Driveway snow melt loop from same boiler as interior radiant

[J-Altus]

Curious if I can plan for a driveway loop off the same boiler that is used for the entire house hydronic system? The driveway loop will be about 600 sq/ft in total. Or is it best practice to run a separate boiler for this?

[Dutchman]

I'd ask your mechanical guy (or contact the boiler manufacturer) but I can't think of a major reason to not use the same boiler.

It's a separate zone, you're burning fuel to make hot water, why have a totally separate mechanical $ystem?

[johnny watt]

It doesn't sound like a good idea to me. Maybe for a small sidewalk or porch, But unless your house has a huge heat load, it sounds like to much load swing to add a driveway.
So if your house is an 90kBTU heating load on the coldest day of the year, and any given day the boiler may or may not be called on to also step up for a 180k BTU driveway load, it seems like it would be oversized and poor design to require the system to modulate down to only heat the house on a moderate heating day. I don't know about return loop water temperatures, but seems like that might be an issue too.
I don't know if its typical in other places but most house heating system in my area do not use antifreeze in the boilers and if they had to in order to add an outdoor loop, it would increase work load for circulation

I would suggest you ask several people who have a lot of experience in driveway heating.

[Dutchman]

Again, a good mechanical guy can figure this out. The driveway temp does not have to be the same as what is being produced for heat in the building. Hopefully the first time poster sticks around and reports back with some real answers.

[Mark Parlee]

Just spoke with my expert who has designed these systems. He is the same one I use in my cases that have HVAC mishaps and we are called in to investigate. He Says " use a separate system for external".

[Ted S.]

I would agree, separate. Size the main boiler for the house for optimal operation of that house load. That would not mean accommodating the infrequent additional large load of the driveway melt system.

[dgbldr]

How are you building that driveway to make absolutely certain it doesn't heave and break the pipes?

[Mark Parlee]

dg, That is even a better case for a completely separate system. When I spoke with the contractor I know that does these systems albeit few that is one of the points he made.