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1000 foot loop lengths

hr Member Posts: 6,106

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  • Ash
    Ash Member Posts: 1
    1000 foot loop lengths

    Hello all, looking for advice. I am trying to help a contractor "fix" a radiant system that was installed by another party. They ran a qty. of 3 - 1000 foot loop lengths of 1/2" pex tubing, buried in a concrete slab. All 3000 feet is being fed by a three station manifold. The heat output device is an atmospheric outdoor wood-fired boiler. My contractor has been called in to find a solution that will allow for even heating of the space. I have heard that running such long loop lengths creates problems with operation of the radiant heat system. We are looking for solutions that will not require tearing up the slab. Any suggestions would be most appreciated.
  • Weezbo
    Weezbo Member Posts: 6,232
    Ash *~/:)

    either you do it or leave it alone. trying will only result in you being the "bad guy".

    it will cost a few dubloons to fix that,trust me.

    one solution that may work is reversing flows...this works like a washingmachine as it were. heat goes in at one side then you reverse the flow and heat goes in at the other side,....

    if you look at PM engineering site and search for an article by John Siegenthaler on solving for that minor technicality you can see some pictures of a 4 way mixing valve with two way motor that accomplishes that particular feat of reverse engineering. *~/:)

    you might be able to pull up something here under search and the word Maxxon....

    the thing about gypcrete is that you might be able to find a few spots of 500 ft mark open it up and make 6 rather than 3 loops
    By the way Bob has a crafty means of making it 'GO" so re read his post a couple of times as it is going to be great advise :)

    follow the link he gave you.

  • more info needed

    GPM flow rate and average loop temperature for fluid are needed to determine head losses. 1,000' is going to be a bear no matter how you handle it.

    What kind of space are you trying to heat? If it's an open warehouse, offices or residential.

    Is it 1/2" or 5/8" tubing?

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  • bobbyg_2
    bobbyg_2 Member Posts: 139

    You have to have someone run the numbers. Do you know what the btu load is for this building?

    1. As an estimate, divide the btu load by 10,000 and that will equal the gpm flow required @ 20 degree temp. drop.

    (estimate only - based on 8.33lbs per gallon, 60 minutes in an hour, 1.0 specific heat of water, 20 deg. temp. difference "this changes when using propylene glycol" 8.33 X 60 X 1.0 X 20)= 10,000

    2. Get the tubing manufacturers pressure drop chart (100% water or glycol) and divide the total gpm required by three (3-loops) and figure the pressure drop of one loop.

    3. Take into consideration the manifold and other piping when figuring pressure drop (head loss) besides tubing. Size pump accordingly.
  • Weezbo
    Weezbo Member Posts: 6,232

    well, :) that too will be an eye opener :)
  • hr
    hr Member Posts: 6,106
    flow reversal

    is a method I have played with on a long loop. One project I ran came out with .5 gpm flow 12.45 feet of head. 12" spacing with bare concrete 120 supply showed return of 75.8. Quite a large delta T through the loop 44.2. About 21K BTU/hr.

    1 GPM is a whopping 41 feet of heat!

    The problem being a cold end of the loop. This is why flow reversal helps even the temperature from end to end.

    Paxton has considered marketing a reverser package for fixers like this.

    A high head pump can soften the blow, but still a large, uncomfortable delta t for a residential application. A pair of 15-58 in series gets you about 38 feet at 1 gpm

    Any pictures of the tube installation? You might change flow direction to help even temperature on every other loop?

    hot rod

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  • Dave Larsen_2
    Dave Larsen_2 Member Posts: 53
    4 way valve

    Weezbo is right, Seigenthaler had a great article a few months back on reversing flow by changing position 180 degrees on a 4 way valve. The hard part is finding a motor that will move that far, but the method will work.
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
    PEX License

    Maybe you should only be allowed to buy PEX in 1000 ft lengths upon presenting a license. :)

    I can see the maufacturer's warning label with skull and crossbones: "Do Not Put All of this in One Loop!!"

