# Control 1 fan w/3 switches?



## grsparky (Jan 29, 2009)

Can someone tell a resi guy what kind of relay to use if I want to turn 1 rooftop unit on from 3 different switches, 2 of which are occ. sensors?


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## Speedy Petey (Jan 10, 2007)

Why a relay at all? 

I assume if someone is in any of the three areas that the fan wants to be on. Correct? 

If so then just wire the switches in parallel. This way if any of them are on the fan is on. 
What do the instructions for the OS's say? Do they require a relay for multiple sensor use?


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## 480sparky (Sep 20, 2007)

Maybe a relay is required as the fan exceeds the ratings of the occ. sensors.


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## grsparky (Jan 29, 2009)

480sparky is correct. Occ. sensor is rated 1/6 HP, fan is 1/2 HP. 
Sensor in each bathroom and elect. room would turn on lights in that room only and the 1 exhaust fan.


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## 480sparky (Sep 20, 2007)

grsparky said:


> ........Sensor in each bathroom and elect. room would turn on lights in that room only and the 1 exhaust fan.


 That'll be a neat trick.


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## Charlie K (Aug 14, 2008)

Easy to do. Change out the one switch to a 2 pole. Add relays to the ones on occ. sensors. Relay in a box (RAB) would be a good choice. Wire a NO contact of each relay in parralel to the one pole of the 2 pole switch. Put this circuit in series with the fan.


Charlie


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## 480sparky (Sep 20, 2007)

Charlie K said:


> Easy to do. Change out the one switch to a 2 pole. Add relays to the ones on occ. sensors. Relay in a box (RAB) would be a good choice. Wire a NO contact of each relay in parralel to the one pole of the 2 pole switch. Put this circuit in series with the fan.
> 
> 
> Charlie


 
How do you switch the lights in each room separately?


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## Charlie K (Aug 14, 2008)

480 Sparky asked:How do you switch the lights in each room separately?


Each occ. sensor will control the light in the room it serves, it will also pull in the relay that will energize the fan. The room with the switch that we changed to a 2 pole- one pole will operate the light and the other the fan. The reason for the relays and the 2 pole switch is to prevent a feedback that would bring on lights in rooms that are unoccupied. Hope this helps.

Charlie


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## 480sparky (Sep 20, 2007)

Charlie K said:


> 480 Sparky asked:How do you switch the lights in each room separately?
> 
> 
> Each occ. sensor will control the light in the room it serves, it will also pull in the relay that will energize the fan. The room with the switch that we changed to a 2 pole- one pole will operate the light and the other the fan. The reason for the relays and the 2 pole switch is to prevent a feedback that would bring on lights in rooms that are unoccupied. Hope this helps.
> ...


If both OCs are tied to the coil of the relay, won't one OC turn on both sets of lights?


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## Charlie K (Aug 14, 2008)

480sparky said:


> If both OCs are tied to the coil of the relay, won't one OC turn on both sets of lights?


No. Each occupancy sensor will have a relay. Two occ. sensors= two relays. One on each. To save on costs you use a 2 pole switch on the third light, the one that is on a regular switch.

Charlie


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## 480sparky (Sep 20, 2007)

Charlie K said:


> No. Each occupancy sensor will have a relay. Two occ. sensors= two relays. One on each. To save on costs you use a 2 pole switch on the third light, the one that is on a regular switch.
> 
> Charlie


 
Each OS would need a 2-pole relay then.


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## grsparky (Jan 29, 2009)

Don't they make a relay with 3 NO contacts to control 1 load? Perhaps a 8 or 11 pin?


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## 480sparky (Sep 20, 2007)

grsparky said:


> Don't they make a relay with 3 NO contacts to control 1 load? Perhaps a 8 or 11 pin?


I'm sure if you look hard enough, you can find a relay that has as many poles as you want. 

Worse comes to worse, you can install a bunch of lighting contactors and turn the whole town on.


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## grsparky (Jan 29, 2009)

Thanks Charlie. We did as you suggested and it worked great.


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## Charlie K (Aug 14, 2008)

No problem. Glad it worked out for you.:thumbsup::thumbsup:


Charlie


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## iaov (Apr 14, 2008)

There are several less than 100 dollar PLC's that are ideal for doing wierd logic/switching problems like this.


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## nolabama (Oct 3, 2007)

we wired cap one banks bathrooms like charlie k says and it worked great


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