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VS circs..........

Steve Ebels_3
Steve Ebels_3 Member Posts: 1,291
Given a system that consists of constant circ pumps with bypass zone valves for all the rooms, which makes more sense? A Delta P circ or a delta T circ?

This is a school job and for example, one of the zones we are recommending pump replacement on has 7 rooms with a total heating load of 138,000 btu's and a head of roughly 22'. We just hung 4 Vitodens WB2B-105's on this system so I would like to start changing the flow strategy to obtain maximum temp drop over the system. As is typical the system is hugely over pumped right now. Calculated flow in the main manifold with all circs running is in excess of 350GPM and they only have around 1.3MMbtu of emitter capability in the whole building.

I'm thinking that a Delta T circ would be just the ticket in this application as the head is not going to change much from no load to full load but the temp drop will be highly variable.

What think ye?


  • Charlie from wmass
    Charlie from wmass Member Posts: 4,322
    I agree

    since the system is bypass type the head should vary only the difference between the by-pass pressure drop and that from the travel through the coil.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
    Smart pumps

    Hi Steve, you may want to consider the Grundfos Magna pumps, and split the load between pumps, as required by the actual flow rates required.  http://www.grundfos.com/web/HomeUs.nsf/Webopslag/OMAT-78QRPT

    Talk to their engineering department to help you make the right selection.
  • How bout

    just shutting off the bypass loops so you will only provide flow when it is really needed.  This would be the ticket for a VS pump.  If you have bypass (3 way) zone valves and the system is properly balanced, your flow rate will never drop as valves close.  Unless I'm missing something here......
    The Steam Whisperer (Formerly Boilerpro)

    Chicago's Steam Heating Expert

    Noisy Radiators are a Cry for Help
  • CMadatMe
    CMadatMe Member Posts: 3,086

    I would look at the Magna. I think you would see a better electrical savings over using a Taco 0013-VDT if that is the pump your looking at. Would have to compare the costs of each pump to make my final decision.

    Did you use the rack system? What a labor saver. Had a hotel where we quoted our customer on competition mod/cons versus the rack and once you started to add all the copper and the labor the Vitodens were actually less expensive.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • hot_rod
    hot_rod Member Posts: 22,120
    mini Magna?

    I keep hearing about this new size mini that fits between the current Magna and the UP series. That would fill a nice gap in sizing. I believe it will accept a 0-10V signal without the need for the additional interface module.

    It will be a nice commercial or large residential solar pump if that is the case.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
This discussion has been closed.