# Multiple Occupancy Sensors and 3-way switches



## TGGT (Oct 28, 2012)

EDIT: (My mistake, I thought it was on the critical branch, I just remembered it was on normal power.)

I've worked with occupancy sensors before, but never with 3-way switches involved. I'm trying to wrap my head around this.

So after looking at some diagrams I think I need to supply the Power Pack with a hot, but instead of connecting the leg from the PP to the lights, I'll run it to my first 3-way, then run my travelers to my other 3-way, then run _that_ leg to my lights.

Does that make sense?

Now if I have several OS's in the room that all control the same lights, will I simply daisy chain them from the power pack with the LV cable? I haven't seen the devices so I can't look at the specific literature.


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## Awg-Dawg (Jan 23, 2007)

If the switch happens to be in the off position, the lights will not come on with the Occ. Sensor.


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## TGGT (Oct 28, 2012)

Awg-Dawg said:


> If the switch happens to be in the off position, the lights will not come on with the Occ. Sensor.


I know, that's what I think is weird about them having 3-way switches on these lights. I understand the override switch, but this had me scratching my head_.
_


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## drspec (Sep 29, 2012)

What about 3 way wall occ sensors? Not applicable in this situation?


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## TGGT (Oct 28, 2012)

drspec said:


> What about 3 way wall occ sensors? Not applicable in this situation?


No, the job spec has them mounted in the drop ceiling.

I didn't create the prints, I'm just trying to make sense of them.


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## drspec (Sep 29, 2012)

The last time I ran into a situation like this, I removed the wall switches and made the joints necessary to feed the power pack. Installed blank cover plates and had no way to override the occ sensor.


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## ghostwriter (Nov 1, 2007)

*3 way occupancy sensor*

TGGT

Why not just use the dry contact in the power pack to feed the three way system?

One power pack controls multiple sensors

If you can power the power pack from the same circuit as the lights also bring the same feed to one side of the N.O. contact. The other side of the contact feeds the three way system

The occupancy sensor(s) is series with the 3 way system. Without the sensor detecting the three ways wont work.


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## keepdry (Jul 24, 2012)

TGGT said:


> EDIT: (My mistake, I thought it was on the critical branch, I just remembered it was on normal power.)
> 
> I've worked with occupancy sensors before, but never with 3-way switches involved. I'm trying to wrap my head around this.
> 
> ...


What you have described is the proper way to wire the three way switches with the occupancy sensors. The switches will override the sensors. The lights can be shut off by the switches if desired. 
You can also daisy chain the occupancy sensors together. However, there is a limit to the number of occupancy sensors you can drive from one power pack. It depends on the manufacturer and the occupancy sensors. You need to force the issue and get the specs on the sensors and power packs.
I have had to add a slave power packs on some jobs due to high number of sensors.


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## TGGT (Oct 28, 2012)

keepdry said:


> What you have described is the proper way to wire the three way switches with the occupancy sensors. The switches will override the sensors. The lights can be shut off by the switches if desired.
> You can also daisy chain the occupancy sensors together. However, there is a limit to the number of occupancy sensors you can drive from one power pack. It depends on the manufacturer and the occupancy sensors. You need to force the issue and get the specs on the sensors and power packs.
> I have had to add a slave power packs on some jobs due to high number of sensors.


After talking about it with 2 foreman, they've come to the same conclusion.

I guess I was over thinking the 3 ways. They're as you said, simply overrides, not expected to be used to frequently operate the lights. Considering it's also going to be in a high traffic room (the pharmacy) I can't imagine that they'd ever be in a hurry to turn the lights off.

Thanks for the input guys.


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## cultch (Aug 2, 2011)

Have you taken a look at the ballasts?

Are there ballasts?


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## TheDuke (Jan 12, 2013)

*occupancy sensors*

you can wire this 2 ways depending on wt you want to do you can hit the sensor first than the switch or the switches first than the sensor so youd be appling power to the switches via the senor or power to the senor via the switches your three ways would wire like usual switch leg would either run to your lights or sensor depending on where your hot is hitting your limited to the number of eyes you can per power pack before you have to add more power packs or slaves


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