Manual Disconnect spring loaded finger blade type

[LarryFine]

SO,, the definition of "applicaton" is where this issue resides unless i can find out in the NEC where it says a quick disc must be cabled to its ampacity.

It won't. Discos are sized by 'class', such as 30, 60, 100, 200, 400, 600, etc. A bolted fault is going to overload the disco as well as the conductors, until an open circuit is developed by the weakest point burning open.

You should start with the desired ampacity delivery level, install conductors with at least that ampacity, install OCP to protect those conductors, and use a class of disco rated at or above the required level.

You need OCP sized to protect the conductors that are necessary to carry the load. Whether the conductors meed to be rated to match the class of the disco is such a non sequitur, it's amazing. The answer is no, by the way.

Now, if the disco's in question are somehow capable of limiting current, then we can have another conversation. But, since the disco's are not, they seem to be just as arbitrarily chosen as the conductors seem to be.

I know you know this stuff already. You're looking for an answer to a question that requires an otherwise-compliant and properly designed circuit in order to give a meaningful response. The disco size is irrelevant right now.

 

[jcassity]

the disconnect size was never my question,, it was the wiring.

 

[jcassity]

the disconnect size was never my question,, it was the wiring.

 

[jcassity]

and by the way,,
our normal disconnects made by EEE serve as disconnects and over current.

so having said that, the wires are matched to the EEE breaker/disco.

Your ref to to my needing an OCP is not in the NEC. The nec says all ungrounded conductors shall have an OCP.< cut and dry to the point,

On battery strings, the nec says an ocp "shall be permitted",, not so cut and dry.

Do my battery cables fall under "ungrounded",, i certainly dont think so.

this is more sticky than fly paper, and no matter how much I know its wrong, i cant refer it to anything that makes it conform to the industry standard. The NEC needs a facelift ot include DC Power.,, right now it just skims the surface.

 

[jcassity]

You should start with the desired ampacity delivery level, install conductors with at least that ampacity, .

You cant do that with DC,, simply flipping through in the ugly's and finding a wire that matches the amperage you are looking for is for AC.

DC is done much differently. You size to the required circulair mills based on the kxLLxA/vd


There is a similair formula for AC but in additon to the multipiers above, two more elements are multiplied as well which are the qfactor of Xc/ Xl. THe path to getting the qfactor alone hosts a whole new set of forumlas,, so thus a chart was formed.

Distance is much much much less of an issue in ac than it is in DC. If it were not, we would still have a DC power grid like in the beginning of all this mess that started in chicago a century ago.

 

[jcassity]

You need OCP sized to protect the conductors that are necessary to carry the load. .

OK,, ill bite,,
tell me where that is written. I want it to be sooooooooo bad.

Your statement would have answered my question in post 1.

 

[RUWired]

OK,, ill bite,,
tell me where that is written. I want it to be sooooooooo bad.

Your statement would have answered my question in post 1.

To keep it simple and to answer your question in post #1, article 310.10 states that...
No conductor shall be used in such a manner that its operating temperature exceeds that designated for the type of insulated conductor involved. In no case shall conductors be associated together in such a way, with respect to type of circuit, the wiring method employed, or the number of conductors, that the limiting temperature of any conductor is exceeded.

Rick

 

[coulter]

...If it were a EEE breaker, ...

I'm probably the only one that doesn't know - Whats an "EEE" breaker?

carl

 

[coulter]

You didnt read my post,, and also,, ...

Yes, I did -

... i never said i had an "engineer" anywhere. ...

Yes, you did

... My answer directly from two engineers was the following: ...

... Your not helping by talking down to me.

Tried to help. Didn't know I was talking down - thought I was asking for clarification.

carl

 

[coulter]

OK,, ill bite,,
tell me where that is written. I want it to be sooooooooo bad.

Your statement would have answered my question in post 1.

I would start with 240.1, and the following FPN, then 240.4, and then the tap rules in 240, paying attention to SDS sections.

Yes, it applies to DC.

However, I'm thinking you already know this. If so, then I'm missing the question again.

carl

 

[LarryFine]

OK,, ill bite,,
tell me where that is written. I want it to be sooooooooo bad.

Your statement would have answered my question in post 1.

I don't see where the NEC excludes DC.

 

[jcassity]

I don't see where the NEC excludes DC.

