Another 220V question

[FeelFree]

Or maybe it's the same. I'm totally confused here.

THE SET UP

I have a 200 amp load center in my cellar. Supply from Con Ed is underground. Inside the load center there are three wires (1/0) coming from Con Ed, one going to one side of the hot bus bar, one to the other, and the third (re-labeled white) going to the neutral bus bar. The neutral bus bar has an insulated wire (looks like a #6) going via EMT to the one inch brass water main about six feet away. The brass water main goes through at least 30 feet of clay soil and drops at least 10 feet (making 20 foot below grade) before connecting to the city's cast iron main. No sneaky plumber has crept in at night and replaced any of the relevant parts with plastic. However, I must get around to jumping the water meter (installed after the load center) one of these days.

There is NO ground bus bar in the load center. None, neant, doesn't exist. This is a total AC system and grounding is via the outside of the cable (or EMT) and the outside of metal boxes including the load center. I can't see without disassembling it but I think the neutral bus bar is connected to the load center electrically. In any event the load center is mounted on a sheet of plywood (so it's somewhat insulated from the wall) and there's a 120V between anywhere on the load center's metal surfaces and either of the live busses. Also between either of the live busses and the neutral bus bar.

All of the above was installed by an expensive licensed master electrician about 25 years ago at the time when the service was upgraded to 200 amp. Con Ed connected their wiring so presumably this is all hunky dorey, in code, and perfectly safe. In any event it's not going to change in my lifetime. Don't even think about suggesting it.

THE ARC WELDER

The main reason for the upgrade to 220V which at the time Con Ed wasn't too happy with (apparently it costs them money and they want to see that they'll recover it quickly) was to install a 30 - 200 amp

220V Sears arc welder. The plug on the end of the arc welder cable is a 90 degree type with a round pin at the top (looks like a piece of tubing cut lengthwise in half so it's not quite round) and two parallel straight pins below. One of the straight pins is longer than the other making one think that it's polarized but I can't see the reason for this.

(I can actually if the US had a REAL 240V system such as I grew up with. In a real 240V system each plug has a hot, neutral, and ground. Between the hot and neutral is 240V; between the hot and ground is

240V; and between the neutral and ground is 0V. There's no such thing as 110 or 120V in the system.)

To plug in the arc welder I installed a black plastic outlet about 6 inches away from the load center, joined to it by a piece of rigid conduit. From the plastic outlet three wires go into the load center, a black to one side of a pair of 40 amp tandem breakers, a red to the other of the pair, and a white to the neutral bus bar. Understand that It was I who decided the round pin should be connected to the neutral bus bar. Even in those days (25 years ago) a round pin looked like a ground but since there's no ground bus bar where was I supposed to put it? Anyway it works fine, doesn't overheat, and as you have doubtless guessed, hasn't electrocuted me or anyone else... yet .

THE TABLE SAW

About ten feet away I have a 10" table saw which used to be a Sears but has been so heavily "breathed on" ( as they used to say in the hot rod business) that they really can't claim ownership any more. The relevant item is that I replaced the motor with a 3hp capacitor-start capacitor-run 220V (actually the name plate says 208V - 250V) Baldor motor. This motor has two and only two terminals--one for the red and one for the black. No green screw or any other color screw that could be a ground. However ground can be achieved via the AC cable which is clamped to the motor. The motor does have some sort of overcurrent protection though, at least I presume that's the function of the red button on the outside. The red button has never operated but it's pretty hard to stall a 3hp motor running a 10" blade even cutting old growth oak or maple.

A 12/2 AC cable with the white relabeled red runs from the motor to a

4 inch metal box mounted underneath the saw. In the 4 inch box is a double pole 20 amp switch and the 12/2 is attached to one end. The other end of the switch has the white (relabeled red) and black from a 12/3 big mother of an extension cord. (Although the extension cord says 12/3 on the outside of the jacket it only has three wires inside: a black, a white, and a green.) The green wire of the extension cord is screwed to the metal box.

