Re-piping Convection Heaters

Bob Gagnon plumbing and heating

   <em>  I would like to re-pipe some convection heaters so I can insulate behind the element and seal the heater to prevent heat loss up into the wall cavity. I would be taking out the old element that is about 6" wide with three pipes passing through the aluminum fins, and replacing it with baseboard elements so I can have room to install foam insulation. I was thinking of running 3 sets of two standard baseboard elements stacked on top of each other. It seems like I will have a lot more surface area than with the old element. Has anyone ever tried this?</em>



<em>Thanks, Bob Gagnon</em>

Mike Kusiak_2

Stacking fin tube

I think you might lose some efficiency in heat transfer by stacking the fin tube elements. Keep in mind that the top fin tube will be receiving heated air from the lower elements, therefore reducing the delta T  between the top fins and the already heated air passing through them. The net effect would be to reduce the effective surface area of the stacked array of tubes.  A lot of the heat transfer efficiency of a convector depends on the chimney effect of the air passing up through the fins. But I guess if you had enough of the fin element and didn't restrict the air flow too much by adding too much insulation behind it might work ok. I have seen some convector elements replaced with single rows of stacked fin tube and it really didn't come close to matching the output of the original finned convector element.

Charlie from wmass

just a thought

Bob how about putting 1 inch of aluminum faced insulation and mounting the element at a 45 degree angle or there abouts? if you used a couple extra elbows you can match the angle to hold the element close to the insulation. WIth pipe insulation the first inch is the biggest bang for the buck so maybe the same here. 

Bob Gagnon plumbing and heating

Charles

That's a good idea Charles, I was only going to put 1" of foil faced insulation, but I thought the extra element, stacked, would allow me to run lower, more efficient, boiler water temperatures. Has anyone done it this way?



Thanks, Bob Gagnon

Charlie from wmass

You do loose heat transfer with stacked

also remember the small tube in the current element has more surface area to volume ratio. perhaps you could use 1/2" element but the air entering the elements gets hotter with each element this reduces the heat transfer rate. do the current elements have tappings off the top? You may be able to run extra elements over the current element.

Jamie Hall

It will help a little

(not a lot, but everything helps) if you make sure the elements run in series, with the inlet (hottest water) at the top, and the outlet from the bottom element.  Your delta T to the air will be best that way.