Plugging Table Saw Into 50 Amp Welder Receptacle

VTHokieAg

Member
I currently have a 50 amp circuit in my shop (with correct associated wiring) that I use to power my welder. I am buying a 220v table saw and would like to plug it into the same receptacle as the welder.

My plan was to make an extension cord (since I need one anyways) with one end matching the 50 amp receptacle and the other end matching the plug on the new table saw. I understand the 50 amp circuit is overkill for the 3hp saw. Will this be okay? I have read conflicting information. Also, would a 25' extension cord be okay? What type of cord should I use and what gauge?

Thanks
 

The 50 amp breaker may not trip soon enough to protect the saw in the event of a short, but other than that it should work just fine.

I needed an extension cord for my wire welder. A professional electrician suggested using 10-2 with ground house wiring. It works just fine. Not as handy to roll up or unroll, but a whole lot less costly.
 
#10 wire on 50 amp breaker is a no-no, breaker is sized to protect the wire, I believe it should be #6.
 
You could use a small disconnect out door type box
That is used for out door air conditioner
Just use the 50 amp cord to feed disconnect then
Get power info from new saw and install
That breaker into disconnect box 220 power
Uses half the amps of 110 so your cord going from
Disconnect box to saw will be fine with 12 gauge wire
And be sure to proper ground the disconnect box and saw
 
The code violation would be the too high amperage breaker for the saw.The saw calls for a 20 amp breaker. This cord will also be costly as you need a rough service end that can lay on the floor.A cord would not be something an electrician would do for you because it is half a job.The cord could be 12 wire but none of this is legal.
 
As for your question about pluging saw into 50 amp outlet. No harm as long as amp draw never exceds 25 to 30 amps,in which case the motor can catch fire and/or melt before breaker trips. Just be sure to use #8 or larger wire (that means replacing origional saw cord as well) or else wire can catch fire when an overload occurs.
I think it's best to have someone that know's what they are doing help you install a sub-panel,it's not much more expense over what you are wanting to do.. I can give you a list of things which might go wrong despite our best efforts to help you. Standing there looking at your shop is far better than having you describe it for us.
 
How would you suggest doing it utilizing the 50 amp service to the welder? I am thinking take out the receptacle, put a small box in, and come off that with what I need for the welder and what I need for the saw. Either way, I am still going to need about a 25' extension cord for the saw.
 
It'll run just fine. Just a question of protection should something go wrong.

That circuit breaker may not trip if something shorts out. Just remember that at 50 amps, a whole lotta heat can be generated before it does trip. Certainly enough to start a fire while the breaker's thinking everything's perfectly fine. I picture cutting through a 6 inch slab of green oak and the saw's motor glowing red. (the saw may have built in protection, but I wouldn't depend on that)

That's true about any circuit breaker to a point - but the probability of it dangerously not tripping obviously increases with the rating.

Personally - I'd just wire up a new circuit for the saw if you have easy access. Materials are cheap enough. But if not, as long as the wiring is all the right gauge, I wouldn't worry too much about it. But I'd keep the saw unplugged when not in use - and seriously consider an inline breaker for it.
 
At the end of the 50 amp line I would remove the receptacle and place a small sub-panel on that line. Box[ nipple] over to another 50 amp for the welder next to subpanel . Pipe or staple up wire to feed saw from 20 amp breaker in new sub panel.Have saw receptacle in mounted box to accept saw card at approx 6 ft length at saws permanent location.
 
So everyone says it's so bad etc cause too much amperage for the cord and saw. Why is that any different than my clock radio with a 18 gauge cord plugged into the 20 amp circuit on my kitchen counter? I always thought the breaker protects the circuit wiring but not what is plugged in necessarily hence why you unplug when not in use
 

What happens is that people mix up short circuit protection and thermal protection . In particular with motor , transformer , welder etc loads.
According to the code book a 40 amp breaker and 12 gauge SOW Cab tire extension cord is legal.
 
If it were me, I would have a short cord with the welder style plug go to a small box with the right breaker for the saw and the breaker would run to the right outlet for the saw cord. That said, I have my own 50A cord which runs to a box which has a low amperage 220v outlet and a 120v 20A outlet without lower amperage breakers. I use this with jobs (such as your table saw) where I am right there. Breakers are to protect the wiring, not what is plugged into the outlets.
 