The other end of the extension cord has the same plug as the arc welder. The black goes to one of the parallel pins, the white to the other parallel pin, and the green to the round pin. All this works fine, never had a problem, no over-heating, no electrocutions...

But, if I read the other posts around here, what I've done is create a secondary ground for the neutral bus bar. The current could flow back from the neutral bus bar in the load center to the round pin on the outlet then via the green wire of the extension cord to the ground screw of the metal box and then via the outside of the AC to the motor and then to the table saw table itself. Is this analysis about right?

SUGGESTED CHANGES

I'm not going to fiddle with the arc welder or its plug, nor am I going to add a ground bus bar in the load center. I suspect the arc welder anticipates that the round pin is a ground and I'm erroneously treating it as a neutral. The real problem here is using a plastic surface mounted outlet. If I put in a metal box and mounted an outlet of the proper configuration (two parallel pins and one round) into the box I could simply connect the round pin to ground and eliminate the white wire to the neutral bus bar. I presume such non-surface-mount outlets exist?

THE ROUTER

The reason this whole topic arose is that as part of the improvements to the table saw one of the extension wings has been converted into a router table with a router mounted underneath. The router has its own cord and three pin plug which up to now goes into a separate outlet totally independent of the table saw. I was thinking about installing a plug off the table saw switch and eliminating one more cord trailing around my workshop but obviously I can't do this now because I'm either missing a neutral or missing a ground.

Or can I? Just as one can plug a double insulated tool into a three wire grounded outlet (110V) are there outlet configurations for 220V with four pins (hot-hot-neutral-ground) which would allow a no-neutral plug (as I have now) to be inserted? If there were I could leave the arc welder as is and change the extension cord for the table saw to four wire (at enormous expense of course) and have my cake and eat it too. The only other way would be to install two 220V outlets next to the load center, one the 4 pin configuration and the other the present

3 pin. Hmmm, could I install these in the same metal box...? Of course this is a waste as under no conceivable circumstances would the table saw, arc welder, and router ever be used concurrently.

What do you think?

[SQLit]

see the body of text for responses

Check the neutral bar and see if it is bolted to the metal. If so your fine. If it is isolated there could be some issues. Might have a screw from the bar into the metal as well, that would depend on the manufacture Very common construction for residential panels up until recently. 25 years ago depending on the region you might or might not have installed a ground rod, that would be a good thing to add. #6 is light for the bonding conductor, check and see if it is not a #4 which is what is needed for a 200 amp panel

A lot of people use the screw in the cover for the ground connection. Having the AC cable be the only source of ground is not a good idea.

Perfectly normal for cords.

NO, the neutral is grounded at the service. As long as you have installed the ground bar in the service box your fine. Todays more modern panels have a bussed jumper from the neutral bar to the ground bar. The neutral is isolated from the can.

The white wire in this case is really a ground. If the box is plastic then you do not have to ground it. If the box is metal your grounded by the grc conduit that you ran if I understand correctly.

Correct, unless you change the cord to the saw to a 5 wire cord. Then you would have the correct number of wires. 2 hot, 1 ground for the saw, and a hot and a neutral for the router. The router needs to be on a seperate circuit breaker from the saw.

[FeelFree]

As I said earlier, there is NO ground bus bar. All grounding is via the outside metal of the load center.

The grounding cable from the neutral bus bar (and probably the box) might be #4. It's way behind all the other wires and I'd have to pull out some breakers to see exactly. This is all just background anyway. However the load center was done by the licensed electrician is how it's going to stay.

[continuing your sentence] ... but can share the same ground. Is this correct?

But I have a problem with your suggestion.

Neither the saw nor the router will ever be used concurrently and neither exceed 20 amps (i.e. a 12/4 extension cord would be more than adequate).

If you're worried about the 40 amp breaker, as I understand it the question of matching the circuit breaker size and wire size stops at the outlet. I could run a tiny load (a two watt clock for example) on a small gauge wire (say 22) plugged into a huge amperage outlet (say

50) and not raise anyone's eyebrows. To be more reasonable, there are plenty of 18 ga 100 watt lamps plugged into 20 amp outlets. The 18 ga zip cord will incinerate long before the 12 ga wire feeding the outlet. Seems crazy from the perspective of matching wire size and overcurrent device rating but I don't see how otherwise it could operate...this outlet only takes 5 amp devices; this one, 7 amp; another, 2 amp... nah, silly.