Yeah, i agree, i wonder who your talking about who said that, cause it wasnt me. I did say the NEC skims the surface and needs a facelift to include DC ie-more detail. There isnt one single AC electrician capable of working DC without first having to get specialized training so we can help them underderstand why a 30A circuit might require 2/0 and then on the next job the same circuit size but a shorter loop would only need 6awg.

You said i need an OCP on the battery stack but you did not ref the article in the NEC.

 

[jcassity]

I'm probably the only one that doesn't know - Whats an "EEE" breaker?

carl

sorry, its a brand name,, many types out there.

see attached 1200A Diconnect breakers / ocp typically installed on battery stacks, this pic happens to be cabled to a Load A power plant. Load B plant battery cables would be Blue.

 

[jcassity]

To keep it simple and to answer your question in post #1, article 310.10 states that...
No conductor shall be used in such a manner that its operating temperature exceeds that designated for the type of insulated conductor involved. In no case shall conductors be associated together in such a way, with respect to type of circuit, the wiring method employed, or the number of conductors, that the limiting temperature of any conductor is exceeded.

Rick

Sorry but the customer will...
A- never be able to understand that and
B- it will not work today because thier load does not put the wire in a situation where it is a fuse link.


However, it is a good reference for use when the future load comes on line here in soon to the tune of 300 additional amps.

The problem here is why were these 350mcm cables allowed in the first place being wired to a 1200A plant???? and........
If it took me this long to drum up an answer, I probably found my own answer to my own questions i just asked.

so far there is no ref in the nec that mandates an OCP required on a battery stack

 

[coulter]

... so far there is no ref in the nec that mandates an OCP required on a battery stack

jc -
You have been given two. Did you not like them?

carl

 

[winnie]

Commenting on post 1:

The equation in the first post sizes the conductors by for current and allowed voltage drop. This sizing of the conductors is almost certainly appropriate for the load being served, however it is not in accordance with the NEC. Sizing the conductors to prevent excessive voltage drop is a design option, not an NEC code requirement.

There may be other codes or design standards which apply to the installation, either by government mandate, or by the customer contract. These codes or standards may spell out voltage drop requirements.

The NEC mandates that conductors have sufficient ampacity that they not overheat when carrying the load current. For short spans, the equation given will result in conductors which are undersized and violate the NEC. For long spans, the equation will give results which are larger than the NEC minimums, and thus acceptable.

There is, in general, no requirement that all of the current carrying elements _match_ in terms of capacity. You can use a 350A conductor with a 1200A disconnect, feeding a 500A bus bar, and not create an NEC violation. However, in general all of these elements must be protected from overload. Something in the system that you described must protect the 350A conductor from overload.

In some limited circumstances, the overload protection may be 'downstream' of the protected conductors (think about the protection for service entrance conductors), but I do not believe that this applies in your case.

on post 24:
The conductors that you describe are most certainly 'ungrounded' conductors. Are they conductors? Yes. Do they carry current as part of a circuit or feeder? Yes. Are they electrically connected to ground? No. As ungrounded conductors, they must follow the various rules for OCPD.

-Jon

 

[jcassity]

Commenting on post 1:

on post 24:
The conductors that you describe are most certainly 'ungrounded' conductors. Are they conductors? Yes. Do they carry current as part of a circuit or feeder? Yes. Are they electrically connected to ground? No. As ungrounded conductors, they must follow the various rules for OCPD.

-Jon

WOW!!!
I feel very stupid,, but I can proceed so i guess thats progress eh?. Your definatly correct and my answer to the "situation" has reached a conclusion and a written path to sucess.

Thanks again for correcting my bad information earlier and thank you everyone for clearing this up.

 

[jcassity]

jc -
You have been given two. Did you not like them?

carl

Like or dislike, thats not my choice but rather what the rules are.

In light of the recent spark provided above, You are greatly appreciated for the help on this issue and yes, the two articles do apply.

 

[coulter]

Like or dislike, thats not my choice but rather what the rules are. ...

One other issue (that I also suspect you are aware of) is 90.1 Purpose (of the NEC):
A. practical safeguarding - Not perfect, not even necessarily great
B. Not necessarily efficient, convient, adequate for good serice or future expansion.
C. Not a design specification.

You don't have to build to minimum standards.

carl