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Variable Speed Pumping

If you normally set up your pumping based on Delta-P and that is what you are used to, your circulator speed is going to get really, really low....

(Sort of like grandpa in his chair: "Uhhh...is he still breathing?")

I love the concept. I mean, after all, it is all about Delta-T when you get right down to it.

Delta-P is an incidental value and while one might control to that, your "20 degree delta-T design" returns at what now, 8, 10 degrees cooler? This means, for all of your efforts you are still moving twice the water you need to, right?

Being on the engineering side (meaning, as a group or industry kind of slow to react to new ways of doing things), I am specifying "both", meaning, the pump VFD's will respond to the greater need of remote delta-P (near the end of the system), or "near Delta-T". The DDC controls take the lead and I make sure that the most remote Delta-P is just high enough to get the requisite flow to and through the furthest terminal unit. Then I reset that setpoint based on low demand if I can.


    PLUMBARIS Member Posts: 22
    Variable Speed Pumping

    Doing a job that I wish to use variable speed pump on. Went to the Taco site and they seem to push VSP by delta T a concept I had not heard of before. It would be easier to set up, anybody have experiance with this set up.
  • I wached that vidieo too

    The question I have is...If the delta t sensors are on the return and supply of a multible zone header, how do I know the flow is correct through each zone, maybe one is fast and one is slow but the return header still shows the 20 degree delta t. You would think you still have to balance the zones first. But I will say this, I have a tekmar 157 control on my solar that varies a small grudfos pump and I wach it just amp up and down till it zones right in on the delta t..it works great.
    PLUMBARIS Member Posts: 22

    Thanks for the reply, this is a residential job so no VFDs or any XYZs either. this is the first variable job I've tackled. So if I understand this right all I need to know is my GPM based on load and the pump will variate by Delta t.
    PLUMBARIS Member Posts: 22

    That is something I didn't think about for there are 8 zones in this system. It has been run thru Wirso's program and the headers will be the adjutable type so I guess we'll see.
  • I guess if you

    pipe it in but connect your sensors to just one zone and keep all the zones open and throttle them one at a time with a digital thermometer so you get the same delta t as the one that has the sensors on, then after you finish balancing put your sensors back on the header it should work fine. hmmmm I think lol.
  • Brad White_204
    Brad White_204 Member Posts: 20
    Pretty Much!

    Well, you WILL have a VFD in one form when you are done. That will free you up to use any other letters you prefer. :)

    A factor in all of this is trust. You have to trust your design instincts and let the system work as it should. Once you see how little pump energy it takes (varies by the square, roughly), you will be impressed as will be your clients.

    Clamp an Amp Meter on the circulator running at full speed and show them the baseline. Then show them the reality. At today's electric rates, Owners should use their hands to applaud you rather than to grab their ankles. :)
  • Wayco Wayne_2
    Wayco Wayne_2 Member Posts: 2,479
    I am currently using

    a variable speed taco 007 on my own system. MY upstairs is heated by Hydro air. I have a sensor in the supply air that connects to the VSP. I control the speed of the circ according to supply air temperature. The hyro air is the 2nd stage. The first is an air source heat pump. As it gets colder outside and the supply air temps start to drop I keep the supply temperature at 120 F by feeding hot water to top it off with the variable speed circ. Works great. WW

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