Got a Q? Wiring 2 motion sensors to turn on a single load - Electrician Talk - Professional Electrical Contractors Forum

Node · 01-07-2009, 09:51 PM

Have a set of stairs with a deck on top and a pathway and entryway. Want to wire the stair lights w/ a motion sensor on each side.

I was thinking common neutral, common line to both motion sensors, and just run the loads back in parallel to my transformer?
Which in the end sounds like its all pigtailed together like a switch to two lights, but in reverse. AKA Ghetto 3 way that doesnt quite work......almost....dunno

will this work, or willl it wreack havok with the motion sensors?

will this work on just any motion senor also?

Alright, thank you in advance for any input and advice.
-Ben Martin

480sparky · 01-07-2009, 09:56 PM

If both motion sensors are on the same circuit, it should work. Just make sure the inrush current of the transformer doesn't exceed the max. load the sensors can handle.

Node · 01-07-2009, 10:16 PM

should be around 100-120w of lights on this switched circuit.

Node · 01-08-2009, 11:58 AM

So I got the cheapest motion sensors I could and tested it out, and talked with my boss who said it was problematic as well.

So it works fine like I expected an everyone else mentioned.

My boss said that the problem is when theres a switch connected to a motion sensor they will turn on or off after 2 or 3 quick switches, and when having two motion sensors together, if a power outage occurs, it may leave one motion sensor on, and one off. And then you must install a seperate switch on each one and have a service call when (if) this happens which would cause the lights to stay on.

-Ben Martin

480sparky · 01-08-2009, 08:54 PM

Some motion sensors have circuitry that uses a quick off-an-on power 'interruption' to turn the lights on no matter what. An brief power failure can emulate that action. Even if that happens, one switch will work. Just turn it off for a couple minutes, then back on and you're golden again.

Node · 01-09-2009, 02:10 AM

So we may end up going the route of a small doorbell transformer, 2x low voltage motion sensors, and then a relay to the transformer.

As this will totally eliminate any chance of this mishap in case of a power outage or other happenings. I would prefer not to have any unnecessary callbacks if avoidable, and this seems easier than trying to explain flick the switch for a few minutes thing

volty · 01-16-2009, 01:10 AM

I usually try to include a lable that says "Warniing - Load side terminals may be energized by backfeed" or the equivalent, as a nicety to the next person working on it.
Or if using a molded case switch as an override, to comply with 404.6(C).

Mike_586 · 03-25-2009, 05:48 PM

Quote:

Originally Posted by Node

So we may end up going the route of a small doorbell transformer, 2x low voltage motion sensors, and then a relay to the transformer.

As this will totally eliminate any chance of this mishap in case of a power outage or other happenings. I would prefer not to have any unnecessary callbacks if avoidable, and this seems easier than trying to explain flick the switch for a few minutes thing

Sounds like a plan. It can be really frustrating trying to explain something really simple (to electricians) to someone who's completely clueless about all things electrical. I my experience, making things as simple/reliable (in operation) as possible for the client is the best way to go.

Don't know how many calls I've gotten over the years for tripped breakers, GFCI receptacles tripped, switched plugs turned off.