Project I'm on has two 42 circuit panels side by side. I needed 2 spares to add a two pole breaker. I noticed every third row of breakers had no wire. Then I noticed the c phase lug was missing. I don't know if its a code violation but it sure looks like a diy's work. This is a commercial building. I even know it was inspected. Why would someone go through the expense of installing the breakers? Major screw-up.
3 phase panels wired with single phase
- Thread starter -marty
- Start date
- Status
- Location
- Massachusetts
Re: 3 phase panels wired with single phase
Perhaps to fool the customer and the inspector?
bdarnell
Senior Member
- Location
- Indianapolis, IN
- Occupation
- Retired Engineer
Re: 3 phase panels wired with single phase
If they bought the panelboards with breakers factory installed. It's actually cheaper than buying blanks (and definitely breakers) later.
Just a thought.
If they bought the panelboards with breakers factory installed. It's actually cheaper than buying blanks (and definitely breakers) later.
Just a thought.
Minuteman
Senior Member
- Location
- The Sooner Nation
Re: 3 phase panels wired with single phase
I thought the same thing as Frank, then I was wondering if it was a used 3 phase that was put to use for single phase.
- Location
- Massachusetts
Re: 3 phase panels wired with single phase
IMO using a 3 phase panel on a single phase system is a listing violation. 110.3(B)
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: 3 phase panels wired with single phase
Bob, what is your reasoning that it is a listing violation?
Square D's QO load centers are available as either 1-phase or 3-phase. Square D's I-Line panelboards are only available in 3-phase. Both the QO and I-Line panels carry the same UL listings per standard UL 67.
Bob, what is your reasoning that it is a listing violation?
Square D's QO load centers are available as either 1-phase or 3-phase. Square D's I-Line panelboards are only available in 3-phase. Both the QO and I-Line panels carry the same UL listings per standard UL 67.
Re: 3 phase panels wired with single phase
Since I've never come across this in my thirty plus years in the industry I was quite taken back. I couldn't think of a code violation except for the listing.
I couldn't think how this would cause a safety problem, it is mostly an inconvenience. The panel is now marked on the inside cover.
IMO this is shotty work to the max. The customer was deceived. He thought he had 2 panels each with 42 circuits. What he actually has is 2 panels with 28 circuits. For the thousands he spent for this upgrade he doesn't even have a spare.
This mistake could have started with a counterperson pulling the wrong panels. The problem might not have been noticed until after it was piped and the feeders pulled in.
But, the owner SHOULD HAVE BEEN TOLD or it should have been corrected.
Word travels quickly in a small community.
Since I've never come across this in my thirty plus years in the industry I was quite taken back. I couldn't think of a code violation except for the listing.
I couldn't think how this would cause a safety problem, it is mostly an inconvenience. The panel is now marked on the inside cover.
IMO this is shotty work to the max. The customer was deceived. He thought he had 2 panels each with 42 circuits. What he actually has is 2 panels with 28 circuits. For the thousands he spent for this upgrade he doesn't even have a spare.
This mistake could have started with a counterperson pulling the wrong panels. The problem might not have been noticed until after it was piped and the feeders pulled in.
But, the owner SHOULD HAVE BEEN TOLD or it should have been corrected.
Word travels quickly in a small community.
Re: 3 phase panels wired with single phase
Marty,
I can one up you, unfortunately. I once was called to a business because a newly installed electric water heater would not work. My new client could not reach the guy who installed the circuit the first time. I found a Square D, 3 phase, QO panel with a phase to A, a phase to B, and a JUMPER!!!! between the B lug and C lug. The 2-pole breaker was on B/C position. I am happy to say, that I gained a very angry but (now) loyal client. Oh, and the client was unhappy enough to finally cost the other electrician his license and my fee to redo the job right.
Marty,
I can one up you, unfortunately. I once was called to a business because a newly installed electric water heater would not work. My new client could not reach the guy who installed the circuit the first time. I found a Square D, 3 phase, QO panel with a phase to A, a phase to B, and a JUMPER!!!! between the B lug and C lug. The 2-pole breaker was on B/C position. I am happy to say, that I gained a very angry but (now) loyal client. Oh, and the client was unhappy enough to finally cost the other electrician his license and my fee to redo the job right.
- Location
- Massachusetts
Re: 3 phase panels wired with single phase
I can not recall seeing a 3 phase panel that was marked as suitable for single phase supply.
I have seen plenty of 3 phase disconnects (most) that will show permissible connections to single phase supplies or DC supplies using the two outer poles leaving 'phase B' pole unused.
That said it would not surprise me if I-Line panel boards could be used this way as it is a bit of an oddity.
Bob
Jim IMO it is straight forward, if the labeling on the panel in question only shows connection to a 3 phase system IMO a connection to a single phase system would violate 110.3(B).
I can not recall seeing a 3 phase panel that was marked as suitable for single phase supply.
