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Too much pump?

Roland_18 Member Posts: 147
My heating system has two TACO 007 circulators. One is for heating and the other is for the DHW. Is it possible that the DHW 007 is too much pump for this kind of duty? The measured delta T rarely exceeds 5*F.

thanks, Roland........


  • furnacefigher15
    furnacefigher15 Member Posts: 514
    Not enough load

    You don't have enough load to cause temp change.

    May have more pump than is required, but I would leave it be so long as you are getting hot water.

    007 is a generic pump more or less for residential hydronics. You may have more boiler than you need for the dhw also
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    two TACO 007 circulators

    Yes it is possible that two Taco 007 circulators are too much for your system. But it seems to me that there is no way to answer your question based on the limited information you have provided.

    For example my system has 4 circulators. This could easily be reduced to three circulators if I put in two zone valves. But with my system, that would be the lower limit.

    Mine is set up primary-secondary as required by the manufacturer. In the boiler loop is a Taco 007 that is provided by the boiler manufacturer to be sure I use the correct size. They also specify that the primary loop be plumbed in at least one-inch size (my installer used 1 1/4 inch size). Since the boiler manufacture specifies this, there is no question that the circulator is the correct size.


    For the indirect hot water heater, the manufacturer of the boiler specifies a Taco 007 circulator, as does the manufacturer of the indirect hot water heater. So there is little question that that is also the correct size. It happens to be a Taco 007-IFC. This is connected across the primary loop closer to the boiler than the boiler circulator. When serving the indirect, the boiler circulator is shut off so all the heat goes into the indirect.

    On the secondary loop are two Taco 007-IFC circulators, one for each of my heating zones. Based on flow calculations, the flow in one zone is about 2.4 feet per second, and the other has a flow of about 2.8 feet per second. One is radiant in slab, and the other is oversized baseboard. My flow calculations for the radiant slab are pure guesswork since the house was almost 30 years old when I got it, and the survey of the lot did not show the piping diagram in the slab. All I know is that five 1/2 inch pipes enter the slab and one 1 inch pipe leaves it. The house has 5 rooms there, so I assume the pipes go one under each room, and are connected somewhere somehow in the slab to the one-inch pipe leaving the slab. The temperature drop from the slab in warm weather is around 1F ro 2F, and in very cold weather it can get up to perhaps 10F. So one might say the 007 may be a little too large.

    I am not convinced a constant delta-T is practical with my boiler. My downstairs thermostat is set at 69F. If it is 50F or warmer outside, the boiler puts out 75F water, so there is no possible way for that delta-T to be more than 6F. Similar things happen with the other zone, but the example would not be as extreme.

    The other zone sometimes gets a temperature drop I estimate at about 1/2F. In very cold weather it can get up to 5F or a little  more. It is likely that this is too high, but it is not clear I should buy a Taco 005 or an ECM circulator. If I were going to repipe this a little, I would get a delta-P ECM circulator and two zone valves. I cannot figure out how to use a delta-T circulator with my mod-con with outdoor reset.
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669

    Sounds to me that the Indirect water heater coil is dirty and not transfering the heat from the boiler.

    Turn off the boiler and run the hot water untill it is gone. ( tank water is cool) then fire up the boiler, If the boiler comes up to temperature real quick and the domestic water takes a long time to heat up - you have a dirty coil inside the indirect water heater.
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