Do jet table saws require a 20 amp breaker?

[Travis Conner]

In the owners manual it recommends you use a 20 amp breaker when running 115v. It pulls 15 amps when wired with 115v. Are they trying to say it's not going to work if you connect it to a 15 amp wall outlet? I'm going to have this saw setup in a storage unit and it looks like they have 15 amp outlets according to the outlet when I remove the cover plate. I run an air compressor that's 15 amps and it works just fine. I thought that was the whole point of the capacitors?

[scott spencer]

Not all Jet saws will have the same electrical requirements. Which one do you have?

[Myk Rian]

Most woodworking machinery is happiest with a 20 amp circuit. They may not trip a 15 amp breaker, but they could be close to it.
I wired my garage/shop with 20 amp circuits. Kitchens are also happy with 20 amp circuits.

[Art Mann]

If your saw doesn't trip the breaker, then you are fine. If you look at the trip curve of an average 15A breaker, you will see that it will sustain 30A current for close to a minute before opening. That is unlikely to happen with a saw rated at 15A. That is an indication of the safety margin built in to NEC compliant wiring. If you start getting breaker trips, then the breaker is probably weak. Tool companies over-specify the current rating a little to try to avoid that nuisance.

[Mike OMelia]

You could always wire it 220, then you would lower your current draw. But seriously, if something draws 15 amps, you should not put it on a 15 amp circuit. Go to Lowes, buy a 20 and swap it out.

[Leo Graywacz]

You can't just swap out a breaker like that. It is there for a reason, to protect the wire. Likely 14ga. If you can determine that it is 12ga wire then you could swap out the breaker.

If the saw doesn't trip the breaker you are fine. They recommend you use a 20 amp circuit. You shouldn't have any issues with a 20 amp circuit and you may on a 15 amp. The worse that will happen is the breaker will trip.

The 80% rule is always good to follow. a continuous draw of 12 amps on a 15 amp line is the max you should do. But that is usually for heaters and lighting. Continuous draw has specific meanings in the NEC. A tablesaw is usually not a continuous draw item as it is frequently turned on and off.

[Howard Acheson]

Electrical codes generally require that the circuit component be of higher rated capacity than the draw of the motor. For a 15 amp motor, the wiring and the breaker would need to be rated at 20 amps.

[Art Mann]

If you actually download and read the NEC, you will find out that the issue is more complex than your generalization implies. I would not say your statement is correct in this particular case.

[Leo Graywacz]

Motor circuits can be wired up with crazy breaker sizes if they have their own protection. I've seen them with 70 amp breakers on a 14ga wire. Usually in industrial settings though. With a residential garage setup I'd keep it at the wire rating. Actually surprised it isn't 20amp. All garage and outdoor circuits around here need to be 20 amp.

[Don Huffer]

It should be said again. Changing out the breaker alone could prove to be dangerous.

Al

[Charles Coolidge]

I have 2 dedicated 240v 30amp breakers for my planer, table saw, and cyclone, 10 gauge wire and cords with twist lock plugs. I have 1 dedicated 240v 20amp breaker for my jointer, band saw, metal lathe, RAS, and mortiser (I only ever run one of them at a time), 12 gauge wire and cords. I also installed 2 120v 20amp circuits, one dedicated to a single outlet the other for shop lights and a second outlet.

The gomer pile electricians wired my 1 year old new garage with a single 120v 15 amp circuit, 5 of the cheapest junk Home Depot outlets they could find and the garage door openers and 6 garage lights (3 inside 3 outside) all on the same circuit. That breaker has tripped like 4 times already, mine never have.

[Charles Coolidge]

It should be said again. Changing out the breaker alone could prove to be dangerous.

Al

Yeah don't give the insurance companies an out if you burn your house down.

[Jamie Buxton]

If you actually download and read the NEC....

Where can I download a copy of the NEC -- for a reasonable cost? The last time I looked, publishers only wanted to sell printed versions, and for a lot higher price than I could justify for non-professional use.

[Art Mann]

You can download a free one that is a little out of date here.

https://archive.org/details/gov.law.nfpa.nec.2011

Very few things have changed in the last few years. You have to buy the latest edition. You may be able to find it from the same web page.

[Travis Conner]

One of the other tenants I was talking to who does work out of his storage unit said the outlets are 20 amp outlets, but instead of taking his word for it I decided to check for myself and it had 15 amp 125v stamped on the outlet. Is the storage facility running 20 amps through wall outlets that say 15? Can you do that? Or if it says 15 amps on the outlet then that is what it is?

