I designed a service for a building being served by a 120/240 3p4w source. I needed 400-amps full 3phase for HVAC equip't, and 400-amps 1phase for lighting loads. I fed a service rated fusible switch with 2 sets of 2#500 kcmil (a-phase and c-phase), 2 #250 kcmil (b-phase), and 1 #250 (neutral), and fused b-phase at 400-amps. The drawing passed city review, but months later the inspector has red tagged the service because the parallel phase feeders are not all the same size (NEC 310-4). I maintain that the electrically the system is safe; do I have a "leg" to stand on?
Delta high leg services
- Thread starter dschomer
- Start date
- Status
- Location
- Illinois
- Occupation
- retired electrician
Re: Delta high leg services
Tell the inspector to read the part of 310.4 that is just below (5) in the 2002 NEC. There is no requirement that the make up of the conductors in B phase match the makeup of the other phases and the neutral. I assume that the load calculations support the 1/2 size grounded conductor.
Don
Tell the inspector to read the part of 310.4 that is just below (5) in the 2002 NEC. There is no requirement that the make up of the conductors in B phase match the makeup of the other phases and the neutral. I assume that the load calculations support the 1/2 size grounded conductor.
Don
david
Senior Member
- Location
- Pennsylvania
Re: Delta high leg services
[ June 07, 2003, 01:19 AM: Message edited by: david ]
[ June 07, 2003, 01:19 AM: Message edited by: david ]
Re: Delta high leg services
To DSCHOMER. You have an 800 amp service with 2 sets of 500 MCM feeding A and C phase(should be 600 KCMIL) and 2 sets of parallel 250's feeding B phase and the neutral. Reducing the neutral is OK. It complies with Art 220-22 There are a number of reasons for not reducing the b phase conductors. The switchgear is 800 amps. What size service is it an 800 or a 400? If this was a circuit breaker could you buy it? I dont't see a 800/400amp service in any cataloges .Right now I have a building that has a 3 Phase Delta service running on two legs A and C. The high leg is burnt out. Why I don't know? What's to stop some one from putting an 800 amp fuse in the b phase with the 2 250 KCMIL. Show me the fourmula that shows fault currrent calculation using a reduced conductor or conductors (point to point calculation). What fourmula do you use for voltage drop? You know, per our City ordinance, you have the right to appeal anything we red tag. You posted this on a public forum so I'm responding . I wish you would have added that we did talk on telephone and I did admit we missed this on the PLan Review and we will take our lumps. I added this comment because we are not infallible. All you have to do is appeal the issue to the electrical commission And there are some issues I won't discuss on a public forum. I don't make too many posts to this fourm. When I see comments like I'm the inspector and I've never seen it done this way I get a little irate. Iv'e seen this before and I red tagged it before.
To DSCHOMER. You have an 800 amp service with 2 sets of 500 MCM feeding A and C phase(should be 600 KCMIL) and 2 sets of parallel 250's feeding B phase and the neutral. Reducing the neutral is OK. It complies with Art 220-22 There are a number of reasons for not reducing the b phase conductors. The switchgear is 800 amps. What size service is it an 800 or a 400? If this was a circuit breaker could you buy it? I dont't see a 800/400amp service in any cataloges .Right now I have a building that has a 3 Phase Delta service running on two legs A and C. The high leg is burnt out. Why I don't know? What's to stop some one from putting an 800 amp fuse in the b phase with the 2 250 KCMIL. Show me the fourmula that shows fault currrent calculation using a reduced conductor or conductors (point to point calculation). What fourmula do you use for voltage drop? You know, per our City ordinance, you have the right to appeal anything we red tag. You posted this on a public forum so I'm responding . I wish you would have added that we did talk on telephone and I did admit we missed this on the PLan Review and we will take our lumps. I added this comment because we are not infallible. All you have to do is appeal the issue to the electrical commission And there are some issues I won't discuss on a public forum. I don't make too many posts to this fourm. When I see comments like I'm the inspector and I've never seen it done this way I get a little irate. Iv'e seen this before and I red tagged it before.
- Location
- Massachusetts
Re: Delta high leg services
Interesting, jerryp what code article are you citing to red tag this?
Interesting, jerryp what code article are you citing to red tag this?
- Location
- Massachusetts
Re: Delta high leg services
2002 NEC
2002 NEC
- Location
- Illinois
- Occupation
- retired electrician
Re: Delta high leg services
Jerry,
Don
[ June 07, 2003, 10:35 AM: Message edited by: don_resqcapt19 ]
Jerry,
So you would red tag a 125 amp service using a fusible disconnect as the service OCPD, because someone could replace the 125 amp fuses with 200 amp fuses??? You can only inspect what is there, you can't red tag on the basis of what somebody might do. Please cite the exact code section that you would use to red tag this installation.
Don
[ June 07, 2003, 10:35 AM: Message edited by: don_resqcapt19 ]
- Location
- Massachusetts
Re: Delta high leg services
Jerry you are getting very close to proving this previous statement.
There is no requirement to have all the phase conductors the same size.
Forget about the engineer, what code article are you providing to dschomer to justify failing his installation.
Jerry you are getting very close to proving this previous statement.
Just change never seen it to I just don't like it and the statement would be on the money
There is no requirement to have all the phase conductors the same size.
