Electric cable snowmelt feasability?

Kevin O. Pulver

I've done several hydronic snowmelt systems, but was considering doing an electric cable system and wanted you guys to kick the idea around before I do it. No oversizing house boiler to handle the occasional load, no glycol, circs, extra controls, extra expansion tank, heat exchanger, etc..
Looks like you could pay a bit extra for cable and and still come out OK. I suppose it doesn't have the "Power" of hydronics does it? What do you think? Thanks in advance, Kevin

hr

Delta-Therm

has designed and supplied some rather large electric snowmelt, that I have seen.

Do a design to get a handle on the btu/ft you wish to provide, then check the available power.

hot rod

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[Deleted User]

yeah but....

and theres a butt in every crowd...ain't there!!

The initial installation costs are substantially less, but the cost of operation per hour per therm can be a deal killer. Typically 2 times the cost of gas around here in Denver.

And if your customer happens to be so unlucky as to be on a KW Demand Billing program, it can be a budget buster.

Remember the scene from Chevy Chases Christmas when he finally gets his Christmas lights turned on, and the whole city goes dark... Yeah, you remember:-)

I got badly shocked once by one of those systems. I walked up to a man door in a parking garage in a ski resort town in the mountains and when I grabbed the dorr knob I got knocked on my keester. Talk about liability...

Then theres the reliability issue. If you're using a series type of heating element, if and when it goes out, that circuit is dead. I know they have newer parallel circuitry available, but it still has single pole leads going to it.

I dunno...

Proceed with caution.

ME

Perry_2

In theory....

this may be a good option.

Is it?

I am not familiar with what is currently out there; but as a homeowner and an Engineer I have often thought about that option - how to do it so it works - and last.

The plant I work in spent several $ million installing a huge heat trace system on piping and other things that could freeze 5 - 7 years ago in the winter. Essentially, the same concept.

The questions I think you should ask are:

1) How often are they going to need it (how often does it snow or ice). I live in Wisconsin, yet I'd guess that arround here it would only be needed 15 - 20 days a year. The sun and weather keeps sidewalks and roads clear the rest of the time. In that case; a person can handle the cost of power to run it and would benifit greatly from the reduced cost. However; if you are in a place where it typically snows every other day....

2) How long will it last.... Really? (same question for hydronic). A properely done concrete slab can be in great condition in 50 to 75 years (of course, a poorly done one wont last 10 years). What about the life of the warming system.

My conclusions are that I would probably go electric in my case; and I'd probably insert into the concrete conduit sections - that I could replace cables in. And then have wiring boxes next to the slab at appropriate places. Each heating coil would be wired separatly so that if one failed the other would not. Each coil would be properely grounded and protected from shorting. I would use items that are commonly sold on the commercial market where durabiltiy is required.

Perhaps not the cheapest system; but it would be repairable as long as the slab lasted.

Perry

Kevin O. Pulver

Thanks guys

The house is maybe a litte over-zoned, I want to use a Knight with buffer for inside, but hate to WAY oversize for occasional snowmelt duty and it appears like this could be OK. I'll watch for parallel vs series circuitry etc... Kevin

LarryC

Perry

Perry,

"I'd probably insert into the concrete conduit sections - that I could replace cables in." If you put the cables in conduit, what kind of thermal contact would you have with the concrete?

I agree that having junction boxes for accesable wiring connections is good design practice, along with temperature sensors, etc.

Larry

Rob_34

Heating Cable Snowmelt

Kevin,

I sell Nexans Cable for snowmelt. It is the oldest manufactured heating cable in the world. Very durable and easily operated. Check out www.orbitmfg.com to see the cables. Don't forget who gave you this lead. I can ship direct to anywhere in the US.

Thanks,

Rob

Kevin O. Pulver

Thanks Rob, I've been talking to Denise S. about Nexans/Orbit for several years about this stuff, and may finally have one that will go through. Kevin

Perry_2

Actaully quite good

if you do it right.

First; you could use a thermal conductive compound, and seal the end of the conduts with some form of connector. Much like "post stressed" concrete tensioned cables are in a greased conduit or tube. Yes the grease leaks a little over the years.

However, I suspect that you could set it up so that the warming element accounts for air tranmission of heat in the tube. Perhaps even depends on radiant more than convection.

Perhaps I'll dig out my heat transfer book sometime and model this.

Perry

[Deleted User]

Grey Schmutz...

THats what a friend of mine used to call the heat conductive compound. You can't wash it off, it has to wear off... Molybenum based I do believe, or is it???

In any case, it WON'T wash off:-(

ME

ALH_4

Fuel Choice

I hate to sound like an environmentalist tree hugger or something, but using electricity for snowmelt seems analogous to using platinum for building bulldozers. Electricity is high quality energy that cannot be easily stored, in addition to being quite inefficient overall. I can see using electricity for small loads, such as a bathroom, where there is no other source readily available, but snowmelt is such a big load in relative terms. It's also a fairly unnecessary load when used simply to avoid shoveling. If one needs to melt snow, it seems that another energy source might be more appropriate. At lease use an electric boiler with a hydronic snowmelt system so it can be retrofitted with something else later. jmho

-Andrew

Kevin O. Pulver

Andrew

I like SOLAR snowmelt, but unfortunately though it IS dependable it's not usually very quick. I thought electric might be a good option since it IS only occasional use. We'll see how the numbers look. Kevin