# What does "20 amp feed through", on a 15 amp switch, mean?



## pgiering (Feb 21, 2011)

Hi, 

I just installed a Panasonic FV-11VHL2 bathroom fan. The installation guide stated it must be installed on a 20 amp branch circut. The bathroom only had a 15 amp branch, so I ran a new dedicated line to feed it, even put it on a GFCI, just because I love my family. Trouble is, I'm having a hard time finding 20 amp switches that accomodate the setup I want to have, which includes one of the gang bays being a double switch, with the top controlling the heater, and the bottom controlling the nightlight. 

Ideally, the nightlight would be on a dimmer, but I'm not keeping my fingers crossed to find this on one half of a double switch. Right now, I'd settle to find a modern looking double rated for 20 amp! I've been able to find the old school toggles in a double 20 amp, but not the broad faced toggles, or anything else that looks modern. 

In my search, I've come across this Decora switch: http://www.google.com/products/catalog?q=double+switch+pass+%26+Seymour&hl=en&cid=11647384874844088723&ei=D7rJTpDwNsWKmAe89IC6CQ&ved=0CCsQrhI#

It states "15A-120V. 2 rocker switches. 20A feed through.", but I don't know what 20A feed through means, if it is a 15A switch. Seems like an oxy-moron. Can someone explain this to me? 

I'm also thinking of going with this one: http://www.smarthome.com/6611WH/Lut...-300-Watt-Dual-Dimmer-and-Switch-White/p.aspx

It looks like it might be just what I want, but I don't see an amp rating - it just says 300 watts. Don't know how to tell if it is acceptable. 

The guy at Home Depot told me that just any 15amp double switch would be fine. Is he right? 

Thanks, 

Paul


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## gregzoll (Dec 25, 2006)

It means exactly as you stated.


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## brric (Mar 5, 2010)

Your first choice seems better to me as you do not need a dimmer on a heater nor on a night light.


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## pgiering (Feb 21, 2011)

@ brric: "Your first choice seems better to me as you do not need a dimmer on a heater nor on a night light." 

Yeah, the only thing is that I like a pretty dark room, so even the nightlight I would kind of like to dim a bit.


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## pgiering (Feb 21, 2011)

@ Gregzoll: "It means exactly as you stated." 

Thanks, but I still don't understand. Still sounds like an oxy-moron, but I'm guessing it must mean something usefull.


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## Techy (Mar 16, 2011)

each switch is rated to break 15A, but the assembly as a whole is rated for 20A


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## Billy_Bob (Sep 11, 2008)

pgiering said:


> ...It states "15A-120V. 2 rocker switches. 20A feed through.", but I don't know what 20A feed through means, if it is a 15A switch. Seems like an oxy-moron. Can someone explain this to me?
> ...


You can use 15 amp outlets and 15 amp switches on 20 amp circuits...

And the wiring for multiple outlets and switches will many times go from outlet, to next outlet, to next outlet.

Or switch, to next switch, to outlet, etc.

So the wiring which goes from one switch/outlet to the next needs to be rated at 20 amps. And you can use the connections on a switch or outlet to make those continuing connections. And for that the connections on the switch or outlet can be rated at 20 amps, although the switch or outlet is only 15 amps.

For example a 15 amp outlet has two screws on one side. From one screw to the next might be rated at 20 amps, however the outlet itself is only rated at 15 amps.

You could not use 20 amps from that one outlet, however two or more outlets combined could use 20 amps.

(With an outlet or switch rated at 20 amps, then you could plug in a 20 amp appliance to the outlet or connect a 20 amp light bulb to the switch.)

In the following diagram, they are using the screw terminals on the outlet to continue the circuit to the next outlet...


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## pgiering (Feb 21, 2011)

@Techy & Billy Bob 

Thank you guys. I get it now. Contradicts what I used to think I understood, which means I learned something new! 

I appreciate your help!

Paul


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## carmusic (Oct 11, 2011)

for information if you are in canada, you cant use 15 amp outlet on 20 amp circuit


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## Billy_Bob (Sep 11, 2008)

pgiering said:


> @Techy & Billy Bob
> 
> Thank you guys. I get it now. Contradicts what I used to think I understood, which means I learned something new!
> 
> I appreciate your help!


Good!

Note: I didn't want to include the following above because this is complicated enough as it is, but... You wouldn't actually use 15 amps on a 15 amp circuit, nor would you use 20 amps on a 20 amp circuit. That is pushing it to the limit! 80% of the rated breaker is better. And I don't think there is a 120 volt "20 amp light bulb". But you could have 20 amps worth of lighting, but would not want to place that all on one circuit (80%).


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## pgiering (Feb 21, 2011)

Billy_Bob said:


> Good!
> 
> Note: I didn't want to include the following above because this is complicated enough as it is, but... You wouldn't actually use 15 amps on a 15 amp circuit, nor would you use 20 amps on a 20 amp circuit. That is pushing it to the limit! 80% of the rated breaker is better. And I don't think there is a 120 volt "20 amp light bulb". But you could have 20 amps worth of lighting, but would not want to place that all on one circuit (80%).


Thanks, Billy Bob. Your explaination was really good. If you don't mind, I have one more question. Simply put, how do I know if a switch is adequate if there is no indication of amperage given? For example, the double switch I mentioned above (http://www.smarthome.com/6611WH/Lutr...h-White/p.aspx), seems like it offers the functionality I'm looking for, but makes no mention of an amp rating (at least that I can see). It says 300 volts, which sounds pretty beefy to me, but what do I know? If I assume that it is adequate, is it also safe to assume that it allows a 20amp feed though, or does it have to state that to be a given? I'm not sure whether that is a standard, or more of a specialty item. Previously, I thought it was as black and white as 15 vs 20, now that I know there is a feed through rating as well, I'm not sure how common that is. 

Paul


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## brric (Mar 5, 2010)

A switch on any circuit must be rated for the load it controls. A 20 amp switch would almost never be needed in a dwelling unit.


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## Jim Port (Sep 21, 2007)

watts/120 = amps. 300/120= 2.5 amps.


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