Sand on top of tubing

jeff_110

I'd like to apologize for my brethren. You have to understand that 50% of all engineers out there graduated in the bottom half of their Class....I've actually had a PE chastise me in writing when I claimed that radiant heating and cooling energy exchange works at the speed of light. Sigh...

Rocky_3

2\" sand under 6\" concrete

How hard should I fight the engineer on this? Being at the bottom of 6" of mud is bad enough, but under 2" of sand as well? Anyone know of any literature directly addressing the perfomance lag associated with this installation method? Any first hand experience? Thanks,
Rocky "Slop Bucket" Pavey

Derheatmeister

www.electrom.com

Check with the Thermal storage of the Electric boilers in sand.i think it's www.electrom.com

They store "off peak" energy in a layer of sand so that it will heat the house in "on peak" hours.

Why the Usage of Sand? Trying to make a indoor Beach? Pavers? Why the Mud? Do not get it !

Paul Rohrs_4

Check out this site

http://www.icpi.org/techspecs/index.cfm?id=36&tech=12

It does not give R-values or performance guidelines, but I'm in the same boat with a large residential project and this clarifies the paver industries SOP.

We are going to have 1" XPS (high density) board down under the compacted base, then our tubing will be over the compacted base, 1" of compacted sand, then pavers. I added 25% to my btu load to buffer the response time.

As you know, air is an insulator. I would say as long as the sand base is compacted, it will be an adequate medium to transfer heat through. I would like some hard data on btu transfer rates thru sand.

Edit: I was searching the web and found this fascinating PDF document on Thermal Storage Systems. This system uses 12" of compacted sand for a thermal reservoir and on page 5 on the design process they suggest they are accounting for a 2.6 btu per inch of compacted fill for a heat transfer rate. Fascinating.

I think I'll contact the company for test data and see if they have numbers or white papers/performance numbers on heat transfer thru compacted sand.

Regards,

PR

kevin coppinger_16

more junk...

science. Sand will mess up the radaint for sure. In some cases the sand over time will cystalize to the tubing and insulate it from heat transfer....Another example would be at the beach during the summerjust under the surface the sand is cool to the touch....if they insisy get them to sign off when it does not work they take the heat...no pun intended.kpc

eluv8

Sand under the concrete

I have used sand underneath concrete and above the insulation to give the moisture in the concrete somewhere to go during the cure process, so that it all does not evaporate off the top. They use sand as apposed to ABC because sand does not have to be compacted. Just dumping sand onto the insulation it is near 100% compaction. Ever try compacting ABC on top of 2" of foam insulation.I always insist that the wire mesh and tubing go on top of the sand and lifted just a bit so that it is in the lower portion of the concrete. I have seen snow melt jobs with tubing in the sand layer and then pavers on top. Seemed to work fine but the job was less then 5 years old. I personally did not do the job just know of it.

Bruce Stevens_2

Erik

I don't understand, where I come from and having built roads for years sand always needed compacting, crushed stone is as compacted as it is going to get when dumped.

eluv8

It is possible I am wrong on this

I am only going by what the concrete professionals in my area have told me, and it is very possible that they are wrong. They did say near 100% but how near I do not know. I guess that is subject to interpretation. I will have to do more research on this. Thank you for the alert. These were residential projects so it is possible they counted it as good enough compaction. Small town and definatly not roads. ON EDIT: I did some research online, and I believe the statement near 100% would be accounting that during the pour of the concrete the weight and moisture of the concrete compacts the sand at that time to an acceptable level. So yes its not but it is after the pour is completed. We are only talking approx. 2" of sand here not 8"-12" just to be clear for any who are considering this installation method.

Bruce Stevens_2

Erik

Think about some one droping a pile of sand in your back yard and then you try walking through it, you will sink quit a bit, crushed gravel some but not as much. One trick they might try is watering it down with a light sray, that will help compactit not 100% but better than nothing

Rob Blair

Come on Bruce

Crushed stone still needs compacting after it is dumped!!

