Jeez, another electrical question

[Rick Christopherson]

Thanks Bill. I think what you see in the lower left of the box is the ungrounded bus bar which I assume would be for neutrals. There are no wires attached to it at all. In fact, all the 115 volt circuits to all the outlets have both the ground and white wire to the grounded bus bar. Also it appears this box is being fed from the other subpanel. The upper right breaker is the main breaker for the box and is 60 amps and the wire is about 10 or 8 gauge stranded. It is two conductor plus ground with the ground wire going to the common bus bar.

When you first asked your question, I stayed out of the discussion because it appeared that from the information we had (at the time), it should have been a simple 2-sentence reply. However, you have received several convoluted responses that are misleading at best, and depending on how they are read are actually quite dangerous.

After re-reading the whole thread, I decided to take the time to bring your picture into photoshop so I could see a little more detail. (Although I still cannot make out all of the detail.)

First and foremost, this is a 240 volt subpanel, which does not have 120 volts available because there is no neutral conductor. The original installation was correct for its purpose, but over time, someone has added single-pole (120 volt) circuits to the panel. These need to be removed. This is the reason why the left-hand bus terminal was not used.

Take a closer look at the incoming feeder. From the picture, it looks like 10/2 romex, but admittedly, they could be larger than they appear.

This panel is correctly wired for 240-volt usage (after you remove the 120 volt circuits). However, if you do need this subpanel to provide 120/240 volt circuits, then you must use a new feeder cable with 3 insulated conductors, and preferrably a ground, but since this is a detached building, that may or may not be required (we don't know enough about this building, so when in doubt, run the ground.)

I'm just going to go through a few problems I see (BTW I am an electrician).

Roger, because you prefaced your first posting by stating you were an electrician, I am going to take you to task for the advise you presented. When you state your credentials, it puts you in a position of authority and knowledge, and as such, holds you to a higher level of responsibility than a typical respondent.

As an electrician, you should not have advised Michael to use the uninsulated grounding conductor in lieu of the neutral (grounded conductor) and treat this as a 3-wire feed by installing a bonding screw into a neutral bus. This violates the NEC on so many levels, I shouldn't have to point this out to you. Not only is it prohibited to have any current carrying conductor be uninsulated, but the ground wire in a typical romex cable is not sized properly for the circuit protection from which it is being served.

[Rick Christopherson]

By the way Michael, I also noticed that at least the upper-left 2-pole breaker has multiple wires going to the lugs. Most circuit breaker lugs are not rated for more than a single wire. Unless this is one of the rare exceptions (which I doubt), then you should pull these circuits out.

[Roger Frazee]

And speaking of feeder neutral the cable he used as the feeder requires the white wire to be the neutral and he used it for a hot (ungrounded) conductor and the bare equipment ground is being used as the neutral....not supposed to be that way...

With all due respect Rick I think you need to reread my responses about the cable with the bare equipment ground serving as the neutral for the feeder because of the 120 volt load. I told him this was the wrong cable to be used.... Because of the bare neutral being an equipment ground.. And that the panel should be replaced and that the cable should be replaced and that he should upgrade the panels and feeders. I told him we could get the panels better configured until he could effect the necessary repairs. A bare neutral is quite fine by the way if the detached building is served by overhead on 3 wires. Allowed under 2005 and when this installation was first installed assuming no other metallic paths other than the feeder from the service equipment at the house.. It could be that I confused things for that I apologize but what is going on in that panel and the installation as a whole is not simple. The panel is not 240 volt as configured it is 120/240 volt though incorrectly done.

The simple answer is he needs to bring this all up to code... I do believe he has made mention of this several times.

As an electrician, you should not have advised Michael to use the uninsulated grounding conductor in lieu of the neutral (grounded conductor) and treat this as a 3-wire feed by installing a bonding screw into a neutral bus. This violates the NEC on so many levels, I shouldn't have to point this out to you. Not only is it prohibited to have any current carrying conductor be uninsulated, but the ground wire in a typical romex cable is not sized properly for the circuit protection from which it is being served

.

Its being used as that now though incorrectly... And what if the cable he used was SE type from panel to panel? Perfectly legal for the neutral to be bare enclosed within a outer sheath if the 3 wire feed to the detached building was code compliant which we have verified it was now and at the time of installation. Phone and water are not connected to the dwelling with the service equipment which supplies the feeder to this detached building.... As for the nm which I told him was incorrect for the reasons you stated ...I even gave him a defined description of why that feeder cable was incorrect. As for the bare in that nm cable being in danger of overheating I doubt it. The whole installation needs to be fixed.. I thought that was what all this discussion was about. As for telling him to continue to use the bare equipment ground in that nm cable till he gets things fixed...I still stand by that knowing that he now understands it needs to be replaced. I refuse to tell him to turn off all the power to his detached building cause he is in terrible danger of burning his shop down. He is not. I think he has understood from the beginning that he has a few problems.