Forget about the engineer, what code article are you providing to dschomer to justify failing his installation.
Re: Delta high leg services
Jerry,
Even with this being the case, are you saying you would approve an installation with violations if the plans were stamped? Engineers make misstakes just the same as inspectors and electricians.
All that is being asked is that you back up your decissions by providing code sections of the violations, which you do seem to be dancing around.
Roger
Jerry,
with this said I don't understand this
How did the plans get as far as plan review if they weren't stamped.
Even with this being the case, are you saying you would approve an installation with violations if the plans were stamped? Engineers make misstakes just the same as inspectors and electricians.
All that is being asked is that you back up your decissions by providing code sections of the violations, which you do seem to be dancing around.
Roger
- Location
- Illinois
- Occupation
- retired electrician
Re: Delta high leg services
Jerry,
Jerry,
Again, I ask, please cite the code setion that you would use to red tag the installation. 310.4 clearly premits one set of conductors to be of a different size than the other sets.
Don
Re: Delta high leg services
To gwz2: The tap is within 10' of the main OCP, and the OCP downstream of the tap is probably about 5' to 7' in cable (just the length of the cable in the equipment).
Thanks to all the responses.
Jerry, I have great respect for your work. If you had demanded the change when everything was just ink and paper, we would have accommodated you (whether we agreed or not) without comment. But, you're demanding a change after the place is built that will cost $12,000.00. We're the ones taking your lumps. I do not believe the design creates a hazard to persons and property arising from the use of electricity.
To gwz2: The tap is within 10' of the main OCP, and the OCP downstream of the tap is probably about 5' to 7' in cable (just the length of the cable in the equipment).
Thanks to all the responses.
Jerry, I have great respect for your work. If you had demanded the change when everything was just ink and paper, we would have accommodated you (whether we agreed or not) without comment. But, you're demanding a change after the place is built that will cost $12,000.00. We're the ones taking your lumps. I do not believe the design creates a hazard to persons and property arising from the use of electricity.
Re: Delta high leg services
We are still waiting for a code citation on this one and it is of direct interest to me because I have a proposal pending on a similar, albeit smaller, service. I can build two different services, one of which would be three phase motor only, and the other single phase lighting and appliance. That approach would raise cost but if it would be more acceptable to most of the AHJs that participate here I can propose it to the AHJ for that locality and keep my financial self out of the wringer.
--
Tom
Jerry
We are still waiting for a code citation on this one and it is of direct interest to me because I have a proposal pending on a similar, albeit smaller, service. I can build two different services, one of which would be three phase motor only, and the other single phase lighting and appliance. That approach would raise cost but if it would be more acceptable to most of the AHJs that participate here I can propose it to the AHJ for that locality and keep my financial self out of the wringer.
--
Tom
brian john
Senior Member
- Location
- Leesburg, VA
Re: Delta high leg services
Jerry:
I think everyone especially DS have been open and fair all we are asking is for some substantiation of the RED TAG. CAJ was venting as all of us have at some time when we feel we have or have not been treated unfairly by the AHJ. This is an open forum and I think DS was correct in questioning your RED TAG and went to one forum where he hoped he might get some insight into this installation being a violation, or not.
Jerry:
I think everyone especially DS have been open and fair all we are asking is for some substantiation of the RED TAG. CAJ was venting as all of us have at some time when we feel we have or have not been treated unfairly by the AHJ. This is an open forum and I think DS was correct in questioning your RED TAG and went to one forum where he hoped he might get some insight into this installation being a violation, or not.
brian john
Senior Member
- Location
- Leesburg, VA
Re: Delta high leg services
MY FINGERS MOVE FASTER THAN MY THOUGHT SHOULD HAVE PROFF READ THE POST>>>>>>>>>SORRY
Jerry:
I think everyone especially DS have been open and fair all (I think) you were asked to do is substantiate the RED TAG. CAJ was venting as all of us have at some time when we feel we have or have not been treated fairly by the AHJ. This is an open forum and I think DS was correct in questioning your RED TAG and went to the one forum where he hoped he might get some insight into this installation is it a violation, or not.
MY FINGERS MOVE FASTER THAN MY THOUGHT SHOULD HAVE PROFF READ THE POST>>>>>>>>>SORRY
Jerry:
I think everyone especially DS have been open and fair all (I think) you were asked to do is substantiate the RED TAG. CAJ was venting as all of us have at some time when we feel we have or have not been treated fairly by the AHJ. This is an open forum and I think DS was correct in questioning your RED TAG and went to the one forum where he hoped he might get some insight into this installation is it a violation, or not.
Re: Delta high leg services
Rule of thumb for loading a closed delta secondary.
The lighting leg transformer will carry two thirds of the single phase load plus one third of the three phase load.
The power leg transformers will each carry one third of the single phase load plus one third of the three phase load.
Wire size is determined by the calculated load.
The stinger leg (B Phase) is usually smaller.
Rule of thumb for loading a closed delta secondary.
The lighting leg transformer will carry two thirds of the single phase load plus one third of the three phase load.
The power leg transformers will each carry one third of the single phase load plus one third of the three phase load.
Wire size is determined by the calculated load.
The stinger leg (B Phase) is usually smaller.
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