Hypothetical-Table 310.15(B)(6)

[Chamuit]

I have a single phase residential service install with 200 amp meter enclosure fed with #2/0 per T310.15(B)(6). The first panel has dual lugs on the main and feeds an adjacent second panel. Each panel is rated at 200 amps and has a 200 amp main. Calculated load is less than 200 amps. Are the #2/0's compliant?

Basically, you are describing what would be a 400A all-in-one service with two 200A OCP inside.

Granted it is not physically what you have.

I believe that you have to use the 400A when using Table 310.15.B.6.

Of course, you also have the problem that the meter enclosure is not rated for such a load.

 

[jetlag]

Basically, you are describing what would be a 400A all-in-one service with two 200A OCP inside.

Granted it is not physically what you have.

I believe that you have to use the 400A when using Table 310.15.B.6.

Of course, you also have the problem that the meter enclosure is not rated for such a load.

THe meter is just something else to fry :grin::grin:What if I were a realestate developer and I build a warehouse to lease in an industrial area , it was wired with 2 or more 200 amp panels with mains all connected to 2/0 line before the breakers. All that can be added now is the lights, a/c , wh , and recepts . It comes out 195 amp so the 2/0 passes . I lease it to a company that connects 200 amp more equiptment to the panels and the 2/0 catches on fire and burns the building up . Who is at fault ? This has to be one of the more stupid codes in the NEC

 

[infinity]

id say no because the 2/0 between the first panel and second is not carrying the entire load of the dwelling.

I know that so what is your point. I said the first wire is carrying the entire load. The second does not but it does not need to be large then the service conductors so why not.

This is my take on the proposed setup. The second set of conductors going to the second panel are certainly not carrying the entire load so T310.15(B)(6) is out, but.....the SE conductors are #2/0 so why would the second set of conductors need to be larger than #2/0?

 

[Dennis Alwon]

The second does not but it does not need to be large then the service conductors so why not.

This is my take on the proposed setup. The second set of conductors going to the second panel are certainly not carrying the entire load so T310.15(B)(6) is out, but.....the SE conductors are #2/0 so why would the second set of conductors need to be larger than #2/0?

I agree. That was exactly what I was saying.

 

[George Stolz]

I'd say it is legal, but it would give me the willies to try it.

Panel A's conductors can be sized according to 310.15(B)(6).

Panel B's conductors are clearly big enough for the load that they serve. As long as the panels are somewhat balanced, the calculated load for panel B should be below the ampacity given in 310.16

The introduction of a second service handle sure throws a curve, doesn't it!

Edit to add: I fail to see the relevance of A's conductors when calculating B's size, however.

 

[Dennis Alwon]

I believe we all have those willies with this installation and I would bet it would be hard to get passed in some areas. Never saw a double lug 200 amp panel anyway. I guess you could add a trough but why--- use a feed thru panel and you are good to go.

Of course, Trevor did say it was hypothetical. Trevor did you come up with this or did someone present it to you?

 

[LEO2854]

I have a single phase residential service install with 200 amp meter enclosure fed with #2/0 per T310.15(B)(6). The first panel has dual lugs on the main and feeds an adjacent second panel. Each panel is rated at 200 amps and has a 200 amp main. Calculated load is less than 200 amps. Are the #2/0's compliant?

T310.15(B)(6)

This is my take on the proposed setup. The second set of conductors going to the second panel are certainly not carrying the entire load so T310.15(B)(6) is out, but.....the SE conductors are #2/0 so why would the second set of conductors need to be larger than #2/0?

Your 2/0 service entrance conductors feed through a 200 amp meater socket into a 200 amp main breaker with dual lugs in panel (A)

Your dual lugs are on the line side of the breaker. Your feeder to panel (B) is also 2/0 and is protected by a 200 amp main breaker in panel (B) those conductors are good T310.15(B)(6)

Your Calculated load is less than 200 amps. But what happens with future loads being added spread out evenly,so the potental is there that the total load could exceed 200 amps so your SEC's are only protected by the 200 amp breaker in panel (A)
so if the total load of panel (A) exceeds 100 amps,,And your total load in panel (B) Exceeds 100 amps.
Your service entrance conductors will be carrying the load of both panels spread out evenly the load could be 400 amps on 2/0 conductors.
I could not find any thing in the code that would allow that:-?

