Boiler Recommendations for Snowmelt & Radiant

CDecker

I have approx 1,591 Sq Ft of driveway with pex installed for snowmelt. I used 5/8" pex on 6-9" centers over 2" of ridged foam board. The slab is 5" thick over the foam (7" thick on the edges - See Photos).

I also have approx 67,400 BTU radiant load for the house (staple-up, basement slab), and the garage (slab) according to detailed heat loss calcs. I estimate that load to be much, much lower on a realistic daily basis, as both structures are currently heated with forced air, and are super tight. The radiant will really only be to warm the floors and take the edge off.

My question... What would you guys recommend for boiler(s) in this situation? I'm not sure a single unit is a good idea, as it would never modulate low enough to efficiently satisfy the house on non-design days when its not snowing... So am I stuck purchasing 2 boilers at this point? I would think the snowmelt boiler would not need to be anything fancy? Does anyone make a reasonably priced mod-con with few bells and whistles that's primary function can be the dumbed down operation of just melting snow?

Any suggestions on how I should handle the house?

Thanks...

hot_rod

Depends on how quickly you want to melt? Probably want 100 BTU/ sq ft or more? How long are the 5/8" loops?
What's in your wallet

This smart fellow has some SIM good tips.

https://www.phcppros.com/articles/1906-the-cold-hard-truth-about-snowmelt-systems-what-they-didn-t-tell-you-in-class

GroundUp

What does your smallest zone consist of and what is the heat loss of it?

CDecker

hot_rod said:

Depends on how quickly you want to melt? Probably want 100 BTU/ sq ft or more? How long are the 5/8" loops?
What's in your wallet

This smart fellow has some SIM good tips.

https://www.phcppros.com/articles/1906-the-cold-hard-truth-about-snowmelt-systems-what-they-didn-t-tell-you-in-class

I was thinking at least 100 BTU/ Sq Ft, even more like 150. The loops are all right around 220'. The shortest / longest are well within +/- 10%.

With regards to the referenced article, I'm familiar with it. I've actually spoke with Dan on the phone as recent as this past spring (he convinced me to use the ridged foam on the driveway this summer).

Any recommendation on Boiler(s)?

GroundUp said:

What does your smallest zone consist of and what is the heat loss of it?

Smallest zone is Staple-Up under the Dining Room, Living Room, Sunroom. 10,481 BTU's

kcopp

IBC SL 26-260
I really think 2 boilers is the way to go...

hot_rod

a condensing boiler would be most efficient, copper tube boilers are still common for snowmelting, properly piped and protected.

Sounds like 250k for the performance you expect. I’d use a dedicated, glycoled boiler

Snowmelt

You could use a swimming pool heater I think. I like my takagi TK 3

Snowmelt

Here is the boiler pic and a result pic. It’s most likely the cheapest way to have snow melt

CBRob

What boiler did you choose?
Did you go with a snow sensor control or something else?

Snowmelt

He does have the sensor from tek mar in the ground, he’s still searching for a boiler.