sberry
Banned
I didn't say everyone made that assumption but it's a common statement on forums, breaker is only there to protect the building wire.
Correct breaker size for 15A compressor?
- Thread starter nolan7120
- Start date
sberry
Banned
If I generalize and say it's often assumed and you do not assume this then why you take it personally?
sberry
Banned
Ok,,, but its a statement that's made quite regularly.
There's no one here better to drive home a point than @sherry. Just look at the post logs. Just click on the "reply" number from the main screen, and you'll see what I mean.
Typically a circuit shouldn't be overloaded beyond 80%, but in an individual dedicated circuit you can run above 80% . If it is a dedicated circuit, just put a clamp on metre on it well it is just about finished it's recharge. Let us know how the amps are from the clamp on metre. Yeah you would be better off running this on a 20 amp circuit, but it doesn't mean you have to. The manufacture specs (if UL listed) supersede.
Typically a circuit shouldn't be overloaded beyond 80%, but in an individual dedicated circuit you can run above 80% . If it is a dedicated circuit, just put a clamp on metre on it well it is just about finished it's recharge. Let us know how the amps are from the clamp on metre. Yeah you would be better off running this on a 20 amp circuit, but it doesn't mean you have to. The manufacture specs (if UL listed) supersede.
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why was this so complicated?
Run the smallest breaker for the wire! the breaker ONLY protects the wire behind the outlet so its OK to run a load up to 100% of the breaker. De-rating the breaker isn't required. The breaker should be as small as the lightest gauge run.
take out 20A for the 15A breaker, it will be safest for a regular outlet. 20A outlets and plugs are keyed to exclude dollar store extension cords.
a extreme example of what not to do.
1.5KW heater plugged into a thin old 50ft extension cord on a 30A RV circuit. The wire was warm. Breakers do NOT protect loads folks run on jury rigged cords.
Run the smallest breaker for the wire! the breaker ONLY protects the wire behind the outlet so its OK to run a load up to 100% of the breaker. De-rating the breaker isn't required. The breaker should be as small as the lightest gauge run.
take out 20A for the 15A breaker, it will be safest for a regular outlet. 20A outlets and plugs are keyed to exclude dollar store extension cords.
a extreme example of what not to do.
1.5KW heater plugged into a thin old 50ft extension cord on a 30A RV circuit. The wire was warm. Breakers do NOT protect loads folks run on jury rigged cords.
sberry
Banned
This is exactly what I mean, there is the statement, breaker "only" protects the wire behind the outlet. This would be accurate if it included that it only protected it for thermal.
sberry
Banned
As I mention, the statement that the breaker only protects the wire behind the outlet would be accurate if it said for thermal. on welder and motor circuits it doesn't do that, it's by a calculated load. About the only place it does this is general circuits.
The wire to the heater would have got warm no matter what circuit it was on. But this makes my point. "why does it have to be so complicated?" This is because there are other methods used in circuit design to protect the wire than a simple,,, 20 for 12 wire and we just hope that stuff connected to it doesnt smoke system.
This is part of how and why 15A plugs and devices are allowed on 20A circuits. As i said in the beginning, the reason that it's dangerous for the 30 isn't because it will overload the wire but that the stuff plugged in to it isn't rated for it. If it was just the wire we could use 10 instead of 12.
The wire to the heater would have got warm no matter what circuit it was on. But this makes my point. "why does it have to be so complicated?" This is because there are other methods used in circuit design to protect the wire than a simple,,, 20 for 12 wire and we just hope that stuff connected to it doesnt smoke system.
This is part of how and why 15A plugs and devices are allowed on 20A circuits. As i said in the beginning, the reason that it's dangerous for the 30 isn't because it will overload the wire but that the stuff plugged in to it isn't rated for it. If it was just the wire we could use 10 instead of 12.
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Alchymist
Well-known member
20 amp outlets will accept either 15 or 20 amp plugs, including "dollar store" extension cords.
more reasons to remove a 20A breaker for a 15A load.
my main point > its possible to have an extension cord or combination of , that doesn't trip a oversized breaker when shorted.
note The OP is using a long extension cord instead of fixed wiring. Q: can the homes owner (his mom) replace his extension cord with a much lighter & longer one on his 20A breaker. A: yes it's highly possible.
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Alchymist
Well-known member
Not precluding the possibility, but pretty remote. Depends on your definition of "oversized. 20 amp on #12 wire is not oversized. Consider the millions of this circuit across the country. If there were a problem it would have been addressed a long time ago.
pattenp
Well-known member
I believe you meant overloaded, not shorted. An overloaded cord can burn up before a breaker trips. A direct short will instantaneously trip a breaker.
see note above (post #50)
This is me sizing a breaker for an external circuit and load, not a building code.
There are lots of fires everyday due to things done beyond the outlets/breakers control.
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Its possible to have a short and not even cause an overload given my 'extreme example above. You guys can argue what the definition of a 'short' is "direct" or otherwise. .
