Kitchen StapleUp - Copper w/Plates

jbplumber

My kitchen has 9' of HWBB that is supplied by a 3/4" diverter tee branch from a 1.25" main. This is the first branch. With outdoor reset, the supply temperature is usually 140* so the output is between 2500 and 3000 btu at those temps. I could probably get by with only 80% of the current heat in this space if the floor were heated since it is a kitchen and that is what I'm considering. I'd like to take the HWBB out and heat is from underneath. This will also free up the kitchen design for future renovations. The flooring is ceramic tile on plywood.


I'm not sure that I could do this but I'd like to try and keep it as a diverter tee branch although I'm not opposed to adding a zone to do it.


I'd prefer to do it in 3/4" copper under aluminium plates and feel free to tell me if this is ludicrous. Unfortunately, I'm stuck for calculations. 3/4" copper at 140* is probably just under 25 btu per foot. I have no idea what it is with plates attached, nor what that translate to on the surface. I got this figure from the Burnham reference Ron Jr gave about a year ago when JohnNY was doing the copper rail job. On a side note I think I saw it or something very similar while watching a TV ad. Also, I was quite surprised to find out that steel gives off about 60% more BTUs per foot than copper but I have never heard of steel staple up. =)


I am rerunning the steel mains under the kitchen and that was what prompted me to start thinking about this, in case I need to open up the gap on the tees or put in normal tees and an extra circulator for the branch.


I'd gladly buy Hydronics Pro and have ready answers but unfortunately it doesn't seem oriented to diverter tee systems.


I'd really like to have an idea of how much pipe and plate it would take to match from the bottom the heat that I currently have up top using the same temps. Many thanks for anyone with ideas or suggestions.

hr

I'd guess

30-35 btu/ sq. ft. for plates and copper at the temperatures you are considering.

As you know the floor output is driven by the floor surface temperature against the room temperature.

The floor really dosen't care HOW it is heated to the 80- 83° surface temperature. The output of a pex heated floor will be the same as the output of a copper heated floor. Of course the copper and plates would offer excellent transfer and quick response. You could drive that output with low temperatures as you use better transfer materials.

Not sure I have seen 3/4" plates, will you build your own? If not 1/2" copper fits fine in ThermoFin plates. Think if I used copper I would run shorter loops due to the better heat transfer from the copper to the plate. A 300 foot loop may run short of temperature before it gets to the end due to this increased transfer.

I have used copper in ThermoFin before. That assembly gets hot VERY quickly compared to the pex/ plate systems I've filmed this response with the infared camera and it is almost instant with copper in fins.

I'm not sure steel transfers heat better than copper, I would have to see the numbers on that Looking at the Slant Fin catalog, copper and aluminum fins has a higher output than steel pipe and steel fins. I'd think copper pipe withy copper fins would be even higher than copper/ aluminum baseboard??

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

jbplumber

Excellent...

The source was http://www.burnham.com/pdfs/htghelper.pdf --- page 48 and it is tarnished copper verses steel which makes me wonder how tarnished because I too would have thought copper emmits BTUs; at least I'm sure that Cu is many times more responsive.


What spacing does the 35 BTU per SQ FT assume? The area I want to heat is 10' x 12' (this excludes all space under cabinetry and what not). It seems like 35 btu/sqft might result in more heat than the 2500 btu it gets now from the fintube?


For some reason I though most transfer plates would hold 3/4" copper but 1/2" would be fine. I'm not sure what brand of transfer plates are sold at my plumbing supply house although I have seen them there. I'll have to check for Thermofin. The joists are 16" OC over a heated basement and will be insulated. Would it make sense for this to be done as 8" OC for the first few joists and then 16" OC after that? That would result in about a 120' loop or less. Also, are there any problems combining using soft copper to do the turns through down and through the joists (so they aren't effectively notched ) and M or L hard tubes for the straights under the plates?


Thanks again.

hr

Ideally

you would do a heatloss calc and design for that room. With the BTU required # you would then see if the AVAILABLE rooms square footage could supply that amount.

If you have 120 square feet to meet a load of only 2500 btu, that should work out fine.

I'd still suggest two plates per joist bay (8" oc) even if the load could be handled with wider spacing. You will get a much more even heat spread with the tubes close together.

Keep in mind with heat transfer plates the transfer is conduction. I don't think the plates would know, or care that the copper is tarnished. The grip in the ThermoFin is very tight and that is the important "connection"

Sure you could use soft copper in the plates or just for the return bends. I prefer to work with rigid copper tube I'd just us sweat ells, maybe long sweep for a better flow.

I would be glad to REM's you some 8" oc 180° bends with swedged ends Pre tarnished

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"