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Thread: Help with hydronic radiant heat

  1. #16
    Retired Defense Industry Engineer jadnashua's Avatar
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    An outdoor reset won't do anything for you if you need to run the loops that high. It basically can be set to adjust the loop temperature based on the return water temp and the outside. If cold outside results in a much lower return temp, it can raise the input temp. You are already running near the max for your system. On a mild day it might save you a little by lowering the input, but won't improve cold performance (at least as I understand it) since you shouldn't get it higher.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  2. #17
    DIY Senior Member zl700's Avatar
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    Quote Originally Posted by alfpark View Post
    zl700 thanks for all your help I have regular air scoops on 90 elbows(not sure of the proper term). My loops are actually 400+' each. Hence the larger circ pump. I agree the 150 is high I just bumped up to try to get warm. My design was done by Fred Seton.
    www.radiantdesigninstitute.com
    All material is from Blue Ridge Radiant they and Fred both said with proper foil double bubble wrap underneath in the joist bays that the transfer plates were not needed. www.radiantdesigninstitute.com/page4.html
    I can still put them on the first floor which is worse off then the second. The first floor is existing constuction had 1X8 lapboard exterior so even though brand new insulation not quite as tight as second floor. The first floor is also 9.5' ceilings over unfinished basement which has 1 loop per joist bay 8" center and has foil double bubble and R13 underneath. It has the boiler and a pellet stove in the basement and stays about 50-60 degrees.
    My dad has one of those infared thermometers. I will get temps for you today.
    I had some air and purged all loops a couple of days ago. Its is definately better but still cant hold 68-70 overnight on the firstor second. Second drops to 64-65 and first to 60 or below. What should I be able to get as a high temp and hold. 67 is comfortable when outside temp is 40ish and no windchill. If I get to where I hold high 60's I should be ok (but would love to get into the 70's even though I am sure I would never set it that high!).
    A couple serious questions I guess are the nail up fins that much difference? Its seems people used to strap copper up and have good outcomes with alot poorer insulation and window drafts!! I cant understand that a flat piece of aluminum can make 5-10 degrees difference especially in the secong floor where it is incased in an insulated bay and has no place to go. Also if I did a sandwich using quicktrax or something similar I would have the same amount of tubbing loops(BTU outut) as I do in the just bays 8" appart for the most part.
    The other question is my flow rate. If I dont have a good flow rate that effects me obviously. My delta T is about 15-20 depending on outside temp and how many loops are flowing (never over 20 but can hold 20) which obviously hinges on outside temp. I am maintaining a miniumum of .5GPM usually more(depends on # of loops open). My loop flows are always pretty equal GPM reguardless of # of loops flowing. Do I need more flow? I am not sure what this will change. I can put a larger pump in currently a taco 0011. Again thanks for the support and help.

    You say 1 loop per bay, 8" on center, so you mean it goes down and back with 2 tubes in 1-16" bay?

    That .5 GPM, is that per tube?
    The tubing is attatched to floor or clipped into suspension hangers?

    Is that one Taco 11 circ for both floors? Is there a boiler pump? and not that it matters much what is your boiler?

    If you have autovents on top of tees, that is not only a lousy way to vent air, with the HV circ you have, depending on where their placed, they can actually introduce air. You should be looking at installing a Spirovent or similar.

    Some observations:

    1/2" shouldn't be run over 300', I prefer 250' (the shorter allows lower amp pumps, even floor temps and quicker reaction time)
    There are many factors involved but the usual design of 1/2 PEX for radiant is around 3/4 GPM per loop.
    Because of the loop lengths, that pump may be required and in fact may not be enough, which is poor design and commonly made as a mistake, I pay attention to all energy costs and with proper design a lower energy use circ(s) could have been applied.
    150 degree water with only 70-75 degree floors tells me the heat is not transmitting.
    With a delta T of 20 (normal design) it appears flow is proper, if it was overpumped is would be less and under it would be more, which still points back to amount of tube and or transfer of heat.

    Several pictures of boiler, piping and manifolds will tell the whole story

  3. #18
    DIY Junior Member alfpark's Avatar
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    I will post some pics tomorrow.
    yes .5 per loop
    pipe goes down and back same bay 16" bays pipes are 8" appart.
    And yes I have autovents on 90's
    my boiler is 148k btu well mclain
    tubing is stapled to subfloor

  4. #19
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    The simple answer here is that you don't have enough tubing in the floor to heat the house. There may be some design issues also, like 400' loops and possibly some pipe size issues but I will bet that you just plain are not getting enough heat into the house. A couple of toe space heater or even some fin tube baseboard will fill in the difference.

