Electrical Requirements

[Mike Leonard]

In preparation for my new JET JTAS-10XL I will need to install a 230 volt outlet in my garage. I just got off the phone with JET tech support and the 3HP motor draws 34 amps at start up and 17 amps full load. To stay within 75% of the breaker capacity I would need a 50 amp breaker. Does this sound right? Is this what you other JET 3HP owners are using?
Are you using 10/3 wire for the circuit or am I way off base here?

I will be installing a sub-panel in the garage and running additional 115V outlets with probably 20 amp breakers and a total of 2 to 3 230V outlets on different circuits. My goal is to rewire the dual voltage motors I have, i.e. dust collector, jointer, etc., to 230V.

Any suggestions/comments are welcomed.

TIA

[Byron Trantham]

I just got off the phone with JET tech support and the 3HP motor draws 34 amps at start up and 17 amps full load.TIA
I'm no electrician but these values sound like 110 V values. I have a 3 HP Unisaw and I am using a 20 amp breaker. I did run 10/3 and terminated it with a twist lock style receptacle. I'm sure others will chime in here and give you more accurate help. Good luck and congratulations on the saw.

[Ray Dockrey]

I am guessing that what they meant was 34 amps total, which would mean 17 amps on each leg. So a thirty amp double pole for 220 would be more than enough.

[Ken Salisbury]

I have a 20 Amp breaker on my Jet CS - never a problem.

[Jim Becker]

I've run my Jet LT cabinet saw on a 20 amp circuit for over three years with no problems. It wouldn't be unreasonable for you to put in a 30 amp circuit, especially if the run is "long", but the 20 amp circuit will do the job no problem in most cases.

I do use twist lock plugs and recepticals, however, as I like the positive connection they afford. If you do this, be sure to look at the package very carefully...it's easy (and apparently normal) for folks to get the 20 amp and 30 amp varieties mixed up in the bins and there is a slight size difference.

[Rob Russell]

It's normal for a motor to draw up to 10x it's FLA (Full Load Amp) rating at startup. You don't size your breaker to that startup load unless you're dealing with large industrial motors and have separate overload relays, etc.

You could run a 30 amp breaker if you want to. Either way, I'd run 10/3. If the 20 amp breaker trips because that motor's startup draw exceeds that breaker's thermal limits, you can swap it for a 30 amp breaker without rewiring. Just make sure you leave enough wire in your subpanel so you can snip off the end you used for the 20 amp breaker and reterminate with a fresh section of wire onto the 30 amp breaker's terminals.

A couple of other things:
In your garage, the 120VAC outlets must be GFI-protected.
Your local AHJ (Authority Having Jurisdiction, aka building inspector) may require that your 240VAC outlets also be GFI. Find that out before you buy the breakers. You can get 240VAC GFI breakers, but they will run as much as $40-$50. I asked ours about it and he said he would not require GFI for 240, machine outlets in a basement or garage as long as they were dedicated machinery circuits.
Pull a permit for the subpanel. If you weren't planning on it - do it. You're far better off having the work inspected now than to get nailed in the future when you sell the house down the road (and have to redo the wiring to the then current code).

Rob (unlicensed, amateur, homeowner electrician)

[David LaRue]

On my Powermatic 66 it the instructions required a 30A 240V. With 10 gage wire. It is a bit more than most specs that I have seen for table saws. I also use a twist lock.

One thing I would add is a disconnect switch box with a lock on the wall. This will give you a little more reassurance that some one does not inadvertently turn on the saw. The twist locks can be a pain plugging and unplugging.

Also, I added a knee operated stop switch to mine(which is great), with a little cover over the on switch as a deterrent from the saw accidentally being turned on while it is plugged in. (I have two small kids)


http://home.comcast.net/~mywoodshop/assets/images/autogen/a_Stop-Switch-200.jpg

DL

[Paul Geer]

Interesting, I decided to look up on my Square "D" slider to see what they recomend for a breaker size for a 3HP AC motor. I found for a current load of 17 amps at 230VAC (3HP) they recomend a 35 amp breaker, and if your running that same 3HP motor at 120VAC, 70 amp breaker!

Like so many of you, I've been running my 3HP TS at 230VAC on a 20 breaker for years with no problem.

Does that mean that all our TSs are over protected?

[Jim Becker]

Does that mean that all our TSs are over protected?

The breaker protects the wiring, not the tool.

[Rob Russell]

The breaker protects the wiring, not the tool.