How then is that different than taking the feed for the router from one of the saw hots and the saw neutral (presuming the four wire set up talked about in the next paragraph) as well as the saw ground?

Update: the illustration in one of my books of a 4 conductor 220 amp outlet looks like it could take both three and four pin. I presume that the neutral is the "L" shaped blade? The only question is thickness of the pins and their distance apart.

Note to self: check the air conditioner outlet. I bet I've used the round pin as the neutral there too.

[SueMarkP]

In the service panel, the ground bus and the neutral bus are one and the same. You may put bare or green grounding wires into that neutral bus along with white "neutrals". If you create a subpanel, then you must maintain separation of the neutral and ground. If any of your branch circuit conductors use romex with a ground wire, you should connect those green or bare grounds to the neutral bus. Relying on the metal chassis ground is not great in many installations, as there could be concentric knockouts, locknuts that don't penetrate the chassis paint, or just loose couplings. I'd run a separate ground in any conduit you have.

There are provisions in the motor code for motor not operated at the same time. Since you created this saw/router combination, I'd consider it an appliance and would feel safe with a single circuit powering both items.

What is different is that UL tests appliances on 20A circuits. Things are designed not to burn up with a 20A breaker. When you use that same idea on larger circuits, all bets are off. However, your saw and router are motors, and motors (with thermal protection)are allowed to exceed normal circuit breaker rules if you need to (so they start up and not trip the breaker). But, I've never had a saw that tripped a breaker that closely matched the nameplate amp rating of the saw -- saws and routers are easy to startup. Full load of the saw could trip a 20A breaker, but I doubt it. I'd encourage you to change the circuit to a 20A breaker and see if things still work well. This will help protect the router. If heavy ripping trips the breaker, you could go to 30A. But the oversize breakers are supposed to be for motor startup and not for overload.

I don't believe any 240V 4 pin receptacle will take a 3 pin 240V plug. Most

240V heavy equipment doesn't require neutral wires (welders, motors, compressors). In most cases, you should be using a 3 pin plug/receptacle with the 3rd pin a grounding pin and NOT a neutral. The exception would be your combination saw/router, as I presume the router is 120V. The saw needs two hots, the router needs one of the hots and a neutral. A 4th grounding wire here would be a really good idea so the saw frame is grounded.

[volts500]

FeelFree wrote:

For a 3 HP motor the conductors must be able to carry 125% of the FLC, which is 17 amps. 17 x 125% = 21.25 amps. If the circuit were interlocked (say with a DPDT switch mounted on the saw) and the router fused at no more than 20 amps (preferably lower) on the load side of the switch, that would be permitted, however, you would still need to provide a 4-wire receptacle outlet separate from the welder outlet.

More like a red flag. That's one reason why 15 or 20 amp receptacles aren't permitted to be installed on 30, 40, or 50 amp circuits. For a 3 HP motor the conductors must be rated for at least the FLC of the motor (17 amps) x

1.25% = 21.25 amps. The max. breaker can be 17 x 250% = 42.5 amps > 45 amps. When wiring motors, the breaker is depended upon for short-circuit and ground-fault protection ONLY and cannot exceed 250% of the FLC for motor starting. The motor overloads (in your case, that red button on the motor) are what protect the motor and the supply conductors from overload, _not_ the CB.

The router should not be connected to a circuit rated more than 20 amps. Since the table saw/router is in sight of the load center, it may be easier/cheaper to run a liquidtite flexible conduit from the panel to the j-box on the table saw, then pull 5- #12 THHN conductors (2 hots for the 240 volt for the saw, 1 hot and 1 neutral for the 120 volt for the router, and one equipment ground). You can then use a 25 or 30 amp two pole breaker for the saw (maybe a 20 if it will hold) and a single pole 15 or 20 amp breaker for the router.

No.

