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Some Installers Still Dont Get It

Ken_40 Member Posts: 1,320
wrong pew.

Pump "size" as in physical size - has nothing to do with "pmping away" dynamics and limits.

All circulators (sic pumps) are "measured" by two properties: 1) is their head (ability to lift water in feet [i.e., p.s.i]) and 2) GPM they can pump.

These two factors, when superimposed upon each other, form X/Y axis performance "curves." At 14' of "head" one circulator may deliver 20 GPM. That same circ. at 10' of head (a/k/a "pressure" or resistence to flow) may deliver 30 GPM's.

Many three piece circs. are soft on head and big on GPM. These tend to be very forgiving with regard to being on the "wrong" side of the PONPC since the differential is low, even the highest (and lowest p.s.i.) points - would have adequate static and/or dynamic "pressure" to never allow air to be "sucked" into the system because the circs. dynamics are less than the worst case scenario possible within the systems configuration.

If further understanding is needed, Holohan's seminal work titled "Pumping Away" would be the perfect read!

The link is up top. I think "Shop" gets you into the virtual bookstore. A must have book if your in this biz.


  • Dan_15
    Dan_15 Member Posts: 388

    Had a boiler tech here today for annual service. We chatted for a while about the Buderus installation, heating curves, etc.

    I told him that the one thing I wished they had done differently with the installation was to "pump away." He told me that these days they never do installations that way. They always pump on the return because it puts less strain on the circ; and if the setup is done correctly there will be no air problems and no need to pump away. I don't have any air problems, but still, I thought that "pumping away" was the gospel.

    Secondly, I described to him how the heating curve has been functioning. I told him that the boiler never really heats up past 155-165* in the winter because outdoor reset and indoor room sensor are doing their jobs well. However, I do experience frequent cycling in the winter which I attribute to the combination of fin/tube convectors that unfortunately populate my house, and no insulation. I feel that my fuel consuption is high overall. It doesnt help that the boiler is probably quite oversized based on my own heat loss calculation and fires at 1.25 GPH. He responded that the boiler should be reaching a 190* high limit regardless of the heating curve, and that something needs adjustment if it is not getting there.

    I relay this story only for your own enjoyment. The tech is is a nice guy and did the service well. But I think I will get better results chatting with Joe@Buderus about what I can do to solve my efficiency challenges.
  • Ken_40
    Ken_40 Member Posts: 1,320
    The tech's naivete is

    understandable. Your tolerance of same is not.

    Pumping away is NOT and absolute necessity in smaller systems, using low-head circulators, like an S-100. Low head pumps cannot develop enough differential to create a vacuum - especially in ranch homes or minimally "tall" systems.

    However, his comments about short cycling and system high temps is grounds for you moving on to another tech, or another company IMHO.
  • Joe@buderus_2
    Joe@buderus_2 Member Posts: 302

    The R2107 is an outdoor reset control. It adjust the system water temperature based on the outdoor temperature. The boiler will not always fire to maximum temperature. It is suggested to contact me while you are in front of the control and we can review the settings.
    Circulators on the supply or return usually do not effect the boiler operation. The choice is up to the installer. I'm sure many opinions can be expressed for and against.
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,537
    pumping away

    and having the circ on the return are not mutually exclusive,it's pumping away from the expansion tank not the boiler. I've seen 1000's of jobs not pumping away of all ages that operate perfectly with no air problems. Would I install not pumping away? No,but unless you have a specific problem there's no payback to repiping.

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  • GW
    GW Member Posts: 4,679

    Ken, does the pump size have anything to do with it? The basic premise is that there's less pressure on the suction side, therefore allowing the air to more easily escape. A pump is a pump, low head, high head, or whatever.

    Dan didn't comment on where the feed was, but many knuckle heads tie the feed on the suc side of the pump on the return side of the boiler. Whenever we replace expansion tanks/pukers/feed valves this is always the case!

    This technician has no clue, although I'm sure he's a nice person.

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    Wilson Services, Inc
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