First and foremost, this is a 240 volt subpanel, which does not have 120 volts available because there is no neutral conductor. The original installation was correct for its purpose, but over time, someone has added single-pole (120 volt) circuits to the panel. These need to be removed. This is the reason why the left-hand bus terminal was not used

.

Possibly but he could have configured it the same way with the other terminal strip on the left using the bonding jumper. Mike stated that two of the single poles are used for a 240 volt circuit to an air conditioner..so that leaves only one 120 volt circuit. But it appears that there are at least 3 grounded conductors on that ground bar so obviously something is amiss. However your analysis that the panel might have been intended for 240 volts only is quite possible. I didn't consider that.

I told him I would tell him how to change the configuration of that panel because I think it serves a marginal safety improvement over what he has now until he effects repairs as mentioned.

He expressed an interest to understand what he has so I made an effort to do that.

Sorry if you don't agree.

However I will concede further long discussions on this forum as I continue to respond here. It seems we prefer the simple.

BTW the actual reason that 5 hp saw in that other thread is not allowed cord and plug is it requires a 5 HP rated single phase 250 volt plug and receptacle required in Article 422 and Article 430 and Article 210....but we kept it simple. No such animal exists in locking or straight blade nema configurations. You can verify this if you like in the UL White Book...the manufacturers are well aware of this...they are not a notoriously wrong as you implied. Robs 7.5 horse power 3 phase equipment has the ability to have cords and plugs rated to that horsepower. Just to further confuse things...

[Michael Weber]

Hi Mike

I apologize for getting a little carried away with this thread but it is critical to me that when DIY are working on their electrical panels that they understand this bonding and grounding so they know the why of what they are doing.

Carry on Mike

Roger, no apologies necessary. Your time to reply and the information provided is greatly appreciated. I believe it will be in my best interest to hire an electrician to update my system and replace the dual subpanels with a properly sized single box.

Thanks again, Mike

[Michael Weber]

By the way Michael, I also noticed that at least the upper-left 2-pole breaker has multiple wires going to the lugs. Most circuit breaker lugs are not rated for more than a single wire. Unless this is one of the rare exceptions (which I doubt), then you should pull these circuits out.

Thanks for the input Rick. The upper left breaker problem is on me. That is the circuit I added to provide power for my compressor and a vfd. The two sets of wires from this single breaker go to different fused shut off boxes and by now I am sure this also violates code. See my response to Roger about getting hold of an electrician to bring all this up to specs. Yours and Rogers input is greatly appreciated.
Mike

[Roger Frazee]

No problem Mike

And yes an electrician is in order.

Have a great day

[Alan Trout]

Not trying stir the pot but just want to make a few comments about the panel in question. Being a Professional Home Inspector there are many issues noted with that panel but in reality not enough information or clear enough photo is present for anyone to make a clear determination including myself and I suggest that you hire a licensed electrician to make corrections as needed.

First I would like to comment about telling someone to go after the home inspector. These comments always bother me on a professional level. This advice may be valid or not. Remember inspectors in most states are not inspecting for present codes, and latent defects most times are not within the scope of the inspection. However I personally do list these things in my report more as a note for understanding construction practices at the time the home was built and how they relate to current building practices. However if the home was inspected and and the items such as double lugged breakers were not listed in the report I would call the inspector and find out why these items were not noted. These kind of items fall well within the scope of most home inspections.

Isolated grounds and neutrals at sub panels did not come into being until about the 1976/1978. Before that time neutrals and grounds shared the same bus bar in sub panels. I am not saying it is right I am just saying that the reality is 30 year old house will not meet present electrical codes and in many/most municipalities they don't have to be brought up to current codes. If that were the case every one of us should start installing AFCI protection because in the 2008 NEC all circuits in a home besides the GFCI protected circuits are required to have AFCI protection.

There is so much liability in this world these day's I am always hesitant to make any electrical recommendations to anyone and more often then not give referral back to a licensed electrician, which in the case is the best solution.

