ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Can someone please help me find the code article that addresses phase balancing for feeders?
Phase imbalance
- Thread starter ryan_618
- Start date
- Status
- Location
- Massachusetts
Re: Phase imbalance
Ryan I used the handbook CD-ROM and searched for Balance, Balanced, and imbalance.
There was "hits" on all of these but I do not think they are what you are looking for.
Bob
Ryan I used the handbook CD-ROM and searched for Balance, Balanced, and imbalance.
There was "hits" on all of these but I do not think they are what you are looking for.
Bob
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Phase imbalance
I'm doing a plan review and on the panel schedules (120/240V 3Wire 1phase) phase A shows 56 amps and phase B shows 156 amps!!! I can't think that this is permitted, but I sure can't find a reference that backs me up. Help?
I'm doing a plan review and on the panel schedules (120/240V 3Wire 1phase) phase A shows 56 amps and phase B shows 156 amps!!! I can't think that this is permitted, but I sure can't find a reference that backs me up. Help?
- Location
- Massachusetts
Re: Phase imbalance
Ryan here are the spots the words I serched for came up in, I will be glad to search more if you have some other keywords to look for.
Imbalance only came up in the handbook commentary in reference to 445.12, as far as Code these are the articles balance or balanced came up in.
80.15(B), 310.4, 517.2, 520.53, 550.18, 551.42, 552.47, and Annex D
Ryan here are the spots the words I serched for came up in, I will be glad to search more if you have some other keywords to look for.
Imbalance only came up in the handbook commentary in reference to 445.12, as far as Code these are the articles balance or balanced came up in.
80.15(B), 310.4, 517.2, 520.53, 550.18, 551.42, 552.47, and Annex D
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Phase imbalance
Bennie is correct.
Phase balancing relates to Voltages NOT amperes!
Bennie is correct.
Phase balancing relates to Voltages NOT amperes!
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Phase imbalance
Bennie: I wish I could answer your question. This is not for my city. Once in a while different cities will have me help them with electrical plan reviews/inspections. In all honesty, I don't know much more about the installation than you. They just faxed me some blurry panel schedules and a one-line diagram. I am going to ask for a full set of drawings on Monday.
BTW: Thanks for the terminology correction!
Bob: Thanks for your help. I'll start cracking the book.
[ October 03, 2003, 07:04 PM: Message edited by: ryan_618 ]
Bennie: I wish I could answer your question. This is not for my city. Once in a while different cities will have me help them with electrical plan reviews/inspections. In all honesty, I don't know much more about the installation than you. They just faxed me some blurry panel schedules and a one-line diagram. I am going to ask for a full set of drawings on Monday.
BTW: Thanks for the terminology correction!
Bob: Thanks for your help. I'll start cracking the book.
[ October 03, 2003, 07:04 PM: Message edited by: ryan_618 ]
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
Re: Phase imbalance
Depending on how the loads were computed, maybe this one will help.
210.11 Branch Circuits Required
(B) Load Evenly Proportioned Among Branch Circuits. Where the load is computed on a volt-amperes/square meter or square foot basis, the wiring system up to and including the branch-circuit panelboard(s) shall be provided to serve not less than the calculated load. This load shall be evenly proportioned among multioutlet branch circuits within the panelboard(s).
Depending on how the loads were computed, maybe this one will help.
210.11 Branch Circuits Required
(B) Load Evenly Proportioned Among Branch Circuits. Where the load is computed on a volt-amperes/square meter or square foot basis, the wiring system up to and including the branch-circuit panelboard(s) shall be provided to serve not less than the calculated load. This load shall be evenly proportioned among multioutlet branch circuits within the panelboard(s).
brian john
Senior Member
- Location
- Leesburg, VA
Re: Phase imbalance
This is not a good practise and may cause a voltage imbalance, but if the overcurrent protection and conductors can handle it, whats the problem. (Unless someone can find a NEC violation)
This is not a good practise and may cause a voltage imbalance, but if the overcurrent protection and conductors can handle it, whats the problem. (Unless someone can find a NEC violation)
charlie
Senior Member
- Location
- Indianapolis
Re: Phase imbalance
Ryan, I am betting the serving electric utility has something in their service manual. We require the load to be as evenly balanced as possible in order to get (and keep) service from us. Bennie did a good job of listing the reasons for our rule. We will not even permit larger than a 100 ampere single phase commercial service from a 208Y/120 volt transformer because of unbalancing the transformer.
Ryan, I am betting the serving electric utility has something in their service manual. We require the load to be as evenly balanced as possible in order to get (and keep) service from us. Bennie did a good job of listing the reasons for our rule. We will not even permit larger than a 100 ampere single phase commercial service from a 208Y/120 volt transformer because of unbalancing the transformer.
