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Are any of my pumps grossly oversized?

ScargoScargo Member Posts: 5
Here is the latest schematic of what I plan to do. I would appreciate any comments. The drawing is to scale. I have 1" going to the Hot water heater and most of the primary and seconday is 1-1/4".I sized circulator pumps so that I have a range of 5-6-1/2 GPM on all zones.


  • ScargoScargo Member Posts: 5

    I am replacing the original boiler in my 1984 vintage house and purchased individual circulating pumps to replace the zone valves. I have seven zones of which two are new. One zone is for the new 40 gallon hot water tank, which has 1" piping. This zone will be a <10 ft. loop. I'm planning on running this directly off the primary.
    The garage zone is new and is for a 36K BTU, forced-air heater with 3/8" dia. core and 92 ft. zone loop. I haven't decided on size, but I am thinking 1/2", aluminum core PEX to feed this.
    The longest zone loop is 167 ft. (3/4" standard baseboard heat is in all of the house) for the second floor.
    MY MAIN CONCERN is the plumbing supply house recommended and sold me B&G NRF-22's for ALL the zones. My impression is that this much GPM is not a good idea for (at least)the two new zones. The supplier says for me not to be concerned. Should I be? I've heard that erosion and noise can occur if the flow rate is way too high....I calculate that I am at 3 to 4X on five of seven zones....based on 4 GPM as ideal for the 3/4" stuff and 8 GPM for 1".
    I have a 4,500 SF house and am installing a Slant Fin, Eutectic EC-10,net rating of 132K BTU, oil-fired boiler and plan on installing a 1-1/4" (primary) and secondary circulation style system. I plan on upgrading to the optional Thermatic control at some point. The supplier is reluctant to down-size (and exchange) any pumps, though they are still in the box.

  • Yes, the NRF-22s would [appear] to be HIDEOUSLY oversized--not only for the zones you specified, but likely for ALL zones. Even the NRF-9F/LW [appears] to be grossly oversized...
  • scottscott Member Posts: 38
    Sounds like overkill

    I like your choice of boiler. I have heard this boiler live fire and it is VERY quiet! Quietest boiler on the marketplace I think! And very efficient!

    As for the pumps, I would return them and install the Grundfos SuperBrute pump.It has 3 Speed versatility to match any application. Also carries a 3 year warranty, has a built in flow check for a labor saver and, like your boiler, they are also VERY quiet!
  • Like This Little Feller

    Sweetest little unit goin.
    I'd do one circ. with seven zone valves.
  • scottscott Member Posts: 38

    Cool pic! I like it!

    Is it quiet with the NX, I heard it with a Riello
  • ScargoScargo Member Posts: 5
    I'd like to make it work with pumps

    I agree that zone valves might make more sense (at least money-wise) but I am way down the road for that, unless it is TOTALLY impractical. I would like to find the appropriate pumps and go forward with my design unless I am compounding a bad situation and only making it worse. I've already purchased a three and a four zone panel for the pumps. I've done all the measuring and calculating and I think my numbers are good. Head and subsequent flow rates for the zones with the NRF-22 pump are as follows:
    1: 9' head=8 GPM
    2: 7' head=12.5 GPM
    3: 5.3' head=14 GPM
    4: 6.3' head=13 GPM
    5: 10' head=7 GPM
    6: 8.5' head=10 GPM
    7: 4.1'/16 GPM

    I still want to do a P/S system...
    I am not doing this myself to save money (and cost is not a major issue) but to enjoy the experience and broaden my knowledge. What pumps do you suggest?
  • Ron SchroederRon Schroeder Member Posts: 998

    One advantage of zone valves over pumps is that zone valves draw a lot less electricity. I like to put the indirect on it's own circ matched to the flow needed for it's heat exchanger and use a second circ to feed the heating zones with zone valves. Taco, Danfoss and Calleffi make zone valves that draw less than 5 watts each.

    If you are going to stay with pumps, then the 3 speed Grundfos on low is probably the best way to go with easily available pumps.
  • ALHALH Member Posts: 1,790
    Zone Pumping

    The flow rate for each zone is determined by the heat loss and desired temperature drop at outdoor design temp of that zone. Once you know the flow rate you need to determine what size pipe will carry that flow below your desired head loss threshhold. Then you know your operating point. Go to the pump curves of the manufacturer of your choice and select a pump just above your operating point. With zone pumping in a residential situation, you are typically in the range of a UP15-10F for each zone. A UP15-58FC on low speed is a little more. One 15-58 with zone valves can generally handle the typical 3 bedroom home.

    My advice is to:

    1. Do a heat loss calc for each zone.

    2. Size your piping based on that flow.

    3. Select your pumps based on that flow and pipe sizing.

    Most likely you will have a hard time finding pumps that are small enough.
  • ScargoScargo Member Posts: 5
    I've picked some pumps

    I've chosen pumps for the secondary circuits that give me a range of 4.5 to 6.5 GPM for all seven of them. The head spec's I listed in my last post were determined using the 6' per 100' rule of thumb. Does this seem OK?

    I would like to know if you think I need a check valve on the cold water inlet of the hot water heater and an expansion tank on the hot water output side? There was not any of this on the (internal) tankless hot water supply of the old boiler; only a flow restrictor...
  • scott marklescott markle Member Posts: 611

    I think your schematic may be flawed.

    I believe you need another circ. to induce the flow direction that you illustrate in your secondary loop.

    Under what conditions will the flow be induced to run in the direction you show at the differential bypass valve?

    Your circs. will be sucking from both sides and a portion of the flow will bypass the closely spaced t's.

    Esentialy the flow direction at the bypass valve section of the pipe work will be opposite of what you show. And thus a portion of that flow will be circulating without picking up any heat from the closely spaced t's

    The arrangement you illustrate requires a zone group pump to create the secondary flow direction that you desire. also I see no reason for the differential bypass in this application.

    You could eliminate the bypass leg, and the circs would induce flow across the t's in the way you desire.

    Seems to me that in this arrangement when system flow is greater than boiler flow you will have the potential for untempered return water.

    I would look into injection mixing P/S schematics and control, this would provide the opportunity for full reset mixing and boiler protection from overly cooled return water.
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