Good Luck

Alan

[Rick Christopherson]

No, Roger, I did read your response carefully. And even though you suggested that the wiring was not correct in the beginning of the response, you went on at greater length telling him that he could correct it by using the ground wire as a neutral. The incoming cable is clearly romex, and in the larger sizes of romex, the ground wire is not large enough to be used as a neutral. Furthermore, you have since compounded your error by suggesting that a configuration that he clearly doesn't have might permit an uninsulated neutral.

When you make a mistake, accept responsibility for it instead of trying to sidestep it.

BTW the actual reason that 5 hp saw in that other thread is not allowed cord and plug is it requires a 5 HP rated single phase 250 volt plug and receptacle ...... No such animal exists in locking or straight blade nema configurations.

I do not pay much attention to who's-who on the forums, so I had no idea you were the same person making this previous statement. However, if you were more up to date on your information, you would know that there are plugs and receptacles far larger than 5 hp. I happen to have a plug and receptacle sitting in my basement that is capable of handling a 52 KVA load. That's a wee-bit larger than 5 hp, right?

[Roger Frazee]

No, Roger, I did read your response carefully. And even though you suggested that the wiring was not correct in the beginning of the response, you went on at greater length telling him that he could correct it by using the ground wire as a neutral. The incoming cable is clearly romex, and in the larger sizes of romex, the ground wire is not large enough to be used as a neutral. Furthermore, you have since compounded your error by suggesting that a configuration that he clearly doesn't have might permit an uninsulated neutral.

When you make a mistake, accept responsibility for it instead of trying to sidestep it.I do not pay much attention to who's-who on the forums, so I had no idea you were the same person making this previous statement. However, if you were more up to date on your information, you would know that there are plugs and receptacles far larger than 5 hp. I happen to have a plug and receptacle sitting in my basement that is capable of handling a 52 KVA load. That's a wee-bit larger than 5 hp, right?

Rick

Again with all due respect those plugs are specialized plugs and are not in the nema locking or straight blade design and are not generally used for connecting 5 horsepower saws...to household supplies. Did you suggest that in the thread.....

I did not tell him to correct the problem by moving the bare feeder neutral over to the left neutral bar. I told him he could do so for the time being until he could get it done right, he understood this... you missed it. It would have been very wrong to tell him to move the configuration to the left neutral bar and forget it... all is fine. That was not my intention and if that is how things appeared to you I can only say that was a misinterpretation of my advice.

As for this thread.. it's a done deal. The cable needs to be replaced. I do not agree that he has to remove his 120 breakers. I would only do this if my mother in law had life support on one of those 120 volt breakers....Turn them off maybe but he does not have enough unbalanced current to overload his feeder neutral as wrong as it may be. Moving it to the left hand neutral bar changes nothing and configuring things from there makes it more understandable to most. My suggestion was merely temporary, if it was poor judgement or wrong my error.

[George Lohnes]

Michael forgot to mention in his original post that this electrical connection was for an underpowered dust collector leading to the Festool tools on top of his Sawstop.

[things seem to be quieting down on the post and just thought I could heat things up some more]

[Tom Veatch]

...the actual reason that 5 hp saw in that other thread is not allowed cord and plug is it requires a 5 HP rated single phase 250 volt plug and receptacle ...

Roger, please pardon my ignorance and understand that I'm not trying to challenge what you say. I'm simply trying to improve my understanding.

Following comments are based on my understandings, and I would certainly appreciate corrections where they fall short.

If a 5HP motor requires a 5HP rated plug and socket, by extension, would not a 3HP motor require a 3HP rated plug and socket? Or, for that matter, would not any plug and socket used for a motor load need to be rated for the HP of the motor? The reason I ask is because I do not recall ever seeing plugs and sockets rated for anything other than volts and amps and I've seen no negative comments regarding using power cords/plugs/sockets for 3HP and smaller motor loads.

I understand that switching devices need to be rated for the HP of the motors they control because of the inductive nature of the load and the voltage spikes and/or arcing that occurs when the switch is actuated. But unlike switches, contactors, etc., plugs and sockets are static devices and aren't intended to be used to make/break a circuit. Thus they aren't subject to the same conditions as switches, etc.

After reading your comment concerning 5HP rated plugs and sockets, I made a fast, admittedly incomplete, search of various manufacturers web sites looking for receptacles that were rated for HP in addition to volt/amps. I didn't find any. I found NEMA 6 and L6 devices in both 20 and 30 amp ratings, none of which were rated by the manufacturer in terms of power. Not saying they aren't out there, just that I didn't find any.

