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can anyone expain to me the correct way to size the piping and select the correct pump for a turbomax 109.  im told to use 2' piping and a grundfoss 43-44.  the distance from the boilier is maybe 20ft max and the boiler is 265k btu. i have no problem spending to much money on 2' piping and a 300+ dollar pump i just want to know how to figure it out on my own and not take the supply house word for it


  • SWEISWEI Member Posts: 7,356
    edited May 2014
    Short version

    probably not.  At a 20ºF ∆T that boiler would require 20-25 GPM depending on the boiler efficiency.  Chart on P.31 of the Turbomax manual shows less than half a foot of head for either of those rates.  I'd be looking at something like a 0010 or a Series 100 for that.  Size the pipe to ADD enough head to keep the flow rate where you want it.  I'm not as familiar with Grundfos curves, but they probably make something suitable.

    If you're pumping the DHW side instead, you would need a lot more pump.
  • ZmanZman Member Posts: 3,517
    Pipe and Circ

    As has been said, There is no need for more than 20-25 GPM with that boiler. If the boiler was bigger you might want higher flows. 1 1/2" pipe would be appropriate for your application.As for the circ, is it pushing water through the boiler? What type of boiler is it? You will be looking at a circ in the $300 range to get that flow rate regardless. The only question is how much head does it need to overcome in the boiler.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • icesailoricesailor Member Posts: 7,265
    edited May 2014
    Tell me I'm wrong:

    Tell me I'm wrong.

    The "boiler in, Boiler out" tapings on the 109 are 2" or 2 1/2". Which means that if you want the rated output in DHW of the Indirect, you need a boiler that will deliver the BTU output to the Indirect to heat the hot water load, when needed AND the heating load added.

    If you are only using the 109 for its volume capacity and output, you still need the rated inlet size. 2". If however, the load of DHW is half what is listed, 2" is oversized. It might only need a smaller tank with less input. Without the heating load, the DHW load determines what size the supply/return is. The coil size inside the 109 is larger than a tank that requires a 1 1/2" supply.

    So, if the DHW load isn't the determining factor of sizing the DHW load, the heating load is. So, the heating load should be the determining factor.

    Some of you all who are not Plumbers AND heaters should experience what happens when you have separate systems for DHW and building heating. And have the DHW load greater than the available energy at intermittent times.

    If after careful designing, you decide that you need a 1 1/2" supply and return to and from a boiler with the appropriate rating, that's fine. But if you are adding DHW to the load, it is an additional load that can be at a maximum when it is being used. The rest of the time, it doesn't exist. If you have a 150,000 BTU boiler connected to a 109, it will only add the rated BTU's to the heater.

    If you decide it is insignificant or non existent, hope it doesn't have sharp teeth.

    For example, if you need to raise 500 gallons of cold water, 100 degrees in an hour, you need a boiler ONLY that will give you 250,000 NET Btu output. I don't have any charts but I think that is around a 1 1/2" supply and return.
  • ZmanZman Member Posts: 3,517
    I should add...

    Ice makes a good point. You will never get more out of the water heater than the output rating on the boiler. They 1 1/2" is based on that.

    The other issue you may have is that, given the size of the heat exchanger in that tank it will drag the boiler temps down as it attempts to reach thermal equilibrium. This is a problem if there is a simultaneous heat load or if the boiler is noncondensing .

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • icesailoricesailor Member Posts: 7,265

    Thank You. I've been trying to make that point or years.

    And, if you put a large Indirect (like a TT109), and run it at 120 degrees stored in the tank, and you don't have any type of positive shutoff device (like a zone valve), and you have a popular massively over pumped system with multiple circulators, you can get Ghost Flow through the tank coil from other zones running and the tank coil isn't calling. And if connected to any form of ODR or otherwise, the DHW coil will either add or rob heat from the heating system.

    An indirect is just another heating zone connected to a heating boiler. Just like a Tankless Coil in a oil boiler like a Weil-McLain WTGO boiler.
  • HenryHenry Member Posts: 726

    If your boiler is 265,000 BTU input and of average efficiency, the net output is around 218,000 BTU. Boiler supply temperature to the tank should be 180F and 30 F DT. The B & G SYstem Sizer shows a 15 GPM flow for 30 F DT.It also shows 1 1/2 black pipe is sufficient 1 3/4 feet pressure loss per 100 ft. Now for a 90 % efficient boiler:

    It is 17 GPM and still 1 1/2 black pipe.

    The System Sizer is free from B & G. Itis also available online as a free software. I find it also usefull when trying to find out if a heat exchanger is getting blocked in condensing boilers. Capacity of the boiler at the rated fire, then check the DT and use the System Sizer to find the GPM.
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