[Steve Gojevic]

One of the other tenants I was talking to who does work out of his storage unit said the outlets are 20 amp outlets, but instead of taking his word for it I decided to check for myself and it had 15 amp 125v stamped on the outlet. Is the storage facility running 20 amps through wall outlets that say 15? Can you do that? Or if it says 15 amps on the outlet then that is what it is?

Yes, there are instances where the NEC allows 15A outlets on a 20A circuit. One of them is on the 20A small-appliance circuits for the kitchen countertops. I don't know the code well enough to say if it would be allowed in a commercial storage unit. The NEC is full of exceptions allowed in certain circumstances. The only way to know for sure what you have is to look at the breaker.

And, like others have already posted, DO NOT put a higher-rated breaker in place of the current one. You have no way of knowing the wire size in the WHOLE circuit. Even if you saw 12AWG cable going from the breaker, there may be a place inside a wall where a 14AWG cable taps off of it. There is a reason for the breaker size (protect wiring from overheating), and it's not just to annoy us woodworkers :).

If it's a 15A breaker, you might trip it if there are other items on the circuit elsewhere. Also, if you load down the saw for an extended period it might trip the breaker.

The wiring in the storage units probably never needed to account for current draws from using the storage units as a work area. One of the major considerations in the NEC is how much usage a circuit would get. It's entirely possible storage unit plugs would be considered a "rarely used" receptacle and the circuit daisy-chains all over the place.

The capacitor on a motor (among other things) produces a "soft start" which limits the inrush current at turn-on. This will lower the chance of the turn-on popping the breaker, but doesn't do anything when it it running.


Steve

[Mike Cutler]

One of the other tenants I was talking to who does work out of his storage unit said the outlets are 20 amp outlets, but instead of taking his word for it I decided to check for myself and it had 15 amp 125v stamped on the outlet. Is the storage facility running 20 amps through wall outlets that say 15? Can you do that? Or if it says 15 amps on the outlet then that is what it is?

Travis

Everything would depend on when the storage facility was built and what were the applicable code enforcement in the inspection. The "Code", NEC, changes with time and technology, and it is not uniformly applied throughout the entire US. Different regions also have additional electrical code compliance requirements based on their local building codes.
Other than something extremely obvious, no one can look at just the duplex receptacle configuration and installation, the panel breakers, and say that everything is, or is not, code compliant. What was "code" in 1985 may not be code for a new installation in 2014.
Can you have a 15 amp outlet on a 20 amp breaker? Yes you can, and depending on the date the original permit was signed off on and it will be code compliant today.
Can you install a 15 amp duplex receptacle on a 20 amp breaker for new construction today? Probably not any longer, and pass inspection.

Here is the tell tale you need to know;
The cord on your saw, if it came with one, will have the male connection. This plug, and the saw have met UL requirements. If the plug fits in the socket, you're good to go. If it doesn't fit, then something needs to change. The UL approval for your saw will be that the wire gauge and cord length of the OEM plug and cord will not exceed the rated ampacity of the plug it was configured with. Don't be surprised to find that the OEM cord is also a 3 conductor 14 gauge cord, and possibly 3C, 16 gauge. That's why it's so short.
I'll bet dollars to do-nuts that you have a 15 amp plug on your saw if it came prewired. The number of electrical devices built and shipped with a 115/ 20 amp plug on the end of the cord are very few.

[Travis Conner]

Yeah it's a 14 guage cord so I believe 14 gauge is rated at 15 amps. I guess it's like the other poster stated, it's just a buffer in case someone has a weak breaker and blames it on the saw. I'll give it a try and see what happens once I get my on/off switch installed.

[Leo Graywacz]

The capacitor on a motor (among other things) produces a "soft start" which limits the inrush current at turn-on. This will lower the chance of the turn-on popping the breaker, but doesn't do anything when it it running.


Steve

The capacitors main reason for being there is to change the vector angle of the sinewave so the motor will start. If you have a motor with one capacitor it will be a start capacitor. It will also have a small switching circuit in the motor to switch to and from the starting windings on the motor. If you have a motor with two capacitors then you also have a "run" capacitor for the motor.


http://forum.allaboutcircuits.com/showthread.php?t=1223