Actually Jim it protects both. There is a whole section in the NEC dedicated to Motors and Motor Controls. I agree that the primary purpose of the breaker is to protect the wiring. It can also serve as an overload device for the motor, though. That's why there are rules and tables that define what maximum size breaker should be used for a given HP motor. For the most part, I think that home workshops are conservatively wired when it comes to the breaker's size in relation to the motor. Most of us just never trip the breaker, even though the NEC would allow us to run a larger breaker based on the HP of our motors and their FLA draw.

Rob

[Paul Geer]

Quote:
--------------------------------------------------------------------------------
Originally Posted by Paul Geer
Does that mean that all our TSs are over protected?
--------------------------------------------------------------------------------



The breaker protects the wiring, not the tool.


Jim, That was meant to be humourous. I guess I don't use enough Standard Smiles or something... :cool: :p ;) :D :confused: :eek: :( :mad: :) :rolleyes:

[Jim Becker]

Actually Jim it protects both. There is a whole section in the NEC dedicated to Motors and Motor Controls. I agree that the primary purpose of the breaker is to protect the wiring. It can also serve as an overload device for the motor, though. That's why there are rules and tables that define what maximum size breaker should be used for a given HP motor.

Thanks for that, Rob. I have always only seen the "primary" pupose in comments on this subject by knowledgable folks in other forums...'learn something new every day!

[Terre Hooks]

You will be just fine with this saw on a 30 amp circuit wired with 10/2. No need to run 10/3, you do not use a neutral with 240v machines.

You should also be able to operate a mid-size DC (1-1/2 - 2HP) on the same circuit. I can run all three of my 1-1/2HP machines on (1) 30 amp circuit with no problem. Even have two of them plugged into a homemade extension cord. :eek:

That 3HP motor will not draw 17 amps unless you get into ripping some 3" thick Maple. It will draw 30+ amps for less than 1 second on start up, not enough time to heat up the breaker.

[Jim Becker]

You should also be able to operate a mid-size DC (1-1/2 - 2HP) on the same circuit.

I would recommend separate circuits for the DC and the TS, regardless. The cost is not that much for the wire, breaker and connectors and it in some areas, you could get smacked around for running two 240v devices simultaneously on the same circuit. (Depends on how the inspector interprets a power tool as a device) It's just good practice to keep them separate. IMHO, of course.

Now, my BS and jointer share a circuit for convenience, but I could never run them simultaneously! My arms aren't long enough. :D

[Hal Flynt]

I ran 10-4 (sounds like an answer, 2 hots, 1 common and 1 ground) from double 30AMP breakers. I bought a roll before I really knew I didn't need both a common and a ground, BUT now I can have 220 and 120 in the same box if I want it.

[Rob Russell]

You will be just fine with this saw on a 30 amp circuit wired with 10/2. No need to run 10/3, you do not use a neutral with 240v machines.

The reason for running 10/3 is so that you can add a 125v convenience outlet on your machine. You'd use it for things like a router table built-in to the saw's extension table or a light on a bandsaw. It means running a 10-4 SJ or SJO cord from a utility box on the machine to the wall and having a receptacle on the machine - sort of plugging it into itself.

[Mike Leonard]

Thanks for the great response guys. I got to thinking that the amps quoted by the tech rep were high so I called my local JET dealer. They are running their JTAS on a 20 amp breaker with 12/3 wire. He did suggest a 30 amp with 10/3 though. I will be running only one machine per circuit. It really is not much more $$ and I don't want there to be any hickups with the local code. I wll need to check on the GFI requirement, thats a point I hadn't thought of. I will give the disconnect switch some thought. Although no kids to worry about (we"re DINKS) and rarely is anyone in the shop but me.

Thanks again for a tremendous response.

[Rob Russell]

I forgot to add this before ...

Twistlocks are a great way to go (have them on mine). Hubbell is a top quality brand - go to ebay for cheaper prices.

As far as twistlocks being a hassle to do/undo - I've never had a problem. To me, a separate disconnect is overkill. I'd rather spend the money on good plugs/receptacles rather than use "big box" brand ones. The disconnect becomes another point of failure and you still need the plugs/receptacles.

Rob (unlicensed, amateur, homeowner electrician)

[Richard Hash]

The reason for running 10/3 is so that you can add a 125v convenience outlet on your machine.

Before you do this check with your local inspector. Some locales will frown upon splitting off a separate 110v line from a 220v circuit (yes, I know there are many appliances that do exactly that, but they are a single appliance). I wanted to use a split-voltage (110v/220v) receptacle in the same box and my local inspector (Houston, Harris county) said "no-can-do, will only allow if it's two separate circuits".