I have seen plenty of 3 phase disconnects (most) that will show permissible connections to single phase supplies or DC supplies using the two outer poles leaving 'phase B' pole unused.
That said it would not surprise me if I-Line panel boards could be used this way as it is a bit of an oddity.
Bob
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: 3 phase panels wired with single phase
Bob,
It is a fact, I-Line panel construction requires three bus bars. They do not offer a version for single phase only.
Most plug-in and feeder busway is also only available with a minimum of three phase bus bars.
Bob,
It is a fact, I-Line panel construction requires three bus bars. They do not offer a version for single phase only.
Most plug-in and feeder busway is also only available with a minimum of three phase bus bars.
kbsparky
Senior Member
- Location
- Delmarva, USA
Re: 3 phase panels wired with single phase
You can utilize single phase services/circuits with 3-phase equipment. Consider the following:
Most automatic transfer switches are 3 phase rated, but are suitable for single phase use.
Same thing goes for safety switches. You can use a 3-pole disconnect to control a single phase load, just leave one set of the lugs empty.
Lighting contactors. In fact, we recently had a service call where one pole of a lighting contactor failed, and all we had to do was shift that circuit over to the spare pole that was essentially brand new.
I-Line panels as mentioned previously may be 3-phase, but 2-pole breakers are readily available. We have installed many 400 Amp I-Line panels on single phase services with good results.
I would imagine that the same would apply to a load center. Just leave the spare bus unconnected (I do have a problem with those jumpers, mentioned in another post).
You can utilize single phase services/circuits with 3-phase equipment. Consider the following:
Most automatic transfer switches are 3 phase rated, but are suitable for single phase use.
Same thing goes for safety switches. You can use a 3-pole disconnect to control a single phase load, just leave one set of the lugs empty.
Lighting contactors. In fact, we recently had a service call where one pole of a lighting contactor failed, and all we had to do was shift that circuit over to the spare pole that was essentially brand new.
I-Line panels as mentioned previously may be 3-phase, but 2-pole breakers are readily available. We have installed many 400 Amp I-Line panels on single phase services with good results.
I would imagine that the same would apply to a load center. Just leave the spare bus unconnected (I do have a problem with those jumpers, mentioned in another post).
Re: 3 phase panels wired with single phase
The jumpers I mentioned would be against NEC unless "B" phase was equipped with a lug designed and rated to handle 2 conductors, i.e. a 2 barrel lug.
NEC 110.14(A) paragraph two: "Terminals for more than one conductor and terminals used to connect aluminum shall be so identified."
There might be other reasons also. I just didn't take the time to look them up.
It also seems to me that if a 2-pole breaker was accidentally installed on the unused bus, there would be a really wierd voltage backfeed from the energized bus through the equiptment to the unused bus. It seems to me that would be similar to an unsafe situation caused by a backfed wire capped off in a panel.(see : 1 circuit fed by 2 single pole breakers in nec forum).
Also, no offense, but why go to the expense and risk the potential confusion of installing a 3 phase panel on a single phase service? The next guy that goes to work on this panel or add circuits to it is in for a rude suprise unless he knows about the condition beforehand. The next guy could be a newly minted service electrician for your company that didn't get the info because it never occurred to those folks that knew about the condition that the new guy didn't know about it.
Lastly, we all have that one hard core inspector that absolutely would not pass such an install no matter what code says. You can appeal, and might win, but we all know that is something you usually only do once. After that, you tend to have a terrible time passing inspections.
[ February 14, 2006, 12:44 AM: Message edited by: Matt Harp ]
The jumpers I mentioned would be against NEC unless "B" phase was equipped with a lug designed and rated to handle 2 conductors, i.e. a 2 barrel lug.
NEC 110.14(A) paragraph two: "Terminals for more than one conductor and terminals used to connect aluminum shall be so identified."
There might be other reasons also. I just didn't take the time to look them up.
It also seems to me that if a 2-pole breaker was accidentally installed on the unused bus, there would be a really wierd voltage backfeed from the energized bus through the equiptment to the unused bus. It seems to me that would be similar to an unsafe situation caused by a backfed wire capped off in a panel.(see : 1 circuit fed by 2 single pole breakers in nec forum).
Also, no offense, but why go to the expense and risk the potential confusion of installing a 3 phase panel on a single phase service? The next guy that goes to work on this panel or add circuits to it is in for a rude suprise unless he knows about the condition beforehand. The next guy could be a newly minted service electrician for your company that didn't get the info because it never occurred to those folks that knew about the condition that the new guy didn't know about it.
Lastly, we all have that one hard core inspector that absolutely would not pass such an install no matter what code says. You can appeal, and might win, but we all know that is something you usually only do once. After that, you tend to have a terrible time passing inspections.
[ February 14, 2006, 12:44 AM: Message edited by: Matt Harp ]
- Status