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Old 12-10-2012, 11:11 PM   #1 (permalink)
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"Pulse and Glide" heating my shop

Haven't been on the forums in a long time! But I had a question and wanted to ask the most intelligent people I know on this subject.

My scenario: I rent a garage, and I've got some plumbing pipes (some pvc, some copper) that can freeze in the shop. The shop is terribly drafty, and it doesn't keep out much cold, so when it's 32 out, it'll be 32 inside within an hour.

The overhead pipes are covered in an "electric blanket" covering that, when plugged in, keeps the pipes warm. These pipes run down to the bathroom, which is closed off and keeps heat very well inside (more so than the rest of the drafty shop). These pipes are uncovered, but again, are "insulated" by the bathroom. It'll usually be 5-10 degrees warmer in the bathroom than the rest of the shop.


The problem
: I turn the heat on at night on a timer, to keep them warm, set for about an hour after the temps go down from 32 until the morning an hour before it goes up past 32. My electric bills tend to go up around $60 a month during the three months of winter JUST to keep those pipes from freezing. I'd like to better insulate them or replace them with better material, but again I rent this shop, and it's on me to heat them.


My question:
Can I pulse and glide the heaters? I can set the timer for the heat to be on for an hour, or 30 minutes, then stop, then come back on, then stop, etc. Would this keep the water from freezing?

I know a lot of this has to do with mathematics, such as how much water is in the pipes, if it's moving (a slow drip, etc), what type of material the pipes are, how thick it is, time that the temp is below 32, etc. But if I heated them for 30 min, stopped the heater, 30 more min, stopped, would it keep them from freezing? And would it significantly cut the electric bill?

Thank you all.

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Old 12-11-2012, 02:29 AM   #2 (permalink)
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Well I dont know if you'd want to do this but if you found the outside shutoff and drained the system when you're not using it you dont need a heater, just blow air through the system for a minute to flush out the water, alternately extreme case you could jerry jug water from home to use for the john , etc , then follow it with the RV antifreeze for a rinse, tc, extreme sounding but should work, good luck , would be way to go if it gets really cold
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Old 12-13-2012, 02:39 AM   #3 (permalink)
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^That would certainly be the best option and the route I'd want to take, but the garage I rent is part of a larger facility in which the owner pays for water for all the renters, and I asked a few neighbor renters and they weren't keen on the idea of not having water in their shops. Otherwise I would have certainly brought out the jugs of water than the extra for a few pipes.
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Old 12-13-2012, 05:56 AM   #4 (permalink)
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well here's an idea that might work , if you ran the water slowly into a sink and had a temp switch you could set , when ever the temp got a bit low it could trigger the pipe heater to come on for a while . good luck
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Old 12-13-2012, 08:00 AM   #5 (permalink)
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You can pickup a cheap programmable thermostat to keep it just above freezing in there. It'll probably pay for itself in a month or two, and you can take it with you if you stop renting the place.
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Old 12-26-2012, 02:12 PM   #6 (permalink)
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I think you're onto something with the on/off timer...

however, Daox's idea is probably the most efficient due to the randomness of the weather. There is no need in freezing the pipes because you set the timer off for too long and there is no need to heat the drafty garage by leaving the timer on for too long.

I think the problem will come from not having a remotely operated thermostat for the wall outlet. You'll have to build your own, or do a deeper google search than I did

It sounds simple enough though. Set a thermostat to a relay to allow power through the outlet.
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Old 12-26-2012, 02:18 PM   #7 (permalink)
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you would be better off insulating and sealing up the shop with those $60/month electricity payments. More comfortable environment too without drafts and would heat up quicker when you need it.
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Old 12-27-2012, 12:44 PM   #8 (permalink)
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Set the heater as low as possible without freezing the pipes.
A Minimum-Maximum thermometer to see how low / high temps get would likely help.

Do something about the draft - that's what's costing you most as it takes the heat out and brings the cold in.

As you have a constant loss, "pulsing and gliding" the heating will help.
Constant heating will simply mean a constant, higher loss.
The smaller the difference between temperatures inside and out, the lesser the heat loss will be.

I'd either insulate the place better, or look for a better place to start with.
You could talk to the owner about insulation, as it also improves his property value.

Quote:
These pipes are uncovered, but again, are "insulated" by the bathroom.
A bathroom isn't a very good insulator

Covering the pipes and heating through a radiator is more efficient than taking away heat from pipes that run through a room..


Quote:
Can I pulse and glide the heaters?
At work, we've just installed P&G electric heating in a natural gas line (expanding gas cooled down, froze the tiny amount of water in it, and locked up control valves)
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Old 12-27-2012, 01:01 PM   #9 (permalink)
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This threshold is based upon research conducted by the Building Research Council at the University of Illinois. Field tests of residential water systems subjected to winter temperatures demonstrated that, for un-insulated pipes installed in an unconditioned attic, the onset of freezing occurred when the outside temperature fell to 20F or below.

Pipes exposed to cold air (especially flowing air, as on a windy day) because of cracks in an outside wall or lack of insulation are vulnerable to freezing at temperatures above the threshold.

weather.com - Severe Weather Readiness

So any visible pipes should be wrapped w/ newspaper and taped up to prevent transfer of heat. Set a trickle at 25F to be safe. Trickle is not a steady stream. Trickle is like right before it makes a small stream like 4-5 drips per second. A trickly will most likely be cheap than electrically heating the shop.
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Old 01-11-2013, 05:47 PM   #10 (permalink)
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Coming from the north, we never bothered with heating hoses or pipes we had outside in the winter. We either drained them, or cracked them open so they would flow water. The incoming water was ~50F even in the winter, so it would keep the pipes warm enough to not freeze through.

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