Bob (Schluter Rep) knows.

    If I was using a wire system like I do understand I would be done by now!!! lol
    Last edited by johnfrwhipple; 05-30-2013 at 06:41 AM.


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    DIY Senior Member DougB's Avatar
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    I have a home, built in 1950 with hydronic heat, in the ceilings. That is right - about 3/4" of cement, and a coat of plaster. Not to brag, it is an 'expensive' home. It is also a PITA home. I guess I got it because I know how to maintain it.

    My home has five zones. All supplied by B&G 1/6 hp pumps (the red ones). I have had on occasion to use infrared to locate the pipes. At 6" on center - I have at least 300 ft in the living room. The house stays perfectly warm, even in Minnesota winters.

    Hope that helps.
    If a hammer won't fix it, it's an electrical problem.

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    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Thanks Doug. Just got off the phone with my Schluter rep and he has nothing but good things to say about this Bekotec system. Apparently we don't have the complete European line up but the mat is here. Bob tells me that the floors actually heat up faster because of less material needs to be warmed. The product is availble in New York so this might be our approach.

    We worked on a job here in Vancouver that had radiant heat in the ceilings - I had never heard about this until that job. Seams odd honestly but it was ice cold outside and the condo was right on the water in English Bay. The unit was warm just like you say.

    I had a chance to discuss a few current projects with Bob and now need to call Ardex about a job up the Sunshine Coast. Bob put a new idea into my head and now I need to figure it out.

    Glad I'm going back to work tomorrow - this research is exhausting. All the reading and phone calls is driving me batty.

    Quote Originally Posted by DougB View Post
    I have a home, built in 1950 with hydronic heat, in the ceilings. That is right - about 3/4" of cement, and a coat of plaster. Not to brag, it is an 'expensive' home. It is also a PITA home. I guess I got it because I know how to maintain it.

    My home has five zones. All supplied by B&G 1/6 hp pumps (the red ones). I have had on occasion to use infrared to locate the pipes. At 6" on center - I have at least 300 ft in the living room. The house stays perfectly warm, even in Minnesota winters.

    Hope that helps.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

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    DIY Junior Member Dean.Collins's Avatar
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    Default ceilings not floors?

    Quote Originally Posted by johnfrwhipple View Post
    We worked on a job here in Vancouver that had radiant heat in the ceilings - I had never heard about this until that job. Seams odd honestly but it was ice cold outside and the condo was right on the water in English Bay. The unit was warm just like you say.

    Why would you heat ceilings instead of the "Floor" where you want the heat?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Radiant heat does just that...radiates. Just like the sun, it doesn't care about the direction - it heats everything. There are lots of applications that put the heat there. Now, if the floor was a slab on grade, it may not be as comfortable as it could be, but if there's heat from below, too...no problem at all.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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