hot water shop floor heat

mokomon

I have a shop floor heat system. Wondering if my installation is ok . It is 4 runs of pex connected to single manifolds. The out water temperature is only about 80Degree Farhenhite to maintain room temperature at 58 degrees. Any changes I should do ?

IMG_7316.jpg

EdTheHeaterMan

Changes are necessary when there is a problem. Can you describe the problem(s) you are experiencing?

Tom_at_NBS

Honestly, sounds like it's running great. 80° water might sound low if you're used to baseboard or radiators, but for a radiant shop slab maintaining 58°, that's pretty much spot on.

Since the slab has so much thermal mass, you only need the floor a few degrees warmer than the room air to hold temperature. Plus running water that cool keeps your fuel costs way down, especially if you're running a condensing boiler or heat pump where low return temps keep it in peak efficiency.

A few quick things worth checking just to be sure:

Check the temp difference between your supply and return manifolds. You want to see around a 10° to 15° drop across the loops. If return water is coming back way colder than that, your pump flow might be a bit slow.

Also make sure your PEX loops aren't over 300' each for 1/2" line, or friction starts killing your flow rate.

Lastly, what kind of heat source are you using? If it's a standard non-condensing cast iron boiler, make sure you have mixing/protection installed. Returning water that cool directly back to a cast iron block will cause flue gas condensation and rust it out over time.

If the shop stays comfortable at 58° on cold days and your loop lengths are balanced, I wouldn't mess with it much. Sounds like a solid setup.

Tom Gabison
National Boiler Supply — commercial boiler & hydronic parts
nationalboilersupply.com

EdTheHeaterMan

The picture looks like a wall hung electric boiler @Tom_at_NBS but I could be wrong.

hot_rod

how many square feet is the shop?

Tom_at_NBS

Ah, I completely missed the picture on my end earlier! Good eye, you're dead on.

That's an Argo wall-hung electric boiler. No gas lines or exhaust venting to worry about, just that heavy electrical whip on the bottom left. That yellow sticker on the front boasting '100% Efficiency' is the dead giveaway for electric resistance. It's doing exactly what it's supposed to—just quietly feeding that 4-loop radiant manifold with the help of that little Grundfos circulator.

Tom Gabison
National Boiler Supply — commercial boiler & hydronic parts
https://www.nationalboilersupply.com]nationalboilersupply.com

EdTheHeaterMan

Still waiting on @mokomon to explain the problems they are encountering!

If there are no problems, and you are just asking what you should do about your existing set up… My advise is very clear.

"If it ain't broke, don't fix it"

mokomon

Thanks for the replys . I wasnt sure if the low output temperature was a problem for the boiler tank as far as rust . I am assuming that it is a closed system that corrosion shouldnt be an issue. Just a note … the shop is 1000 sq ft, 4 -250' runs of pex making it single zone. 18 deg differential between in and out temps.

hot_rod

no problem with low supply temperature.

With 80 SWT, 62 return , assumed flow of 2 gpm, (1/2 gpm per loop) you are delivering 18,000 btu/ hr to the space.

The differential is just an indicator of the heat being delivered at that point in time. It may be wider on cold start and could tighten to 10 or less as the thermostat satisfies. Residential radiant designs around a 10-15 delta, for example.

Is 58 warm enough for working in the shop?

Was 58 on a cold day, or design day?

mokomon

mokomon

58 is warm enough when i am working in the shop in the winter. Winters here only hit about 34 F, some times 28F