## Help with radiant floor in shop (7 Posts)

• ### Help with radiant floor in shop

We are currently building a 60x50 clear span steel building with 12' side walls and three 10x10 garage doors. The slab has been poured with four 437' loops of 3/4" barrier pex spaced at 18" centers. The top of the pex is 2" below the top of the 6" slab. There is also 1.5" blue foam board under the whole floor and around the perimeter. If my calculations are right the heat loss on the building should be around 97,000 BTUH. I based my calculations off of 100,000 BTUH. I came up with a flow of 10gpm with a head loss of 4'. I was thinking a Taco 008 pump would be best with these numbers. Im just looking for an experienced persons input on this system. Also any information on hooking the manifolds up to a wood boiler.
• ### Pump

Wood boiler is good, what's your back up going to be?

You can you a water heater tank or tankless.

I would go with the variable speed 008
Or the bumble bee.

As far as manifolds go, go with roth, viega or wirsbo.

With the out door boiler go with a flat plate hex.
• ### 4 loops, 400 feet long

18" on center with a 97,000 load. Looks like 2.5 gpm per loop and 14' of head, according to a quick RadPad calc. A Grundfos 26-64 would work. or a mini Magna if you want an ECM.
• ### Delta T in the RFH

For projects like this, I usually design around 30 degrees. Allows for longer loops and an easier install overall.

Based upon that, I come in at (97,000/30x500) = 6.5 gpm total

Four loops = 1.6 gpm per loop

Then looking at some pex charts based upon this flow I find 8.8 foot of head loss.

Circ size just for the radiant floor is 6.5 gpm at 8.8 FOH.

With this info, you end up right on the 007 curve. But I don't know the rest of the system, mix valves, ....... so the 008 also works great. As well as the 0015, on speed medium.

The larger the Delta T in radiant, especially in a shop allows for more "off the shelf" circs and components.

Dave H
• ### need toi know more

as Dave mentioned, what other devices are in the circuit? If it has a 3 way thermostatic mix valve, for example, those can have a large pressure drop if they are not specific to radiant.

I came up with similar numbers using Siggys software.
The 008 is clearly not big enough. You also need to figure in the other piping components. It is likely you will end up with a 26-99 grundfos.
Have you read Idronics 10?  www.caleffi.com/sites/default/files/coll_attach_file/idronics_10.pdf

Hot Rod,