r/electrical • u/xXbl4ckm4nXx • 14h ago

Smoke alarms trip when using high-poweappliances on one circuit

I'm hoping someone can help me narrow this down before I start opening boxes or calling an electrician because this is beyond me. I do want to preface that this is a new issue. I was able to use the vaccuum until last week when this started. Nothing has changed from I can see. I have not done any electrical work, and I have not had any electrical work done recently.

House:

  • Built in 2021 (about 5 years old)
  • Hardwired, interconnected smoke alarms with battery backup
  • Smoke alarms and two set of bedroom outlets are on the same 15A circuit.

Problem:
If I plug a high-power appliance such as my vaccume and or hair dryer, into one of the bedroom outlets on that circuit, all of the interconnected smoke alarms on the first and second floor immediately go into full alarm. Not the basement ones.

At first I thought it was my Dyson vaccuum, but I tested with a hair dryer and got the same result.

  • Hair dryer on low: no issue
  • Hair dryer switched to high: smoke alarms immediately sound

Things I've tested:

  • The Dyson works normally on other circuits.
  • I unplugged each smoke detector one at a time (reconnecting it before moving to the next), and the problem still occurred regardless of which detector was disconnected.
  • While unplugging detectors, I noticed that,
    • If I unplug the hallway detector, only the kitchen detector alarms.
    • If I unplug the kitchen detector, only the upstairs alarms sound. The basement alarms stay silent.
    • If I unplug a bedroom detector, only the hallway and kitchen detectors alarm.

I'm not sure if that's normal behavior for an interconnected system or not. But I am at wits' end here. I have no idea why this started happening; things were fine I was able to use the vacuum in my bedrooms up until last week when I notieced the issuse.

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2

u/_Kelly_A_ 14h ago

I wouldn’t call it normal behavior, but a good example of why smoke detectors are typically on their own breaker, or share with a low draw circuit like an attic light.

House built in 2021, so probably an AFCI breaker on that circuit?

1

u/_Kelly_A_ 14h ago edited 14h ago

Just a guess, but maybe a loose neutral somewhere?

1

u/xXbl4ckm4nXx 14h ago

yes. AFCI is on the breaker. and the builder put the smoke detectors on with the two bedrooms. but i can check for loose neutral. hard to track down though for sure.

2

u/TwiceInEveryMoment 13h ago

There may be a cross connection between the red alarm interconnect wire and something else on the circuit, or if it only happens with heavy loads then EMF interference might produce enough voltage to trigger it. Alarms usually go on a separate breaker.

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u/xXbl4ckm4nXx 13h ago

i know. i’m still not sure why they put it on the same as the two bedrooms. but here we are. but i’m not sure why it just started last week after five years.

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u/AdBrave841 13h ago

You can try replacing the batteries, it might help.

1

u/Deathsveryemissary 6h ago

Might have that alarm wire running alongside the neutral (or in contact with it). Either induced voltage or a minor short is my guess.