Adding radiation... easily?

Dan_8

Last fall I re-did the near boiler piping and controls for the heat in my house, leaving the fin-tube BB radiation alone. For the most part I'm very happy with the way that it's working but it has pointed out that the balance of heat loss to radiation for one of my zones is pretty far off the others. Because of that I'm looking to add a bit more heat in the problem zone. Eventually I'd like to go with either in-floor radiant or panel radiators (or a combination of both) throughout the house but time really doesn't permit the full blown fix just yet.

The inlet side of the baseboard in my problem room comes up through the floor, runs along the outside wall and then runs through an inside wall into the next room before heading back down to the boiler room to pick up more BTUs for the return trip. I'm thinking that the easiest fix would be to tap into the run just before it heads through the wall and run down the interior wall with more BB for six or eight feet and loop back to catch the existing run. It’s not the best location since it’s on an inside wall and doesn’t really work to distribute the heat around the room but it’s the easiest for the short term.

That solution isn't terrible and even with pulling and cutting the wooden baseboard trim that's currently there and plopping in an additional piece of fin tube I think I'm looking at only a half day or so. However, given all that I've currently got going I would have a much easier time sliding a smaller job past the scheduling committee (the lovely Carolyn presiding). So, I'm hoping against all hope that someone here can make a suggestion for a band-aid that will increase the output of my 10' of baseboard by 50% with almost no work at all (perpetual motion machine?).

Here's a bit more detail on what I'm seeing wrong and why I'm pointing the finger at radiation

I'm using a Tekmar 371. It's running an injection loop and fully resetting the four fin tube BB zones that it controls. As most of you probably know, the 371 tries to run constant circulation to all the zones that it controls. Generally that means that one of the zones will run constantly and the other zones will have some amount of off time since so few things in life are perfectly balanced. While happily watching my system run on the really cold days (my friends think I'm nuts because I have a chair in front of my distribution panel, my wife is certain of it) what I was noticing was that one upstairs bedroom zone was running all the time but the other zones were only on half of the time or even less. This was with all the zones set for the same room temperature (70F). What was even more interesting was that the control appeared to be spiking the temperature as high as it could while the upstairs zone was on alone and then allowing it to fall back a bit when the other zones were active. The quick drop in temp might have just been caused by the other zones dumping cold return water in but the 371 also ramped the injection pump down at the same time so I'm assuming it was targeting the lower temp rather than being unable to prevent it.

There are a few down sides to this. The main one is that my boiler ends up having to run a good bit hotter than otherwise necessary in order to make temp in this one zone because of the lack of radiation in it. Not only does it run hotter but on the really cold days it ends up bouncing off the high limit of the boiler aquastat which means that run times are limited somewhat compared to what I could get with a lower supply temp. Because the temperatures are varying so much in the mixed loop the piping for all the zones is making more noise than it should as the temp fluctuates. It seems to me that adding radiation to the one zone is the first thing to change to try and sort out my problems.

When doing my system design I used heat loss figures from the SlantFin Hydronic Explorer program. All my existing radiation agreed fairly well with the values that it gave me and all the zones looked at least reasonably balanced relative to one another. However, that one bedroom is really using up more heat than you'd think (or the other zones are using a lot less I suppose). The problem zone shows a heat loss of 5300 BTUH at -15F design temp. You'd think that 10' of fin tube would just handle that okay but it gets behind even with the mix temp hitting ~190F and is drastically out of balance with the other zones. The house is only 10 years old and well insulated with decent (but not top of the line) double pane windows. No major discrepancies between sections of the house as far as build quality or insulation that I can find.

I will happily lay out even more detail if desired but this note is already about five times longer than I had hoped to make it so I'll leave out the pictures, drawings and pages of numbers unless asked.

Thanks for any help...

Mike T., Swampeast MO

No perpetual motion machine

But perhaps replace with the same length of high-output baseboard? Other than that I guess you could wrap tinfoil around about half of the length of the b/b in the rest of the rooms ;>)

Is the offending room already on its own zone? If so, couldn't you start there with your panel/radiant conversion without too much fuss from the scheduling committee?

Steamhead

High-output baseboard as Mike says

is probably your best bet. Personally I like Slant/Fin Multi-Pak 80 for h/o, but there are other brands out there too.

But I'd want to know how much baseboard is already on that loop. You can only get so much heat thru a 3/4" pipe. About 60 feet of standard baseboard is the upper limit.

If there's more baseboard than the loop can handle, consider splitting the loop into two or more zones. With a little planning you can maybe split the bedrooms off from the living rooms or something similar, and control each zone with its own thermostat or room sensor. The Lovely Carolyn might raise her eyebrows at a larger project like this, but she'll love the increased efficiency and lower fuel consumption.

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Dan_8

HO might be the answer for this HO

Thanks both of you, for some reason I had convinced myself that the HO BB wasn't really “H” enough for my purposes but maybe that was a bad bit of thinking on my part? I don't know just what kind of BB I have now but I believe it's fairly standard and I've been running under the assumption that I'm getting 500-550 BTUH/ft out of it at 180F. From a quick peek at the specs on the SlantFin page I'd be getting that kind of output at 150F with the Miltipak 80 which would be reasonable I guess.

Also, right now the BB goes almost, but not quite, all the way across the wall so I think that I could squeak another couple of feet in if I covered the whole wall. With a bump in output of 20-30%/ft and a couple more feet I think that I'd have the 50% that I seem to think that I need. Minor cuts on trim at both ends to accommodate the extra 3/4" of thickness and I'll be off to the races.

This are only one of two bits of BB on this zone. The other piece is right next to it and it's the upstairs bath. Total zone BB is about 14' so I think that I've got lots of room to pull more heat out of it.

As far as digging in and doing it correctly right now... Despite all my planning on the original job The Lovely Carolyn raised a good bit more than an eyebrow (it might have been a rolling pin but it felt like a crowbar when it hit) when my brothers in law and I did the cutover. A 20 hour day of us goofballs clanging around in the basement is not a 9.5 month pregnant woman's idea of a good time I think. You can only imagine the words that she used when we managed to blow up a 1/2" ball valve at 2:00am while trying to unsweat it because brother in law number two didn't like the aesthetics of an extra coupling. Needless to say her ability to withstand my heat fetish is somewhere near the end and hasn't recovered yet ;')