Lightening and household smoke alarms

[Logicon]

My home was constructed 4 years ago. We have 5 standard smoke alarms and 2 combo smoke/CO detectors in the house. They are all hardwired to the home power. All alarms activate whenever a single unit activates.

The problem, whenever we have relatively close lightening strikes, the alarms go off. I haven't found anyone who can tell me why or what to do about it other than that i should replace ALL of my alarms in the house because one or more are defective. With 7 units in the house, I am not really interested in that solution yet.

I would like to know why this is occurring and any ideas people have to solve the problem other than full replacement.



Marc Whitney

http://www.thelogicongroup.com

 

[dpc]

I had similar issues with wired smoke detectors going off due to RF interference. I switched to battery-powered smoke detectors - no more problem.

If you want to keep the wired detectors, first make sure the ground path (green wire) is good - tight connections with no corroded terminals, etc.

The next thing to try is to install some type of common-mode filter on the incoming ac power leads, probably some clamp-on ferrite beads or something similar. The ac power leads make a great antenna for picking up RF and lightning can generate a lot of that.

I would not be convinced that replacement of thee existing units will 100% solve the problem, unless the new units have beefed-up isolation and filtering.

David Castor

http://www.cvoes.com

 

[VEBill]

Assuming North America: Those type of smoke alarms are typically wired up using 14-3 cable (3 wires, plus ground wire); same cable as used with 3-way switch devices and split outlets in the kitchen. The 'extra' wire carries the trigger signal between the units.

It's probably the trigger signal that is most sensitive to EM pulses from *nearby* lightning strikes. If the strikes causing false alarms are further away, then it's probably riding in on the power line.

If it was me, I'd pull one down (should have a little connector), figure out the manufacturer, track them down and give them a call. Maybe they have a new version, and maybe they'll help you out. Certainly worth a call if you can contact them.

If not, then ask the local electrical supply house to recommend better models. They're usually only about $15 each, so it's not a huge expensive to replace them all. But it might require professional installation due to the wiring in of the new connector.

(You're supposed to replace smoke alarms after about ten years (?) anyway as the radioactive source decays. So even in the worst case, with four years use, it's not a total loss...)

If there's an external relay wired into your house alarm system, it needs to be compatible with the smoke alarms.

You should ALSO have a few battery powered versions scattered around.

We get lightning here too, and it sometimes triggers off my house alarm and even makes the telephone ring (not to mention causing $500 damage on two occasions). But I don't recall the smoke detectors being triggered.

Good luck.

 

[VEBill]

PS: the CO2 versions would be much more than $15.

 

[itsmoked]

You mean the CO versions.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[VEBill]

Yes, scratch the "2". Thank you.

 

[MiketheEngineer]

And most codes now require that the smoke alarms be wired to activate all when one goes off.

Maybe your "teen" is "smoking in the bathroom"??