Bus taps

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Brandon Loyd

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Can anyone tell me if either one of these installations are illegal?

1st. The gutter is fed by a 400 amp breaker some 30'+ away with 400 amp wire. Then, using a multi-tap polaris fitting, they branch out with #12 wire to feed the 4 fusible disconnects directly attached to the gutter, which have 15 amp fuses installed, each having their own set of wires. I have seen this many times and never questioned it as the #12 wire, to me, is protected by the 15 amp fuses. Am I right or wrong?

2nd. These two fusible disconnects are fed via a bus tap from the bottom of this panel. They are within 10'. This installation appears to be code legal to me as well. Am I right or wrong?

Gutter Tap 1.JPG

Buss tap 1.JPG
 

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No you can't use #12 to feed the panels from a 400 amp feeder. The 25' rule would limit you to 1/3 the feeder.

240-21B1-01web.gif
 
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Brandon Loyd said:
Can anyone tell me if either one of these installations are illegal?

1st. The gutter is fed by a 400 amp breaker some 30'+ away with 400 amp wire. Then, using a multi-tap polaris fitting, they branch out with #12 wire to feed the 4 fusible disconnects directly attached to the gutter, which have 15 amp fuses installed, each having their own set of wires. I have seen this many times and never questioned it as the #12 wire, to me, is protected by the 15 amp fuses. Am I right or wrong?
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This would seem to be a violation of 240.21(B)(1)(4).

Brandon Loyd said:
2nd. These two fusible disconnects are fed via a bus tap from the bottom of this panel. They are within 10'. This installation appears to be code legal to me as well. Am I right or wrong?
Click to expand...

Can't tell without the tap conductor sizes or feeder OCPD size. It may also 240.21(B)(1)(4).
 
Refer to the "Tap Rules" in 240.21
The length of the tap is your prime determining factor.
The most lenient would be the 10 ft tap rule which would require 40 amp conductors as a minimum.
 
The 25' tap rule says I need 40 amp wire says I need 133.33 amp wire. The 10' tap rule says I need 40 amp wire. Which one do I need to use?

The tap conductors at the gutter are less than 10' from the actual tap itself, but the line side OCD is over 30' away from the tap.
 
Brandon Loyd said:
The 25' tap rule says I need 133.33 amp wire. The 10' tap rule says I need 40 amp wire. Which one do I need to use?

The tap conductors at the gutter are less than 10' from the actual tap itself, but the line side OCD is over 30' away from the tap.
Click to expand...

The "length" refers to the length of the tap conductor, not the length of the feeder before the tap is made. The length of your tap conductors from the tap point to the wireway to the OCPD in each fused disconnect appears to be less than 10'. The 10' tap rule would apply.
 
Just to supplement what David told you.
Look at 240.2 for the definition of a tap conductor.
You will see a conductor with a 400 amp ampacity connected to a 400 amp OCP is not a
"tap"
 
So to sum it all up, if my tap conductors are less than 10', my wire just has to be rated for 1/10th the OCPD. Does this sound right?
 
What about all those 12's shoved into one port of those Polaris connectors? A dist. block may have served them better in this instance.
 
Cow said:
What about all those 12's shoved into one port of those Polaris connectors? A dist. block may have served them better in this instance.
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Cow is right. Even though the 12 in and of itself needs to be up sized to a #8, I would be more concerned with the use of the Polaris in violation of it's listing.
 
Can anyone explain why you have BLK/RED/BLU and BRN/OR/YEL conductor identification in photo #2?
 
infinity said:
Can anyone explain why you have BLK/RED/BLU and BRN/OR/YEL conductor identification in photo #2?
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It's fairly common for us to come across old installs with bl/rd/blu as 480v colors. Just like everyone else around here we pull BOY and so you get installations that look like that.
 
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