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Solar Glycol Loop good Variable Speed Pump Selection?

nmsolarken Member Posts: 6
Hello Folks,

I'm new here and have a question I'm hoping someone can answer.  I have an existing solar thermal system, 480 sq ft I use for both dhw and radiant.  The question is about a choice for the glycol loop pump.  I'm looking for a variable speed pump as a means to provide increased flow when needed to keep the panel temp down.  I've looked at the Taco 008-VDT and 0010-VDT and have heard they have some problems.  Are there any alternatives anyone on this forum has experience with and can recommend?  Another question - the comments about the 008-VDT on this forum seem to be a couple years old - have they fixed the issues?


  • hot_rod
    hot_rod Member Posts: 20,827
    variable speed solar pumps

    The solar controllers on the market will work with most any brand of circ. Usually they are equipped with a 1 amp relay, so watch the power requirement of the circ you are considering.

    Remember to calculate the additional pumping power required in glycoled systems.

    With a separate solar control you get a nice digital readout screen, some data logging like pump run hours, and the ability to do heat quanity monitoring. Some brands and models also have SD card slots to move data back and forth from a laptop.

    If there was a problem with then Taco product, I'm sure they have addressed it.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • JamieLeef
    JamieLeef Member Posts: 13
    Try Grundfos

    There is a solar-rated Alpha model. Controller-based variable speed is a fine choice but if you just need a new pump that should work. The delta-T mode is great.

  • nmsolarken
    nmsolarken Member Posts: 6

    Thanks for the comments.  I've decided to go with an external controller on a Grundfos 15-58.
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