Does copper fin tube + Runtal = problems? Or heat/happiness?

Barry Freeman

Hi there,

We have an old Victorian house and at some point the radiators were removed and replaced with a separate baseboard/copper fin tube loop on each floor. It is horribly inefficient - only the first two rooms on the loop really get warm.

We are currently renovating two bathrooms on separate floors, one above the other. These bathrooms and the rooms next door are at the end of the loop and receive barely if any heat (yes, we’ve had people in to let air out, drain the system, etc.) I would like to put in Runtal wall panel radiators in the bathrooms (they can operate efficiently at lower temps). Runtal says these panels can go at end of the loop (I’m willing to sacrifice the heat in the next room - we use space heaters anyway). The plumber says they won’t work at all and will mess up the system - copper fin tube is 3/4” and Runtal is 1/2”. I’ve also asked about putting these rooms (bathroom solo, or both end rooms together) on separate loops realizing that there will be added expense. The plumber is resisting. The electrician says to run the pipe under the floor and put in electric (of course) heat. The GC hasn’t anything to say. Any thoughts? Much appreciated!

Jamie Hall

I presume that all of these things are in series? That is, that the outlet from baseboard number one feeds baseboard number two which feeds... etc. until you get back to the boiler? Frankly, that's a miserable way to do the job, and it's no wonder that you are having problems. There is no reason why the Runtals wouldn't work, however, if cut in in series that way. How well is another question, since by the time the water gets there it's probably pretty lukewarm.

Since you are renovating those two bathrooms, and they are stacked, I would run a separate loop to them from the basement. I'd also run a new return from the baseboards which are working, and a new feed to the rooms next door. Surely there is room in the new plumbing stack for that (a total of four 3/4 inch lines). Then hook them together in parallel in the basement (you now have effectively three loops)(that is, connect the two new feeds to the existing feed, and the two new returns to the existing return), with balancing valves on each loop so you can get them to heat the way you want them.

hot_rod

Here is an example of which Jamie speaks. Any heat emitters in series present temperature drop and higher pumping powe requirements compared to parallel piped.

I'd highly recommend a home run system where each panel has it's own S&R and all see the same water temperature.

It works for any emitter really, fin tube, panel rads, cast iron rads, radiant loops, etc.

Ideally one would calculate the heat load for each room and the heat emitter would be sized accurately to that number.