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  • Weezbo
    Weezbo Member Posts: 6,232
    i think it woul not be as much of a challange:)

    10,000' loops are available :) think about it...:)

    sucha Deal! we have for the guy you should have called in the first place:)
  • Brad White_89
    Brad White_89 Member Posts: 4
    Forget loops that long, Weezbo

    I want to see the hydraulic decoiler!
  • Weezbo
    Weezbo Member Posts: 6,232
    it would look a bit like the uncoiler for 2000 mcm cable for

    electrical transmission lines :))and NO it Wont fit on my van :))

    ok ok ... "Joe, blow on the end of that line so we can tell which loop is which " :) whtzzamatter ? you look a little green around the gills ;) just take a DEEP breath and giveit a go ladd:)
  • Ron Schroeder
    Ron Schroeder Member Posts: 998
    Gee Weezbo I Think

    if you mount a set of bracketts behind the seats and another set at the rear bumper you could mount it horizontaly above the roof no wasted space in the van.;-0
  • Weezbo
    Weezbo Member Posts: 6,232
    Thats why we are the guys to figure these things out*~/:)


    maybe its a heliothrope... maybe its an alien vessel .. no its

    Mercedes new box kite/weezbo uncoiler ! :)

    any whoo back at the plan determining the location of the middle ground is a good thing i am certain the installers had difficulties installing the tubing,and indeed it will prove to be somewhat of a challange to bring around to right.

    there is nothing easy about what we do it is only that we make it look easy. having to reverse flows in the winter here on a Glycol loop of such length makes you an engineer like it or not:)) bust out the pencil....why do you think God put an eraser on that end?
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    1000' of 1/2" transcends ignorance to true stupidity. At moderate load you'll expend more energy to move the water than needed to heat the space!!!!
  • Makes perfect sense to me...

    "If they didn't want you to install it all in one piece, why don't they sell it in shorter lengths, or put some instructions on the box. Any dummy can install this stuff. It ain't rocket science ya know:-)"

    The preceding was told to me by a DIY "GC". I told him good luck with his jack hammer surgery, and high tailed it to the jeep and left...

    4 way reversers do have their limits. And those limits generally only raise their ugly heads when you're at design condition.


  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    How could I forget?
  • Weezbo
    Weezbo Member Posts: 6,232
    lets see if we can get rehau or Uponor 1/2\"X4\"Camlock fittings

    lash it up to a gas powered 296 gallon a min pump shoot the preheated stuff into the - 38 degree slab and Getter Done! :)
    Lets not stand around daydreamin ladds...the last one took ten days to bring up to 58 degrees....
  • Mike C_3
    Mike C_3 Member Posts: 62
    I know why!!

    > 1000' of 1/2" transcends ignorance to true

    > stupidity. At moderate load you'll expend more

    > energy to move the water than needed to heat the

    > space!!!!

    They ran 1k foot loops because that's what comes in the box! Silly people!!!
  • Mike C_3
    Mike C_3 Member Posts: 62
    I know why!!

    They ran 1k foot loops because that's what comes in the box! Silly people!!!
    1000' of 1/2" transcends ignorance to true stupidity.
    It's kinda like spilling a HOT cup of coffee on your lap and blaming it on them being too hot.
  • GMcD
    GMcD Member Posts: 477
    Abandon and do new proper loops in topping

    While there may be some possible techno-fixes to make that system "sort of" work, at the end of the day, maybe it will be cheaper and happier for all parties if that existing system was abandoned and you do a new set of loops in a topping layer and get on with life.
  • S Ebels
    S Ebels Member Posts: 2,322
    Pardon me for being blunt

    The system has a 99% probability of failing to heat the place at design regardless of what "fix" is attempted. Reversing has its limits in that if you are able to heat only 1/2 the slab at a time, the overall output will be reduced substantially. Been there done that, got the jack hammer to prove it.

    Find another way to heat the place and tell the building owner your sorry his system will never work. Advise him to have his attorney take the matter up with whoever installed the aborted mess. If the building owner was the "third party", he can sue himself.........poetic justice of some kind there.

