load ampacity ruling on switches article?

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rong111

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I would assume wall switches can carry 80% of their continuous rated amperage just like the entire branch is supposed to. I cannot find the article that states this. unless it is actually 100%(the rated ampacity of the switch). could someone please state the article that regards the rating of residential wall switches?

thank you,
ron g.
 
rong111 said:
I would assume wall switches can carry 80% of their continuous rated amperage just like the entire branch is supposed to. I cannot find the article that states this. unless it is actually 100%(the rated ampacity of the switch). could someone please state the article that regards the rating of residential wall switches?

thank you,
ron g.
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Take a look at 404.14.
 
"snap switches shall be used within their ratings". I don't agree but hey they make the rules. I guess I have overcharged a lot of folks for larger than necessary. personally I just feel more comfortable that way.

thank you for providing the art#.

ron g.

edit: I just wanted to point out on the appropriate ocpd,awg,on permanent fixtures to match the branch ability. I never spec'd a switch larger than the branch!
 
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this is a serious question which I guess is open to interpretation. say there is a .25 amp motor on a switch with some other load like lighting. or say there is a .25 amp motor on a switch which is daisy changed via the bus bar to another switch carrying a heater,lighting or some other load. do those switches then become derated to 80% of capacity? even though the motor accounts for only a fraction of the switches rating. I would figure a combination load would automatically derate it but I don't know about that small. is that up to the installers discretion or does any presence of a motor derate them period?

I did not mean to be smart. I just want to make sure I am not charging people 3x the price for switches on small heaters etc.

ron g.
 
I have no idea what you are referring to regarding "a .25 amp motor on a switch which is daisy changed via the bus bar to another switch carrying a heater,lighting or some other load." Your OP is regarding "wall switches". Code calls these snap switches. The only switches that are typically connected to a bus bar are, under Code, 404.11 Circuit Breakers as Switches.

The only time snap AC-only snap switches get "derated" are when used with a motor. 404.14 says 80%... and that corresponds with Article 430 requiring motor disconnect, conductor, controller, etc. ratings to be at least 125% of motor FLC. In some cases, switches will have an inductive and/or motor HP ratings, and that rating will override 404.11 in an inductive- or motor-only application.
 
I was using the wrong terminology sorry for that. by bus bar I meant the tab on the snap switch. if one switch is connected to another in series. I assume they all get rated to 80% then.

if a heater has a small blower I assume the snap switch gets rated at 80%.

I am sorry I don't know this. I just don't like to overcharge people but this is how I always understood this. I see many times an ahj has passed a 15 amp switch on a 12 amp heating element with a .5 amp blower. I hope I have not been wrong specifying 20 amp snap switches in those situations.

ron g
 
rong111 said:
I was using the wrong terminology sorry for that. by bus bar I meant the tab on the snap switch. if one switch is connected to another in series. I assume they all get rated to 80% then.

if a heater has a small blower I assume the snap switch gets rated at 80%.

I am sorry I don't know this. I just don't like to overcharge people but this is how I always understood this. I see many times an ahj has passed a 15 amp switch on a 12 amp heating element with a .5 amp blower. I hope I have not been wrong specifying 20 amp snap switches in those situations.

ron g
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FWIW, you are not wrong as much as you may be over-rating the switch. As I said, motors are the only load that gets figured at 125% (inverse is 80%) under 404.14. In the case of a 12A heating element with a .5A blower, it's required to be rated not less than 12A+125%(0.5A)=12.625A. But other article sections may override this minimum rating....

For example, if this switch serves the purpose of disconnecting means for a fixed space heater under 424.19, it's required to be rated 125% of total load of motors and heaters... 125%(12.5A)=15.625A... so that makes your use of a 20A snap switch the correct call.
 
just one other question please. does this apply to bathroom fans with heaters? the nec does not really cover bathroom fans but they do cover heaters. I do not know if this applies. the heaters usually have a 20 amp fuse even if they are only 1000-1400 watts. the manuals never say anything about the switch. just 20 amp branch recommended. if the fans come with a switch it is 15 amp.

thank you
ron g.
 
Although the code does not make any explicit provision for mixed load types, I think that both an inspector and physics would accept for the motor load x 1.25 plus the non-motor load being less than or equal to the rating.
 
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