Rob

hot_rod

Sands not a very good conductor

Google around for the conductivity of dry sand....
Add some portland to it and things get better. Think gypcrete.

washed pea gravel is considered self compacting. Good compaction, bad consolidation, which could be an issue if you need to dig into it.

hr

Bruce Stevens_2

Rob

When working on roads you are expected to get 95% compaction and stone will meet that when dumped not that it will hurt but that is the what I am going by. If you dump stone in a 3' X 3' X 1' box I will ask how much it will compact, dump sand in and tell me how much it will compact.

Rocky_3

Wow

I am stunned this is considered to be a viable heating method. Electric heat cable buried 10" below concrete in sand. I cannot help but think the response time is measured in weeks, not hours ;-)

thanks for sending it along

Rocky

Gordy

What roads do you work on?

Bruce I have been in heavy, and highway construction for 24 years. As Hot Rod said pea gravel comes close to 100% compaction IF it is CONTAINED on all sides.

Where I come from everything gets compacted per IDOT, or Tollway Athority specs. 95% does not cut it, unless it is an integral abutment style for a bridge. And no sand is not even close to 100% compacted when dumped.

Gordy

Bruce Stevens_2

Gordy it

has been a few years but yes I worked on Fed funded interstate hyways maybe I confused someting but I am sure it was 95% thought brige abutments were a bit higher if I am wrong enlighten me Thanks

Rob Blair

Name your gravel

You tell me what kind of gravel and I will dump it in that box from a bucket and I will bet that I can compact that more than a few inches.

Rob

Bruce Stevens_2

Rob

Yes you will just saying a good crushed gravel will not compact as much as sand

Rocky_3

Engineer acquiesced

After explaining the "beach" scenario, and a very helpful letter from Elaine Hoffman of Uponor regarding response times if tubing embedded in sand, (Thanks, Elaine!) the engineer omitted the sand layer. Now I'm working on getting him to let me tie the tubing to the rebar as opposed to it being at the bottom of a 6 inch slab.

Regards,
Rocky

[Deleted User]

my sandman neighbor

did an interesting thing; after afixing his pex to his ply subfloor, he put down sleepers between the loops, poured sand on top of everything to fill all the voids, and then put down his finish flooring

[Deleted User]

and i'm so fast,

that when i hit the light switch, i'm in bed before the light glows away

[Deleted User]

wow in another sense

read the fine print; they're counting on using the preheat from the earth's core

Jeff Elston_2

Sand dry sand

For what its worth

Scanned from page 11 of "Soil and Rock Classification for the Design of Ground-Coupled Heat Pump Systems"

Now wet sand is a different story!

Gordy

Sometimes

They have trouble getting outside the box if you know what I mean Geoff. This translates to all fields of engineering.


Gordy

[Deleted User]

The Sun's a beaches.

Brad and Geoff are both fine rare finds. They've not lost their common sense glands. I know a lot of engineers who don't have that capacity.

As for sand, and things moving at the speed of light, in our situations where we use sand over the tube (snowmelt with pavers on top) we tell the coustoemr NOT to expect the system to react as fast as it would were it patterend cement. BUt that stuff (cement) is guaranteed to crack, where as the pavers come pre cracked :-)

Once the system starts working, and the sand becomes more conductive due to moisture, it'll work decently.

I always tell my students to SELL The fact that their heating systems travel at the speed of light. "Let's see your forced error heating system top THAT!"

It does get an eye brow raise from most consumers. You know, the one where their left eye brow is about a mile high, and their right eye ball is red, swollen, evil looking and focused on you. You know "the look" :-) aka BULLs eye.

But it is true. The speed of light. That was what I named my old 1958 extra heavy duty pick up truck. That way, if I was late, I'd tell them that I'd gotten there in the speed of light, except I got held up by traffic...

Happy Easter. By the way, any one know why the Easter Bunny hides his eggs?

Me either.

ME

Terry Trommeshauser

re: easter bunny
i heard he was embarrased about doin the chickens, hence the hiding.

happy easter!