Ice melt system question

[[email protected]]

Hey everyone, I have a specific question regarding how to make an ice/snow melt system durable. I'm confident with my design (3/4" pex, loop design, etc), however my architect, builder and even local heating guys are all telling me they see these things failing at around the 5 year point. It seems that it is both the hard joints and the control joints, and sometimes even within the middle of a section (though that's the least common).

I'm in the Chicago area. We get good & serious cold snaps and dramatic swings, but nothing as extreme as many of you I've read on this forum. They're claiming it's just the heaving & movement of the concrete in combination with the pex being at it's most brittle/vulnerable when cold (I don't plan on leaving it idling all winter; I'll manually watch the weather and turn it on when needed).

I see plenty of people here planning ice/snow melt systems and I'm not reading about rampant failures. So what's the secret (or what are the people I'm working screwing up) to keeping the pex from breaking?

TIA for any replies.

 

[Bondo]

Ayuh,.... The pex has to be sleeved in plastic conduit pieces at all the joints,....

I'd think maintaining yer antifreeze at 35° is the trick to long term survival,...

Is there gonna be a thermal break, under the slab,..??

 

[[email protected]]

I'm pretty sure the glycol mix wasn't the issue. I was told that all the [failed] systmes had what I was planning, and that is dipping down below the slab & insulation (think of a plumbing p-trap) to have some move-able slack where the control joints are.

Thermal break under the slab? Unless you mean the 1" thick r-15 insulating foam I would put into place, I don't know what you mean. When I read 'thermal break' in concrete, I think of a strip of insulation between what will be warm (e.g. foundation or house slab) and what will be cold (driveway, patio, etc.).

I hadn't planned on a thermal break between the garage floor (will have radiant in flooring) and the drive melt system. I plan on running the pex for the drive melt UNDER the foam insulation for the garage so that when the snow melt system is on I'm not dragging cold return liquid through my otherwise nicely heated & balanced garage floor. This could be wrong, but it seems to be the consensus from what I've been reading.

 

[Randy in Maine]

I think I would likely run a new zone for just the driveway heater. With 2" of foam under the driveway to give me the thermal break I want.

 

[yeldogt]

Lots of sideways in NYC have them -- I was looking at one and they had the pex running inside another pipe.

It needs a huge boiler

 

[[email protected]]

Randy, the driveway is certainly going to have it's own zone(s) (it'll be multiple loops and separate from the garage system). After all, I'm going to run the garage continuously at one temp and the driveway will be on/off at another. And definitely yes there will be foam (1 or 2") underneath). The R value of the foam will determine the thermal break, though it's really mostly important that I've got enough there (probably R-15) so that I'm heating the slab and not the earth. None of this addresses my question of why 'my guys' keep experiencing a broken line around the 5 year mark.

Yeldogt - the pex inside something else (like pvc? or preferably more conductive) is going to be a PITA to install, and really hamper the heat transfer from the pex to the slab. Heat calcs have been done before. It's not that bad (BTU load for snow melt) since the slab just has to be kept at just above freezing, unlike trying to heat a space to a comfortable temp. I'm not worried about that. I'm just trying to ensure the lines don't break.

Thanks for all the replies though. Keep 'em coming.

 

[little jimmy]

Steve, we have ice melt in our drive ways to the ER entrance and in our helipad at work. I cant tell you why but when they installed them they used a heat exchanger and made it a closed loop on its own. We also were told to not run the temp out to the zones above 110 degrees. It has been working great for going on 8 years with only a sensor needing to be replaced. We watch the weather and only heat when we need to also. We are in South Dakota so we have some really cold weather also. Its great to not scoop all that snow so I really like ours.

 

[6768rogues]

I have seen several systems used commercially in western NY. I am not aware of failures.