  5. #20
    DIY Junior Member alfpark's Avatar
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    Last edited by alfpark; 01-08-2010 at 08:34 AM. Reason: adding another link

  6. #21
    DIY Senior Member zl700's Avatar
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    Good pictures
    The main issues are now that I've seen pictures:

    1. No boiler pump, this should be primary/secondary piping
    2. Mixing valve is too small (high C.V.) restricting flow (3/4 passes only about 43,000 BTU's)
    3. Loops are too long
    4. 1" piping to small (would be OK with 6 1/2" loops)
    5. Manifolds are too small for that many loops (that looks like ones for 3/8" loops)
    6. A detailed radiant design may determine that plates are needed, if plates wont do it or enough, supplemental heat may be required such as a kicspace heaters, convector, air-ocer hot water coil or baseboard, probably run on high temp zone
    7. When finished there will be way to many loops on one pump and manifold, as you are feeling now already. Strong consideration should have been given to using 2 pump/manfold/mixing valve setups (up and downstairs)
    8. Tubing is a bit close to joists that act as a heat sink, should be closer together for a true 8" cc.


    If you followed the design, Fred needs some instruction on proper design and installation techniques. You wont even see such a farce in a boiler manufactures instructions.

  7. #22
    DIY Junior Member alfpark's Avatar
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    Quote Originally Posted by zl700 View Post
    Good pictures
    The main issues are now that I've seen pictures:

    1. No boiler pump, this should be primary/secondary piping
    2. Mixing valve is too small (high C.V.) restricting flow (3/4 passes only about 43,000 BTU's)
    3. Loops are too long
    4. 1" piping to small (would be OK with 6 1/2" loops)
    5. Manifolds are too small for that many loops (that looks like ones for 3/8" loops)
    6. A detailed radiant design may determine that plates are needed, if plates wont do it or enough, supplemental heat may be required such as a kicspace heaters, convector, air-ocer hot water coil or baseboard, probably run on high temp zone
    7. When finished there will be way to many loops on one pump and manifold, as you are feeling now already. Strong consideration should have been given to using 2 pump/manfold/mixing valve setups (up and downstairs)
    8. Tubing is a bit close to joists that act as a heat sink, should be closer together for a true 8" cc.


    If you followed the design, Fred needs some instruction on proper design and installation techniques. You wont even see such a farce in a boiler manufactures instructions.
    I spoke to him today and the only issue on my pics he had was the mixer and taco does that. that mixer is a 1" it comes with those nipples.
    http://www.blueridgecompany.com/image/item/320

  8. #23
    DIY Senior Member zl700's Avatar
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    If it's a Taco 5000 series mix valve, scratch that statement from me

  9. #24
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    Id say You would be better off running a primary secondary loop. I normally dont run any radiant loop over 200-240 ft.

  10. #25
    HVAC designer and consultant Ottawa_HVAC_Guy's Avatar
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    Quote Originally Posted by Peter Griffin View Post
    The simple answer here is that you don't have enough tubing in the floor to heat the house. There may be some design issues also, like 400' loops and possibly some pipe size issues but I will bet that you just plain are not getting enough heat into the house. A couple of toe space heater or even some fin tube baseboard will fill in the difference.
    Quote Originally Posted by zl700 View Post
    Good pictures
    The main issues are now that I've seen pictures:

    1. No boiler pump, this should be primary/secondary piping
    2. Mixing valve is too small (high C.V.) restricting flow (3/4 passes only about 43,000 BTU's)
    3. Loops are too long
    4. 1" piping to small (would be OK with 6 1/2" loops)
    5. Manifolds are too small for that many loops (that looks like ones for 3/8" loops)
    6. A detailed radiant design may determine that plates are needed, if plates wont do it or enough, supplemental heat may be required such as a kicspace heaters, convector, air-ocer hot water coil or baseboard, probably run on high temp zone
    7. When finished there will be way to many loops on one pump and manifold, as you are feeling now already. Strong consideration should have been given to using 2 pump/manfold/mixing valve setups (up and downstairs)
    8. Tubing is a bit close to joists that act as a heat sink, should be closer together for a true 8" cc.


