looking for a creative solution for a bad install.....

Mark Eatherton1

one of them internet whack jobs? Tube density works out to 18" on center. Sure sounds fishy to me...

ME

Blackoakbob

Looking for a creative solution for a bad install........

I have just looked at a basement radiant floor install that is a bit shy on tubing. I was told there is 900 feet of 1/2 pex, in three loops of 300 foot loops, " 1 outside, 1-middle and 1- center" covering a floor area of 1300 sq. ft. It is laid on 2" styrofoam and has a 4" cement cover. About 1/2 is carpeted and 1/4 bare cement and 1/4 floating wood floor. The owner did have the flooring installer take the radiant into consideration when selecting padding. There is also cieling delivered WA and low cold air returns so it's not the only heating source for this area. that's why I thought I could salvage the radiant to make it more of a kid friendly basement floor. The heat source and pumping is not in yet so I can work from that end. In addition, above is a ceramic tile utility, laundry, and entry area. The tile is on a plywood floor on I-beam floor joists that measures 12 x 24 and has a total of 16 joist spaces. The HO would like heated also. Thanks for any ideas you could share!
Best Regards,
Bob

Ken_8

The real question is...

How close to the tubing's thermal limit is the system now? Can you press that temperature a tad?

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Blackoakbob

No one claims responsiblity......

but I was told the idea was to run the loops, each thru the whole floor space so if a tube leaks you wouldn't lose heat in one area. It always amazes me how people can rationalize anything into believablity. LOL I have never see this type of tubing in the area, a cream colored pex rated at 180 @ 100 psi. But that's what I have to work with.
Mark, as long as I have your kind attention, would you have an idea what I could expect for heat output with this spacing at say 140 degree supply water, a continously circulating pump for the cement floor and a second pump for a 2 loop staple-up with plates for the ceramic tile floor? I'm thinking of some kind of buffer tank to give me some volume to make up for the low mass.
Best Regards,

Blackoakbob

It isn't used.....

at this time. So I can be creative to get the most out of it. Any ideas you can brainstorm, Ken, will be apreciated.
Best Regards,

Ken_8

I don't have enough data to crunch the

numbers, but it would seem even at 18" o.c., that at max design temp in situ tube should get at least 25 BTU/SF. The fact that they puit 2" rigid under the pour and that it's a basement (assumed to be surrounded on four sides with dirt) should make the load minimal.

You have to start at the beginning however. What's the rooms DTD (design temperature difference) and the U-factor of the walls and floor? etc.

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ALH_3

Supplemental

I'd install a few panel radiators to supplement the floor. Run them at the same temp as the floor, stage them so the floor does as much as it can. If the flooring isn't installed maybe they could skip the carpet and do a finished concrete floor, tile, or even more of the floating wood floor. Make sure that pex has an oxygen barrier.

This sounds like it could be a lot worse. At least the loop lengths aren't 1000ft. Embedding loops isn't anything strange, though the reason given isn't really that valid. If the loops are embedded right then the floor can be a more even temperature than simply running them serpentine. Maybe I'm misunderstanding.

Constant circ and reset sounds like a great idea. Go with some extruded plates and a modulating boiler, maybe even two temperatures with an actuated 3-way mixing valve.

At least that's what I'd do in an ideal world. At the very least the panel rads seem like a good way to supplement that carpeted area.

I'd be more worried about the carpet than the tube spacing.

-Andrew

Blackoakbob

I agree with you, ....

Ken about the heat loss calc, I'll be runninng one the next day or two. I do like to think about system design as I am doing the heatloss, especially on jobs like this where you have part of the system that can't be changed and becomes a fixed point to start at.
I'll let you know the particulars, thanks for your interest.
Best Regards,

hr

That works out

to about 16" on center in the slab. Should be enough to cover the heat load in most basements, although a heat load calc would be a good idea.

We use wide spacing and larger delta t in commercial work all the time. Meets the load, but a bit uncomfortable for residential application due to striping. Floor covering will help. You should be able to push 140, if needed. balancing the hard surface coverings against the carpet areas may be a bit of a trick.

Upstairs I would use transfer plates. Again, a heat loss and calc would spell out needed BTUs and supply temperature. And other good info

hot rod

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