Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: RSI on September 22, 2017, 11:36:50 PM
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I am starting a new topic since the other is way off the original.
I have a customer that put some tubing in his sidewalk (two 1/2" loops) and wants to use it to melt ice.
I have never set any up before. I would assume you need to use tempered glycol at a lower temp to protect the concrete and not draw too much heat from the OWB. The last reply in the other thread said not to use tempered water. It seems like it would be a huge heat load running full temp water into the concrete.
This is going to be connected to a HeatMaster G100.
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I personally don't have any ice melt applications but I did ask about it when I did my garage (for the outside apron) and the contractor told me you needed to use an antifreeze solution as you mentioned and the water temp should not exceed much over 120 degrees to prevent cement cracking. I don't know how you would do that without tempering it.
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That is what I would assume too. I may have misunderstood the other reply.
I am thinking about using a single manifold for basement floor heat, garage floor and snow melt. The idea was to use actuators on each loop so they can be turned on independently. It would be a much simpler and cleaner install if it would work.
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I am starting a new topic since the other is way off the original.
I have a customer that put some tubing in his sidewalk (two 1/2" loops) and wants to use it to melt ice.
I have never set any up before. I would assume you need to use tempered glycol at a lower temp to protect the concrete and not draw too much heat from the OWB. The last reply in the other thread said not to use tempered water. It seems like it would be a huge heat load running full temp water into the concrete.
This is going to be connected to a HeatMaster G100.
Andifreeze for sure, however you want to keep the slab idled say 40*, and use high GPM and highest temperature possible (of your temper) when ramping up for quick melt. 1/2" tubing isn't the best choice for snow/ice melt as you want to have massive GPM movement though the system with minimal delta T.
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Use 5/8” tubing instead of 1/2”.
I have a separate loop for the sidewalk with glycol. Using a 20 FPHX and a tempering valve. Using a Taco pump controller and when the timer is turned it kicks in both the pump for the secondary loop to the 20FPHX and the pump for the glycol. If a large enough line is used and spaced properly 80 degrees is plenty to keep the sidewalk clear.
The snow melt is an open system and I took a one gallon air tank and welded the extra fittings in then mounted it high on the basement wall so its the same level as the sidewalk.
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We just did a G100 where the customer had some 1/2" loops stubbed out of his carport slab for snow melt. He wants to hook up later. Right now we just did the house with infloor and forced air.
What lengths are max on 1/2 Pex on snow melt to avoid too large of a deltaT? I'm assuming the problem is uneven snow melt.? I'm not concerned about low return water temps to the furnace as it has separate stirring pump on the rest of the unit to keep things a reasonably even temp in the tank.
I can see where larger lines would allow longer loops in a snowmelt system but I would think 1/2" would be OK for small areas?
We run into snow melt pretty rarely down here so I like these threads.
I like mlappin's using a small open tank for expansion. Would basically act just like a furnace water jacket if you pump away from that point.
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Yep, snow melt returns to the tank then a 1” pipe nipple in the bottom to draw off of.
A 1/2” line will give a uneven melt when first started, eventually once the cement warms up a little and the return temp of the glycol starts to rise those uneven spots melt pretty quick after that.
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Makes sense. I just was thinking short loops could minimize that.
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Makes sense. I just was thinking short loops could minimize that.
Mine are 5/8” but took almost 250 ft a run. Still get a few streaks when first turning it on especially with a wet heavy snow. Once it’s running and all of its melted off 60 degrees is almost enough to keep it snow free.
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We just did a G100 where the customer had some 1/2" loops stubbed out of his carport slab for snow melt. He wants to hook up later. Right now we just did the house with infloor and forced air.
What lengths are max on 1/2 Pex on snow melt to avoid too large of a deltaT? I'm assuming the problem is uneven snow melt.? I'm not concerned about low return water temps to the furnace as it has separate stirring pump on the rest of the unit to keep things a reasonably even temp in the tank.
I can see where larger lines would allow longer loops in a snowmelt system but I would think 1/2" would be OK for small areas?
We run into snow melt pretty rarely down here so I like these threads.
I like mlappin's using a small open tank for expansion. Would basically act just like a furnace water jacket if you pump away from that point.
You could ramp up on the flow rate a little more than recommended if you are stuck with 1/2". Could calculate out to 4.5 f/s or so and see what pump you would need for that flow rate, and what head loss you end up with in the loop. If you are short enough you my be ok.
