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Author Topic: Plate size for in floor heat  (Read 10290 times)

RSI

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Re: Plate size for in floor heat
« Reply #30 on: December 29, 2017, 03:57:38 PM »

I just skimmed through all the replies so may have missed something.
What I would do is turn off the floor heat and turn up heat in house and wait a few minutes for water temp in return line to stabilize. Then open the valve in the main line and see if there is a large increase in the return line temperature.

If there is, then the plate is way too restrictive. You may be able to get it to work better by partially closing the valve as mentioned above but you probably won't get enough BTUs for the floor and even partially closed will still be slowing down the flow.

If it would be a big pain to re-plumb for a 5x12 heat exchanger then I would just get a 3x7 50 plate or larger.
How many pex elbows are in the line? I would remove the ones shown in the picture and just use plastic bend supports instead on a new single piece of pex.

Another option that may be required is to put a pump between the 1st tee and the plate heat exchanger and run at the same time as the floor pump. If you do that, you can probably leave the rest of it the way it is.
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E Yoder

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Re: Plate size for in floor heat
« Reply #31 on: December 29, 2017, 04:03:57 PM »

I just skimmed through all the replies so may have missed something.
What I would do is turn off the floor heat and turn up heat in house and wait a few minutes for water temp in return line to stabilize. Then open the valve in the main line and see if there is a large increase in the return line temperature.

If there is, then the plate is way too restrictive. You may be able to get it to work better by partially closing the valve as mentioned above but you probably won't get enough BTUs for the floor and even partially closed will still be slowing down the flow.

If it would be a big pain to re-plumb for a 5x12 heat exchanger then I would just get a 3x7 50 plate or larger.
How many pex elbows are in the line? I would remove the ones shown in the picture and just use plastic bend supports instead on a new single piece of pex.

Another option that may be required is to put a pump between the 1st tee and the plate heat exchanger and run at the same time as the floor pump. If you do that, you can probably leave the rest of it the way it is.

Good advice. Throttling the valve is a limp mode option. I mentioned that as somewhere in this thread he mentioned having very very low return water temps when the house heat was running. The flow was too low to have anything left to do the floor heat.

-edit- I think the 105 degree temps mentioned was after the mixing valve. So I could my advise about low return water temps may not be accurate.
« Last Edit: December 30, 2017, 09:55:44 AM by E Yoder »
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justinb

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Re: Plate size for in floor heat
« Reply #32 on: January 04, 2018, 07:11:10 PM »

A quick update.
  I definitely need to dig down around the foundation this spring and put in foam boards.  The ground around the garage is soft and not frozen.
I increased the garage pump to speed 3 and opened the manifold valves wide open.  The garage is maintaining heat now and will respond reasonably well to increases from the thermostat.  The return temp on the manifold is now around 70 instead of 50-60 like it was before.

Tough to gauge wood consumption this week as its so stinking cold, but Im going through a lot.
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wreckit87

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Re: Plate size for in floor heat
« Reply #33 on: January 04, 2018, 07:22:38 PM »

A quick update.
  I definitely need to dig down around the foundation this spring and put in foam boards.  The ground around the garage is soft and not frozen.
I increased the garage pump to speed 3 and opened the manifold valves wide open.  The garage is maintaining heat now and will respond reasonably well to increases from the thermostat.  The return temp on the manifold is now around 70 instead of 50-60 like it was before.

Tough to gauge wood consumption this week as its so stinking cold, but Im going through a lot.

Thanks for the update, glad it's working better. One wouldn't believe how much difference that perimeter insulation makes! If you can, when it's time to do so, I like to run the foam up past the bottom plate of the wall (higher) to make a thermal break all the way into the insulated wall. It's tough to make it look decent though. A 4 foot horizontal sheet outside of that vertical sheet is beneficial also, to keep any cold from creeping down under the vertical sheet, which I forgot to mention you want deeper than the foam under the slab. Say your underslab foam is 6" under grade, you want to go at least 8" with the vertical to overlap that lip
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