tap rule apply????

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Jeffr24

Member
Location
Hamilton, mi
I need your help. I have a picture of one of our panels. We blew two 300 Amp fuses based on the failure of a tap block. I wanted to have the panel rewired for better protection. I got grief from my boss. he states, " we are not going to rewire every panel just because a new code book come out. If you check the Tap rule for this installation, we are in compliance". I tried to discuss personal protection, lost production, plus the $200 cost per each 300 Amp fuse. What do you see wrong with this picture. I think my point is substantiated, but not enough ammunition for my boss. I will answer questions you have about the picture.
 

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looks to me like you have a "tapping a tap" violation (240.21). I general, I dont see your concern in using a tap rule - so you had a fault and a fuse blew. Larger wire or a smaller OCPD wouldnt have changed anything. From an electrical shock perspective, a smaller OCPD wont be any safer. From an arc flash standpoint, I dont think there would be a very big difference either.
 

kwired

Electron manager
Location
NE Nebraska
I agree, there is tap rule violations, tap rules have changed very little in a long time- boss comments about rewiring because of new code book mean little - it wasn't ever right in the first place.

That said the failure you had still would have taken out the fuse even if tap rules were not in violation.

Looks like someone already attempted to make some wrong's right by adding the breaker.

If you want to make it even more right, why not replace all of what is there with a real panelboard?
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I need your help. I have a picture of one of our panels. We blew two 300 Amp fuses based on the failure of a tap block. I wanted to have the panel rewired for better protection. I got grief from my boss. he states, " we are not going to rewire every panel just because a new code book come out. If you check the Tap rule for this installation, we are in compliance". I tried to discuss personal protection, lost production, plus the $200 cost per each 300 Amp fuse. What do you see wrong with this picture. I think my point is substantiated, but not enough ammunition for my boss. I will answer questions you have about the picture.

It is messy looking.

It does not appear to be compliant. Some of it may be OK, some appears like there is no way it is compliant. My inclination would be to start by getting rid of the big "tap block" and wiring the incoming 350 KCM direct to the disconnect switch. The rest of it could be fixed fairly straight forwardly with some class J fuse blocks.
 

kwired

Electron manager
Location
NE Nebraska
It is messy looking.

It does not appear to be compliant. Some of it may be OK, some appears like there is no way it is compliant. My inclination would be to start by getting rid of the big "tap block" and wiring the incoming 350 KCM direct to the disconnect switch. The rest of it could be fixed fairly straight forwardly with some class J fuse blocks.
My guess is someone decided they need a main disconnect at some point and added it - otherwise the supply raceway would likely have went to the disconnect enclosure. But nothing is wrong with the tap from the big tap block to the disconnect - assuming that disconnect does contain overcurrent protection and the tap is sized accordingly to the protection. Load side of the disconnect we seem to have multiple taps - to what are already tapped conductors.

Then again, seems the disconnect may be 350 amps and only supplied with 3/0 conductors. Still like the idea of replacing all of that mess with a real panelboard with deadfront cover.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
My guess is someone decided they need a main disconnect at some point and added it - otherwise the supply raceway would likely have went to the disconnect enclosure. But nothing is wrong with the tap from the big tap block to the disconnect - assuming that disconnect does contain overcurrent protection and the tap is sized accordingly to the protection. Load side of the disconnect we seem to have multiple taps - to what are already tapped conductors.

the picture says it is 3/0 wire and a 350A CB. I suppose it is possible there is appropriate OCPD upstream for the 3/0 conductors.

if you got rid of the tap block you would have room for a couple class J fuse blocks to feed the #2 wires that feed the smaller power blocks. would still need to change the wire coming out of the disconnect to the polaris connectors.
 

kwired

Electron manager
Location
NE Nebraska
the picture says it is 3/0 wire and a 350A CB. I suppose it is possible there is appropriate OCPD upstream for the 3/0 conductors.

if you got rid of the tap block you would have room for a couple class J fuse blocks to feed the #2 wires that feed the smaller power blocks. would still need to change the wire coming out of the disconnect to the polaris connectors.

I edited my last post before reading this one.
 

Jeffr24

Member
Location
Hamilton, mi
the picture says it is 3/0 wire and a 350A CB. I suppose it is possible there is appropriate OCPD upstream for the 3/0 conductors.

if you got rid of the tap block you would have room for a couple class J fuse blocks to feed the #2 wires that feed the smaller power blocks. would still need to change the wire coming out of the disconnect to the polaris connectors.


There are 3-300 amp fuses in the bus duct swing plug. I was confused why there is 300amp fuses for 350 McM wire, then reduced to 3/0 and running to a 350 amp disconnect. I was trying to explainto my boss that if the panel was rewire to have smaller fuse blocks installed, we would protect wiring and more costly downtime in the event of a fault.

Still agree with majority of the posts......clean up this mess. Does that justify a $2000 cost?
 

Jeffr24

Member
Location
Hamilton, mi
I agree, there is tap rule violations, tap rules have changed very little in a long time- boss comments about rewiring because of new code book mean little - it wasn't ever right in the first place.

That said the failure you had still would have taken out the fuse even if tap rules were not in violation.

Looks like someone already attempted to make some wrong's right by adding the breaker.

If you want to make it even more right, why not replace all of what is there with a real panelboard?

This happened prior to me working there. Supposedly, they were trying to save money by installing the j- panel and reusing the Disconnect. This is where we look stupid, reusing items and rigging what we have to "make it work". My boss is an electrician......but I have never seen his physical license.
 

John120/240

Senior Member
Location
Olathe, Kansas
What is a Polaris connection?

A multi port wire connector. In this picture they are insulated with the black rubber coating.
ps: picture courtesy of some one here at Mike Holt I think. Polaris is a brand name, There are other manufactures
 

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