    Penny wise and pound foolish,....... you get what you pay for,............... you never get what you don't pay for........ and all those other common sense things apply here.

    I really find it difficult to generate any sympathy for the installer of this mess. He/she/it? shouldn't have been messing with something they obviously knew nothing about.

    Just another system giving radiant a bad name.

  • Jed_2
    Jed_2 Member Posts: 781
    bad name

    I tend to think it doesn't give radiant a bad name, just installers of radiant a bad name, "IF" the contracted installers exhibited such incompetence. But, I tend to doubt ther are many, if any, heating/radiant contractors who would do this.

    I ran into this last year from a very good Customer. He called me one day with a rather desperate tale of just this situation. He relayed that he had been called in to install a boiler system for a boat/storage/repair building that was being renovated. The boat building company had obtained the tubing, laid it out, and poured the slab. This was a building approx. 110x40/50'x20+h. I can't recall the # of loops, but they had set it up for three manifolds staged on the long wall. Wanted ONE zone, and all the loops were 1/2" x 1000'.

    "Will you size the circulator to give me "SOME" heat output?", I was asked. Well, I used HDS, and made some calls. I was aware of the Paxton reversing control, but would have none that for this. The circs turned out to be outrageous, and through ½" tubing, I thought the tubing walls would disintegrate rather quickly. The required output for this building was quite large. And the desperate Contractor was asking for "SOME" heat.

    I told him I thought the best solution would be to abandon the slab tubing, lay out all new tubing over the existing slab (at least they did put 2" foam board down), and re-pour a thinner slab over that. They had the elevation clearance to do that.

    Well, I found out later they somehow jacked the slab, cut/spliced the tubing to workable lengths, and patched. I have no idea what process they used to break the 1,000 coils, but they did, into 250's. I guess if you're a sizable company, have the manpower, and engineering personnel, you can correct most anything. But, their engineers are Marine Engineers. Go figure.

    We sold the Contractor the boiler, and all was well with the world after that.

    I guess my point in all of this is that radiant didn't get a black eye in this case. But it cost the ignorant owner a great deal of money. DIY's beware.

  • S Ebels
    S Ebels Member Posts: 2,322
    Not always but........

    I can give you dozens of examples where a poorly installed radiant system has been used to label ALL radiant systems.........the wrong way.

    Here's one that's like a gift that keeps on giving.

    About 8-9 years ago a local farmer installed a radiant floor in his new milking parlor. Who did the design, I don't know, but I do know that he and his farm help laid the tube and the local lowball price jockey installed the boiler. The poor misguided souls set up the radiant system to use the same water temp as the boiler with no mixing of any kind. 180-200* directly from the boiler to the floor. I'll leave the results of fresh manure on 100*+ cement to your imagination.

    Now........here's the point. At the time, this guy sat on about every farmers co-op board in the area. He was heavily involved in political stuff both at the county and the state level and he was also a county commisioner for years. I can't even begin to count the number of farmers that I have heard about "them radiant floors" from. I have heard about how bad radiant floors are from folks who live 60-70 miles away from this guy. It's now 8-9 years later and I still encounter horror stories of poop baking onto the barn floor and having to be removed with a chisel.

    On average a disgruntled customer (rightly so or not) will tell an average of 17 people about his bad experience. A satisfied customer will tell 3. Those are statistics from the National Hardware Retailers Association.

    We fight an uphill battle with radiant in the first place and losing industry wide credibility due to a hack job by some penny pinching HO or troglodyte contractor just plain makes my blood boil.
  • siggy
    siggy Member Posts: 79
    I'll run the number


    Send me the circulator used, and spacing, floor covering, etc for the slab and I will run it through the Hydronics Design Studio to give you some numbers on temperature drop and flow along the floor circuits. Siggy
  • Doc Radiant
    Doc Radiant Member Posts: 57
    Abandon it...

    I agree - unless the heating load is rediculously low and those loops were installed in a counter-spiral pattern (highly unlikely), the best bet is to abandon those 1000 foot loops.

    Education remains the key to success. To bad the installer didn't know any better.
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