Extruded aluminum plates revisited

Bob Gagnon plumbing and heating

heating my house with staple up 8" on center, in northern mass. this winter it was below zero. i now run my staple up 4" on center where i need more heat output. most of my radiant jobs are staple up, and i didn't get one call in the real cold weather. bob

Steve Minnich_1

Extruded aluminum plates revisited

IF THERE IS ANYBODY STILL NOT SOLD ON THE FACT THAT THIS IS A SUPERIOR DESIGN, PLEASE VISIT www.radiantengineering.com.

These guys wrote the book on it in my opinion.

Gotta keep our customers comfy guys!

Steve

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John@WattsRadiant

Staple Up

Radiant Engineering claims (through their "modeling") that you'll only get 10.5 Btu/hr/sq ft with tubing directly stapled to subfloor, 8 inch on center, 200 Deg F supply, under a 3/4" subfloor and 7/8" hardwood. That is completly untrue. In the last two houses I've lived in; I delivered about 20 Btu/hr/sq ft under 3/4" subfloor and 1/2" hardwood at 140 Deg F supply with synthetic rubber at 8 inch spacing; delivered about 17 Btu/hr/sq ft with 155 Deg F supply - floors were 3/4" subfloor + 3/4" hardwood + carpet & pad; again with synthetic rubber.
So I guess my own personal experiences tell me the numbers (at least on direct staple up) that Radiant Engineering generates are completely inaccurate and misleading.
Everyone will draw their own conclusions as to what methods "work" best (and use their own criteria to judge that), but it sure seems to me that there is a lot of false info floating around out there when it comes to staple-up. Bottom line, it works and works well, when it is designed and installed correctly (heat loss per sq ft; exact floor construction taken into account, etc).
John

heatboy

I gotta' ask.......

What makes the rubber some much better than PEX in regards to heat transfer? Is it just a better material or is it that it can be flattened when stapled tightly to the sub-floor? What is the pressure drop per foot compared to PEX and wouldn't stapling tight enough to increase the contact area also increase the pressure drop due to the staple squashing the tube?


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Troy_3

rubber better heat transfer?

Hb you are joking right? I've never heard anyone be so bold as to suggest that rubber will transfer heat faster than pex? I've heard you can drive a truck on it. (never understood that advantage) I even heard years ago that it could withstand 360deg. ( now there is a selling point). Never know when nuclear reactor will be sized for a residence. No not for this guy. I replace my garden hose every couple years but it hangs outside my house and so changing it is no big deal.

zeb_3

I believe

it was Mr. Eatherton that had posted a study that was done somewhere that resulted w/ rubber producing more btu's than pex(both w/o plates). Correct me if i'm wrong.

Boilerpro_2

Its true in staple up...

Rubber hose transfers more heat. Can get about 27 Btu/ sq ft. with staple up at 180F supply, 160 F return (if my memory isn't too faulty). More contact area and, how this, no squeaks. In slabs, pex has the edge from the studies I've seen.

Boilerpro

Steve Minnich_1

I personally

would never use rubber. Again, my comfort, not theirs.

Steve

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Troy_3

Plates

Call me crazy but I will continue to install plates on every underfloor job. I will sleep well knowing even if the owner throws down a rug or covers their tile floors with wood I have a chance of keeping them warm. Rarely do I see a floor covering not change before the first occupants move in. Who knows what will happen during this structures life. I was just in a new house that has so much furniture in the family room that you can barely walk between it. How will that inhibit heat flow? I have had to fix too many tube only jobs that were not making it. I know those contractors won't be getting referrals.

Chris Maderia

Plates

The true fact is that boths way work. I always design and recommend to my customers that they use them. Why? How about a better transfer of heat throughout the floor spreading the heat more evenly, no potential for hot spots, faster floor response time and lower supply water temp. You have to remember that the customer has to live 7 days a week with the system and we don't. It's up to each individual contractor to explain the advantages and disadvantages of both, wich system you recommend for that application and why. Let the customer decided where he wants to put his dollars. The difference in the investment between using and not using plates is what you have to overcome. Hey, give the cash to your oil or gas company or invest it in the plates. They will pay for themselves.

Radiant heat being so forgiving allows much flexability in system design and that's what allows either method. Is one better than the other. While of course, the use of plates provides a much better radiant system than without. I would relate it to this. Is it better for your hydronic heating system to have your circ on the supply or return? The system works both ways. But we know that pumping away (circs on the supply) is better for the system.

Unknown

Now I find this reasoning very common and very interesting, since at the Wirsbo training seminars they tell us that with all their testing, as much as they'd like to sell us more pipe there is no justification for going under 8" o.c. in a 16" o.c. joist bay: it has practically no effect on water temps or heat ouput, contrary to most of our intuition. Apparently it's not tubing surface that is the bottleneck to heat transfer in that installation.

That's for suspended tube. You aren't doing a direct contact staple to the bottom of the subfloor without plates, are you? That might be a different can of wax where you are getting a little direct conduction maybe..

Steve Minnich_1

Amen

to that Chris!

Steve

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Bob Gagnon plumbing and heating

spacing

i don't see how 4" spacing won't increase heat output. i did my house 8" on center and you can feel cool spots on the floor above, between the pex. is is suspended tube mostly. bob

Troy_3

Chris

Very well said!

Unknown

Can't pretend I've modeled it, and I don't usually work without plates so I can't relate from experience... just passing along what they told us.

If anyone knows why for sure, I'd like to hear it. I assumed that more tubing didn't change the joist air temp appreciably and that's the primary method of heat transfer in suspended tube. I can't imagine why you'd be able to notice cool spots in between tubes suspended 1" below your subfloors. What kind of water temps are you running out of curiousity?