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which circulator?(Primary/Secondary)

Steve_45 Member Posts: 39
I want to put in a Dunkirk 4EW.90T Boiler with four zones in a primary/secondary configuration. The four secondary circulators I'm thinking of using are Taco oo7's on 3/4 copper tubing. The runs are 101 ft., 126 ft, 110 ft, 111 ft. repectively Totals include runs and baseboard. approx. 92,000 BTU which includes 20% over for a DHW heater. What circulator should I use for the primary loop and what circulator should I use for the DHW heater that will also come off of the primary loop in a parallel run as discribed on hydronics.com. I have been visiting the wall regularly so that my question was, HOPEFULLY, not poor. I hope I have include all the 'Right Stuff' Based on info at Hydronics.com I've calculated all the head pressures to be between 6 and 7 pounds.(I think)
Any help/suggestions would greatly be appreciated.


  • Weezbo
    Weezbo Member Posts: 6,232

    why ?
    do you like pumps?
    zone vlaves will work for you i am sure of it.
    leave one pump on the boiler and recirculater can be placed any where on the supply or return and you wont have any problems. if you use a spirovent then pump "away"if you are a coin vent taco air bleeder fan stick a couple of those in call it good stick the recircu on return ahead of boiler. zone your water maker too. why waste money.
  • Justin Gavin
    Justin Gavin Member Posts: 129
    Your Primary Pump

    You don't really need a large primary pump. You should be able to use a Taco 007(or whatever is supplied with your boiler) for the system pump. Look at the pressure drop of your boiler. Convert the pressure drop to ft/hd (I believe it is 2.3 psi for every ft/hd). Than measure the primary loop and multiply by .06. Add that number to the pressure drop of the boiler and that will give you the ft/hd requirement. Next assuming you will operate using a 20 degree delta T figure 9.2 gpm of required flow.

    Look at the Taco pump curve find 9.2 gpm's and go to the head requirement and make sure you are in the middle 2/3 of the pump curve. 8 times out of ten the boiler pump supplied with the boiler can handle a primary loop.

    Now the tricky part. You are going to have to remove the pump from the return and and move it to the supply. Make sure you place the expansion tank on the suction side of the pump and go from there.

    Use the same princible for the Indirect hot water heater. Pressure drop, convert to ft/hd, add the piping in the loop, multiply by .06, add piping ft/hd to water heater ft/hd to get the ft/hd requirement and size for 9.2 gpm and you should do just right. You might find out that you can use a 007 as well for that loop. You should be if it is a small to medium tank.

    One more thought, make sure that whatever electrical circuit you are wiring all the pumps up too can handle the AMP draw of all those pumps or you will be popping breakers.

    Good Luck,

  • Steve_45
    Steve_45 Member Posts: 39

    Thanks guys for your response and advice. One other
    questions. If I'm using a primary/secondary layout
    is it still necessary to add 20% for the Amtrol 40 gal
    DHW heater?

  • Steve_35
    Steve_35 Member Posts: 546
    Boost output for DHW

    IMO, it's never necessary to boost the output of a boiler to allow for DHW production unless it's a darned tiny boiler. I would either upsize the boiler, install a larger indirect or discuss with the end user if the boiler was 50K input or less.

    Otherwise we always prioritize the DHW.
  • hr
    hr Member Posts: 6,106
    Size the boiler

    to the largest load. Sounds like your heating load is somewhere around 78,000 BTU/hr?

    A boiler sized to handle that load generally is adequate to handle most residential DHW production.

    You could calculate you actual DHW needs, however many homes get along fine with a 35-40,000 Btu input tank type water heater.

    Your boiler (90,000 input?)with a 50 or 60 gallon indirect should be fine. Indirect water heater manufactures will have output data available on their spec sheets, to confirm actuall gph production when matched to your boiler. I'm sure Dunkirk could provide a tank and spec sheet for your application.

    I'm still not sure why you need a primary secondary arrangement?

    If you are designing a hot water baseboard only system with an indirect, basically a one temperature system, skip the P/S piping and spend the money instead on a nice boiler control with outdoor reset and DHW priority.

    This would be a nice energy efficient system offering a control option to priortize the DHW load, and modulate your system supply temperature based on outdoor temperatures. Most of these controls also have a boiler return protection feature.

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