Basically, just check first. You're not going to save yourself much (if any) money running 10/3 and splitting off a 110v line, and it might be a better idea to dedicate your circuits...

[Rob Russell]

Before you do this check with your local inspector. Some locales will frown upon splitting off a separate 110v line from a 220v circuit (yes, I know there are many appliances that do exactly that, but they are a single appliance). I wanted to use a split-voltage (110v/220v) receptacle in the same box and my local inspector (Houston, Harris county) said "no-can-do, will only allow if it's two separate circuits".

Basically, just check first. You're not going to save yourself much (if any) money running 10/3 and splitting off a 110v line, and it might be a better idea to dedicate your circuits...

Interesting - what the inspector told you would have violated code. I don't have my code book here, so I can't dig out the section, but all ungrounded conductors to outlets on a yoke need to be opened simultaneously. Think of a multiwire circuit - both hots need to open up at the same time.

From what he told you, you'd have a 2-pole breaker for the 240-volt outlet on the yoke and a separate breaker for the 120-volt outlet. If your 240v breaker pops and you go to pull the receptacle to check the wiring - the 120 volt outlet is still hot. That's life-threatening dangerous.

I would have asked him for a code cite - politely :-).

[Don Abele]

Being in the military I move about every 2-3 years. I have a full shop of tools and have most of them wired for 240v. To make my life easier I bought a sub-panel many years ago and individual circuit breakers for each and every tool. Yes, it is WAY over-kill. The lights that exist in the garage run off the main panel and then I always wire in 3-5 more 4 foot fluorescent lamps from my sub-panel (I'll never be in the dark unless I trip the houses' main breaker).

My subpanel has a 50 amp main breaker in it and I tap into the main panel with another 50 amp breaker (I have a whole collection of about every type of breaker because each new place I move into has a different type of box). Since each of my receptacles are dedicated to a single machine, I've never had a problem with needing GFI's, even with the 120's that I wire for "hand tools". If I ever did, I would just invest in a single 50 amp GFI breaker which would protect the entire sub-panel (of course at a cost of about $75).

For all my wiring I use 10/3 inside of metal conduit. Again, way over-kill, especially when I also use it for my 120v boxes/tools (I terminate the red inside the 120v boxes or the white for the 240v boxes). I bought a 100 foot bulk spool and it was cheaper and easier. Of course working with 10/3 is a PITA but I know I'll never exceed it's capacity.

I always size my breakers using the HP-amp draw and then move to the next larger breaker. I have a Square D sub-panel and they have an excellent calculator for determining HP-amp draw:

http://www.squared.com/motodata/calcmotor.html

For me this means (and yes, this table is conservative but highly recommended by many electricians that I have worked with):

1.0 HP = 8 amps - use a 10 amp breaker - 18g wire up to 50 feet
1.5 HP = 10 amps - use a 15 amp breaker - 14g wire up to 50 feet
2.0 HP = 12 amps - use a 20 amp breaker - 12g wire up to 50 feet
3.0 HP = 17 amps - use a 30 amp breaker - 10g wire up to 50 feet
5.0 HP = 28 amps - use a 40 amp breaker - 8g wire up to 50 feet

These are all for 240v - double the amp draw for 120.

Each and everytime, I've acquired permission from the owner (when I have been renting) in writing, and obtained a permit. I also verify it with my home-owners/renters insurance as well. Again, better safe than sorry.

Be well,

Doc

[Russ Filtz]

Rob, I too had to run separate 120 and 240 circuits when I rewired my garage. To eliminate the 120 hazard if the 240 trips, my local codes also required separate outlet boxes for 120 and 240, no mixing. I could however run all the wires through the same conduit (as long as I sized the tubing right).

[Bruce Page]

I'm no electrician but these values sound like 110 V values. I have a 3 HP Unisaw and I am using a 20 amp breaker. I did run 10/3 and terminated it with a twist lock style receptacle. I'm sure others will chime in here and give you more accurate help. Good luck and congratulations on the saw.

That is exactly the same setup I have on my 3hp Unisaw. I have never tripped the breaker.

[John Davidson]

Mike,

I have worked 15 years as an industrial electronics/electrical tech. 125 % of full load current is the way to go. That figures at about 21 amps. Then if your intent is to protect the equipment as well as the wire you would size down to the next standard value as long as you don't go below FLA. 12/2 with a 20 amp breaker should work fine unless you intend to make the run more than 50ft. If you go over 50 ft then you need to go up to the next standard value to insure that there in no significant voltage drop to the equipment. This is what all my training indicates and also the same set up I have on my own Jet 3hp saw.

