Turning snow melt on

LancePL

Homeowner who just had snow melt installed. Could not afford snow melt controls right now to automatically enable the system. Is it best (least expensive) to turn it on hours prior to the snow hitting or waiting till the first flake and turning it on? In the second scenario obviously it may take more energy if the driveway gets a couple inches of snow before it melts??

JimGPE_3

The question is larger than that....

The real question is whether the designer designed this as an idling system or an instant-on system. An idling system maintains a minimum slab temperature at all times, snow or no snow. Then at the first snowflake, it kicks in to get the slab above freezing.

An instant-on system is sized to haul the slab from ambient to above freezing at or about the moment of snow fall. You can see this would be a much larger capacity system.

Which one is more economical depends upon how often it snows.

But in any case, he will need to operate it as it was designed, not as he wishes.

LancePL

System is not at idle. The boiler is designed to handle the load from a cold start and it will melt the driveway. Which it does. The question is, would it be less expensive to turn it on two hours prior to snowfall or as the first snowflake appears. The second option may allow for a couple inches of snow before the driveway gets tempered. Does it take more energy to then melt this snow??

JimGPE_3

Sorry -

You understood the issue much better than I gave you credit for!

I think the chances of melting 2" of accumulated snow are remote, so that would not be the answer.

If you start it at the first sign of snow, I suspect you are going to get some accumulation before the slab is hot enough to melt snow, so that probably is not the answer.

The optimum solution would be to turn it on so that the slab hits 33F just as the snow really gets going, so that you melt it as it falls. No wasted heat to atmosphere awatiting the flakes, no accumulation of snow.

But if you can predict ahead of time when the snow will acutally hit you have a big career opportunity waiting for you in weather forcasting.

I suspect you go with the 2hrs ahead ploy.

As far as how much heat it takes to melt the snow, snow is snow. It will take the same amount of Btu's to melt a given mass of snow no matter the timeframe. The waste (non-snow-melting) heat will be lost to atmosphere from the hot slab when there is no snow to melt. Minimizing that time will be the key to energy efficieny. Also, optimizing the temperature of the slab will save energy - make it just hot enough to melt the snow and no hotter.

Troy_3

snowmelt and energy

From a simple energy used standpoint it would be less if you waited till the snow was covering the slab. The snow will act as an insulation blanket and prevent some of the convection from wind stripping away the heat. I believe that the energy used would be less but maybe less convenient. Hopefully the drive is pitched to allow the water to run off. We want to turn the snow to water but not have to turn it to a vapor.

hr

What about

adding a pole mounted snow sensor. Fairly inexpensive, easy to retro fit. Not quite as nice as a slab sensor, but much better than nothing at all. It measures outdoor temperature and snow or ice fall. I use the ETI brand.

I also add a 12 hour spring wound timer to all my systems. If a storm is forecast the homeowner can start ramping up before it hits. Make sure to get one without the "hold" feature

hot rod

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Mark Eatherton1

Cheap and simple tripple whammy....

THe ETI snow sensor, a 12 hour twist timer, and a sensor buried in the slab to limit the slab temperature to a reasonable temp to melt the snow. Not as effective as a tekmar 600 series control, but also not nearly as expensive. If they're not home, the ETI picks up the call and handles the load. If they ARE home, and they know theres a bad storm a berewin'. give the twist timer a kick in the pants. Snowmelt works better proactively than it does reactively for sure.

BTW< make sure you have easy access to the ETI sensor. It needs regular cleaning and maintenance. I know of one that is mounted in the middle of a terrcotta tiled roof, and it ain't NEVER going to see the required maintenance....

Live n learn.

ME

LancePL

Thanks for the replies...exactly the info I was looking for. Poor man's Tekmar!