heated driveway and heat loss

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  #1  
Old 11-24-08, 10:45 PM
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heated driveway and heat loss

The local auto body shop has recently closed so I am thinking of installing a heated driveway to escape the unwanted accidents from sliding down my steep driveway. I was told several years ago to run a seperate boiler for this but I see it unnecessary to install a whole seperate system for something I will be using a handfull of times annually.

Can anyone help with a diagram of a mixed system including radiant floor heat, cast iron radiators and pavement heating.

Also, how do you do a heat loss to size up the boiler(s)?

I must say, in my 10+ years of internet experience, this site is on the top of my list.

Thanks everyone for all your comments and suggestions.
 
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Old 11-25-08, 06:22 AM
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Snowmelt is a non-trivial task. Properly done, it requires good base prep, insulation, rebar and concrete. You can do asphalt but it requires attention to tubing type and asphalt application technique, lest the tubing melt or be crushed during paving and rolling.

Depending on the size of the driveway, you are probably looking at multiple loops and thus a need for a manifold, etc. There will be a bunch of sizing, etc. best done by radiant-type software. Heat transfer through the concrete/asphalt, thickness of slab, amount of insulation underneath, outdoor temperature, temperature drop through the system, supply temps required, etc. etc. all play into a snowmelt installation that actually works. It also helps to have a driveway that sheds water effectively rather than leaves puddles....

For the boiler end, this is a good application for a flat-plate heat exchanger (FPX) to isolate the snowmelt from the boiler (and the rest of the system). You'd need a circulator on the driveway side, and likely one on the boiler side to handle the head/flow requirements of the FPX. The driveway side would use a glycol mixture, naturally, to avoid freezing. There are dedicated snowmelt controls, as well as controls that will handle the building plus the snowmelt. tekmar among others makes them.

You are designing a fairly complex system. It would probably pay hugely to have it designed and spec-ed by a real hydronic engineer. There are firms out there like NRT (The Radiant Design Specialists | Northeast Radiant Technology, L.L.C. -- not an endorsement, but I've heard they are good) who will provide such services for DIY installs.
 
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