The neutral is a current carrying conductor. The equipment grounding conductor does not carry current under normal conditions......only during a ground-fault. AC's don't use a neutral.

[gerry]

If this is the service entrance with main disconnect, it is REQUIRED that the ground and neutral be bonded in that panel which usually means the same bus bar. It/they must be bonded to the cabinet as well.

Only branch panels generally have isolated ground bus bars.

gerry

[FeelFree]

OK. Leviton's Cat #275 is a three pole 4 wire 50 (or 30) amp 250V plug which has the same configuration as the plugs currently on the end of the table saw extension cord and the arc welder cord except that there's a neutral (which is "L" shaped for 30 amp and straight for 50 amp) and unfortunately the dimensions (length of blade, distance between blades) are not the same. BUT, this offers a solution. The plug has loose blades so I could leave out the neutral for the arc welder plug and put it in for the table saw plug. Either would then fit into a Leviton Cat #279 a 50 amp 3 pole 4 wire grounding power outlet. #279 also has the advantage of being metal and box-mountable so I'll toss the present 3 wire plastic outlet and put this in its place, mounted in a 4" box with the hot-hot-neutral-ground connected to where they should be. Need a 4" box with 3/4 knockouts though.

I also had some further thoughts as to the router. Working from the 4 pin plug I talked about in the previous paragraph, I'll have a 12/4 extension cord ($1.55 a foot!) going to a 4" box screwed to the wooden frame of the saw stand (the present box). Next to that box I'll mount a small handy box and connect it to the first 4 inch box with a rigid box connector. After the handy box and connected via another rigid box connector will be another 4 inch box. The first 4 inch box has the original double pole 20 amp switch and connects to the table saw motor via the AC. The handy box has a single pole switch/pilot light combination which controls the wire continuing through to the second 4 inch box in which is mounted a 20 amp GFI (they do come in 20 amp I hope?) which is where I plug in the router. (Hey, if I'm blowing the big bucks on two plugs I might as well go whole hog and make at least the router really safe --at least electrically. I'll still be able to cut off my finger.) I'd put the switch and the GFI in the one box but I don't think a duplex outlet/GFI combination face plate exists.

The only weak spot now is the 12 ga extension cord running on a 40 amp breaker but I promise I'll keep a nose out for burning insulation and I'll feel it regularly to check its temperature .

I have a couple of other questions but I'll open up a new thread.

[The Masked Marvel]

If it is the main service panel (it sound like it) , not a sub panel the neutral and the ground buss are one and the same (as you note) All grounging conductors and all grounded neutral conductors connect tothe same bus, and the bus is connected to the panel and to the grounding conductor to the water pipe and/or driven grounding rod.

You will not get 220V but you *will* get 240V (2*120V) from a 3 wire

120/240V single phase system. (4 wire, 3 phase will yield 120/208V instead (120*sqrt(3)=208))

Your welder outlet has line1 line2 and ground -- fine Your saw has line1 line2 and ground -- fine Your router needs either line1 or line2 AND neutral AND ground. Once you leave the main panel the neutral and grounding conductors (while at the same potential) NEVER again shall meet, and the neutral (white or light gray) must be insulated. The ground may be bare or green or green w/ yellow stripe.

While you could theroetically (if you have 3 wires plus ground on th esaw circuit) use a 4pole 3wire 120/240V grounded (4 pins/slots) connection, you would be best to run a new 120V circuit for the router, -- 12-2 w/ gnd is cheap. Do not use the grounding wire for a grounded neutran and vice versa.

[FeelFree]

What's an FLC? According to the label on the motor (it's hard to read because I have to get under the saw and read the words upside down) volts = 208 - 230 (just like that with a dash in between the two numbers) and the amps are 15.2 - 14.6 (same remark). Other items are AMB (ambient temperature?) 40; SF (service factor?) 1.00; Duty Cont (continuous duty?); insulation rating B; Thermally protected; Type Cap (capacitor run?); plus some part numbers etc.

From the above I would presume that at 208V it draws 15.2 amp and at

230V it draws 14.6, therefore most of the time it's going to be 220V drawing around 15 amp. To be on the safe side put it on a 12 ga 20 amp circuit which is where it is. If we take your 125% it would work out to 18.75, still within the 20 amp.

