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I was alerted by some vibrating noise in my basement and opened a little access hatch to learn more.

I saw a metal box with electric wires in it. This box is screwed in a larger pipe, which seems to run although the heating/vent is off. The 2 metal elements were vibrating against each other, causing the sound.

  1. What is this box is for?
  2. Why is the pipe vibrating while the heating system is turned off?

Small metal box with terminated wiring

isherwood
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Greg
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  • Seems like a simple junction box to join two cables. I can't see the second cable in the picture or where it comes into the box. – crip659 Feb 18 '22 at 10:30
  • 1) Are you 100% certain this is screwed on to the pipe behind it? 2) What "little access hatch" did you open? – FreeMan Feb 18 '22 at 12:25
  • A bit of context would be great. Where do the ducts go? Where do the cables go? – isherwood Feb 18 '22 at 14:27
  • @crip659 The cable goes **into** the duct. – Steve Wellens Feb 18 '22 at 15:29
  • I'm still curious if the "access hatch" is the cover for the box or a panel removed from the wall to give access to the box. If it's a panel in the wall, was there a cover over the box? If not, that doesn't meet code. – FreeMan Feb 18 '22 at 17:21
  • It's probably feeding an extra duct fan/blower. – JACK Feb 21 '22 at 12:57

2 Answers2

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It's a junction box for some item installed in the duct (based on the "other" wires appear to go out the back into the duct.) Terminology wise, we tend to reserve "pipe" for a round tubular object with a bit more structure used for carrying water or gasses at pressure, while duct refers to the thin sheetmetal for moving air at barely any pressure around the house. You have a duct there.

That might be a duct booster fan, or a motorized damper, off the top of my head for most likely in-duct electrified objects, though the booster fan is more likely since damper actuators (the powered part) are usually external to the duct.

Booster fan image from phyxter.ai, whoever they are.

Ecnerwal
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  • This is great, thank you for the answer! And sorry for the lack of vocabulary, moved from France a couple of years ago so I'm not yet super fluent with technical terms :-) Quick additional question: would the fan constantly work? I'm surprised it's running while the heating system is entirely off - no air flowing anywhere in the house. – Greg Feb 18 '22 at 17:27
  • Far better than my French, to be sure. No problem. Learning is good. Normally these fans are run with the system fan, not independently, but that's "normally" not "universally" - or there may be a failure in a control causing it to run. Or it might be part of a continuous ventilation setup separate from the actual heat delivery, even though using similar ducts. – Ecnerwal Feb 18 '22 at 17:31
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It’s probably powering a fan, possibly either part of a radon mitigation system or for extra ventilation.

nobody
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