Two seperate sources, no transfer switch

[qcroanoke]

What code section prohibits this?
Have a situation where the customer has two 225 amp panels with each having a seperate
feed but they are both tied together by a breaker in each panel.
So what we have is a situation where one main breaker would always be off unless there is a failure of the primary feed then that breaker would be opened and the 2nd main would be closed to put the load on the back up feed.
Please I know how dangerous this is, so lets leave that out of it.
What code section can I beat them with and prove to them its a code violation
And a transfer switch is needed.

 

[augie47]

I will be glad if someone can tell both you and I that there is a Code section that address this at least to the extent of labeling, but I know of no such provision.
If they were fed from different services, most POCOs would have input, but if both are fed from feeders I know of no violation.
Proper legends and even a "lirk key" system would be well advised.

 

[iwire]

Possibly the prohibition against conductors or OCPDs in parallel.

 

[qcroanoke]

I will be glad if someone can tell both you and I that there is a Code section that address this at least to the extent of labeling, but I know of no such provision.
If they were fed from different services, most POCOs would have input, but if both are fed from feeders I know of no violation.
Proper legends and even a "lirk key" system would be well advised.

They are services, not feeders I should have been more clear on that.
Probably should say that this is a building going in a poco sub-station. I know poco's can do most anything but we can't......

 

[augie47]

Is each from a seperate POCO service entrance ?

 

[iwire]

Also there could be an issue of panel protection.

A 200 amp buss supplied by two 200 amp sources is a violation.

 

[augie47]

Bob is Good !

I had not thought about the buss rating.
The arrangement would be a violation of 408.36.
In addition, I think you will find your POCO will prohibit the arrangement (backfeeding) with a Kirk-Key or similar means to prevent it.

 

[ron]

702.6 to prevent the inadvertent interconnection of the normal and alternate source.

 

[iwire]

What if both sources are 'normal'?

 

[jim dungar]

The installation of a Main-Main service is very common. There are many different methods that can be used to prevent a paralleling of the sources.

In fact, many residential loadcenters have provisions for field installing this type of service.

 

[ron]

If they were both normal, then both breakers would be on all the time. The OP says "one main breaker would always be off"

 

[jxofaltrds]

If they were both normal, then both breakers would be on all the time. The OP says "one main breaker would always be off"

Could it be that simple?

 

[markstg]

What if both sources are 'normal'?

They probably both are Normal. Normally (pun not intended) a Utility to Utility ATS is used, where the load stays connected to the one that's hot, and doesn't retranfer when power returns to the Other Normal source if the source it is connected to is OK.

 

[ceb58]

Mike, I would ask how is this system classified? If it is classified as 700 or 701 system then you could start with 700.1 or 701.2 They both state "these systems are intended to automatically supply................." Then 700.6 A or 701.7 A

 

[rbalex]

In absence of a definite means to prevent (even brief) paralleling, I would suggest a close reading of the first paragraph of Section 110.9. Take careful note of where in the circuit the fault interrupting rating must be based; i.e., the line side of the circuit breakers. In parallel, neither breaker would ever actually have to interrupt the combined fault; they would only need to interrupt the single contribution of one source (Unless the fault were internal to a breaker ? but then all bets are off anyway ). Some downstream OCPDs may need to interrupt the combined fault currents though.

 

[markstg]

Mike, I would ask how is this system classified? If it is classified as 700 or 701 system then you could start with 700.1 or 701.2 They both state "these systems are intended to automatically supply................." Then 700.6 A or 701.7 A

From the description of the install by the OP, it is neither.

 

[hillbilly1]

I know this is similar to what is done in large airports, but I think they use some means to interlock it whether it is automatic or manual such as a kirk key.

 

[augie47]

Beyond the "human" element involved to prevent back-feeding and general concern by most, I-Wire's reference to the buss rating and rbalex's insight into the AIC problem present to valid Code issues.

(Some days it's a pleasure to be here and see the knowledge exhibited)

 

[BILLY101]

Around here the utility Companies don't generally adopt the NEC for their distribution system.
Office buildings and such come under a different authority and the NEC is adopted.
The case in this thread doesn't detail how the (2) services are controlled. Possibly by discipline of which cutout is closed/opened at any one time.
Also utility Companies are painfully aware of backfeeds at all voltages.
My sense is this is considered safely manageable by trained personnel.

BILLY

 

[hillbilly1]

Beyond the "human" element involved to prevent back-feeding and general concern by most, I-Wire's reference to the buss rating and rbalex's insight into the AIC problem present to valid Code issues.

(Some days it's a pleasure to be here and see the knowledge exhibited)

I think we hashed this out in another post a couple of months ago too.