The router draws around 15 amps too. On startup I've had it blow a 15 amp breaker but then there were a couple of lights on that circuit. See my other post for the router/GFI suggestion.

Ah no. That would be hard-wiring the saw/router into, of all things, the load center! I suppose the problem really is that I'm constructing a non-UL-approved device (a router/table saw combination) using some common electrical wiring items and trying to apply the rules for wiring a house to something which isn't house wiring. If I were to hard-wire it, it would indeed become part of the house. As long as I keep that outlet between me and the house wiring I might be violating some "Can't use non-UL-approved devices" rule but any such violation disappears the moment I unplug it. Anyway I imagine that such a rule applies to the sale of appliances etc, not to their use.

Yes. See my other post.

Well that's my point. I need to look at it and probably reposition the white (i.e. cap it and ground the round pin).

[SueMarkP]

I think you got it. Buy the plug/receptacle for the worst case of equipment, but you don't have to wire to pins in the plug you don't need (like neutrals on welders).

If you buy the decora style GFCI's, you can get handi box covers with a small rectangle for a switch and a big rectangle for a GFCI. If the router has a 15A plug, buy a 15A GFCI -- they'll all rated for 20A passthrough. No need to pay extra for a T slot if the router doesn't have a 20A plug.

If you really don't want to change this receptacle because you need it for something bigger and you can't run a new one, consider buying a small loadcenter or AC disconnect box and put a 20A double pole breaker in it. Total cost will be about $20. Then run your 12-4 cord (or better yet 10-4) between the plug and the load center. Connect the output of the load center breaker to the 4" handibox with the GFCI and switch with 12-3 NM cable or a flex raceway with 4 #12 wires. You could even mount this loadcenter on the side of your saw.

[Chris Lewis]

According to SueMarkP :

One slight caveat - Our code (but I'm not too sure of the NEC) permits you to use just about any kind of plug/receptacle you want for anything, provided two things are true:

- you're not exceeding the current/voltage ratings of the plug/receptacle. - No other plug/receptacle in the building of the same type is wired any other way.

Which means, for example, you could use a 50A 3 prong outlet on a 120V/15A circuit, as long as you're not using that same outlet type for anything else in the house.

Or, more in keeping with this situation, you could use a 4 prong outlet for an (initially) three wire circuit, as long as you're not using the same outlet type anywhere else.

The intent in the rule is to provide for "keying" of specific outlets for specific purposes (by choosing a unique receptacle type), without introducing the hazard of plugging the wrong thing in.

Still likely to give an inspector cause for alarm tho.

[volts500]

File this thread in your FAQ under "How to butcher your workshop wiring _and_ spend more money than it takes to do it right."

[Chris Lewis]

According to volts500 :

Heh, yeah. But it is code-legal ;-)

I have mentioned that what I commented about is extremely rarely appropriate in a residential setting. It's more for certain industrial/control applications & requirements.

If _I_ was trying to permanently sling a 120V router under the wing of a

240V table saw that needs to be moved around, I wouldn't do any of that. I'd ensure I had a 240V and 120V outlet near each other, and merely tie-wrap the two power cords into a loose bundle to reduce any tripping hazard. Easily reversible, convenient and legal.

If, on the other hand, I was installing (or building) a integrated tool that needed both 120V and 240V, I'd install a four wire circuit of the appropriate ampacity, and use a four prong cirlock (locking) plug/receptacle that matches that ampacity/voltage combination. The locking receptacle is (normally) beyond what code would require, but, since I'm building the circuit from scratch, a few extra bucks are worth it.

[volts500]

Not even close.

