extruded plate output chart

pat_3

i have been using extruded aluminum plates for several years.my supplier has changed brands a few times but the newer brand always appears to be of the same high quality.it has recently come to my attention that the output charts for the last 3 brands are drastically different.one output chart shows 8" center spacing ,20degree delta t,r-1.0 covering material will give an output of 35btus per sq ft using 122degree water.identical scenario with another brand gets 24btus per sq ft ,3rd brand gets 14btus per sq ft.however slight the differences between one brand to another,i don't understand how the output charts can be so different.thank you in advance for any responses.

Unknown

room temperature assumption may change.
whether it's Average or Supply water temperature on the chart may change.

pat_3

i agree,but could that account for such a drastic difference

Unknown

between the two, you could be looking at an effective 15 degree water temperature difference, that could be a good 8 BTUs/sq ft.

beyond that though, testing methods, downward loss, whether or not the subfloor is included... these can cause changes as well.

If the plates are similar size and similar gauge, obviously the output shouldn't be horribly different at the same o.c... If it's not some combination of the things I've mentioned already, I'd be at a loss.

ALH_4

Chart

FWIW, this chart is one I created from Radiant Engineering's FEA modeling of original Thermofin-C. The different lines are different flooring R-Values. There are some assumptions built into this chart, but I feel confident that this is pretty accurate for most situations. You can see how drastically the floor covering affects the output. Unfortunately, I think marketing affects the assumptions some manufacturers make in creating their published numbers.