It should be 14 awg cord for that load and length. Cant idiot proof everything.
Its possible, but shorts and ground faults typically blow clear and/or trip the cb. Overload conditions, melting insulation, and excessive heat is the bigger watchout causing ignition of adjacent combustible mtls.
sberry
Banned
I agree, its why the small cord comes with a 15 end and not a 30, cant buy a listed cord with the wrong end. Only listed for fault protection to 20A breaker.
So if I plug my table lamp (wired with 18-2 zip cord) into an existing 20a circuit receptacle, I should run to the dist. panel and replace the 20a with a 10a?
OCP would be best incorporated into ext cords and individual device cords.
Nope that is wrong. The OP is using an extension cord. A 15A breaker is perfect for his dedicated compressor load. Advising anything less than 12 AWG <50' might infact cause CB tripping. The solution isn't automatically increasing the CB size! Just because the motor nameplate says 15A doesn't mean its will draw that much for any length of time, so need to derate anything. I guarantee if the OP measures the current youll all eat crow for dinner. You guys took 40+ responses and still don't grasp the OPs situation nor agree with anybody else! Why should it change now
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pfft really? are you using retards logic or what.
OCP in line cords? sure thing UK has this, that's called a nanny state.
Using your logic why don't you just change all your 15A CB to 20A youll never have nuisance tripping again. haha
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Alchymist
Well-known member
Guess you haven't seen all the string lights with fuses in the plug?
Nope that is wrong. The OP is using an extension cord. Where in this post did the OP ever mention an ext cord? which post? The ext cord was only mentioned for your extraneous heater example only.
A 15A breaker is perfect for his dedicated compressor load. Maybe, but it may trip on startup. And you don't know if he is using a single recept or a duplex. NEC has requirements for these 2 conditions. Oh nevermind, you don't own a code book. Didn't mean to go over your head.
Advising anything less than 12 AWG <50' might infact cause CB tripping.
No one ever advised any ext cord for the Op's purpose.
The solution isn't automatically increasing the CB size! Just because the motor nameplate says 15A doesn't mean its will draw that much for any length of time, so need to derate anything. What is derated?
He already ran #12's to a 20a recept hanging off a 20A cb. Done everyday. Where's the problem? A 20a is better to eliminate startup tripping. I would hope and expect the mfr sized the motor so it is not running at FLA's - but ya never know.
I guarantee if the OP measures the current youll all eat crow for dinner. I doubt anyone cares what the compressor draws as long as it doesnt trip on startup and is not overloaded. You guys took 40+ responses and still don't grasp the OPs situation nor agree with anybody else! Certainly not with you. And you just added a wealth of clarity with no basis. Good Job! Why should it change now
....
That was to humor your obsessive-compulsive issue of protecting random loads plugged in to receptacles by adjusting the branch circuit OCP.
Question - did you forget to take your meds today or did you double-dip?
I'm not sure if the extension cord was mentioned in this thread but it was in another thread I had posted about seeking help when choosing a compressor. My exact setup is a 20A breaker, with a 20A receptacle (with 12 gauge wire) attached to the fuse box in the basement, with a 50' 12 gauge extension cord snaking up the stairs and into the garage.
I can always change it back to a 15A breaker and receptacle. Or just leave it. I am rather curious about the current it will draw so I'm going to order a digital clamp meter and will test it out on Friday when I finally have all my parts and will be breaking it in.
I can always change it back to a 15A breaker and receptacle. Or just leave it. I am rather curious about the current it will draw so I'm going to order a digital clamp meter and will test it out on Friday when I finally have all my parts and will be breaking it in.
manwithtools
ALLIANCE MEMBER
Just an FYI on the clamp on amp meter in case you are not aware, you can't just put that around the three conductor cord, You need to have that around an individual hot leg. Easier to do inside the breaker panel than anywhere else. Be careful if you go that route.
I'd say if you are using a compressor of any size, you'll want to stay with the 20 amp particularly if you have a 50' extension cord - at least it's 12 gauge.
I'd say if you are using a compressor of any size, you'll want to stay with the 20 amp particularly if you have a 50' extension cord - at least it's 12 gauge.
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sberry
Banned
They are made to run on a 20A,,, just like a radio or alarm clock can connect to 20. Anything with a 15 end is listed for 20A circuits. These little comps are problematic on 20's and terrible on 15's
No it wasnt mentioned in this thread. Nice to have all details in one place.
No biggee. Do not waste your time changing out anything to 15a. You are good to go exactly as you are.
And it is a good thing your 50ftr is 12. Make sure nobody kills themselves tripping down the steps with that cord. This is exactly why code specs out recept placement to eliminate as much of this stuff as possible.
Make sure the compressor has oil in it.
Power up the compressor now and you can take amp readings later.
sberry
Banned
I have had to add 25 ft of 16 to my chop saw to keep it from popping a breaker on starts. Its not such a problem as the operator is there with it. My roofing comp is down on the ground unattended and actually sprung a leak where it was running out of sight. For this I use 60ft 14 as we don't want it to thermal overload the wire with a more continuous run. It comes factory 14 cord as do most of them. A little voltage drop doesn't hurt, it slows inrush.
