Radiant Shower Floor

Mike T., Swampeast MO

Shower 3' x 8'

If I install only two 3/8" copper tube runs (18" center, 1/2" from bottom) in traditional mud-base floor (about 3-4" thick) can I expect horrid "striping"? Worse yet, cracking of the base?

Avg supply temp tops at about 130 degrees, 110 typical. Truly constant circulation modified by outdoor reset and stopped only by outside cutoff.

This should give me my desired output. Closer tube spacing would require measures to modify the available supply temp. Really no good place to mount a proportional floor temp valve & controller as it would wind up being the high point in a gravity conversion system with very high volume--think I'd be begging for air lock at the control valve.

Similar (copper in aluminum extrusions 8" on center mounted under wood floor + cement board + tile) works great with minimal striping. Have serious doubts about output with this method in the shower as it has 8' of N & 3' of E exposure with 12 sq.ft. of glass block.

John Ruhnke1

Add r value or run the two pipes closer together

Mike,

Try adding rvalue to the floor, then you can run more tube. Running PEX instead of copper increases the r-value. Rubber increases the r-value much further than pex would. Maybe put the copper inside some rubber tubing for insulation. Some kind of a staple up system, with or without plates can raise the r value. This will allow you to run more loops under the floor, still using the higher water temps and decrease surface temps so not to be uncomfortable to the bear foot. Play around with the design calculators from differant manufactures until you get something with enough r-value that looks right. Also you can play with the delta tee, run a loop in the bathroom first and the shower last. Then restrict the flow to that loop, thus increasing the delta t. This will drop the water temps before getting to the shower.

JR

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Boilerpro

Or try using the minitube method..

Run a loop off the main system from the supply to return with a circuit setter. Run the floor loop p/s off this loop with its own pump. Adjust flow at circuit setter until floor temp is right. Or you could use a manual three way valve to reduce the temp. Since you have outdoor reset, both these could work well....As the main system resets, so does the floor temp only on a shallower curve. Adding insulation also could work well.


Boilerpro

hr

Closer spacing for sure

Go with 3/8 or the Wirsbo Quik Trak tube and 6" on center. 3/8" soft copper forms easily also. Lower the supply temp somehow or that will be one "hot potato" to stand on

This is a tube mat for a concrete counter top project, made from 3/8" hard copper heated and bent.

hot rod

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Mike T., Swampeast MO

SUPER idea there...

...surround the copper with a garden hose!

Raises r-value; allows close spacing; isolates the mud base from the expansion of the copper; avoids further controls (am more concerned with complexity/access than cost).

Any guesses at the r-value of a small garden hose?

Mike T., Swampeast MO

Am shooting for

89 degree surface temp (35 btu/hr) from floor. Temp required by heat loss also seems perfect for comfort on a shower floor.

This is at outside design temp. Since I'm tapped directly into reseted mains, there is some variance in the surface temp (but less than you would imagine--reduced heat requirement to the space = higher surface temp but the reset makes a conundrum whereby supply temp conspires to lower the output with surface temp staying remarkably constant.) Gaak! That's the only way I can explain why my bath floors stay 78 degrees plus/minus about 2 degrees regardless of supply/outside temp.

I can't imagine any below-floor scheme that would give me 35 btu/hr given my relatively low supply temp. The joists run the short (3') way and I couldn't get too much floor contact from the plates. Warmboard or similar directly below the mud base would only increase conduction and I'd be certain to have to further regulate supply temp.

John Ruhnke1

Yes, I like the manual three way mixing valve idea..

I just looked up a picture of a job with a three way manual mixing valve in my radiant precision book. Page 4-7 and figure 4-6. If the bathroom loop is set for 90 degrees at design temp and the main loop is set for 130 degrees design temp by outdoor reset conntrol. With a three way valve, the bathroom can be proportionally reset as the loop tracks up and down its reset line. Thus they both drop in temperature proportionally at the same time as it gets hotter out.

JR

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Boilerpro

More than one way to skin a cat! NM