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Snowmelting Design

SM
SM Member Posts: 37
Do you have any recommendations as far as brand?

Comments

  • SM
    SM Member Posts: 37
    Lots of questions

    I have lots of question about snowmelting systems. A local doctor in my area is going to pour a pad (approx. 1500 sq./ft.) in front of her new home. Last winter she said the ice did not leave until April in front of her garage which faces north and is in the woods.

    My questions are I have read about the different classes of snowmelt. What would be a good design Btu/ft for this? She is not concerned if it would take 8 to 12 hrs after a snowfall for the snow to melt. She is concerned about the ice lasting until April. Can a person get buy with 100 Btu/ft.? I am sure it would work better at 150. She is not looking for any thing fancy just something she can turn on when the snow flies and have it be gone in a day or so.

    What is the best anti-freeze out there on the market?

    I would suspect that most boiler manufacture do not recommend anti-freeze so a heat exchanger would be needed?

    On boiler, what is recommend that could be vent out the basement wall, as this new house does not have a chimney in it?

    I have a copy of radiant living that had a job for a stair way in NY somewhere, anyhow I see that they used a nice looking underground manifold box. Any recommendation on where a person might find one of these?

    With 5/8 wirsbo pex could a person make 250 ft loops?

    Design delta T of 30 -35 okay?

    Thanks for the help!
  • hot_rod
    hot_rod Member Posts: 15,048
    Spend the extra

    amount to design 150 BTU's per foot, in my opinion. The cost to go from 150,000 to 225,000, will be the least of your expense!

    Never had a customer complain the snow or ice disappered too quickly :) I'd also highly recommend a slab snow sensor. Tekmar offers one of the best. This will allow the system to fire as needed.

    A spring wound 12 hour overide is another good option. If severe weather is forcast the manual switch allows you to get a jump on things.

    I'd look into a condensing boiler, they love these temperatures, and it is almost impossible to shock them. Simple PVC side wall venting. Copper tube would be another good choice, with proper return temperature protection.

    Using glycol should not be a problem, in any boiler. Take care with aluminum HX boilers to get approved glycol.

    I like DowFrost HD propylene glycol for this application. Use the best blend water you can find, and be sure to clean and flush before adding the glycol.

    Insulate under the slab for quickest response. Edge insulation is critical.

    I'll bet this turns into an expensive 1500 square feet of system. Crunch the numbers! With all the above stuff you'll get above the $10 / square foot range easily.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Mad Dog
    Mad Dog Member Posts: 2,595
    I used large lawn sprinkler boxes on a recent large snowmelt

    we did. They were 2 feet by 1.5 feet by 12 inches deep. worked out fine. Really do your homework on the actual costs. I found out the hardway that 10 per s.f will put you in the poor house if you are including the slab and edge insulation too. Next time' id have the concrete guy do that and the wire mesh. Listen to smart snowmelt dudes like Mark Eatherton and Hot Rod - they've done it all. I will post pics of our job when the boilers go in in a few weeks. Mark Eatherton was a tremendous help to me. I hope this picture helps.Mad Dog

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  • Mad Dog
    Mad Dog Member Posts: 2,595
    Sorry guys i told you my computer was screwed up

    first ray nitschke and now Glenn Stanton.. Anyway they are just large lawn sprinkler boxes. MD

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  • SM
    SM Member Posts: 37
    Where did you pick.....

    Where did you pick the box up at? Does it have a meteal lid?

    Thanks
  • hot_rod
    hot_rod Member Posts: 15,048
    The rage seems to be

    toward the Munchkin for this application. Mz and Weil are other mid priced options, although both require a special, aluminum friendly, anti freeze. Maybe a HX would be safer with the aluminum block boilers?

    The Viessmann is another small modulating condensor, not sure I have seen one dedicated to snowmelt yet, shouldn't be a problem but check with a dealer or rep.

    They all need a drain nearby as they will sweat big time at these low temperatures :)

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Iowa H20 BTU
    Iowa H20 BTU Member Posts: 1
    snowmelt boxes

    I design and sell mostly commercial SIM systems & use carson industries as a source for manifold boxes, they make irrigation meter boxes up to five feet long.
  • Tim Doran_2
    Tim Doran_2 Member Posts: 131
    Give me a call

    I would be glad to help you design this system. What part of the country are you in?

    Tim D
    952-997-5334
  • The_1Heatingdude
    The_1Heatingdude Member Posts: 1
    snow melt air issues

    I have recently acquired a new account. Approximatly 1800 sq ft snow melt in the chicago land area done by the other guy. There are loops installed in the stamped concrete driveway that are 300ft to 525ft each. I opened the supply manifolds and installed ball valves in each., there are also valves on each return. I did this to pressure test the loops because the home owner claims there are couplings in the pour.The job waws completed two year ago. The system has air lock issues every season. The boilers are located 8ft below grade in the basement. The loops are all above and the system is controlled by a tekmar snow sensor. During the summer months the system has discharged glycol enough to air lock the system requiring more glycol be introduced into the system and purge as necessary. I suspect that the boiler or boilers are going off on pressure relief. Where else can it be going? The relief valves are piped to the sump pit and I have done one week air pressure tests on the loops with 80psi and no leaks present. Is it possible I have pressure building up from hot solar temps during the summer months, or do I have weak pressure relief valves, help......photos of this ugly job to follow, thanks to all who take the time to read this. The Heating Dude.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    The urge to purge...

    You need a good charging pump with large cajones, or the ability to put all of the systems pumps into series in order to get enough velocity to get the bubbles to go down hill. Also, don't try and purge more than 1 or 2 circuits at a time, or the flow will dissipate to the point that the bubbles hang up.



    You also might try injecting a liquid ounce of Dawn Detergent into the system to help get the bubbles back down to the air eliminator.



    300 to 525 exceeds the 10% deviation rule, so once you get it purged, you will probably have to go back and balance flow thermodynamically or the long loops will be short flow.



    Also, it doesn't sound as if there is an expansion tank on the system. If there is one, it could have its diaphragm stuck and is not accepting any fluid, or it has failed, or it is undersized. Glycol and water have a higher coefficient of expansion than does straight water. Also, watch the percentage of glycol. More than 35% will cause a whole host of other issues.



    I've checked snowmelt systems during the summer, and have not seen significant increases in pressure due to solar thermal gain. With that said, I think that it should be illegal to have a snowmelt system that does not also provide some sort of solar DHW preheat or other thermal function during non snowmelt seasons. You have a great solar collector, albeit unglazed, sitting there basking in the sun. I think it was Mario Andretti who uses his snowmelt system to heat his Olympic sized pool during the summer months. With a water source heat pump attached, a person could kick some serious BTU BUTT.



    NEVER let a relief valve terminus be in a situation where it can not be supervised. I even put a small plastic cup below the relief valve terminus so I can see if it is possibly discharging or seeping. I call them my "witness cup".



    If as you say, the system is losing its charge due to thermal expansion in the summer months, when it cools down, it probably pulls a vacuum, and when it does, it draws air back in through the air elimination device, which makes a GREAT vacuum breaker.



    Also, to anyone who reads this NEVER allow an automatic make up system to be connected to your glycoled systems unless you enjoy seeing concrete spalling directly above your tubing...



    A picture is worth a thousand words...



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
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