Switching fan and light

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Re: Switching fan and light

Peter d Thank you for your input. I'm curious, what would be the potential voltage difference in Pauls question.

Paul
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So what is the voltage between Phase A of a 120V Y system and Phase A of a 277V Y system? And what is the voltage between Phase A of a 120V Y system and Phase B or C of a 277V Y system? Or what if the secondary was derived from a 480 to 120/240 transformer, then what's the difference in potential?
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Thank you Justin
 
Re: Switching fan and light

Originally posted by wireman3736:
What happen to the tie handles on a single device with more then one circuit? :confused:
Click to expand...
It would be impossible on a single device that has both a 120 volt and 277 volt circuit on it. Not only that, that requirement only applies to receptacles.

Justin,

I'm not sure. Someone else will surely know.
 
Re: Switching fan and light

I had the same problem in class from one of Mikes books. He used the same scenario, and plotting the curves from the same voltage made it 356 volts or 384. I have this on another computer at work and not here tonight. If my math is correct then this would be a violation. However if they are from different phases the number goes down because of where in relation you would have to plot your curves. Draw a three phase wave form and look a the relationship of say phase A at peak and Phase C at the same time. Since the C phase will in the negative portion of the wave the numbers actually decrease.
I agree with all the posters who say this is not a good idea. I also would like to ask the original poster how this was going to be accomplished from 1 single pole switch?
 
Re: Switching fan and light

i dont know why not just put a small transformer to down step from 277 to 120 volt and use the common switch to control the light and fan??


i done this few time where we have 277 lighting circuits and 120 volts for fan so my suggest is use the small downstep transformer it work pretty well


merci, marc
 
Re: Switching fan and light

Not sure where the switch is located at but could you either pull out the 120v or the 277v from this box and install a cut in box somewhere else close. Then install either the light or the fan in this box. This would seperate the volts and you would be OK in the code. this would be cheaper than install relays or transformers.
Bye now
 
Re: Switching fan and light

James,

Many commercial applications require that the fan comes on with the light. Otherwise, I might agree with you. Or you throw in the divider between the switches.
 
Re: Switching fan and light

Pual
Is this in a bathroom? Is this a combo fan-light? If so, can you rewire the light to 120 volts and then use 1 switch of 120 volts to operate both?
 
Re: Switching fan and light

James...pay attention!
He has a 277 volt light and 120 volt fan.Obviously it isnt a fan light combo.
 
Re: Switching fan and light

canadian
I'll try to pay attention next time. So we have a fan and a 2 or 4 bulb fluorescent light. The light is 277 v. Can you install a 120 volt ballast in the light and hook with the fan leaving 1 120 volt switch for this. Of course you will need to pull out the 277 v wiring. A good ballast will run you $20. Just another idea. Again, I hope I pay attention to what I wrote.
HA,HA
Jim
 
Re: Switching fan and light

The following response is from Mark Ode is the Underwrites Laboratories principal representative on CMP-4. :D

This is not permitted since the switch must be listed for more than one circuit so would be a violation of Section 110.3(B). See the attached text from the 2004 UL White Book.

SNAP SWITCHES (WJQR)

General Use Snap Switches are so constructed that they can be installed in flush device boxes or on outlet box covers or otherwise used in connection with wiring systems recognized by the National Electrical Code.

Door switches are evaluated for use only in combination with a specific switch, special switch box and cover. See Switches, Door (WLFV). Flush snap switches that have been investigated for use without separate outlet boxes with Types NM and MNC cable in accordance with the National Electrical Code are so identified by specific marking on the carton in which they are packed.

Snap switches have not been investigated for switching a load between two alternate sources of supply. Double throw enclosed switches (see Switches, Enclosed [WIAX]) or switches Listed as transfer switches (see Switches, Miscellaneous [WPZX] and Emergency Lighting and Power Equipment [FTBR]) should be used for this purpose.

Multi-pole, general use snap switches have not been investigated for more than single circuit operation unless marked "2-circuit" or "3 circuit."
 
Re: Switching fan and light

Well that is intresting...in a lack of common sense sort of way. :roll:

I can use a two pole 250 volt switch to control a lighting circuit supplied by a multi wire branch circuit that may not even need handle ties, resulting in 240 volts between the poles of the switch.

But I could not use the same switch to control the same lights supplied by two 2 wire branch circuits, these could even be on the same phase resulting in 0 volts between poles.

Maybe I am missing something but I see no logic with this.
 
Re: Switching fan and light

I would be a bit leery of installing a 277 volt light fixture in a bathroom unless there is an individual disconnect switch next to each fixture which could be a snap switch.

The light switch should be on 120 volts and the 120 volts would control a relay that controls the 277 volts. This way, there is a way to have the switch downstream of a GFCI for extra safety.

If power continuity is important, I would investigate using a 24 volt control circuit. Barehanding 24 volts in the rain has a bit of a sting to it but nothing serious as 120 volts. Honeywell makes a packaged control transformer and double pole double throw relay all mounted on a 4"x4" metal cover. You would need to go to an HVAC supply house to get it. The part number is R8239B1043. It is also a handy gadget for controlling jobsite temporary lighting.
 
Re: Switching fan and light

Honeywell makes a combination 24 volt transformer and power relay that are mounted on a 4x4 steel box cover. You can get this in single pole double throw and double pole double throw. The primary voltage of the transformer is 120 volt - the last one that I touched did not have higher voltage taps.

You see these a lot on forced hot water heating systems to activate the circulating pump. The relay does have 240 volt and 277 volt ratings.

Besides this application I could see using this for temporary lighting control on a jobsite particularly residential. For a residential site I can run 3-ways and 4-ways for this really fast using thermostat wire.
 
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