# lights and a exhaust fan



## Adam12 (May 28, 2008)

Ive been trying to figure this out but having a hard time.........

We have 2 seperate rest rooms with two seperate lighting circuits which are 277v. Both RR's will share a common exhaust fan which is 120v and will turn on with the lights. To make things a little easier we are going to make both RR's the same lighting circuit.

Now my question is, how can this be wired to a relay to turn on the exhaust fan when the lights are turned on, without back feeding from one RR to another?  Can it?


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## william1978 (Sep 21, 2008)

You could use a contactor or get a 277v exaust fan.


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## 480sparky (Sep 20, 2007)

One circuit:











Two circuits:







​


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## JohnR (Apr 12, 2010)

The code requires a separation between adjacent devices 300V< so you might want to look at 404.8 (B) to make sure you are ok . I would ask the AHJ what they thought . 
Also putting a little label about more than 1 supply source power would make me feel more comfortable. - another way to do this would be use 2 contactors (read RIB) with the 120V contacts in parallel that has 277v for the coil something like a RIB2402B would work .


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## Dennis Alwon (May 9, 2009)

I am not following. Can you not have 2 sp switches that controll the lights in the respective RR's and then have 2 sp switches wired in parallel to feed the fan. This way either switch is up the fan is on.


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## Bob Badger (Apr 19, 2009)

Pretty common thing in commercial bathrooms. They want a single fan that ventilates both rooms to be controlled with the lights in each room, they do not want the fan on it's own switch.

We use "RIB" relays for that.

http://www.functionaldevices.com/


If they want a motion sensor it is easy as well.


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## 480sparky (Sep 20, 2007)

JohnR said:


> The code requires a separation between adjacent devices 300V< .......... .



Each diagram only shows one device in the box.:whistling2:


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## Toronto Sparky (Apr 12, 2009)

Or a rely on each light and parallel the n/o contacts to control fan.


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## JohnR (Apr 12, 2010)

480sparky said:


> Each diagram only shows one device in the box.:whistling2:


 Yeah thats why I mentioned the AHJ, kind of up to him if he does.:wallbash:


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## Electric_Light (Apr 6, 2010)

The lighting load in restrooms can't be that big. Can you just wire them into 120v? If they have newer universal voltage ballast, they'll operate on 120-277v. If not, change the ballasts.


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## JohnR (Apr 12, 2010)

It is something about those universal ballasts though, if you have connected them to one voltage and want to connect them to another, you will cook them if you do. 

We had a job where the foreman wanted to test each and every highhat so he made an apprentice connect them to a extention cord and light it up. Well later when connected to the real circuit voltage of 277, all 47 fried.


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## MDShunk (Jan 7, 2007)

JohnR said:


> It is something about those universal ballasts though, if you have connected them to one voltage and want to connect them to another, you will cook them if you do.
> 
> We had a job where the foreman wanted to test each and every highhat so he made an apprentice connect them to a extention cord and light it up. Well later when connected to the real circuit voltage of 277, all 47 fried.


Interesting. 

I have noticed that some automatic voltage ballasts that quit working on 277 will continue to function fine when repurposed at 120.

Whenever possible, I buy ballasts for the voltage that they will be used at, with the exception of multitap ballasts.


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## Electric_Light (Apr 6, 2010)

JohnR said:


> It is something about those universal ballasts though, if you have connected them to one voltage and want to connect them to another, you will cook them if you do.
> 
> We had a job where the foreman wanted to test each and every highhat so he made an apprentice connect them to a extention cord and light it up. Well later when connected to the real circuit voltage of 277, all 47 fried.


Make and model on ballast and how long did it take for them to fry?

They're not supposed to be like a furnace control module with universal setting that locks the setting in place after ten calls for heat. 

I ran 120 to 277v from 108v to 305v(full permissible range) and allowed them to run for a few hours at each voltage, and back and it continued to work. The test was conducted on Sylvania QTP 4x32T8/UNV ISN-SC with four lamps in place. 



> I have noticed that some automatic voltage ballasts that quit working on 277 will continue to function fine when repurposed at 120.
> 
> Whenever possible, I buy ballasts for the voltage that they will be used at, with the exception of multitap ballasts.


It sounds like the front-end power factor converter failed. Even without the converter, the 277v input provides enough input voltage to DC rail and ballast will continue to work, but I'm not sure if it will continue to provide high power factor though. 

They do have their advantage beyond being multi-voltage compatible. Say they're connected to 120v nominal. With standard electronic ballast, power consumption varies roughly proportionally (as opposed to squared exponential for resistive) with voltage. So, when line drops to 108v, input and light output will drop. When it rises to 132v during low demand, output and power will both go up. 

