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flow rates for radiant in floor heating

I installed a radiant system in a concrete slab covered with tile. The system is now about 15 years old. For the first several years the system was great with wonderful heat transfer although there were a few cold spots. Lately however the system barely warms the tile whereas the tile used to get really hot. I though therer might be air in the system and I have tried to bleed the system repeatedly. Lately I have noticed that the flow rate through the system is barely a trickle and the temperature of the water in the return line is barely warm, probably 75 to 80 degrees. I know the circulator is running but is it possible that the circulator is wearing out and not pumping at the same rate when it was new? This is the only thing that I can think of other than the problem of air in the system. Should I just go ahead and replace the circulator and see what happens?

Comments

  • Rudnae
    Rudnae Member Posts: 47
    When was the last maintenance done?

    Steve, it sounds like a system flush and restore is what you need, not just a pump replacement. In my experience the pump either works or does not, I have not come across one that has "slowed down". Also, if there is air in the system, where did it come from? This system has been operating "trouble free" for 15 years, I wouldn't expect air to be an issue at this point. Have you checked the air eliminator for blockage? If you don't have one already get a side stream filter installed, completely drain, clean and treat the system and then see what happens. JMHO.
  • Steve Latici
    Steve Latici Member Posts: 2
    radiant heat system

    Thanks for the reply. I suspected that circulators either work or they don't. I think the problem may be in the balancing valves. I will try your suggestion about draining the system and see if that makes any improvement
  • Rudnae
    Rudnae Member Posts: 47
    Just make sure that you are using the right fluid

    Steve, if you are going to drain down the system, 1st make sure you dispose of the fluid properly and not just down the drain, as it is most likely toxic. 2nd make sure that if you need glycol you put it in, in the right percentage, also if you need inhibitors you should check those levels as well. Good luck.
  • Dave Larsen_9
    Dave Larsen_9 Member Posts: 10
    what materials were used?

    I have a couple of questions Steve. What type of tubing? do you have an oxygen barrier? what type of boiler? Antifreeze? If you have 15 year old antifreeze then it is probably very acidic by now and eating away at your system.
  • hot_rod
    hot_rod Member Posts: 24,509
    Any strainers, or filter ball valves

    in the system? A good place to find a slow spot in the road.

    If you can disconnect the tube circuit from the boiler you can power flush with a garden hose at pressure up to 100 psi.

    But make sure the boiler with it's 30 lb relief and the expansion tank is isolated from that pressure.

    The early PB systems were famous for sludging up tube. Same with some of the non barrier tube, Solar roll early Entran systems, even non barrier pex under the right conditions.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Plumdog_2
    Plumdog_2 Member Posts: 870
    Pumps CAN go away after a time

    I've seen plastic impellers get eaten away until nothing is left but a stump. It can't hurt to check it if your fluid is moving slow.
This discussion has been closed.