I've previously had no qualms about using a 6-20/L6-20 device on a power cord for a 3HP motor (20 amp circuit) and by extension, would have had no qualms about using 6-30/L6-30 devices for a 5HP motor on a 30 amp circuit. In the absence of power rating on the devices, I see no substantiative difference between the two cases.

For any readers not familiar with the designations, NEMA 6/L6 devices are 250 volt 2-pole, 3-wire, grounding devices - IOW, 250 volt single phase grounding plugs and receptacles.

[Chris Padilla]

Tom,

Well, aren't those plugs rates at, for example, 30 A @ 250 V? 30*250 = 7,500 W =~ 10 hp?

Is it that simple?

[Roger Frazee]

Tom

Any motor or motor appliance needs to have a matching hp rated plug this generally is a result of disconnect issues under load. By that I mean a plug and receptacle is allowed to be the disconnecting means only if it is rated the same as the motor in horse power. You get into problems with nema plugs for single phase 250 volt 2 pole 3 wire grounding above 3 horse power. Personally I agree there isn't likely to be any problem with 2 or 3 hp on a L6_20. Maybe not even with 5 hp I don't assume to be an expert on this. IMO the manufacturer is not allowing cord and plug or extension cords on the 5 hp sawstop because there is no 5 hp nema configuration for that saw . Can you get 5 hp plugs... sure.. but these are specialized plugs and not typical for general use for cord and plug tools and likey not configured for the voltage we are talking about. I could be wrong on this...Rick seems to think so.

At anyrate here is the UL list of corresponding hp ratings for cord and plug. If you call sawstop I think you will likely get the reasoning I have discussed as to why their manual says NO cord and plug. Do I think there is a great issue one way or the other....must not be as everyone here seems to be doing fine with their saws on cord and plug . I am simply trying to answer why a 5 hp saw 230 volt single phase like the sawstop is not allowed cord and plug by the manufacturer. You may have to click on it a few times for it to be readable.

[Tom Veatch]

Tom,

Well, aren't those plugs rates at, for example, 30 A @ 250 V? 30*250 = 7,500 W =~ 10 hp?

Is it that simple?

Chris, I really don't know when you get into the plug/receptacle area.

If you look at switching devices, those intended for motor control are rated both in amps and in power (HP) at a given voltage. Typically, the HP rating is the more restrictive of the two. I.E, if you take the volt/amp rating of the switch and convert to the equivalent HP (volt*amps/746), the result is greater than the switch's HP rating. In effect, the device is "derated" for motor loads.

For an example, take the Leviton MS302 motor control switch. It's a double pole switch rated for 600 volts and 30 amps. It's power rating is 2HP-120V, 5HP-240V, 10HP-480V, 15HP-600V. Converting the 30 amp rating at those voltages gives the respective HP values: 4.8, 9.7, 19.3, 24.1. Those calculated values are all much higher than the actual power rating of the switch.

I've always assumed, rightly or wrongly, that's because of the inductive nature of a motor load. When you break the circuit feeding an inductive load, e.g. a motor, the collapse of the magnetic field in the coils induces a voltage spike that you don't see when you break a circuit feeding a resistive load. Again, my assumption has been that's the reason for "derating" the switching device. Since plug/receptacle devices aren't typically intended to be used as disconnects under load, my assumption has been that separate HP/inductive load ratings really aren't appropriate. If that assumption is correct, then the answer to your question is, "Yes, it is just that simple".

But, that is just my assumption supported by never having seen a power rating on plugs/receptacles separate from or in addition to the normal volt/amp ratings. And you know what they say about "ass-u-me".

[Tom Veatch]

...Any motor or motor appliance needs to have a matching hp rated plug this generally is a result of disconnect issues under load. By that I mean a plug and receptacle is allowed to be the disconnecting means only if it is rated the same as the motor in horse power. You get into problems with nema plugs for single phase 250 volt 2 pole 3 wire grounding above 3 horse power. ...

Thank you, Roger. That chart is an eye-opener. I may just save that in my "wall-chart" folder.

I notice that you don't get up to the 3HP rating with 6/L6 devices until you hit the 50 amp level.

I assume from your comment on use as a disconnect there's no real problem involved in using a NEMA 6-20 plug/socket to feed a 3HP load as long as it's not used as a disconnect device. I'll have to remember not to unplug my 3HP table saw (NEMA 6-20, 2 HP L-L rating) while it's running.

Now, I'm understanding why the electrician ran the 30 amp circuits for my air compressor and cyclone to disconnects rather than to 30 amp receptacles (5HP motors hardwired to the disconnects in both cases).

Thanks, again.