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Major hydronic heating mess up!

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by slowzuki, Mar 4, 2008.

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  1. slowzuki

    slowzuki Feeling the Heat

    Joined:
    Feb 1, 2007
    Messages:
    486
    Loc:
    New Brunswick, Canada
    My slab was poured with 1/2" pex loops in 2004 I think it was? Anyways, just getting around to sizing a pump for the floor heat now. Take a guess at my zone lengths. Yup, 1000 ft per zone. Actually a little longer even.

    Now luckily the longest loop is my shop so I can live with a not so warm floor or use my jackhammer to split it into a pair of 500+ ft loops.

    The living quarters are different. Now, the first part starts in the bathroom with 6" tube spacing so at least the floor in there will be warm! I don't have good pics of were the tubing layout goes from there other than it is 9" spacing. I can't even guess a hidden spot to jackhammer out to split the zone. I may try raising the supply temp or going euro with a 4 way on a timer to reverse the flow every 30 minutes.

    How did this happen? Easy, I sized my own loops trusting a table type reference I had printed out without calculating the head loss myself since we were in a real big rush due to winter coming. Turns out the table was very, very wrong. I recommend double and triple checking everything before the pour. If in doubt, shorten your loops. You can always plumb them in serial flow later.

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  2. Sting

    Sting Feeling the Heat

    Joined:
    Jan 8, 2008
    Messages:
    477
    Loc:
    Wisconsin
    new construction = low thermal loss

    Try it - pump cooler water longer and just a bit faster than normal pump head - not too fast a GPM

    Pumping a bit too fast limits the loss to load on the head end so more is still available at the far end

    reversing is a good idea - just more architecture to support.

    run a day and test the floor temps with a good non contact instrument - raise the head end temps and test again.

    Boiler protection will be a good thing to have.
  3. slowzuki

    slowzuki Feeling the Heat

    Joined:
    Feb 1, 2007
    Messages:
    486
    Loc:
    New Brunswick, Canada
    I'm already planning on using a 4 way motorized on outside reset w continuous circ. Problem is the pump sizing, to get 1 gpm through a zone I'll need a Taco 009 so on cold days I'll be getting some monster temp drop over the loop. We are heating via wood stove right now so I don't need to meet those 5 worst days a year but it would be nice. I calc'd I'd need 2 gpm on the worst days so thats not gonna happen for sure.

    The pumping costs are a bit concerning too for a 009 vs an 003 that I should be designing for using the continuous circ.
  4. ericjeeper

    ericjeeper New Member

    Joined:
    Dec 28, 2007
    Messages:
    85
    Loc:
    central Indiana
    wow I say wow.. 1,000 feet is a whole lot of friction to overcome.

    My biggest mistake loop in my house is a little over 300 feet.. and I Had to bump my only circ pump up to a 013 from an 010 I believe/. In order to get enough flow rate to keep from only heating the first 150 feet of tubing and the center of the room floor being cool.
    Maybe your local fire dept will bring out their Thermal imaging camera. We used one on my shop floor over the weekend to find the areas that I left un tubed for mounting a post type vehicle lift. Every tube shows up like they are laying on top of the floor.
  5. Stlshrk

    Stlshrk Member

    Joined:
    Mar 4, 2008
    Messages:
    152
    Loc:
    VA
    If they won't bring out the Nifty. The cheapest idea I would try first before jackhammering would be to take a handheld infrared thermometer and try to map the system out to find where you need break points.

    you could mark or map to create yourself a diag of the layout underneath.

    Take a look on ebay item #230228858789

    Just and idea.
  6. slowzuki

    slowzuki Feeling the Heat

    Joined:
    Feb 1, 2007
    Messages:
    486
    Loc:
    New Brunswick, Canada
    Found we have a spot type at work. Thinking I could pump hot water into the cold slab and grab some chalk to map it out. The trouble is splitting my living are into two loops, the jackhammer point I think would be in the middle of my hall, which is acid stained concrete.
  7. atlarge54

    atlarge54 New Member

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    My floor radiant is in a crawl space total of 800+ ft of 1/2" pex in five loops. Taco 007 flowed about 2.5 GPM total, Taco 009 flows about 5 GPM. Loops run from 200+ ft to 80 ft. Not sure how much flow resistance is due to the 1" mixing valve. Don't know if that's any help but it might give you some idea of what you're dealing with. From what I've learned on this forum radiant poured in a slab is a whole different creature. Slab radiant would almost be worthy of it's own thread.
  8. heaterman

    heaterman Minister of Fire

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    Loc:
    Falmouth, Michigan
    You're in trouble. Not doomed, but in trouble none the less. Aside from the fact that you have to run a high wattage pump for the rest of your life, you'll find that you have no temperature left after about 500 feet. Hot Rod came up with a device using a motorized 4 way valve on a timer that reverses the flow in the loop at a time period of your choosing. This deals with the no temp issues very well. If he's reading this maybe he can post a diagram or chime in here.
  9. slowzuki

    slowzuki Feeling the Heat

    Joined:
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    486
    Loc:
    New Brunswick, Canada
    I'll have temp left when it isn't so cold outside but yes, I would like to have even heat when it is -30 C!

    I was able to get some pictures blown up of the tubing in the background of some pictures, I can split the loop in the living area under the kitchen cabinets and snake the returns through a wall to my header. The shop will be a bit interesting as the break is in a floor area about 2 feet from a wall. I may jackhammer a 2 ft long trench to tuck the return into an 4" PVC electrical chase I had put in the floor.
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