The universal input units will compensate and maintain the same power input, but they will flicker if the voltage changes suddenly (i.e. motor starting)


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## JohnR (Apr 12, 2010)

Electric_Light said:


> Make and model on ballast and how long did it take for them to fry?
> 
> They're not supposed to be like a furnace control module with universal setting that locks the setting in place after ten calls for heat.


Well it has bee about 7 years now so I really don't remember but most of the ballasts we were using were either Triad or Universal Would have been roughly a UNV120/2774832 or something close, had 2- 32w compacts or 1 42-48w lamp. Some of them had 2-26w but Again It has been a while. It took about 45 sec to fully smoke IRC. 
I never did get why the foreman wanted to test them anyway.


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## Electric_Light (Apr 6, 2010)

JohnR said:


> Well it has bee about 7 years now so I really don't remember but most of the ballasts we were using were either Triad or Universal Would have been roughly a UNV120/2774832 or something close, had 2- 32w compacts or 1 42-48w lamp. Some of them had 2-26w but Again It has been a while. It took about 45 sec to fully smoke IRC.
> I never did get why the foreman wanted to test them anyway.


The one I tested are from 3rd quarter of 2009. I would expect that there's been changes in seven years. 

Older ballasts often had quite a bit of inrush current, but the Sylvania model I mentioned only has a inrush of 2A or so at 120v so it's a lot easier on switches, contractors as well as the semiconductor parts in itself.


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## Wiredude (May 14, 2010)

My company did exactly this on a recent job. As I remember we used a contactor, an pulled a leg of 120v off something in the area.

As for the ballasts being connected to first one voltage, then another, I know this was a issue in some brands and/or earlier models, however I know as of about 3 years ago, at least GE ballasts no longer had any sort of 'voltage memory' and could be connected to different voltages regardless of previous connections. I believe other manufacturers have since followed suit, however I don't have any documentation to prove it.


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## JohnJ0906 (Jan 22, 2007)

480sparky said:


> Each diagram only shows one device in the box.:whistling2:


What about 210.7(B)?


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## 480sparky (Sep 20, 2007)

JohnJ0906 said:


> What about 210.7(B)?



What about it?


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## JohnJ0906 (Jan 22, 2007)

480sparky said:


> Two circuits:
> 
> 
> 
> ...


One device, a 277v lighting circuit and a 120v fan circuit (per OP) - how will you comply with 210.7(B)? (means to simultaneously disconnect the ungrounded conductors at the point the circuits originate)


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## 480sparky (Sep 20, 2007)

JohnJ0906 said:


> One device, a 277v lighting circuit and a 120v fan circuit (per OP) - how will you comply with 210.7(B)? (means to simultaneously disconnect the ungrounded conductors at the point the circuits originate)



I would be more concerned about using one grounded conductor between the two..........:whistling2: But I drew that schematic for two circuits from the same panel.


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## Toronto Sparky (Apr 12, 2009)

Are you allowed two voltages on a two pole switch? Not that I've ever seen.


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## Bkessler (Feb 14, 2007)

Adam12 said:


> Ive been trying to figure this out but having a hard time.........
> 
> We have 2 seperate rest rooms with two seperate lighting circuits which are 277v. Both RR's will share a common exhaust fan which is 120v and will turn on with the lights. To make things a little easier we are going to make both RR's the same lighting circuit.
> 
> Now my question is, how can this be wired to a relay to turn on the exhaust fan when the lights are turned on, without back feeding from one RR to another?  Can it?


For me, I can wire the building from the ground up no problem, on time, under budget. And I'll lose sleep over that very question myself. My suggestion is,

Get a 12 by 12 by 8, (you'll appreciate the spaciousness)

Install it in a real easy place o reach with the shortest ladder possible, Try and mount it so it's centered between the two bathrooms.

Run a 3/4 to the panel.
run one up to the rooftop, 
run one to the mens room.
one to the womens.
Get an icecube relay
pull the wire,

Go to lunch.


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## jroelofs (Aug 30, 2009)

Bkessler said:


> For me, I can wire the building from the ground up no problem, on time, under budget.  And I'll lose sleep over that very question myself. My suggestion is,
> 
> Get a 12 by 12 by 8, (you'll appreciate the spaciousness)
> 
> ...


This is exactly how I do it also. Use the 277v circuit that feeds the lights to switch the 120v circuit for the fan using an ice cube relay.


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## frenchelectrican (Mar 15, 2007)

480sparky said:


> One circuit:
> 
> 
> 
> ...


 
There is other option which I don't use the cube relay is get 277-120 transfomer just a small one something like 300 or 500 va size and ya are done with it so you have 120 volt circuit for fan motour so that way you don't have to worry about 210.7(B) come back and hunt ya.


Merci.
Marc


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