"Tapbox"

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paawwlwall

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I am working on an industrial building and have run across something that I am not sure is permitted by code or not. They have several items labeled as "Tapbox's" and I am trying to find where in code this is permitted and the guidelines if it is permitted. I have attached a picture to try and explain what is going on...

I know there are issues going on with over-current protection a lot of these feeds from the "tapbox" are going to MLO panels.

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Any help would be greatly appreciated.

Thanks
 
paawwlwall said:
I am working on an industrial building and have run across something that I am not sure is permitted by code or not. They have several items labeled as "Tapbox's" and I am trying to find where in code this is permitted and the guidelines if it is permitted. I have attached a picture to try and explain what is going on...

I know there are issues going on with over-current protection a lot of these feeds from the "tapbox" are going to MLO panels.


Any help would be greatly appreciated.

Thanks
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1. I have no idea how to properly estimate the arc-flash potential from this type of installation, but it scares me. I see the PPE, so my guess is the buses were live when the picture was taken?
2. The "tap connectors" may be allowed by the tap rule, but only if they are considered properly protected at the MLO box end. Would the sum of the load breakers be considered sufficient protection? I doubt it. If the taps are between 10 and 25 feet long, the requirement is:
The tap conductors terminate in a single circuit breaker
or a single set of fuses that limit the load to the ampacity of the tap conductors. This device shall be permitted to supply any number of additional overcurrent devices on its load side.
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3. At the MLO panel itself the arc flash hazard could be worse because of the lack of an overcurrent device between the panel and the high energy feeders to the tap box.
 
GoldDigger said:
1. I have no idea how to properly estimate the arc-flash potential from this type of installation, but it scares me. I see the PPE, so my guess is the buses were live when the picture was taken?

Correct it was a maintenance electrician opening the box live. The next project we are working on is Arc Flash assessment. (wish me luck)

2. The "tap connectors" may be allowed by the tap rule, but only if they are considered properly protected at the MLO box end. Would the sum of the load breakers be considered sufficient protection? I doubt it. If the taps are between 10 and 25 feet long, the requirement is:

The only protection on primary feeders coming in is circuit breaker located in another building there isn't even a safety disconnect for maintenance purposes. The taps are a mixture of between 10-25 feet and much longer runs (some are over 75 foot runs.

3. At the MLO panel itself the arc flash hazard could be worse because of the lack of an overcurrent device between the panel and the high energy feeders to the tap box.
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Agree!!
 
What size is the OCPD for the tap box? Is this installation ever been considered exterior of the building( see rust)? The guard rails seem newer as the hinge door cannot be opened 90 deg. What year would you estimate the initial install?
 
Just to be clear, you would only get to apply the word "tap" if the upstream overcurrent protection device (i.e., that provides power to this "thing") has a higher rating than the ampacity of the conductors leaving this "thing." But I suspect that is the case here. All of the "tap rule" situations require the wires from the tap point to the next downstream component terminate on an overcurrent device that is rated to protect those wires. So they cannot land on an MLO panel. It appears to me that what you have here is a very unsafe installation.
 
mwm1752 said:
What size is the OCPD for the tap box?

Well its a screwed up situation on that see attached image below....

Is this installation ever been considered exterior of the building( see rust)?

Yes I think this used to be outside.... for a little background it used to be 7 individual buildings and they took them over and built one roof and combined them if that makes sense.

The guard rails seem newer as the hinge door cannot be opened 90 deg. What year would you estimate the initial install?
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I am not sure of exact date of install but I have found dates on some distribution gear from the 1950's
 
charlie b said:
Just to be clear, you would only get to apply the word "tap" if the upstream overcurrent protection device (i.e., that provides power to this "thing") has a higher rating than the ampacity of the conductors leaving this "thing." But I suspect that is the case here. All of the "tap rule" situations require the wires from the tap point to the next downstream component terminate on an overcurrent device that is rated to protect those wires. So they cannot land on an MLO panel. It appears to me that what you have here is a very unsafe installation.
Click to expand...

I agree this is just one instance of this type of installation there are a total of (5) what they call "tapbox's". The system is very old and unsafe for sure... I was just trying to digest all the things wrong and provide specific code references for violations.
 
paawwlwall said:
Here is the sketch from above forgot to attach it....
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OM*! The only protection on anything in the box is the primary OCP of the transformer???
I don't think the company tech was wearing enough PPE.

BTW, what is the primary protection on the transformer?
 
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paawwlwall said:
Yea notice I'm nowhere near the thing......don't understand who thought this was a good idea scary stuff
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Also makes you wonder what else you will find if you look hard enough.

Only way to make work on this safe would be to open the primary side of the feed transformer, and the location of that breaker does not seem to be listed on the tap box. :)
 
delectric123 said:
I also see #10 Service Cord tapping off the bus. Isn't their a code requirement that tap conductors should have 1/3 ampacity of feeders?
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Yes, unless the tap is shorter than 10 feet and meets a bunch of other restrictions, in which case it could be 1/10. 240.21(B)(1).
And the determiner is the overcurrent protection device on the feeders, not the ampacity of the feeders. In this case there is no OCPD protecting the feeders either! You have an illegal tap feeding another illegal tap.
 
As far as a provision of the code that permits this type of installation, the closest thing I have seen is a "bussed gutter". They used to be fairly common in this area and are addressed in 366.23. If the busbars in the photograph were supplied from the load side of the 800 amp breaker, this would be a simple excercise in the rules for feeder taps.
 
Not a feeder as the tap is before main. Even in 1951 NEC the termination would still require OCPD, six switch, grouped ect;. Any work to be done should be updated to present code. Dangerous situation needs remedied
 
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I appreciate the correction, but I said "IF" the busbars were supplied from the "LOAD" side of the 800 amp circuit breaker, it would be a simple exercise of the tap rules. The original poster asked for the provision of the code that would allow this type of installation. With the conditions stated in my reply, that was as close as I could come. Everbody else had already noted the many obvious code violations shown in the diagram.
 
mwm1752 said:
Not a feeder as the tap is before main. Even in 1951 NEC the termination would still require OCPD, six switch, grouped ect;. Any work to be done should be updated to present code. Dangerous situation needs remedied
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From what we know this is not service equipment - so that makes it either a feeder or a feeder tap, or less likely, a branch circuit.

I think the term "feeder" is correct - it just happens to be an improperly installed feeder, and the smaller conductors are all "feeder taps" - even if improperly installed that is the correct name for them.
 
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