As was mentioned in another thread I really don't care for some of this stuff on old circuits and building wire with lots of splices. I hooked one up for someone in an older building and actually had them get a cord for it as the routing was a lot shorter and it was in reality a better circuit and way more direct. I got back to an outlet only a few ft away and straight to the panel.
As was mentioned in another thread I really don't care for some of this stuff on old circuits and building wire with lots of splices. I hooked one up for someone in an older building and actually had them get a cord for it as the routing was a lot shorter and it was in reality a better circuit and way more direct. I got back to an outlet only a few ft away and straight to the panel.
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sberry
Banned
I went to a house to weld something on a wood stove. The wire was a mess and the same deal, found an outlet in the laundry and ran a cord to it vs the local one in the room I working in that looked like it was hooked to a bowl of spaghetti that had went thru a beater.
toplessHO
Well-known member
The HF air compressor will run fine on any standard 14 AWG / 15A home circuit as long as the distance from the receptacle to the panel is not outrageously long. I have run these types before with the ceiling light on and even managed to open and close the garage door too.What you've done with 12 AWG / 20A circuit and outlet is more than enough.
These compressors are typically 1.5-1.7 HP but say 2 HP. A true 2 HP compressor will trip a 15A breaker every time. If it doesn't you might have a bad breaker.
you will get shot down every time on this
max load on a 15 amp circuit is 12A.
need to go by nameplate rating not your calculated HP one.
Once again this has nothing to do with a code book, no work is being done here that requires an inspection.
These little compressor motors are designed to be portable E.g run on a 15A household receptacle. It might be problematic when there's extension cords involved and perhaps other loads present. IDK maybe read the compressor manual, some helpful stuff. Most importantly there's a thing called 'duty cycle' requirement. It'll probably tell you not to use an extension cord too, but we are smarter than the average code book waving electrician. If it gives random nuisance trips trouble shoot things by plugging it in closer to the 15A panel breaker, don't just increase the breaker to 20A. The comp. manual warned us or gave a clue about extension cords E.g increased resistance on start-up. The key thing to remember on these compressor is the motor is under more or less constant load so electrically it acts like constant power input. Please let that sink in!
Knowing ohms law and how these motors work on start-up is more helpful than any code book! What would you do without a code book? codebooks are designed for wire pulling apes who memorizes the little bits and pieces that might affect the passing inspection from some other monkey. "ours not reason why, just to do and die." . Perhaps your brain shuts down when reciting code. "over my head" wow yer a legend in your own mind. I probably forgot more about electricity than you've ever known.
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alfredeneuman
Well-known member
In SoCA, ALL dedicated compressor circuits require both a permit and an inspection.
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there I fixed it for youIn SoCA, SOME compressor hookups require both a permit and an inspection.
Thx mine works fine on a regular 15A outlet.
Alchymist
Well-known member
I find this somewhat amusing based on your posts.
The HF air compressor will run fine on any standard 14 AWG / 15A home circuit as long as the distance from the receptacle to the panel is not outrageously long. I have run these types before with the ceiling light on and even managed to open and close the garage door too.
These compressors are typically 1.5-1.7 HP but say 2 HP. A true 2 HP compressor will trip a 15A breaker every time. If it doesn't you might have a bad breaker.
Not a whole lot of 15 amp receptacle circuits anymore. Most over the past decade or so have been 20 amp circuits. And I'd guess 99% of new builds will be 20 amp receptacle circuits. 15 are mostly for a few lighting circuits, and a lot of new construction jobs even skip that.
Bib Overalls
Well-known member
I just love these electrical threads, the ones where the OP has a simple question and gets a simple answer in one or two replies. Then, the the pros, semi-pros, advanced do-it-yourselfers, and the occasional troll argue an irrelevant point for four pages. GJ wars.
alfredeneuman
Well-known member
Back to the original question
This multi page thread all could have been answered with 1 word,
Yes
This multi page thread all could have been answered with 1 word,
Yes
That's why I stepped in after 45 posts,
This electrical forum is plain weird. Strange that some here act like I'm a threat to their livelihood or something, tossing personal insults when I call baloney on their game. I could make a statement like "the sky is blue today" and mmo822 here would argue strongly against it>( WTF guy , this aint king of the hill.. sheesh. Reminds me of fantasy island "da code, da code." lol) Are they using this board to troll for easy work? 
Id advise anyone to get a second opinion from another source ( a visit from a local electrician will probably be money well spent ) before embarking on any plan of work from this forum.
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Alchymist
Well-known member
That's why I stepped in after 45 posts,
Id advise anyone to get a second opinion from another source ( a visit from a local electrician will probably be money well spent ) before embarking on any plan of work from this forum.
Once you have been on this forum for a while you get to know who you can trust and who is blowing smoke.