The motor will draw a good bit more current at startup but with little to no load it will come up to speed in much less than a second. At speed it will not draw more than 17 amps and the breaker will not have time to heat up and tripp during the start up time. I have never tripped the breaker on my saw.

[Bart Leetch]

I forgot to add this before ...

Twistlocks are a great way to go (have them on mine). Hubbell is a top quality brand - go to ebay for cheaper prices.

As far as twist-locks being a hassle to do/undo - I've never had a problem. To me, a separate disconnect is overkill. I'd rather spend the money on good plugs/receptacles rather than use "big box" brand ones. The disconnect becomes another point of failure and you still need the plugs/receptacles.

Rob (unlicensed, amateur, homeowner electrician)

I have never seen a problem with twist-lock plugs accept when they are used for equipment where the cord runs across the floor, in this case I have seen the cord get caught & jerked breaking the wall receptacle.

[Jim Becker]

I have never seen a problem with twist-lock plugs accept when they are used for equipment where the cord runs across the floor, in this case I have seen the cord get caught & jerked breaking the wall receptacle.

Of course, you're not supposed to trip on them! Part of that solution is routing them to the outlet in such a way that they are not underfoot. If that is not possible, a cord cover is a good idea, both to protect the cord and to protect your knees...which really, really hurt when they smack into a concrete floor! :rolleyes:

[David LaRue]

I have never seen a problem with twist-lock plugs accept when they are used for equipment where the cord runs across the floor, in this case I have seen the cord get caught & jerked breaking the wall receptacle.


I must have bought the cheap twist locks from the big box. Personally, I unplug and replug the saw when I took on or off the guard (past tense now that I have the overarm guard) with blade changes, plus anytime I leave the saw unattended. So it ends up being a bunch of times. The twist locks that have are hard to twist. But I have made it easy to line the plug and receptacle up with a index mark with a sharpie.

Yes, the lockout switch is overkill for some. But the boy scout in me saws better safe than sorry. The could of - should of - in regards to safety with kids around is my motivator. It may not be for everyone. :)

Dave

[Jim Becker]

I must have bought the cheap twist locks from the big box...The twist locks that have are hard to twist. But I have made it easy to line the plug and receptacle up with a index mark with a sharpie.

I had that problem with one set (my original jointer postition)...and then I discovered that some schmuck put a 30a receptacle in the 20a bin at the big box. That makes for an "uncomfortable" fit. Once I replaced that incorrect component, I haven't had any trouble at all with the twist locks. They work easily. (The mark to show the mating position is a great idea, however...they do go together better when the prongs are lined up properly! :D )

And I agree with unplugging during any maintenance. A kill switch is great for killing the shop, but I still wouldn't trust it for when I'm changing the blade. There is something comforting about seeing the shiny part of that plug when your hand is down the saw's gullet with a sharp WW-II against your wrist...

[Don Abele]

Whenever I am going to put any part of my anatomy near any fast moving, sharp, pinching, etc. parts that's when I'm glad that each of my tools is on it's own circuit breaker. I just open that one breaker and I know there is no way it's going to bite me. And since the breaker box is in the shop with all the tools, I know no one can get by me and flip the breaker shut.

Regardless of how you do it, you should always have that 100% piece of mind that there is no way electricity is going to get to that piece of equipment (and the on/off switch on the tool doesn't count).

Be well,

Doc

[Jim Becker]

Whenever I am going to put any part of my anatomy near any fast moving, sharp, pinching, etc. parts that's when I'm glad that each of my tools is on it's own circuit breaker. I just open that one breaker and I know there is no way it's going to bite me. And since the breaker box is in the shop with all the tools, I know no one can get by me and flip the breaker shut.

So...what if you accidently opened the wrong breaker? The "ultimate breaker" is the plug on the end of the cord! If it isn't connected to the holes in the wall, there is no chance of any power getting to the tool. I'm not smacking you around, just pointing out the obvious.

[Don Abele]

Good point Jim and yes, I do agree with you that seeing the plug end is the absolute best way to go. With that said, all of my breakers are labeled as to what piece of equipment then run and I ALWAYS try to turn the machine on (then turn it back off) to make sure.

Another point of safety that's easy with my sub-panel. When I'm done for the night, I open the breaker in the main panel that supplies the sub-panel. This completely ensures me that no one is going to turn anything on while I'm not there.

Be well,

Doc