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Circulator for Primary Loop

1Ron_L1Ron_L Posts: 13Member
Changing heating unit to an HTP Elite modcom boiler with an HTP indirect Ultrastor 60. I have infloor radiant with 11- 300' loops and a Taco 011 pumping to them all with a pressure differential bypass valve installed. At present it is a closed system running through a heat exchanger and I understand that I will eliminate that HX with the new boiler and that I will pipe direct from the boiler and I will need to add a primaryloop with closely installed tees and a circulator for the boiler and another for the indirect. My confusion is in the understanding about what circulator to use for the boiler primary loop. The chart with the boiler says that I need a range of 8-12 GPM flow with a corresponding pressure drop of 15'-33'. Does that mean I need to look for a pump with that flow rate and also 15-33' of head? I think i'm confusing pressure drop with head here and it's just not connecting in my brain. That would be a rather large pump so I guess that it not right. Can you guys help me to understand what I would need here and how I'm misinterpreting this pressure drop/GPM chart. Perhaps a suggestion for the circulator on the indirect also.


  • hot_rodhot_rod Posts: 12,042Member
    Which model are you looking at? I think that is a fire tube design, should have low pressure drop as shown here.

    I prefer a hydraulic separator for piping to give you air, dirt, magnetic and hydraulic separation.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GroundUpGroundUp Posts: 673Member
    Are all 11 loops on one zone? What model Elite are we talking here? We'll need some more info.
  • hot_rodhot_rod Posts: 12,042Member
    That seems like a lot of circ for the job?

    1/2" loops at 300' length is a tad over 3' head, plus any piping etc in that circuit.

    11 loops at 1/2 gpm each 5.5 gpm. Not sure why that high head circ is in three? Seems more in line with a 007 or 15-58 size circulator?

    Unless a tankless water heater is being used as a boiler?

    Will the indirect be on a zone valve, or separate circ?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • 1Ron_L1Ron_L Posts: 13Member
    Thanks for the responses.

    1. The boiler is a regular Elite EL-110 boiler. The specs are attached. It is not a fire tube or wall hung.
    2. The system was heated by a Light Duty Phoenix. Problems with as couple of them over a few years. That is why the HX is now there. Removing that for the regular Elite boiler and hence the primary loop needed. Heat load is 78000 BTU as I remember
    3. 11 loops, 5 zones over 3 floors. 2nd floor is Quick Trac, Main floor is under floor with Joist trac plates, Basement is tubing over insulation board
    4. So based on chart, which size pump do you like for the primary circuit?
    5. I agree that the main pump is large. That's what was there. I think that it reflects itself in a Delta T of only around 10 degrees so maybe pushing too much, too fast. Since I have to reconfigure some of the piping anyways, would a variable speed Delta T pump be better. Since the differential bypass is there, maybe not a Delta P pump. Recommendations?
    6. The indirect will be on a seperate circ. Again size Recommendations?

    Thanks in advance for the info.
    BTW, I'm a remodeler not a heating guy but like learning how systems work. Bob, liking the Coffee with Caleffi videoes and bulletins. Learning alot. Thanks

  • ZmanZman Posts: 5,334Member
    edited June 18
    This is the boiler resistance characteristics. They are using feet of head to represent flow resistance.
    If you superimpose those points on any circulator's performance curve, you will get the operating flows where the 2 curves intersect. The dashed line is estimating additional piping losses.
    It looks like your 0011 would be a good fit for that side of things.
    Personally, I would use a delta p circ like the taco VR1816 in constant pressure mode and either eliminate or max out your pressure bypass for the heating side. For the indirect a simple 007 should do the job.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • 1Ron_L1Ron_L Posts: 13Member
    Zman, that really helps my understanding on how to interpret.
    Just so I understand your comment, is the 011 what you would put on the primary loop? Seemed like a big pump for a small loop so that's what was confusing me. Then a Delta P on the main side pumping to all the zones?

    Just to clarify my original post on the zones I did forget that that in addition to the 11- 1/2" pex loops which are for the 1st floor and basement, my 2nd floor has 2 zones on zonevalves. longest is 55' of 3/4 pipe going to uponor maniflolds on the 2nd floor and then going out to quick track 5/16" loops. all around 100'
  • ZmanZman Posts: 5,334Member
    Your boiler has a very restrictive heat exchanger. Is is essentially a long tube coiled around a cylinder. It takes quite a bit of circulator to get the required flow rates.
    As for your radiant zones,mixing and matching tubing sizes can be problematic. You may need to either add some balancing valve or continue to over pump it.
    If you can take the brain damage, you can map out the resistance of all your components and tubing to see how different the zones are.
    Here is the info you will need. 7th edition - full copy/cdam_manual_0611_webready.ashx?version=042520190111
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • 1Ron_L1Ron_L Posts: 13Member
    Zman, Love it, thanks. I get OCD when learning about new stuff.

    So looks like an 011 for the primary loop and keep the same for the zones. Would a similar ECM type pump be better and more efficient for me. If so recommendations? You mentioned the VR 1816. Would that be good for both applications? My plumber mentioned a VT2218 but gave me no reason. I need reason! i will look at the charts for them. Would appreciate your input.
  • ZmanZman Posts: 5,334Member
    The VT2218 is a delta t circ. It is going to get really confused with your mix of tubing sizes and lengths. I think the VR1816 would work for you but would need to do some number crunching to be sure. What is your differential pressure valve set to now?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • 1Ron_L1Ron_L Posts: 13Member
    Zman , thanks again. I see your point on the delta t circ. It would be different on different piping.

    I set the bypass valve like the instruction says. Close bypass, all zones calling and open till you feel the higher temp flow through. Not sure there is a #. The system worked fine and space was quite comfortable this past winter. Just that I need to change the boiler and alter some of the piping to accommodate so new circulators are now entering the picture and those are my concern to get it right.

    I quickly read through the Uponor manual you linked. Will figure best I can for the flows and head for the zones.

    So the VR1816 pumping the zones and the 011 pumping the primary loop? I could use the existing 011 and move to primary loop and the VR new for the zones. I have an 008 stainless that I’ve been pumping the domestic through the HX. I think I could use that now on the indirect so as not to have to buy new for that.
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