The ground does not need to be heated 4 foot deep to melt the snow on the side walk. this is a snow melt system, not a keep snow off my walk system, so in really cold snows, or fast, deep accumulations, there will be build up on the sidewalk or drive, but the system will get it all melted. The heating wires are put in the concrete about 1.5 inches below the surface. 50 watts is about 170 BTU. 1 watt is 3.412 BTU. 1 sq/ft of concrete that is 1.5 inches deep is about 11.1 pounds. it takes 0.2 BTU to raise 1 pound of concrete 1 degree F. To raise the temp to 32 degrees F from 0 degrees F, it would be 71.04 BTU's Okay, that leaves us with 98.96 BTU's Going with a medium snow, not real wet and heavy, but not real light and fluffy, the snow would weigh about 10 pounds per cubic foot. and if we get an inch of that in 1 hour, that would be 0.83 pounds. it takes 0.5 BTU's to heat ice by 1 degree f. To bring the snow from 0 to 32 degrees f, it would take 13.28 BTU's Now, this is the real BTU hog, it takes 144 BTU's to go from ice at 32 degrees F to water at 32 degrees F, per pound. That would be 119.52 BTU's in our example. The total BTU's so far is 204.38, so that puts us into our second hour, cause we only have 170 BTU's per hour. In the second hour, we wont' need the full 71.4 BTU's cause the concrete is already warmed to 32 degrees F, but it will take some BTU's to maintain that temp, lets say 30% of the original to make it 21.31 BTU's to maintain the concretes 32 degree temp. total 225.69 BTU's. Because heat moves to cold, we will waste BTU's heating the concrete below the wires as well. Lets say we use another 100 BTU's to heating the concrete below the wires during the time it is melting the snow on top. Total 325.69 BTU's go with 340 BTU's to add some extra in for the heck of it. So 2 hours to melt 1 inch of snow, and the use of 100 watts per sq/ft. 15000 watts for a 3 by 50 sidewalk. 15 KW times $0.12 per KW, and you get $1.80 to remove 1 inch of snow. If 1 inch takes 2 hours, and if 8 inches would take 16 hours, then we would be talking about $28.80 to have a snow free sidewalk. Then, if the average snow fall is 60 inches for the year, that would be about 120 hours of use, and $216.00. of course, there are other variables that you would need computer modeling to take into effect, like speed of winds, and the thermal loss of the concrete, and insulation value of snow after it starts to accumulate, rate of snow fall, etc... but if it costs lets say even $400 a year to remove 60 inches of snow for your sidewalk, that is cheap compared to being in eh hospital because of a heart attack from shoveling that much. Possibly cheaper then paying someone to do it as well, not to mention, waiting on them to get it done. Oh, best I could find was raw turkey rolls being0.81 BTU's to heat by 1 degree for 1 pound. Michael _____
From: blindhandyman@yahoogroups.com [mailto:blindhandy...@yahoogroups.com] On Behalf Of Dale Leavens Sent: Wednesday, February 24, 2010 10:16 PM To: blindhandyman@yahoogroups.com Subject: Re: [BlindHandyMan] Radiant floor heating. Well, it takes half a day to thaw a 20 pound turkey in my house at 72 degrees F. My patio weighs about 11 tons and is sitting on frost that penetrates about 4 feet and just now it is 0 degrees F out there with a slight breeze. That would require a load of heat to melt the snow even if the patio was laid on insulation. If I was Han Solo I'd probably pet my wookie ----- Original Message ----- From: Michael baldwin To: blindhandyman@ <mailto:blindhandyman%40yahoogroups.com> yahoogroups.com Sent: Wednesday, February 24, 2010 10:44 PM Subject: RE: [BlindHandyMan] Radiant floor heating. Then go to h <http://www.suntouch <http://www.suntouch.com> .com> ttp://www.suntouch. <ttp://www.suntouch.com> com click on the ProMelt Mats link read the info, and download or open the pdf link SunTouchR ProMeltT Brochure, and see what it says for yourself. it is possible I miss read 50 watts on 240 volt systems, and 36 watts on 120 volt systems. Michael _____ From: blindhandyman@ <mailto:blindhandyman%40yahoogroups.com> yahoogroups.com [mailto:blindhandyman@ <mailto:blindhandyman%40yahoogroups.com> yahoogroups.com] On Behalf Of Dale Leavens Sent: Wednesday, February 24, 2010 9:27 PM To: blindhandyman@ <mailto:blindhandyman%40yahoogroups.com> yahoogroups.com Subject: Re: [BlindHandyMan] Radiant floor heating. I don't believe that for a moment. If it is below freezing it is going to take a lot of heat just to raise the temperature of the surface above freezing. A cement walkway has a lot of mass to bring up to temperature. Then there is the latent heat. it takes something like 40 calories of energy to change the state of water from solid to liquid alone without actually raising the temperature. finally, you need to heat enough area to keep the snow and ice liquid distant enough for it to run away and not just freeze again. In locations where one only gets occasional snow and ice and the ambient temperature does not drop much below freezing then electric may be effective. Other locations like small areas, steps which are sheltered for example may be cost effective. Even the hot water systems aren't widely used except under a loading area like for example an ambulance entrance and that usually under a roof and behind a wall. The ambient atmosphere will draw huge amounts of heat off a surface very effectively. If I was Han Solo I'd probably pet my wookie ----- Original Message ----- From: Michael baldwin To: blindhandyman@ <mailto:blindhandyman%40yahoogroups.com> yahoogroups.com Sent: Wednesday, February 24, 2010 9:17 PM Subject: RE: [BlindHandyMan] Radiant floor heating. I installed the SunTouch brand in our last house, and it was great on the feet. It didn't raise our electric bill by any noticeable difference. I installed 45 square feet on a 120 volt system. After the tiles were warmed up, it never really ran that much. I am now installing it here at our new place, under the tile. it is expensive to install. I think it was over $300 for the 30 inch wide by 14 foot long mat. i tried to find the watts per square foot on there site, but was unable to. I know i saw it there before. So, there is my recommendation for a brand if you want to do this. It does look like they have heating mats for the snow. 120 volt mats draw 36 watts per square foot, and 240 volt ones draw 50 watts per square foot. There is a sensor, so they only operate when it is snowing, so unless you get a lot of snow, or are doing a large drive way, the cost would not be all that bad. Michael _____ From: blindhandyman@ <mailto:blindhandyman%40yahoogroups.com> yahoogroups.com [mailto:blindhandyman@ <mailto:blindhandyman%40yahoogroups.com> yahoogroups.com] On Behalf Of Dan Rossi Sent: Wednesday, February 24, 2010 7:03 PM To: blindhandyman@ <mailto:blindhandyman%40yahoogroups.com> yahoogroups.com Subject: [BlindHandyMan] Radiant floor heating. I've been doing a lot of research into heated floors. There are two main kinds of radiant floors, electric or hydronic (water). You can bury pipes in the cement floor, or place them in the joist bays beneath a wood floor, then use hot water flowing through the pipes to heat the floor. You can also use electric mesh mats under a layer of cement or cyramic tile to heat the floor. Depending on where you live, this could be pretty expensive. Heating a floor inside a house is a lot less expensive than heating a driveway or sidewalk. Electrically heating a driveway to melt snow would be for the rich only I would expect. heating the floor in the house would be much more cost effective. -- Blue skies. Dan Rossi Carnegie Mellon University. E-Mail: d...@andrew. <mailto:dr25%40andrew.cmu.edu> cmu.edu Tel: (412) 268-9081 [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