 

[elohr46]

I have a single phase residential service install with 200 amp meter enclosure fed with #2/0 per T310.15(B)(6). The first panel has dual lugs on the main and feeds an adjacent second panel. Each panel is rated at 200 amps and has a 200 amp main. Calculated load is less than 200 amps. Are the #2/0's compliant?

what you have there is a line side tap and would have to follow the rules in 230.82 (2008 nec). I think the 2/0's would be compliant per load calc.

 

[hurk27]

T310.15(B)(6)



Your 2/0 service entrance conductors feed through a 200 amp meter socket into a 200 amp main breaker with dual lugs in panel (A)

Your dual lugs are on the line side of the breaker. Your feeder to panel (B) is also 2/0 and is protected by a 200 amp main breaker in panel (B) those conductors are good T310.15(B)(6)

Your Calculated load is less than 200 amps. But what happens with future loads being added spread out evenly,so the potential is there that the total load could exceed 200 amps so your SEC's are only protected by the 200 amp breaker in panel (A)
so if the total load of panel (A) exceeds 100 amps,,And your total load in panel (B) Exceeds 100 amps.
Your service entrance conductors will be carrying the load of both panels spread out evenly the load could be 400 amps on 2/0 conductors.
I could not find any thing in the code that would allow that:-?

230.90(A) exception 3 allows just that.

what you have there is a line side tap and would have to follow the rules in 230.82 (2008 nec). I think the 2/0's would be compliant per load calc.

230.82(1) allows overcurrent devices to be tapped line side.

 

[K8MHZ]

T310.15(B)(6)



Your 2/0 service entrance conductors feed through a 200 amp meater socket into a 200 amp main breaker with dual lugs in panel (A)

Your dual lugs are on the line side of the breaker. Your feeder to panel (B) is also 2/0 and is protected by a 200 amp main breaker in panel (B) those conductors are good T310.15(B)(6)

Your Calculated load is less than 200 amps. But what happens with future loads being added spread out evenly,so the potental is there that the total load could exceed 200 amps so your SEC's are only protected by the 200 amp breaker in panel (A)
so if the total load of panel (A) exceeds 100 amps,,And your total load in panel (B) Exceeds 100 amps.
Your service entrance conductors will be carrying the load of both panels spread out evenly the load could be 400 amps on 2/0 conductors.
I could not find any thing in the code that would allow that:-?

Maybe I need a line drawing but I can't see how the 200 amp breakers would allow for anything close to 400 amps.

As I understand (or not) the second 200 amp breaker is on the load side of the first. That limits the current to 200 amps even if the second breaker is 2000 amps.

 

[LEO2854]

230.90(A) exception 3 allows just that.
.

Yes i can see that 230.90(A) exception 3 Because the calculated load does not exceed 200 amps at this time.

But what about 90.8 wiring planning. dont we have to take future use into consideration?

 

[LEO2854]

Maybe I need a line drawing but I can't see how the 200 amp breakers would allow for anything close to 400 amps.

As I understand (or not) the second 200 amp breaker is on the load side of the first. That limits the current to 200 amps even if the second breaker is 2000 amps.

The SEC 's are protected by the 200amp breaker in panel (A).then you have a 200 amp feeder conected on the line side of the 200 amp breaker in panel (A)feeding a 200 amp breaker in panel (B).

Lets say panel (A) is drawing 180 amps and panel (B) is drawing 180 amps
. So now you have 360 amps flowing through the SEC's and 180 amps on the feeders between the two panels ,,but neather breaker would trip because the breaker in panel (A)can only see 180 amps

 

[roger]

Yes i can see that 230.90(A) exception 3 Because the calculated load does not exceed 200 amps at this time.

But what about 90.8 wiring planning. dont we have to take future use into consideration?

