Feeder taps and outbuildings?

[PCustoms]

In the past few days I saw a post on here about feeder taps and detached garages. I glanced over it and moved on. Tonight dad calls me and asks about how to wire the new garage, using what sounds like a feeder tap, and I'm not so sure.

Buildings are in Maine, no permit/inspection but I want to see it done right


Going by memory here, but meter is on a pedestal and has a main breaker. This breaker is 200A and feeds the automatic transfer switch to the house, which is 100A. Electrican is telling him to tap off the 200A breaker and feed 100A to the garage using a self piercing tap connector.

Run is 70 ft.

1. Is this a legal tap?
2. Any experience with these connectors? I think it was an ilsco kuplet

As far as I am aware this is all 4 wire feed after the initial breaker, and all grounds and neutrals are seperate.

 

[wyliesdiesels]

is the ATS part of the main service panel?

Does the garage need to be fed with generator power?

 

[PCustoms]

is the ATS part of the main service panel?

Does the garage need to be fed with generator power?

Switch is separate.

I thought he wanted to feed it from the generator, but sending a few texts to confirm breaker sizes he says he is going to tap before the ATS.

I swear I had a pic, but going from memory it was meter main with 200A into the ATS with 100A. I remember the 100A, as I was suprised it ran the double wall oven and we'll pump last thanksgiving with no issues.

 

[Radix2]

If he is tapping off the 200A breaker... he has put in 200A wire.

How is he going to "feed 100A" off of the 200 A breaker?

 

[Bert_]

The tap sounds perfectly legal. There really aren't many limitations for outside taps. The issue you might run into is whether there is room for the wire and extra connectors. Depends on the box.

I have seen those connectors used but I have never installed one so no real experience.

 

[Bert_]

If he is tapping off the 200A breaker... he has put in 200A wire.

How is he going to "feed 100A" off of the 200 A breaker?

No he doesn't.

The tap can be #1 aluminum if it terminated to a 100A breaker.

 

[PCustoms]

If he is tapping off the 200A breaker... he has put in 200A wire.

How is he going to "feed 100A" off of the 200 A breaker?

No he doesn't.

The tap can be #1 aluminum if it terminated to a 100A breaker.

This is really the crux of my confusion. So the existing wire is breaker ed at 200A, we can legally tap off that with a 100A rated wire?

Why does this wite not need proper rated overcurrent protection?

Just trying to understand the code here.

 

[jim111]

240.21(B)(5) in the 2014 NEC

 

[PCustoms]

240.21(B)(5) in the 2014 NEC

Can you summarize for me?

 

[jim111]

Long section but basically outside taps properly installed are considered protected by the disconnect they are feeding, if said disconnect cannot draw more current than the tap conductor is rated for. By "outside" meaning exterior of the structure in a protected box of course

 

[TRWham]

This is really the crux of my confusion. So the existing wire is breaker ed at 200A, we can legally tap off that with a 100A rated wire?

Why does this wite not need proper rated overcurrent protection?

Just trying to understand the code here.

It's all in 240.21(B). The downstream overcurrent protection also protects the tap conductors from overload. Only if there were physical damage to the tap conductors that caused a short could you overload between the tap and the downstream circuit breaker. In that case, the short circuit protection is provided by whatever is protecting the feeder conductors. Short circuit current is normally so high it trips nearly instantly and the smaller conductors can carry the large overload briefly.

 

[Bert_]

It's all in 240.21(B). The downstream overcurrent protection also protects the tap conductors from overload. Only if there were physical damage to the tap conductors that caused a short could you overload between the tap and the downstream circuit breaker. In that case, the short circuit protection is provided by whatever is protecting the feeder conductors. Short circuit current is normally so high it trips nearly instantly and the smaller conductors can carry the large overload briefly.

This is a good explanation.

Simple version is the 200A breaker will protection the #1 wire from shorts (a short will draw thousands of amps, it will trip a 200 almost as easily as a 100).
The 100a breaker on the other end protects against overloading the wire.

 

[dcg9381]

I learned something new here: IF the above is accurate - meaning 100A rated wire splice on a 200A breaker (and feed), protected (at the sub panel) by a 100A breaker and any "short" between the 200A and 100A is inherently protected by the fact that a short will generate enough amps to trip 200A before the wire burns. Kinda surprised that this is OK, but I get it per above.

I've used the ilsco kuplet type connectors before and they are great.
If you have copper on the 200A feed, stick to copper on the splice. Vice versa for Aluminum (like wire). With aluminum - watch for torque spec and you may or may not need oxidation guard.

If you use aluminum - watch size per feed. I just ran one of these and the 2-2-2-4 Al wire - amp rating may drop if you put it in conduit.



I'm (personally) not crazy about doing it this way - I'd probably find a way to get a 100A breaker in at the pedestal (even if it meant putting in a new main panel).. Or pull 100A off the house.. But this isn't the cheapest way to do it, but DIY I can't imagine more than a $400 or so, assuming there is room.

 

[alfredeneuman]

The 'physical protection against damage' means that where exposed, it needs protected by PVC80, Rigid Conduit (or Intermediate Metal Conduit), or EMT.
The run has to be all outside except at the terminals. The pedestal is already outside but the garage needs to have a disconnect or main breaker panel either outside or immediately on the inside.

 

[PCustoms]

I'm (personally) not crazy about doing it this way - I'd probably find a way to get a 100A breaker in at the pedestal (even if it meant putting in a new main panel).. Or pull 100A off the house.. But this isn't the cheapest way to do it, but DIY I can't imagine more than a $400 or so, assuming there is room.

I'm not either, and I recommended he do a sub from day 1 (main panel doesn't accept 2 breakers). Regarding to disconnect at the garage, the conduit should be straight up the outside wall and then LB into the back of the panel.

I wish he had gone off the house panel, but it was full and somehow he deemed it easier to run from the meter/ATS on the pedestal. Problem is I am assuming by dad's questions last night he wants me to finish it at Thanksgiving....

 

[Bert_]

Seems like some are turned off by the idea of a feeder tap, I personally like them. If you have a main that accepts multiple wires or a separate terminal box it is much more versatile than a panel with breakers to each building.

Almost every farm service I install is this way. Often a fused disconnect when it's over 200A feeding multiple buildings and panels off the load side of the disconnect.

 

[PoorOwner]

Here is a video I found useful when I tried to understand the subject on feeder. Turns out I wasn't doing a feeder tap but a splice since the wire I used was the same size.

 

[PCustoms]

Here is a video I found useful when I tried to understand the subject on feeder. Turns out I wasn't doing a feeder tap but a splice since the wire I used was the same size.

 

[sberry]

number 6 is good for 200A fault protection. I will agree the explanation above is good. This is a fundamental principle of a power strip, breaker after the cord. It is part of the basic design of many or most dedicated circuits, motor and welder circuits where the applied load is the thermal limiting factor and the breaker is a switch and fault protector.