The thing many lay persons (Billy Bob abd Bubba lol) fail to understand is the overcurrent protection device (fuse or circuit breaker) is sized to protect the wires from the panel to the load. If you use wire (say to a saw) with an ampacity of say 20 amps, IT MUST BE PROTECTED WITH A 20 AMP OVERCURRENT PROTECTION DEVICE NOT A 50 AMP.

First you size the load,,,,,,,,,,then you size the wire to have a minimum ampacity of 125% max continuous load plus stay within voltage drop requirements,,,,,,,,,then you size the overcurrent protection device to protect the wire.

Next is thermal overload protection for a motor IS NOT THE SAME AS overcurrent protection for the wires.

The wire size must be rated at least 125% of the saws max continuous load, then size the fuse or breaker to protect that wire

Also in determining wire size, in addition to ampacity, the wire needs to be big enough so as to keep voltage drop at a certain maximum.

This isn't rocket science for electricians and engineers just give us the max current draw of the load and the wire length and we can size the wire and breaker.

John T Long retired EE so no warranty but believe this to be correct and code proper
 

Obtain one of those welder extension cords with the 50amp male and female plug and receptacle . Run a foot or two of 8 gauge HD extension cord from the saw and place a 50amp male welding plug on it. Plug it all together and use the saw.
You will now also have a 25ft extension cord for your welder.
If there is ever a hard short like to line or line to ground . A 20,30 , 40 or 50 amp breaker will all trip with the same speed.
 
From the manual:

Required Power Supply Circuit- 15 amps

Full Load Current Rating- 14 Amps

Power Connection Device- NEMA 6-15

Cord length will be about 20 or so feet
 

Not for a motor load. The cable does not rely on the breaker for thermal protection.
We still have people that can't tell the difference from short circuit protection and thermal protection.
 
I don't disagree - I'm not talking about "code".

I'm talking about safety and convenience.

I LIKE having a breaker that trips if a motor gets stuck.



I know it doesn't HAVE to protect the equipment plugged into it, but... why not protect it anyways?

For a stationary tool like a table saw - wouldn't it be better to size it so the saw IS better protected, even if you don't have to???



If a motor did get stuck, wouldn't it be safer if the breaker tripped?

Not trying to argue - just not understanding why that wouldn't be better.
 
1) Required Power Supply Circuit- 15 amps

Use 12 Gauge wire as 80% of 20 amps = 16 and protect it with a 20 amp breaker
NOTE that close you may consider 10 Gauge wire and a 30 amp breaker, but 12 and 20 is still legal

2) Full Load Current Rating- 14 Amps

Again, 12 Gauge wire will suffice protected by a 20 amp breaker or you could oversize as noted above

3) Power Connection Device- NEMA 6-15

That's the Receptacle NEMA 6-15R and Plug type NEMA 6-15P to use, any shop or home depot etc will have it

4) Cord length will be about 20 or so feet

Without looking at a chart at only 20 feet the sizes above shouldn't cause voltage drop problems

NOTE it takes 3 to 6 times the running current to start a motor, depends on type and load etc., so if starting trips a breaker the NEC allows use of a bigger breaker provided the motor still has thermal overload protection.

Im still rusty on this stuff so no warranty

John T
 
Yo JMOR, Best I recall (remember its been a longggggggggg time since I practiced) the breaker protects the wire to the branch circuit receptacle (20 amp breaker for 20 amp rated wire) while the appliance (like a 1 amp device with 18 gauge cord) may or may not have its own fuse protection. Its indeed true the breaker could allow 20 amps to flow through the 18 gauge appliance cord BUT I DONT KNOW THE ANSWER ????????????? Told you I was rusty lol

Maybe Buick or DrSporster or Dusty MI knows, some of them are still practicing...

John T
 

The higher amperage breaker is required to prevent tripping the breaker during startup.
Locked rotor current will trip a 20,30,40 and even a 50 amp breaker.
Sizing breakers for motors and transformers is different than sizing a U-ground receptacle for a portable 1500W heater.
 
If something "shorts out", resistance is 0, so current tries to go to infinity in short period of time (probably microseconds, certainly quicker than what you would see on a meter): Ohms law, V=IR or I=V/R. I.e., the breaker will trip quickly on a dead short as current (amps) climb.

