Clarification on Tap Rule.

[dixson]

A church decided to install a new A/C system. The original setup was... 125A 120/240v breaker in the MDP in building A is feeding 125A breaker in a disconnect which is located in bldg B. It is approx. 400' away and the conductors are 1/0 TW.
The electricians for the A/C company disconnected the 1/0 conductors from the 125A breaker in bldg B. Installed a 3 port lugs on the end of the 1/0. They then used #4 thhn to reconnect the 125A breaker in the disconnect and #4 to tap of a new 30A fused disconnect for the new A/H.
The way I read the code, they should install a new disconnect before they start tapping of the feeder. Is that correct?

 

[petersonra]

Let me restate what I think you are saying you have. 125 amp circuit 1/0 comes from building A to Building B.

At Building B the 1 / 0 splits and becomes two number fours. One of the number 4 wires goes to 125 amp circuit breaker the other to a 30 amp fuse. I guess I don't have a big problem with this as far as Taps go. You just have two taps. Nothing wrong with that. Not sure a number 4 is protected by 125 amp circuit breaker though.

I'm also not sure whether you're required to run the feeder direct into the disconnecting means for the building. I think even if you're required to there's probably a six handle rule that as long as they are grouped together you would be okay.

So probably the only issue is the number 4 wire protected by 125 amp circuit breaker.

 

[dixson]

Yes that sound right.

The way the code seems to read is that a feeder tap can only be 10' or 25' feet not 400' long. If you say it falls under the unlimited length rule then a disconnect is required and readily accessible.

 

[infinity]

I agree the #4 cannot be feed the 125 amp CB. In general tap conductors must be protected based on their ampacity but this gets tricky because the load is an AC unit which allows conductor to be protected for short circuit and ground faults by an OCPD larger than the conductor size.

 

[dixson]

If I understand what is being stated, I can find a underground feeder being protected 300 feet away, expose it, cut it, tap into it and set a panel. As long as the I adhere to any one of the tap rules, I'm OK.

 

[petersonra]

If I understand what is being stated, I can find a underground feeder being protected 300 feet away, expose it, cut it, tap into it and set a panel. As long as the I adhere to any one of the tap rules, I'm OK.

The 1/0 is not a tap conductor because it is fully protected by the 125 amp circuit breaker. The two number 4 conductors are tap conductors. A tap conductor is required to terminate at a single overcurrent protection device rated to protect the ampacity. The tap conductor that terminates at the 125 amp circuit breaker probably doesn't meet this requirement.

This is one of those cases where doing something simpler would have been more cost-effective easier and would have met code. All they really had to do was feed the 1/0 conductors through the new connectors and leave them terminated at the existing 125 amp circuit breaker. Then a tap conductor could have been run to the 30 amp fuse block.

 

[dixson]

Although I agree with your assessment, I feel there is something wrong. In the event of a emergency, you would have to exit the building, enter another building, find the MDP, find the breaker to the feeder before you can deenergize the feeder. It just seems like there has to be a disconnect located near the tap. Since the system has changed, proper labeling would be required.

 

[kwired]

Although I agree with your assessment, I feel there is something wrong. In the event of a emergency, you would have to exit the building, enter another building, find the MDP, find the breaker to the feeder before you can deenergize the feeder. It just seems like there has to be a disconnect located near the tap. Since the system has changed, proper labeling would be required.

That is not the case though. One could run a single feeder to the separate building (in fact you normally have to supply a separate building with a single feeder) and have up to six disconnecting means at the building. A person wouldn't ordinarily do this for a 100 - 200 amp supply, but can definitely be more cost effective to split say a 600 amp feeder into multiple 200 amp main breaker panels, then to install a 600 amp panel or hit a 600 amp disconnect and then tap to the same 200 amp panels.

 

[petersonra]

Just because the code does not require something does not mean you are prohibited from installing it anyway. We tend to talk about the minimum code requirements here, but you are free to make a design decision to exceed those minimums.

For instance, you could decide to run nothing smaller than #10 wire. It might not be required but you can make that design decision.