I have a hydronic heating system. A previous plumber installed this device which I assume turns off the pumps in the event of dry plumbing so that the pump and boiler don't run dry.

This is wired in series with a power strip which has been dismantled to wire this in series with the hot line. Then the devices are plugged into that power strip.

I have not tested it but I imagine if the pressure drops then this circuit opens. But it cannot be correct that this is spliced into a power strip.

What is this sensor called and what is the correct way to wire a receptacle to a sensor like this?


  • 1
    Can you provide a focused close-up of the sticker on that sensor? And a picture of the power strip and how it's connected to the rest of the system? Definitely doesn't look right. Usually a low pressure sensor would be enclosed in a box, labelled and certified, cabled properly with the wires enclosed, and would be connected directly to the boiler in a way described by the instructions and wiring diagrams.
    – jay613
    Dec 10, 2021 at 2:43
  • Unfortunately I cannot because this is from my cabin a few hours away. However, the power strip's cord is split open, the hot line is cut, and it's spliced into this sensor.
    – Matthew
    Dec 10, 2021 at 4:53
  • 1
    This seems to be an excellent example of why plumbers plumb and electricians electric. Your plumber doesn't seem to know much about electrical code if he opened a power strip and tapped into it. This seems to be the kind of work that was proceeded by the phrase "here, hold my beer".
    – FreeMan
    Dec 10, 2021 at 13:03
  • @FreeMan do carpenters fish?
    – jay613
    Dec 10, 2021 at 13:46
  • Probably, but not as well as fishermen, @jay613
    – FreeMan
    Dec 10, 2021 at 14:01

1 Answer 1


You should purchase components that are designed and certified to provide safety functions including preventing over-temperature, over-pressure, over-current, and you should install them according to their instructions, local code requirements, and common sense using accepted parts and techniques

This answer is abstract because your installation violates every single concept above. I could tell you to purchase sensor model X and connect it in a certain way, but your installation really needs a complete rethink from someone competent.

Here are some things you would see if this were done properly (enlarge photo for legibility): An instruction manual, that was followed, left behind secure and protected. All critical safety components have labels on them, are certified as required by local code, and their instruction manuals are part of the package so they can be verified to meet the requirements of the boiler and code. The cabling is done properly with correct materials installed correctly, by local electrical standards and according to the boiler's instructions.

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  • Gotta give you a + for your answer. Also, whoever did this installation combined steel fittings (the Tees) and copper. Bad bad bad. It will lead to electrolysis corrosion. The installer should have used copper or brass (more commonly available in fittings). Either that or use dielectric couplings to prevent electrolysis. Dang, maybe I'm getting old and grumpy, but I HATE hack jobs by supposed pros who don't know what they are doing. ....OK, that's my rant for the day. Dec 10, 2021 at 13:51

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