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Adding Radiators

jimbob Member Posts: 2
We recently added 4 radiators to our hydronic system, in the basement. This added about 30% to our radiator SF area. We had a new boiler put in about 4 years ago, and the rest of the single story house gravity system was converted over to a circulator, pipes were changed over to 1" copper (maybe 1-1/4). The present pump is a Grundfos 15-42 which according to their site is a low head, with a max GPM of ~16 GPM max. When we added the radiators to the system, they were plumbed off the main floor system. We had a plumbing contractor do this work, so no engineering. We are having some problems getting the basement radiators to work properly, not surprising given the physics of a hot water system. I didn't question the plumber's technique since we are pumped. The radiators do work, just not very well. The plumber recommends that we upsize the circulator, to cover the added head and the added pipe run, and radiator SF area. Recommending a Grundfos 26-99 which is capable of 34 gpm max. At 12' of head (max difference between the lowest radiator and the highest radiator)the gpm drops to 24 gpm according to the pump curve. He says that we may have to throttle some of the upstairs radiators, to keep them from running us out. We have already done this with the pump we have now, and it has improved performance somewhat in the basement, but when it gets really cold, we will have to crack them back open, which means the present situation is untenable. Does anybody have any thoughts about the road we are going down? Is our plumber on the right track?


  • Mark W
    Mark W Member Posts: 22
    Why not?

    Why not make the basement and main living area into separate zones?
  • kevin coppinger_4
    kevin coppinger_4 Member Posts: 2,124
    I agree w/ mark

    but you are falling into a trap w/ the "solutions you are working on...Did you check out the heating Q&A off the the side of this page? It has a section on gravity hot water, Very helpful.kpc

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  • jimbob
    jimbob Member Posts: 2
    adding radiators

    Yes I checked out the plumbing q & A. While very informative, I checked it out too late, when the work was done and we had the problems. My question is, can we engineer our way out with a pump or do we need to drop back and put in second zone? As you think about the answers, think in terms of what we MUST do, not what is ideal. I have already come to the conclusion in hindsight that we should have just done a second zone.

    In surfing around here on the wall, I do find the thread about DIY interesting. I hired a plumber because I thought he would know what the h--- he was doing. Lots of them said they would not touch it because they didnt. This guy said he would because he had experience with this stuff. So much for that.
  • Glenn Harrison_2
    Glenn Harrison_2 Member Posts: 845
    Did he just \"tee\" into the main line?

    Did he just cut in a pair of tee fittings into the main line for each radiator in the hopes that some of the water would go down into the rads? If so, you have two problems, 1 being that heat likes to rise, which makes it harder to get it down to the rads, 2 water will take the path of least resistance, so the water would much rather go thru the tee's in the main line, than turn into the tee branch and go down to the rads. You have two solutions. 1st, remove the standard tee's, and install monoflo tee's on the supply and return of each rad. the monoflo tee's have scoops in them, which will force some of the main line water down into the rads. 2nd option is to install balancing valves in the main line between each set of tee's and close the valves down until the basement rads heat properly.
  • Mark W
    Mark W Member Posts: 22
    It is unlikely

    that you can "engineer" your way out of it with a bigger circulator.

    There's no harm in trying I suppose, but it seems like a band-aid type approach to me, and not getting to the heart of the problem.

    And who wants to be fiddling with radiator valves all the time just to try to achieve a modicum of comfort?

    If all areas of the house are to be used an equal amount of time, and you want it all to be relatively the same temperature all the time, you could stick with the one zone set-up, but as a previous poster mentioned, it would probably require some re-piping to make it work properly.

    I would still be more inclined to split it into two zones, and throw on a couple of digital setback thermostats while you're at it.
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