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I don't know what length they were, just getting ideas on how much I can stretch it. My guess is they're between 100-200'.
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And I agree with Schoppy, I’ve seen it more than a few places, 120F is the recommended highest temp to run in concrete.
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The line was already put in by the home owner before I was ever there and it obviously can not be changed.
If the temperature of the glycol should be similar for the sidewalk as the in floor heat, why can't they be on the same manifold? Am I missing something else here?
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No not really, but the sidewalk will produce a HUGE temp drop when first turned on, as long as the floor has priority with the sidewalk secondary no reason they both couldn’t be run as the same sub system.
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I was under the impression snowmelt should run with water under 100℉ to minimize heat loss into the ground, but I imagine warmer would be fine for occasional ice melting. I don't see why you're idea wouldn't work too, RSI.
Didn't mean to derail your thread.
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From my experience with mine, 120 degrees does melt snow faster, especially if you don’t have any sensors to detects snow fall like mine, I just have a electro mechanical timer on the kitchen wall by the back door. Believe it’s a 6 hour timer. If I wake up in the morning to quit a bit of snow I’ll turn the knob an exact number of turns to crank the temp up to around 110-120. If your on the ball and start it as the snow starts to fall 80 is plenty, if its a light fluffy snow 60 will work, ay 60 a wet heavy snow will cool the cement off enough between runs to where it doesn’t melt, in that case 80-100 degrees works better. On something like snow melt going a little overboard on insulation isn’t a horrible ideal.
i run primary/secondary loops in my basement, snow melt is dead last and it will pull very hard on start up especially if it’s been very cold for several days, the glycol will be the temp of the cement when first starting, if its been zero for awhile, the glycol will come in at zero. I also am using a Taco ΔT pump for the house loop as well.
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Good info.
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I did security at recoding artist John Mellencamp's home while it was under construction. He fired a contractor half way through and worried the clown would come and vandalize it.
There was what I now understand to be pex tube along his driveway, and throughout the construction. No OWB, but whatever his heat source, his matching HUMMERS didnt have to slip and slide in the Winter.
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I don't know what length they were, just getting ideas on how much I can stretch it. My guess is they're between 100-200'.
I put 1/2" in my sidewalk at home because I had a bunch of leftover tubing. 6" OC, my runs are about 175ft long (2 loops). I start mine cold, but it only takes about 10 minutes to get the return temps up to 100 degrees and then 3 hours to start melting. I put it on a 12 hour manual timer to spin a B&G NRF22 pump through a 3x8" 20 plate. I set a 100 degree supply temp right off the plate and run a 33% ethylene glycol mix. By Delta T goals, it's performing just fine that way but having done many other systems with 5/8" and a few 3/4", they definitely perform better in terms of speed. My apron at home is set up the same way but with 5/8" at 6" OC, ~250 ft loops on a 5x12" 40 plate. Also 100* setpoint, takes about 1/2 hour to get the return up there but starts melting in a little over an hour.
I have one system at a military development facility here about 4 years old, where I continue to do other work on their 75,000 sq ft building so I can see how it performs. That was 5/8" at 6" OC also, but an 8" slab and 4,000 sq ft in size. NO INSULATION per the engineer's demand, despite hours of arguing. Tubing is suspended in the center of the slab. It's fed by a Lochinvar Mod/Con and I set the temp at 75* to try it out, it's doing very well so far. There is a precip sensor telling it when to run, and I've never seen snow sit on it for more than an hour. Pair of Grundfos 26-150 pumps shove 33% ethylene through the loops. It moves heat very fast, but it runs almost constantly in the winter. A single snowflake will trigger the precip sensor. I'd hate to see the gas bill on that bugger.
That said, I'd never run an atmospheric system on anything that goes in a slab. Everything is always closed loop. Call me crazy, but I refuse to send a bunch of oxygenated fluid into an inaccessible space to gum up and destroy the system's efficiency over time. You know that black slimy shat that's in your strainers when you blow em down? Yeah, that same shat settles to the bottom of the slab tubing. I've torn apart many a slab that were full of that garbage because someone either didn't know any better or was too cheap to buy $200 worth of HX and expansion tank. It's cheap insurance my friends, please stop doing this