Numbers/input on heat transfer panel efficiency for staple-up radiant: omega vs joist track style?

modconwannabe

In pricing an install for ~800 sq ft, about 35 joist bays, the Wirsbo joist trak or ThermaFin type panels are many times the price of Omega style transfer panels: $6 and up for 4 ft lengths vs under $3. I assume that the material and thickness of matter, as well as the manner in which panels are attached to a floor, however I've read anecdotal evidence all over the map, and so wonder if there is more than a marginal benefit to the pricier panels, i.e. imperceptible benefit at 2 times the cost.
Anyone have experience, or numbers, or both?

Rich_49

Contact area between tubing and pricier plates is far superior along with the fact that contact between the plate and sub floor is also a much higher percentage both make the pricier panel the choice for those interested in BEST PRACTICE . Based on the size of the house you mention you have to ask yourself is 600 to 700 dollars worth the risk of being Good or a zero ?

modconwannabe

Thanks for the input RIch. Everything you said is what I've heard, but I guess I'm hoping someone has numbers to support it. IE it may be a technically better implementation, but result in minor-to-imperceptible gain in efficiency. I've yet to see numbers anywhere, only claims by manufacturers.

SWEI

Radiant Engineering in Bozeman Montana has data they will happily share. They also make plates in several different styles, which they sell at competitive prices. If you've used any of the Watts Radiant aluminum plates, they used to be the OEM.

hot_rod

I've never seen any test data or FEA on the thin "flashing grade" transfer plates. Dale and Bob at Radiant Engineering have plenty of output numbers and many years experience.

Siggy has also run FEA and has written two or three articles on the results, in the archive at PM mag.com.

Two issues with the thin versions were the loose tube fit, and they would or could make an "oil canning" noise when they heat and cool.

One of the radiant manufacturers that promoted thin plates advised leaving one side un-fastened to eliminate the oil canning. Not a lot of conduction transfer with that method

Plus the poor contact to the floor as Rich mentioned. unless you use a couple dozen fasteners per plate. '

Gordy

Really this boils down to logic does it not. Conduction between water and tube, between tube and plate, between plate and floor. BTUs become one. The thicker the gauge of plate the more BTUs absorbed, and stored. Think of it as water flowing through a bunch of unsoldered pipe water being BTUs. If it all leaks out by the end of the pipe not much return on investment.

You can crunch the numbers to realize cost, but those numbers may not impress the client enough to spring for the difference. The approach , and explaination is key. I presume this is why your in search of information to back up the claim.

SWEI

Labor costs for the various styles of plates are similar. Once you add tubing and the (required) insulation I'll venture to say that plates might represent perhaps 30-40% of job. I would propose a 30 year minimum life for a properly installed emitter system. Factor in a conservative 3-4% annual increase in fuel costs and do the math.

hot_rod

The main challenge with any staple up or plate from below is the BTU/ sq. ft required for the load. And the biggest obstacle often becomes the floor covering. Look at the largest load in that BTU/ ft number, see what supply temperature is required and go from there. Carpet and pad, matched with high load rooms... not such a wise installation.

RE claim to fame with the thicker aluminum plates , in addition to grip and contact patch, is that it transfers the heat out to the very edge of the plate much better than thin gauge plates. When you watch them perform with an infrared camera you see that temperature flux clearly, also in the FEA that was done. That lessens or eliminates the heat stripping across the floor surface, also. The heat transfer to the room is dependent on the entire floor surface reaching a temperature. If only strips of the floor are warming, it's harder to cover the heatload. That was a big issue with bare tube staple up. Very hot directly over the tube, but 2-4" away the floor was much cooler, so the heat flux was often too low to cover design conditions.

From there the only solution was to crank the supply temperature until the floor coverings started to cry, or the subflooring glues started to un -hinge

Crunch the numbers carefully and design for the lowest possible supply temperatures. In some cases that may require 3 tubes per joist space.

RobG

A little off topic but does anyone make an extruded plate that snaps in from the bottom? I've got a ceiling job coming up for an addition and it would be nice to be able to put up the plates on the furring strips and then snap the tubing in.

Rob

SWEI

Bottom meaning the radiating surface side?

Radiant Engineering's Thermofin U plates are extruded. The tubing doesn't really snap in, but it has a fairly snug fit.

RobG

That's what I' m looking for! When you say snug, will the tubing stay in place if installed at about a 70 degree room temp or would I need to use aluminum caulk and put up temporary supports until it's bonded? In the past I used the regular extruded plates and had to put up one piece at a time with the tubing. What a pain in the ***. I wish I had come here earlier and asked this question. My supplier was no help.

Thanks,
Rob

Gordy

Go to their website Rob plenty of info.

SWEI

Give them a call -- they are quite helpful.

The plates come in both 4 foot and 8 foot lengths, with and without pre-drilled mounting holes. Pricing is competitive and I always appreciate dealing with manufacturers directly whenever I can.