Snowmelt in Summer

PhillipJones · July 27

We are doing a large snowmelt system this fall that will be about 20,000 SF with 3/4" tubing on 6" spacing, and (6) 399,000 btu boilers. The homeowner is also interested in harvesting heat out of the driveway in the summer for pool heating and domestic pre-heating. Any control strategies are welcome. There will be (5) remote manifolds fed by 2" dual-insulated pex, each with a Grundfos UPS 32-160 circulator. I'm thinking a pair of closely spaced tees somewhere on the system side to add a summer heating zone that would not affect the boiler side. The circulators will be on high in the winter, but could be switched to low for summer. A flat-plate HX would be needed, but don't want it sitting on the main system due to flow restriction.

hot_rod · July 27

if you size the HX correctly it should not add but a few ft head

You could add a couple manual valves and tees into the SIM supply return lines, direct to the hx, piped just before it goes into the boilers

PhillipJones · July 27

20260727_112704.pdf

Ok. I've sketched where I might add a HX for summer auxiliary usage. The system will use a Tekmar 671 for control in the winter. I was planning to power the 5 system pumps through 5 of the 6 boilers, to balance the electrical load. However, if we opt to use the system in summer, should I think about a separate switching relay that could turn on just 1 or more circulators in summer? I doubt we'd need them all for summer auxiliary.

hot_rod · July 27

where is this located? How large of a pool?

In sunny warm climates pools can too warm in the summer.

The driveway is basically a large un-insulated collector, efficiency can be quite high, but when ambient is near pool temperature.

So how many days is the driveway surface warmer than the pool? And the pool actually needing heat? Will it be worth the $$ to try and capture this "free" energy.

A handful of pool specific solar collectors may be a lot less $$, if you have a place to mount them. Typically the pool pump circulates through pool collectors. So no HX additional piping, controls. Or tying into those 4" lines near the sep!

More ideas here.

https://www.pmmag.com/articles/94473-pavement-to-pool

Screenshot 2026-07-27 at 10.24.59 AM.png

PhillipJones · July 27

Good point, HR- I may just try to steer this back to basics. Adding a bunch of tech to save a few bucks is not always worth the squeeze. The project is in Ohio, and I doubt the pool or domestic heat load would be sufficient to merit the additional cost. Just because you can does not always mean you should. Thanks!

hot_rod · July 27

I’d guess if they have the $$ to run six boilers to melt snow, they could afford a pool heater or HX 😉

Kaos · July 28

This makes sense is if you can use the snow melt boilers for heating the pool. In that case you already have the HX, so you are only adding in the controls to use the driveway heat when warm. The article @hot_rod linked to has good points on how to set it up and control it.

The one challenge with this setup is you need to protect the HX in the winter time from freezing.

HydronicMike · July 28

@Mark Eatherton was a big proponent of this. I wonder if he ever figured it out.

hot_rod · July 28

https://forum.heatinghelp.com/discussion/comment/1901031#Comment_1901031

you don’t see or hear of many, maybe the numbers don’t work so well.

The fittings, hx and parts to tie into the 4” piping may be more than what it contributes to the load ?

GroundUp · July 30

We did this in a rehab facility once upon a time, but without the snowmelt part. Tubing was cast in a concrete pad under the parking lot and then overlaid with asphalt so it technically could have melted snow, but was not intended for it. We had cascaded Lochinvar FTXL boilers for space heating and then dual indirects for DHW along with a large tube and shell HX for the pool. The fluid in the parking lot was constantly circulated when the outdoor temp was above a certain temp (I think 75*?) and then diverted through an injection setup to preheat the return loop to the boilers via a sensor on the parking lot return piping. I was never there after install, but was told by a coworker that it worked surprisingly well with 130+ degree temps coming in from the lot on a perfect day. Probably not very cost effective considering those days are minimal in Minnesota, but it was a cool project to be a part of.

PhillipJones · July 30

I agree, @Kaos. Since the pool heater is already in place, and domestic hot is already designed, it seems a little late to pull all this into the snowmelt scope as an afterthought. I have the feeling, also, that independent systems will be best in this case anyway. Thanks everyone for the feedback, and the article from Siggy.

artcom3 · August 10

This is the type of system that requires one of two things. An experimental attitude ( and wallet) or TRANSYS. I can’t remember if i ever modeled heating by driveway, but we talked about it a lot.

depth of pipe
albedo of driveway
Sunshine profile (orientation and weather)
DHW and Pool profiles.
Rejecting space cooling heat to pool
Volume of water
Heat loss rate (weather, surface evaporation and heat loss, ground contact)
Hydronic heat pump using the driveway preheat or direct to HX
Etc and good luck. I’d run it, but i dont currently have a system up and running.

Snowmelt in Summer

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