My heating system stopped working this morning. It's an oil-fired hydronic system with 5 zones and hot water tank. This is what I have diagnosed so far:

  • The thermostats are calling for heat.
  • The relay inside of the aquastat is clicking and connecting the two sides.
  • The boiler is heating, and the gauges are showing 170F at 30psi.
  • No water is flowing through the valves. The valves are installed on the return side. I manually opened one of the valves, but still no hot water is flowing through. The pipes in/out the valve manifold are cold to the touch.
  • The recirculating pump is showing a light as in the image below. It looks purple (see image), and I recall seeing this being green in the past. Looking at the pump documentation, I see that the possible light colors are white, red, orange, and green, so I'm assuming that the purple is worn-out white. Seems that orange is normal, green is eco mode, but it's unclear from the documentation what a steady white light refers to, if indeed purple = white.
  • I can't feel the recirculating pump working, and the pipe coming from the return side is cold. But these circulators are known for being super quiet.

Question: Based on your experience, what should be my next step or diagnosis attempt? Replace the aquastat? Replace the circulator?

recirculating pump


  • 1
    Potentially dumb question: "hydronic system oil boiler" I presume that's an "oil fired" boiler, not that it's boiling oil, right? (Not that it matters unless you've got Huns storming your castle.)
    – FreeMan
    Oct 19, 2023 at 14:00
  • 1
    @FreeMan Yes, thanks! Just edited the question.
    – Cheery
    Oct 19, 2023 at 14:06
  • Do you know if you have hard water? Possible that the outlet/inlet of the pump is blocked with sediment. Disassembling of the pump to clean might work.
    – crip659
    Oct 19, 2023 at 14:36
  • @crip659 I have hard water and a water softener system. Definitely worth looking at. Thanks.
    – Cheery
    Oct 19, 2023 at 14:38
  • Buildup from hard water in a hydronic closed loop should be quite limited, unless it's leaking (in which case rust is the more usual culprit blocking the rotor.)
    – Ecnerwal
    Oct 19, 2023 at 14:41

1 Answer 1


Sounds most like a bad circulator, but you could perhaps verify that power is being applied to the circulator wires (seems likely if there's a light on it.)

The sheet here (which may or may not be your exact 007e) https://www.tacocomfort.com/documents/FileLibrary/SS_007e_iSheet_102-563.pdf

Says not running and led red means rotor blocked or insufficient supply voltage. For blocked rotor it suggests an attempted unlocking procedure, (initiated by disconnecting and reconnecting the power supply) followed by (if unsuccessful) disassembly and cleaning. And if that does not work, replacement. "Purple" is not an LED color it admits to. White, green, orange and red it admits to. So it's probably (what it calls) red that you see.

  • I purged the air out the system. Did not feel any air coming through the pipes, but then hot water started flowing. I can feel the pump working now. The LED is orange. But it flickers different colors when you touch it, so it's probably letting me know it's time for a replacement.
    – Cheery
    Oct 19, 2023 at 19:41
  • It's expected to go between orange and green in normal operation, per the linked manual. And it might well flash white when started, as well. If it spends much time on red, consider getting a spare (but the warranty starts ticking as soon as you buy the spare, so...)
    – Ecnerwal
    Oct 19, 2023 at 23:16
  • maybe you had an air lock. do you have an air separator? also recommend a dirtMag Oct 20, 2023 at 5:00

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