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Delta P response time

I used a 15-58 on a 2 zone M/F system on a Prestige(Solo 110), but forgot the differential B/P valve,,, It seems easier to me to use a Wilo Eco then re-pipe-in a B/P valve.



My question is,,, as the zone valves are spring-loaded closure(and close fast),, will the ECO respond fast enough to prevent thumping? 

Comments

  • meplumber
    meplumber Member Posts: 678
    Delta P

    So you have a Prestige piped monoflow into a 2 zone system with zone valves on the 2 zones?



    Is the boiler piped into the monoflow through hydronic separation or closely spaced tees?  What is the flow rates needed in your 2 zones?
  • Brad White
    Brad White Member Posts: 2,393
    edited November 2010
    Wilo Stratos Eco Response Time

    Hi Dave-

    Good question. I just did a little experiment to confirm what I would have said off the cuff.



    Depending on what your DP (feet of head) setting is, has everything to do with timing.

    When I first energize the Eco, it ramps to 100% speed in about 20 seconds, give or take two, then settles at whatever head setting the dial is set to.



    When running at a low head (mine is at 4, as low as I can get it to go), and I close the valve, there is no discernible response, it seems to not react that I can tell.



    When running at a higher head (12 feet, not quite full speed), opening and closing valves (just ball valves at branches, not control valves and I closed just one at a time), the circulator speed seemed to settle in about eight seconds, after which, no change. When the valves are again opened, a similar time, settling to the higher speed.



    From this I would surmise that if there is any chatter, it will not last long. But if you mean "thumping" as "making steam", I wold not risk it.



    If you can make it work though, you cannot beat the energy use of ECM circulators in general.



    Any chance of getting a slower-acting actuator though?
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • Thanks Brad,,,

    There is no-way to stop the circ on a Solo 110 as soon as the heat-call ends, the lowest post-pump timing is 10 sec.

    Within that 10 seconds is when the "thumping" happens within the zone because of the quick closing ZV`s.



    Although the Eco is a great circ,, it seems a pressure differential bypass valve will still be needed.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    edited November 2010
    Who's zone valves do you have Dave?

    Honeywell's new curved top zone valves are a slow action valve specifically designed for these applications. I've not had to spec or install any yet, so can't give any first hand experience, but I think I was told that they are retrofittable for the old motor/switchgear without having to replace the bodies.



    Might save you some time and trouble. Also, all the VS circ manufacturers tell you to not use a PAB with their pumps. It confuses the pump because it "sees" the hole and keeps running at high speed trying to fill the hole.



    HTH



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Thank You too Mark,,,,

    I used the White-Rodgers 13S16-102 because of their low c/v factor.
  • Delta P responce time

    First, let me explain Delta P.  The head setting on the dial on the ECO (or LED display on the Stratos) is the differential pressure the pump produces at max speed.  Delta (or differential) P means the pump electronics are programmed to reduce the differential pressure by half at zero flow (dead head).  In the case of the ECO, 4 feet on the dial translates to 2 feet at zero flow,  16 feet on the dial is 8 feet at zero flow.  draw a line between the head at max speed vs the head at zero flow and that becomes the performance curve.



    The lower the setting, the lower the head difference between max speed head and head at zero flow - hence little head change when set at min (4 feet).



    Will the ECO's relatively slow response time eliminate the banging valves?  Depends on if the pump is set too high and if the valves close at the same time.  I would bet if the Eco was set low enough to provide comfort the banging would go away.  Question:  what speed was the Grundfos 15-58 set at?  Let's assume the system flow is say 6 USGPM (60,000 BTU's) with both zones open and 3 USGPM (30,000 BTU's) with only one, the 15-58 on speed 3 produces 14' head @ 6 US and 16.5' @ 3.  The ECO set at 8' produces 6.5' @ 6 US and 5' @ 3 USGPM.  NOTE:  The differential goes down on the ECO when the flow goes down (makes sense as less required flow results in lower friction loss and that is the only thing these circs are designed to do - provide flow by overcoming friction loss).  This is why I am 99% confident the banging will go away (sorry, I'm never 100% confident on "The Wall")



    Will ECM pumps eliminate the requirement for a differential by-pass?  Absolutely.  Will a differential by-pass effect the operation of an ECM pump?  Yes, if the pump is providing enough pressure to open the valve (highly doubtful, especially considering the differential pressure strategy).  If the by-pass is closed, obviously it will have no effect.



    If a manual by-pass is used, Mark is correct, the pump will see this as a leak (or an always open system) and run faster that it needs to (no adverse effect on the pump but will waist energy).
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