Small Radiant Heat Floor Tankless Electric Hot Water - Help
Comments
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This room is going to need cooling in summer, the minisplit or something similar is needed anyway. I'd say heated floor for comfort and let the minisplit do the rest of the work.
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OK, if that's what you want you don't need complicated controls at all. Just an outdoor thermostat to turn the circulator on at whatever outdoor temperature you decide is right. Then set the thermostat on the water heater to give a floor temperature that feels good to you.
If the turnon temperature for the heated floor is below its break-even point, you don't need any control other than on-off, it's not going to overheat the room.* When it's on it just runs continuously. Then let the thermostat on the minisplit fine-tune the room temperature.
*(The exception would be if the room has enough solar gain to overheat. And it looks like it might. In that case you could run into a situation where the room is hot but the floor is on because the outdoor temperature is low. If that happens, a second indoor thermostat could turn off the floor if the room gets too hot. In any case, these are simple controls.)
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Im a hydronics guy first and foremost. Air is about the worse way to transfer heat energy.
Radiant heat is comfortable and quiet. It heats the objects in the room not the air.Blowing hot air that stratifies in the room doesn’t come close to keeping the occupants, and their feet warm and comfortable, as a radiant panel plus the noise of the fan.
But the OP already knows all this.
Use the mini split for the cooling season
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Hi, Again from left field… is there any way to significantly improve the insulation under the floor? 🤔
Yours, Larry
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Yeah, my experience is that rooms that are well insulated and well-sealed don't generally have cold floors, even if they aren't above heated space. Stratification is much less pronounced as well. If you have air leakage the cold air sinks which is what makes the floor cold.
An ounce of insulation is worth a pound of hydronics.
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I'm a pretty big wet-head but @ag27 is doing what I consider to be optimal for comfort: heat the floor so that it's comfortable on a typical winter day, not the design day. Install some sort of air handler sized to provide cooling in the summer but use it to supplement the floor in the winter.
To me the hydronic way would be to have an air-to-water heat pump and a hydronic air handler that provides both heating and cooling. Have the heat pump heat the floor too.
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it’s such a small space to throw that much technology and $$ at.
I think adding some additional heat emitters to the radiant, like the Jagas or similar would keep it 100% hydronic. He is 2/3 the way there with his hydronic start, the floor system.
Those recessed radiators in front of the fixed glass of those doors would be and easy install from below. Put some heat energy where the loss is, across the glass.
If they want simple, and low cost add some electric, oil filled, plug in radiators😒
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Eh, @hot_rod a space this small screams for electric resistance. Hydronics add nothing but cost and complexity here.
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He already has hydronic under floor system. Just not enough radiant panel area for the load. Carpet is hitting him also.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
How thick is the padding immediately under the carpet?
With the carpet (padding too?) and plywood it seems your not getting the heat transfer. If it was my space, I would increase the supply temp 120 -125 or so, using the small electric water tank as astutely suggested.
Let us know what you do and if it works.
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I think OP mentioned adding concrete(1") on top of the deck,
abandon the under floor, and then pipe new tube on top of the plywood, then mud it in at 1 inch, they make self leveling soup just for this, then tile that, or manued/fake wood,
no carpet
known to beat dead horses0 -
I don't see any reason to do this unless you've tried increasing the water temperature as hot as it can go and it's still not enough.
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if the floor square footage cannot cover the load of the space, it really doesn’t matter what method you use to install the tube?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
more closer tubes, and a hot/warm slab w/tile,
I didn't, don't do the math
known to beat dead horses0 -
keeping at or below 82f surface temperature is where you hit the wall. In a 70f ambient room that is around 24 btu/ sq ft
The only option is to deal with a colder ambient temperature. At 65 ambient, you can move 30 btu/ sq ft. That may be fine in a working shop, probably not in that nice sunroom
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Yep. OP had said calculated load was 3.5 kW which is 12,000 BTU/hr. Room is 144 square feet. That's 82 BTU/hr per square foot. There's just no way to get that with a heated floor.
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