1...A router connected to a 40 amp circuit is code-legal? NOT. 430.32(D) Exception. 2...A 20 amp GFCI is permitted to be connected to a 40 amp circuit? NOT. 210.21(B)(3) Same GFCI is actually expected to protect conductors/equipment at 20 amps? NOT. 3...Conductors supplying more than one motor are permitted to have an ampacity of 125% of the largest motor with NO regard for the FLA of the second motor when no interlock circuitry is provided? NOT. 430.24 Exception #3 4...A plug is permitted to be jacklegged just because someone is to cheap/ignorant to comply? 50 amp plugs are permitted to be installed on #12 extension cords just because one can? Using a jacklegged plug is a recognized wiring method? NOT 5...A jacklegged table saw is declared an "appliance" for lack of anything else to call it? Same "appliance" doesn't need to meet any code requirements simply because it can be unplugged? One can wire the equipment with baling wire and put a plug on it. Is it still code legal?

Your statement:

"Which means, for example, you could use a 50A 3 prong outlet on a 120V/15A circuit, as long as you're not using that same outlet type for anything else in the house."

Is simply wrong.

50 amp receptacles are _not_ permitted to be installed on 120/15A circuits per NEC Section 210.21(B)(3). They are only permitted on 40 or 50 amp circuits. You're misinterpreting a simple non-interchangablity clause {406.3(F)} to mistakingly conclude that any given receptacle can be installed on any given circuit. NOT.

That would certainly be an improvement over what has been suggested in this thread.

If the equipment were UL Listed, etc., I would concur. However the UL equipment would have conductors sized to handle both motors or have an interlock to prevent both from operating at the same time if smaller conductors were used. The smaller motor would also be protected accordingly. Not real difficult to do, even if the "appliance" were homemade.

[Chris Lewis]

According to volts500 :

Etcetera.

I'm afraid you misunderstood my posting. Tho, I can see how that's possible, so I will clarify.

In _our_ code (CEC) it is permissible to use "other than normal" plug/receptacle pin configurations _provided_ that you're not exceeding ampacities of the circuit (breakers, cable, installed equipment, plugs and receptacles), and there is no other equipment that uses the same plug/receptacle combination in a different way.

This is most often used in industrial applications to "key" specific components to specific circuits. Eg: this was done for alarm/fire systems in a machine room, where the fire control system would kill all of the power to the machine room _except_ for the alarm/fire control system itself - which was separately breakered.

IIRC, they installed a dedicated 120V/15A circuit that has a single 240V/15A locking receptacle wired for 120V, and plugged some of the alarm circuitry into that. They would have used 120V/15A locking receptacles, but they already were using that for something else.

Yeah, by this rule, you could install a four pin 50A receptacle on a 120V/15A circuit (if no other code section intervened), if you had no other equipment that used that style of receptacle for anything else. But that would be silly.

NEC. I had already qualified my comments for CEC. Tho, CEC may well also outlaw such extreme examples.

That's why I suggested it.

Right - that should be obvious, but I didn't want to go into that much detail.

[volts500]

The OP is in the USA, so what does the CEC have to do with it?

So, according to the CEC, if I'm going to wire an equipment in a factory, I have to inspect each equipment plug/receptacle in the factory just to make sure some jackleg didn't use the proper configuration that I need for that equipment for some other jacklegged piece of equipment?

Does a 50 amp load connected with a 50 amp plug not exceed a 15 amp breaker and wire with a 50 amp receptacle, as you say is ok to do? Or are you interpreting that this is ok since the plug connecting the load was jacklegged?

Yeah, like to prevent real hazards like plugging a single phase load into a

3 phase receptacle. BAM. Or plugging a 120 volt load into a 240 volt receptacle that some jackleg leg decided to wire however he pleased.

Puleaze. A shunt trip activated by the fire alarm for a machine room doesn't involve any kind of plugs, it's supposed to be a hardwired control. In fact, a hazard would be presented if it had a plug should the FA power become unplugged. I've wired commercial/industrial buildings for 27 years and I've yet to see a Fire Alarm system in same that wasn't hardwired to a dedicated circuit, on the emergency power system (if available), and had battery back up.

M-I-C-K-E-Y M-O-U-S-E, get run off the job, hack work.

You didn't qualify anything....only that you misinterpreted a basic non-interchangability code rule. Try looking up what the CEC says about devices installed on branch circuits. I think you will find that the requirements are similar to the NEC.