    If you followed the design, Fred needs some instruction on proper design and installation techniques. You wont even see such a farce in a boiler manufactures instructions.
    You're missing a pump! You need 2 pumps to make this work. Your loop designer might have given you a passable design, but the heat generation (boiler, boiler piping, pump and controls) design is completely wrong. You can't possibly ensure that you have enough flow through your boiler (or infloor system) with that piping arrangement. As zl700 mentioned: you MUST have a primary-secondary pumping arrangement. Start with a proper boiler design, then see if there are any other problems. Primary-secondary pumping systems tend to have much fewer problems than simple pumping systems.
    And it doesn't mater which 3-way valve you are using - you have to install 2 pumps for this to work properly. Cutting corners always ends up with problems...

  11. #26
    DIY Member rrekih's Avatar
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    I have also put in a system that is mounted under floor.
    I need to do some fine tuning but all seems to be ok.
    I looked at your pictures and see that you mounted the pipe away from the joists.
    I mounted mine up as tight as possible to the joist.
    One thing I did notice is the mounting clips seemed to be spaced far apart.
    I used talons with no more then 2ft apart.
    The longest run I have is around 300ft, knowing full well that I was going over the recommended max 250ft.
    I am only doing approx. 1500sq. ft. and use a Grundfos 26-99 superbrute but plan to change to primary / secondary system.
    With the sq. ft. you are using you should have 2 pumps.

  12. #27
    DIY Senior Member zl700's Avatar
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    Don't put the tubes next to the joists, the joists serve as a heat sink transfering heat off the floor you wish to heat.

  13. #28
    DIY Junior Member S+W's Avatar
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    What ever came of this situation and design? I am looking at the same designer but for a slab situation. Not getting the warm and fuzzies here.

    TIA,
    S+W

  14. #29
    General Engineering Contractor ballvalve's Avatar
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    Well, I see this is a very old resurrection. This guy just needs some HIGH HEAD pumps. I have one grunfos beast that runs 6 loops. Also when you guys do radiant on a wood floor, do it right and put sleepers ON TOP of the subfloor and invest in some cheap 4 or 5 to 1 mortar to fill it all in. THEN lay your flooring - Now you are not working upside down and your heat transfer is up 200%. And you have a virtually fireproof layer between floors. - along with some thermal mass which you have none of with that stupid upside down staple up perversion.

  15. #30
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
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    First, a proper heat load analysis performed on dedicated radiant floor heating software will tell you tube size, length, flow and average water temperature.

    A proper radiant floor heat load would have told you if your plan to go "plate-less" - at any design temperature - would satisfy the load (thermostat) before you started your project. Whereas, it is true that nearly all common floor coverings are compatible with hydronic radiant floor heating, it is also true that you have to have the system designed by a professional (few online radiant floor suppliers qualify) to have reasonable expectations of success.

    I have a new 3/4" solid oak over 3/4" plywood decking and am quite comfortable with design water temperature of 110F here in Minneapolis. This means, when it is -13F (our outdoor design temperature) the house will be 68F. My design software dictated the use of heavy extruded aluminum plates to reach my design goals. By contrast, my first sub-floor hydronic radiant system, circa. 1991, was a straight staple-up and still operates at 180F and required several panel radiators to supplement the low-output of this crude application. I experimented with fiberglass, foil-faced and kraft-backed. I also installed bubble-foil and compared the performance. It is now the very rare design that I will allow a bare tube staple-up or suspended tube radiant panel. In vast majority of cases, both new construction and retrofit, some type of proper efficient emission plate must be used to get reasonable, efficient or even effective heat transfer.

    You could still do a heat load if you really want to know what temperature you must operate at to be comfortable or just crank it up until the house is warm.

    By the way, bubble foil is a scam, professional radiant floor people can find no useful purpose for it. Those who advocate its use for radiant floor heating should not be taken seriously.

    http://www.healthyheating.com/Page%2...6_bldg_sys.htm

    Before spending money on questionable radiant floor heating practices, look for a former RPA certified designer. Certified designers were tested by an independent, third party, process.

    http://www.badgerboilerservice.com/images/RPA.pdf
    Last edited by BadgerBoilerMN; 05-29-2012 at 07:10 AM.

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