different amperage circuits in one switch box

[Stevenfyeager]

Is it allowable to have a 15 amp light circuit (on #14 wire) in the same light switch box with a 20 amp circuit (on#12 ) ? And if so, do the grounds all connect together? Thank you.

 

[Strathead]

Is it allowable to have a 15 amp light circuit (on #14 wire) in the same light switch box with a 20 amp circuit (on#12 ) ? And if so, do the grounds all connect together? Thank you.

Yes and yes. There is a limit of 250 volts between switches in the same box, but no amperage restriction and all normal grounds always tie together and bond to metal enclosures, regardless of the size difference.

 

[don_resqcapt19]

Yes and yes. There is a limit of 250 volts between switches in the same box, but no amperage restriction and all normal grounds always tie together and bond to metal enclosures, regardless of the size difference.

Actually the limit is 300 volts.

404.8(B) Voltage Between Adjacent Devices. A snap switch shall not be grouped or ganged in enclosures with other snap switches,
receptacles, or similar devices, unless they are arranged so that the voltage between adjacent devices does not exceed 300 volts, or unless they are installed in enclosures equipped with identified, securely installed barriers between adjacent devices.

 

[FionaZuppa]

300v, so if the two+ circuits were from same pole of any one phase, the diff will always be zero.

 

[Strathead]

Actually the limit is 300 volts.

I say Duh! That's what I get for rushing. 277v switches. Thank you for the correction.

 

[Sierrasparky]

Is there actually a code section that states grounds from different circuits need to be tied together. I would figure that as long as the each circuit ( cable) has a complete ground path and that each metal box is grounded I see no point in wadding up all the grounds in a box.

 

[iwire]

Is there actually a code section that states grounds from different circuits need to be tied together. I would figure that as long as the each circuit ( cable) has a complete ground path and that each metal box is grounded I see no point in wadding up all the grounds in a box.

250.148 is at close as it gets.

If the box is metal there is no choice, all the EGCs will end up together via the box.


If the box is plastic you could keep the 20 amp and 15 amp EGCs separate from each other but why would you do that?

You provide a lower impedance path by tying them altogether.

 

[Strathead]

Is there actually a code section that states grounds from different circuits need to be tied together. I would figure that as long as the each circuit ( cable) has a complete ground path and that each metal box is grounded I see no point in wadding up all the grounds in a box.

I see there is semantics here. iWire basically said it also, but to be clear, "ground tied together" to me, means electrically tied together. I could bring each ground to a separate legally tapped ground screw in a metal box 24" apart if I wanted to and that would be "tied together". Perhaps you had a perspective that the OP was asking. Some times it is hard to ignore years of common wording and get that the question asked isn't the one answered.

 

[Sierrasparky]

250.148 is at close as it gets.

If the box is metal there is no choice, all the EGCs will end up together via the box.


If the box is plastic you could keep the 20 amp and 15 amp EGCs separate from each other but why would you do that?

You provide a lower impedance path by tying them altogether.

The only reason not to tie all the different circuits together is that when you have say a 4 gang box or greater you will need to have large wire nuts or crimps. I can usually make a neater job keeping them separate.

 

[Frank DuVal]

The only reason not to tie all the different circuits together is that when you have say a 4 gang box or greater you will need to have large wire nuts or crimps. I can usually make a neater job keeping them separate.

That does not pass inspection around here. On rough in inspection the AHJ wants to see all bare wires connected together. Yes, sometimes that means several crimps or green wirenuts. And on plastic boxes, a separate wire (or a long one) to go to all the devices mounted on the box.

 

[kwired]

300v, so if the two+ circuits were from same pole of any one phase, the diff will always be zero.

two switches on same 277 volt circuit has zero potential between devices when both switches are closed

When at least one switch is open there is 277 volts potential between the "open" load conductor and the supply conductor of the other switch - so that is likely the situation where the 300 volts mentioned in code comes from.

Most automatically put barriers in multigang device boxes when a 277 and 120 volt circuit are on adjacent switches. Reality is there may or may not be over 300 volts between the devices, depends on which phase conductors of each system are used.

 

[kwired]

The only reason not to tie all the different circuits together is that when you have say a 4 gang box or greater you will need to have large wire nuts or crimps. I can usually make a neater job keeping them separate.

Won't claim that I never violate this, but I think that NEC wants all EGC's in the box bonded together, how you do it is your choice.