Electrical Service Question

[VermontMWM]

Hi A friend asked whether he could add a new panel in his shop. Please let me know if this is wrong. He has a 200a main service disconnect at the meter with a 200a breaker. This feeds a 200a main lug panel in his home. I said he could add a 60a breaker in his panel which would feed the panel in his shop. Initially he wanted to tap off the 200a breaker and feed a 60 a panel in his shop. I told him he could not feed a 60a panel off a 200a breaker. He does not want to run from the house because it is too far away. So, he can feed two 100a panels from the 200a main but not two 200a panels; that would require a 400a service...correct? Just trying to get this clear in my head. Thanks for the assistance.

 

[iwire]

In a nutshell code wise the only issue is the calculated load.

You could supply ten 200 amp panels from a 200 amp service as long as the total calculated load was under 200 amps.

 

[VermontMWM]

Thanks. I have not been up to his house to see the meter, etc. So, I am going by what information I had. I figured the calculated load would have determined his service size. He has a Wood Shop/barn which is where he wants the panel. He is trying to do this cheaply, but I am trying to keep him legal. Thanks again for the input

 

[Smart $]

... Initially he wanted to tap off the 200a breaker and feed a 60 a panel in his shop. I told him he could not feed a 60a panel off a 200a breaker. ...

It is possible to tap off the 200a breaker. First, the total calculated service load (house and shop) must be 200A or less. The tap conductors ampacity and shop panel ocpd must meet the requirements of 240.21(B).

 

[VermontMWM]

I need to get a look at his 200a Main disconnect and house panel. He may even have a panel in his shop that he has not mentioned. Still, what I have told him so far is true, yes?

 

[kwired]

I need to get a look at his 200a Main disconnect and house panel. He may even have a panel in his shop that he has not mentioned. Still, what I have told him so far is true, yes?

I told him he could not feed a 60a panel off a 200a breaker.

Not always true. Tap rules can allow this, and since this is feeding a separate building outside feeder taps have no limit to length, so if you tap with a 60 amp conductor all that is required is that it has a 60 amp overcurrent device at the load end of the tap.

 

[VermontMWM]

yes, he can feed his new panel with a 60a OCPD. But he cannot feed a 60a panel with a 200a OCPD.

 

[Smart $]

yes, he can feed his new panel with a 60a OCPD. But he cannot feed a 60a panel with a 200a OCPD.

We told you he could, maintaining specific NEC criteria and you still say he can't. So perhaps you can tell us why not...???

 

[VermontMWM]

Three words...Authority Having Jurisdiction. It took awhile, but I heard back from a local State Inspector. The conductors would have to be protected with a properly sized OCPD. So, you would not protect a 60a panel with a 200a breaker. Also, care would need to be taken to assure that the buss that the breaker would be installed on, would not be exceeded by installing the required breaker. Some panels limit the buss to a lower amperage; for most good quality panels it is not an issue, but a "heads up" to check those ratings as well.

 

[petersonra]

Three words...Authority Having Jurisdiction. It took awhile, but I heard back from a local State Inspector. The conductors would have to be protected with a properly sized OCPD. So, you would not protect a 60a panel with a 200a breaker. Also, care would need to be taken to assure that the buss that the breaker would be installed on, would not be exceeded by installing the required breaker. Some panels limit the buss to a lower amperage; for most good quality panels it is not an issue, but a "heads up" to check those ratings as well.

does the state have a local rule on this that supersedes the NEC?

 

[Smart $]

Three words...Authority Having Jurisdiction. It took awhile, but I heard back from a local State Inspector. The conductors would have to be protected with a properly sized OCPD. So, you would not protect a 60a panel with a 200a breaker.

Conductor protection and panel protection are two separate issues, though in many instances, both can be achieved with one ocpd.

I'm not suggesting 60A conductors or panel be protected with a 200A ocpd. Tap rules of 240.21(B) permit connecting conductors, with an ampacity less than the supply ocpd rating, to a feeder (or feeder terminals), on the condition the load end of these tap conductors terminate to an ocpd with rating equal or less than the tap conductor ampacity. In other words, tap conductors are protected by load-end ocpd. FWIW, practically all service conductors are protected by load-end ocpd... just to give you a very common example of the principle.

So if you have 60A tap conductors protected by load-end ocpd, and that ocpd is ahead of or the main breaker of the 60A panel, the panel is also protected.

If the AHJ has adopted the NEC yet disallows such, they should have amendments to the tap rules as a matter of public record. If it is just the inspector disallowing such, he does not have a comprehensive knowledge of the Code.

 

[kwired]

Conductor protection and panel protection are two separate issues, though in many instances, both can be achieved with one ocpd.

I'm not suggesting 60A conductors or panel be protected with a 200A ocpd. Tap rules of 240.21(B) permit connecting conductors, with an ampacity less than the supply ocpd rating, to a feeder (or feeder terminals), on the condition the load end of these tap conductors terminate to an ocpd with rating equal or less than the tap conductor ampacity. In other words, tap conductors are protected by load-end ocpd. FWIW, practically all service conductors are protected by load-end ocpd... just to give you a very common example of the principle.

So if you have 60A tap conductors protected by load-end ocpd, and that ocpd is ahead of or the main breaker of the 60A panel, the panel is also protected.

If the AHJ has adopted the NEC yet disallows such, they should have amendments to the tap rules as a matter of public record. If it is just the inspector disallowing such, he does not have a comprehensive knowledge of the Code.

:happyyes:what he said:happyyes:

 

[ggunn]

Three words...Authority Having Jurisdiction. It took awhile, but I heard back from a local State Inspector. The conductors would have to be protected with a properly sized OCPD. So, you would not protect a 60a panel with a 200a breaker. Also, care would need to be taken to assure that the buss that the breaker would be installed on, would not be exceeded by installing the required breaker. Some panels limit the buss to a lower amperage; for most good quality panels it is not an issue, but a "heads up" to check those ratings as well.

I'm pretty sure you could protect a 60A panel with a 200A breaker as long as the conductors between them are rated to 200A. I don't know why anyone would want to do this, but I don't think it would be a code violation.

 

[kwired]

I'm pretty sure you could protect a 60A panel with a 200A breaker as long as the conductors between them are rated to 200A. I don't know why anyone would want to do this, but I don't think it would be a code violation.

As Smart$ said, there are two different things being protected. The panel, and the conductors.

The panel must be protected at 60 amps if that is all it is rated for. A 60 amp main breaker can accomplish that no matter what is on the supply side of the feeder.

The conductor would need to be at least a 60 amp conductor, but if the conductor is a feeder tap, then the supply side overcurrent protection does not need to be 60 amps. Which tap condition of 240.21(B) applies will determine what the supply side protection could be. As mentioned in OP we are dealing with a feeder tap supplying a separate building. Though not always the case, that generally means the feeder tap will be outdoors, and I think it is in the OP's case.240.21(B)(5) permits outside feeder taps to be unlimited in length - with conditions of course, but they generally are not that hard to comply with, and many of them are reinforced by art 225 requirements anyway.