DIY Hydronic Floor Heating

[Ormston]

Originally Posted by buffalobillpatrick

To push 1gpm through 800' takes 3.2X energy vs. 1gpm through 250'
Read: Modern Hydronic Heating by John Siegenthaler, P.E.

I don't doubt it takes more power to pump around 800'

With 800' I only need to pump 1/2 GPM and very low flow temps to provide enough output.
Guess it depends on how leaky the house and how fast you want it to respond.

Steve

[Drake]

1.5" thermal rates very near are 10, and it will be installed under cast in place first floor above a full insulated basement(no ground contact). I can always add more if needed.

Does an older edition of Modern Hydronics offer enough basic info to understand a simpler control panel construct or might newer components, HE pumps, outdoor reset mixer only be discussed in new edition(quite pricey)?

[buffalobillpatrick]

"(no ground contact)."

That makes all the difference, I thought lower level was slab on grade.

Don't know what's in the new one.

[buffalobillpatrick]

800 / 250 = 3.2

The old book has that sort of info.

[Drake]

I have not had the opportunity to purview the book. Does it detail/explain the components that go into a simple "control panel" enough so that one could assemble their own?

[buffalobillpatrick]

Yes

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My listing

[buffalobillpatrick]

In my current house I installed radiant heated floors. 2 runs of 1/2" pex suspended between each 16" deep TJI on 16" centers (this is not a good method, as I found out later for low temp. Modcon boilers) but it works because of my high insulation levels & triple pane with an outer 4th layer of glass storm windows + 80g buffer tank.

Based on boiler firing rates at design temp. Of 0*F somewhere around 8-10 btus / ft2 / hr.

ICF basement & 8" SIP upper 2 levels.

Radiation & convection moves the heat from the pex into each plenum.
The pex is hung to the subfloor with plastic electrical clamps, but makes zero contact.

About 10" below the pex is a layer of Reflectix. It keeps somewhere around 80% of the heat above it to conduct through 1.25" OSB subfloor + 1/2" cement board + 1/2" of tile & thin set & radiates into rooms above.

After 14 years. I see no degradation over this time. The bottom surface of the Refectix has very low emissivity, so IR don't radiate much downward.

15-20*F dT in loops that are 500' (way too long)

It actually heated just fine for 1st 10 yrs. with only 2 X 10W El-Sid low head DC pumps on each zone, probably 3 qts / min flow.

Now I have zone valves & 1 Taco 008 high head pump.

About 2 yrs. ago I finished a 450ft2 TV room in basement. I removed the Reflectix above that room. Now that room is heated from the radiant ceiling (floor of room above) It stays about 2*F cooler than room above. It has a bathroom that has 2KW electric supplemental heater.


Some things that I would do different:

For pumping efficiency the loops should be limited to 200-250' of 1/2" pex.

For low temp. Heat source such as Modcon boiler or Heat Pump. The pex should be placed in a concrete slab on 6-8" centers with R20+ EPS underneath.

[Drake]

Are expansion breaks needed in concrete hydro floors? With all the internal tubing etc how would they be done?

[randen]

With the concrete floors constant temp. no expansion are required. Our floors are near 2000 sqft with no cuts. I would not want to entertain the chance of cutting into a tube that may have floated a little closer to the concretes surface with a relief cut.

Another issue would be if you covered the concrete floor with a ceramic tile, if the relief cut did propagate a crack it would also crack the tile.

Better a nice flat virgin concrete slab.

Randen

[Drake]

Also was worried how a shifting joint might damage tubing. So lots of internal reinforcement is a good thing. Slab will only be 15' x 35'.