If the system wiring (say 12AWG on a 20A circuit) and receptacle are appropriately sized, something that draws close to that 20 amps will warm the circuit wire up but wouldn't likely start a fire. That is why ampacity charts derate wires in conduit vs open air where heat is more easily dissipated.

That being said, having adequately protected circuits doesn't guarantee "no fire". If an appliance fails in a manner that draws more current in the internal wiring (or cord) than the design calls for, then you've got a problem. This typically happens when a conductor breaks and causes arcing.

Arcing also causes house wiring fires in adequately sized circuits when, say, a mouse chews threw the insulation or a staple is installed too tight. In both cases the insulation is broken and arcing occurs. I've personally experienced both situations. Fortunately they didn't cause large fires but melted wires and charred 2x4's were evidence of the problem. Inspectors tell me they always check metal staples and find that DIY'ers are the ones who typically hammer them dead tight.
 
Your plan will work just fine.

Look at the motor, it will probably have an overload reset button. If it does, that will protect the motor in case it gets bound up. Otherwise, you'll need to be careful not to push it too hard, be ready to turn it off if it gets stuck. Probably not a problem if you are the one running it, could be an issue with a helper or employee though.

That motor runs 17 amps full load. A 12 gauge cord is good for 20 amps.
 
One thing is for sure, its not likely that the table saw will ever trip that circuit breaker. A couple of things come to mind. I often work in power plants. In the Admin office areas, they have normal 20 Amp 110 outlets, but outside of the Admin areas, you will not find 110 outlets where the receptacles are less than 30 amp. So, any power tools used out there that are 110 volt have to either have 30 amp plugs on them, expensive to do since they couldn't be used at most other customer sites using 20 amp receptacles that 30 amp plugs won't fit...or, use much cheaper adapters with a 30 amp plug on the source receptacle end, 20 amp style receptacle on the tool end. Now, the power plants new owners are requiring that the adapters are also GFI. No biggie. Another thing to keep in mind, is that 25' extension cord that you plan to use. You will probably have to make your own, one rated for the maximum current draw of the saw. You're not going to be able to find one on the shelf that you can replace the ends at Menards, Home Depot, Lowes or most places. In general, they tend to use 14 gauge wire, maybe a "heavy duty" one might use 12 gauge. They won't work. They will heat up and cause your motor to heat up as well. Figure out your current draw, whatever the tag on the motor says, go to one of those places, whack off a 25' piece of four conductor cable/wire/cord for L1, L2, Neutral, and Ground that is rated or that amperage draw, put matching rated ends on it and be done with it.

Good luck.

Mark
 
Its best to run a sub panel with the proper sized breaker for the saw. You could power the sub by plugging it into your 50 amp welder plug or you could hard wire it. If you hard wire off the back side of the welder plug and you are sawing while someone else is welding you might lower the voltage enough to make both tools avt sluggish depending on how hard yoy are pushing the saw or the welder.
 
In modern texts they state either E=IxR or to add confusion V=AxR. You change both the Eto V and the I to A . The modern student is so confused by alll these letter changes they don't know any Ohm's Law.Voltage stated as E is from the early term "electromotive force" which was for voltage .
 
(quoted from post at 13:55:08 10/22/15) From the manual:

Required Power Supply Circuit- 15 amps

Full Load Current Rating- 14 Amps

Power Connection Device- NEMA 6-15

Cord length will be about 20 or so feet

According to the national Electrical Code for this motor's specs at 14 amps, not the 17amp which a 3HP motor typically draws.
Minimum of 20amp cable. Non time delay fuse of 45amp max. Time delay fuse of 25amp max. Breaker size of 30amp max.
Now some people are going to think that a 30amp breaker is too much for a 20 amp cable. Ain't so.
 
I have the same set up in my shop,I mounted the correct size breaker on the saw for protection then plug that into the extension cord.
 
Just an update. I called a local electrician for our town and he came out and looked at my situation today. He is going to put a new circuit in just for the saw and put the receptacle closer to where I will be using the saw. I'm supplying the 12/2 wire and he's doing everything else (breaker, receptacle box, receptacle, conduit, and hooking up to breaker box) for $100. Thanks!
 

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