- Location
- Massachusetts
Re: Phase imbalance
Along with what Charlie has said most of the jobs we do have a specification that places the burden on us (the EC) to make sure the initial load balance is with in a certain percentage.
Here is the spec for the job I am on now.
Dave or Bennie I have never heard of balance related to volts, always amps, can you give some more info?
As the EC I have some influence on the balance of the amp load, but no influence on the voltage.
[ October 04, 2003, 12:24 PM: Message edited by: iwire ]
Along with what Charlie has said most of the jobs we do have a specification that places the burden on us (the EC) to make sure the initial load balance is with in a certain percentage.
Here is the spec for the job I am on now.
You can see this is a general specification as this job has no 3 phase delta.
Dave or Bennie I have never heard of balance related to volts, always amps, can you give some more info?
As the EC I have some influence on the balance of the amp load, but no influence on the voltage.
[ October 04, 2003, 12:24 PM: Message edited by: iwire ]
Re: Phase imbalance
Iwire: It's like the old cliche "what comes first, the chicken or the egg". Load affects the voltage balance. Voltage balance affects the load.
Voltage in a transformer winding attempts to reach an equilibrium. A low current winding will have an elevated voltage that will supply the zero sequence current to the transformer. This current is in the form of circulating current producing unwanted heat.
These are my own words, Dereck, both Charlie's, and many others can express this much better than I can. I only need 8 more years to become an engine ear.
Iwire: It's like the old cliche "what comes first, the chicken or the egg". Load affects the voltage balance. Voltage balance affects the load.
Voltage in a transformer winding attempts to reach an equilibrium. A low current winding will have an elevated voltage that will supply the zero sequence current to the transformer. This current is in the form of circulating current producing unwanted heat.
These are my own words, Dereck, both Charlie's, and many others can express this much better than I can. I only need 8 more years to become an engine ear.
G
Guest
Guest
Re: Phase imbalance
[ October 04, 2003, 11:15 AM: Message edited by: awwt ]
Is that under the Great-Grandfathered clause?
[ October 04, 2003, 11:15 AM: Message edited by: awwt ]
- Location
- Massachusetts
Re: Phase imbalance
I got you Bennie but the voltage at my service may not be equal before I add any load (transformer may serve other services)
Are you saying I should move my loads around until I get equal voltage on each phase?
It seems like a no win situation anyway as the load is always changing, the way the spec I put up reads it looks to me like they want me to balance the load and let the utility worry about the volts.
I got you Bennie but the voltage at my service may not be equal before I add any load (transformer may serve other services)
Are you saying I should move my loads around until I get equal voltage on each phase?
It seems like a no win situation anyway as the load is always changing, the way the spec I put up reads it looks to me like they want me to balance the load and let the utility worry about the volts.
charlie
Senior Member
- Location
- Indianapolis
Re: Phase imbalance
Bennie, whenever a person is in a field as long as we have been, we can be as sharp as an engineer in that narrowly defined part of engineering. In other words, I consider you to be an engineer in your field of endeavor. I am an engineer in power electric distribution. I can not go to another area and be worth a d - - -, I have to stay put. Real electrical engineers have the ability to move around and pick up very quickly.
The bottom line is that I really respect your knowledge and experience even if I don't agree with you all the time.
Bob, that is exactly what they and the electric utilities want you to do.
Bennie, whenever a person is in a field as long as we have been, we can be as sharp as an engineer in that narrowly defined part of engineering. In other words, I consider you to be an engineer in your field of endeavor. I am an engineer in power electric distribution. I can not go to another area and be worth a d - - -, I have to stay put. Real electrical engineers have the ability to move around and pick up very quickly.
The bottom line is that I really respect your knowledge and experience even if I don't agree with you all the time.
Re: Phase imbalance
Charlie, coming from you this is a meaningful compliment. I will work on the areas where you don't agree
I have been fortunate to have been associated with some of the top scientists and electrical engineers in the world. They were from Australia, New Zealand, the UK, Japan, and Russia. I usually hired out by request from the National Science Foundation. I had a good record for performance and received some commendations. I have one signed by Alexander Haig, and one by the Prime Minister of Japan, Mr.Ito
Charlie, coming from you this is a meaningful compliment. I will work on the areas where you don't agree
I have been fortunate to have been associated with some of the top scientists and electrical engineers in the world. They were from Australia, New Zealand, the UK, Japan, and Russia. I usually hired out by request from the National Science Foundation. I had a good record for performance and received some commendations. I have one signed by Alexander Haig, and one by the Prime Minister of Japan, Mr.Ito
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