90.8(A) is just wasted ink, it is simply a comment, not a requirement.

Roger

 

[jetlag]

Maybe I need a line drawing but I can't see how the 200 amp breakers would allow for anything close to 400 amps.

As I understand (or not) the second 200 amp breaker is on the load side of the first. That limits the current to 200 amps even if the second breaker is 2000 amps.

The second breaker is on the line not the load side of first breaker . The code allows it if the load calc is less than 200 , but it wont be done on my job . Any way I dont believe the lugs on the first 200 panel would be rated for 400 amp.

 

[jetlag]

90.8(A) is just wasted ink, it is simply a comment, not a requirement.

Roger

Yes but you can see how easily some one could come in and add loads to the second panel without thinking about it being necessary to open the first panel and investigating that the panels are wired to a conductor for 200 amp total . Most people have never seen that anywhere.

 

[roger]

Yes but you can see how easily some one could come in and add loads to the second panel without thinking about it being necessary to open the first panel and investigating that the panels are wired to a conductor for 200 amp total .

I can't prevent unqualified people from doing stupid things after I leave. When you install a fusible disconnect for a 150 amp load how do you know someone will not come behind you and install 200 amp fuses

Most people have never seen that anywhere.

I don't worry about most people, a qualified individual will look beyond the immediate, if they don't, they shouldn't have their paws in it anyways.

I don't see how any of this has anything to do with article 90.8(A) though.

Roger

 

[K8MHZ]

The second breaker is on the line not the load side of first breaker . The code allows it if the load calc is less than 200 , but it wont be done on my job . Any way I dont believe the lugs on the first 200 panel would be rated for 400 amp.

I don't see where this is allowed in 230.82.

Even so, if more than one switch is used as a service disconnect the conductors must be sized according to calculated load. If the load exceeds 200 amps as suggested it may, then a 200 amp conductor would be too small.

Now, since we all know that the calculated load in a new installation is likely going to change over time. That's not the NEC's concern.

Here is a case where following the NEC to the letter makes, to me, a poor installation.

I would size the inter-panel conductors for 200 amps and the meter to panel and meter to weatherhead for 400.

Consider the post Bob made about a marina getting sued over a fatality because they did not exceed the NEC requirements for GFCI protection.

Another question I have is the location of the first disconnect. Where is the neutral and grounding electrode system bonded?

 

[infinity]

I believe we all have those willies with this installation and I would bet it would be hard to get passed in some areas. Never saw a double lug 200 amp panel anyway. I guess you could add a trough but why--- use a feed thru panel and you are good to go.

Of course, Trevor did say it was hypothetical. Trevor did you come up with this or did someone present it to you?

Someone asked me this question recently so I thought that I would put it out there for comment. At first I said it was non-compliant due to the second set of conductors not carrying the full load but then they would be required to be larger than the SEC's so that wouldn't make any sense.


So then I thought would it would really matter if it were one 200 amp panel or several fed from the same set of of SEC's providing the dwelling load calculation were 200 amps or less?

I agree it's a poor design but is there a code reference that prohibits it?

 

[jetlag]

I can't prevent unqualified people from doing stupid things after I leave. When you install a fusible disconnect for a 150 amp load how do you know someone will not come behind you and install 200 amp fuses
I don't worry about most people, a qualified individual will look beyond the immediate, if they don't, they shouldn't have their paws in it anyways.

I don't see how any of this has anything to do with article 90.8(A) though.

Roger

An attorney will beat you on this in court if someone dies in a fire , for installing a 200 panel with a main that cannot be loaded to 200 amp , with out causing a fire , remember a panel of 12 are like the people you are calling stupid when it comes to electricity . Remember the post about the fish tape ran in a panel at a marina ? :grin::grin: All this could be avoided by using the feed through lugs on the first panel to fed the second , what has any one accomplished by wiring to the line in ?

 

[roger]

An attorney will beat you on this in court if someone dies in a fire ,

Nope, I don't buy it and you didn't answer my question about the fusible switch.

Roger