100 Days of Article 100: Switches

[Music] article 100 covers several types of switches and we're going to cover most of them there's a couple we're not going to cover that are pretty obscure and and really not worth covering in too much detail but the first switch we're going to talk about is a general use switch that's a switch that's rated in amperes and can interrupt its rated current at its rated voltage it's used in general distribution and branch circuits so here in the photograph we have four general use switches next time you see a fuse disconnect like this or an infused for that matter take a look at it and you'll notice that it's probably listed as a general use switch the most common type of general use switch is a general use snap switch which of course we all have in our houses or apartments that's a general use switch that can be installed in a device box or its cover or otherwise used with wiring systems recognized in the nec so a general use snap switch is one of these guys right the light switch in your bedroom is a general use snap switch it's all covered in article 404 so you got a 404.9 for example until you got a connector to an equipment ground you go to 404.14 it's going to tell you the ratings of the general use snap switches right it's going to say look you can put a 15 amp switch on a 20 amp circuit as long as you don't have more than 15 amps going through it so general use snap switch here in article 100 nice and easy we also have a motor circuit switch which isn't quite as simple a motor circuit switch is a switch that's rated in horsepower okay let's call timeout really fast that's probably the most important part if your switch does not have a horsepower rating then it is not a motor circuit switch all right this switch has a horsepower rating you might have to squint your eyes to see it but it says one horsepower at 120 volts so that is a motor circuit switch it can interrupt the maximum overload current of a motor with the same horsepower rating as the switch if it's rated one horsepower at 120 volts a one horsepower motor 120 volts should be about 16 amps an overload on that motor would be a hundred and fifteen hundred and twenty five percent of that motor so that would be what 20 amps so this switch should be able to interrupt 20 amps right it's single horsepower single horsepower overload is about 20 amps so this should be rated for 20s but most importantly it's got to have that horsepower rating if it's a motor circuit switch the other type of switch that we have in the nec is a transfer switch and a transfer switch is a device that transfers one or more ungrounded conductor connections from one source to another so it basically isolates the utility from a different source of power like a generator now it's not just utility it could isolate you know your generator from a fuel cell or wind system or you know some other system but generally speaking we're using this to isolate the utility from our backup power system now why do we have a transfer switch well the reason we have a transfer switch is if you didn't have a transfer switch you're connected to the utility and then you plug your generator into your house and turned it on well if the utility lost power and you put your generator in and turned it on you're going to be back feeding the utility remember transformers work both ways they'll take you know 7200 volts and transform it down to 240 but they'll also take 240 and transform it up to 7200 volts so when a person installs a transformer or i'm sorry a generator at their house without a transfer switch they are really making it dangerous for our utility workers because that's back feeding utility voltage to the utility workers that are trying to figure out where the power outage is so a transfer switch is a very important piece of safety equipment and that's why you have requirements for them whether it's an emergency system a legally required standby system or an optional standby system an article 700 701 or 702 you're going to find that if you decide to put in one of those systems you got to have transfer equipment you got to have a transfer switch be sure to like follow subscribe and ring the bell

Channel: Ryan Jackson

Views: 2,211

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Id: 8uqHRjjHX-w

Length: 4min 42sec (282 seconds)

Published: Sun Oct 24 2021