Clear taps.

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K2X

Senior Member
Location
Colorado Springs
I got to help with my first full service to a comercial retail store. yeah!!! But we failed inspection. bummer. The inspector said that the clear taps, (in the gutter), were not rated for the fault current from the transformer. So Monday we are changing the gutter to a bus gutter..... . 400 amp 120/208 service. 2 parallel runs of copper 250's into the gutter tapped into 3 disconnects, then into 3 panels.

My question. All of our journeyman electricians seem to think the clear taps should be ok. The GC does these retail stores all over the country and says they do clear taps all the time with no problems. Should these clear taps be a problem with our local inspectors??

Also what i picked up from different conversations, AIC, and under 10,000 amps kept comming up, I think. Could someone explain AIC.

Thanks for any replies and for all the help in the past.
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
We may both learn something here as I never heard of such a thing as an AIC requirement for clear taps.
AIC ratings are applied to devices that control the circuit such as breakers, fuses and disconnects.
One real good source of information for you may be here:
http://www.bussmann.com/2/SPDTableofContents.html
 
don_resqcapt19

don_resqcapt19

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Staff member
Location
Illinois
Occupation
retired electrician
Taps won't have an AIC rating, but they will have a Short Circuit Current Rating (SCCR) and this rating must be equal to or greater than the available short circuit current at the point where they are installed. There are connections with high SCCR ratings available.
 
J

jim dungar

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Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
110.9 is for fault current interrupting (AIC) ratings of protective devices.
110.10 is for fault withstand (SCCR) ratings of all other equipment, including terminations and conductors.
 
N

nrp3

Member
Location
NH
Very interesting post. I have to replace two parallel runs of 500 AL this spring to an apartment building. One of the neutrals has rotted away in the pipe. I am considering making a splice point outside the building because the electrical room is too small for the reels or a puller. The gutter in there now is too small. How they got all that in there in the first place is beyond me. Some of this is contingent on where the break is in the neutral.
 
mxslick

mxslick

Senior Member
Location
SE Idaho
from the link said:
This category covers power distribution blocks rated 600 V or less and intended to be used on the load side of service equipment.
Click to expand...

I dunno, I can interpret that as meaning if that particular manufacturer's block is intended for load side use only. Does that block fall under this specific category? Is there another category for line-side power distribution blocks?

Power distribution blocks are intended for use in installations covered by ANSI/NFPA 70, "National Electrical Code" (NEC), and installed using the manufacturer's installation instructions.
Click to expand...

What does the manufacturer's instructions and/or markings on the block say?

Power distribution blocks are considered suitable for use on circuits having available fault current not greater than 10,000 rms symmetrical amps, unless marked with a larger value. Power distribution blocks are marked "Short-Circuit Current Rating" together with the value of the rating and the maximum voltage. A power distribution block may additionally be marked to identify an overcurrent protective device (fuse or circuit breaker) to be used ahead of the power distribution block.
Click to expand...

I see this as saying that IF the block has an acceptable short circuit rating and DOES NOT state an overcurrent device rating it should have been ok for the OP's application.

So whether the inspector is right or wrong in this case will depend on the manufacturer's instructions for the taps in question.

A good catch by the inspector though, I don't think most inspectors would have thought about the ratings of a tap other than wire size.
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I knew ILSCO also had a brand of the connectors and I contacted them.
I was a bit suprised at the answer.

The PBTD series do not have SCCR.

If you need something that has it, you might look at the Power Distribution Blocks PDB series.
Their rating is 10,000.

Mary

Mary Slagle
ILSCO CORP.
CSR Southern Region


I am still awaiting a reply from Burndy
 
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O

OTT2

Senior Member
Location
Orygun
So it looks to me that unless the Manufactureres Installations state that their PDB is approved for use in service equipment or service equipment rated
[110.3 (B)] then you are not allowed to use them ahead of a overcurrent device. I've never really thought that this would be the case.

I would guess that most of these PDB's are not service equipment rated!

I agree with mxslick, this is a good catch by the inspector.

I've included a link that does have service equipment rated PDB's with a SCCR
of up to 100,000 amps.

http://www.marathonsp.com/PDFs/135PB flyer.pdf
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
OTT2 said:
So it looks to me that unless the Manufactureres Installations state that their PDB is approved for use in service equipment or service equipment rated
[110.3 (B)] then you are not allowed to use them ahead of a overcurrent device. I've never really thought that this would be the case.

I would guess that most of these PDB's are not service equipment rated!

I agree with mxslick, this is a good catch by the inspector.

I've included a link that does have service equipment rated PDB's with a SCCR
of up to 100,000 amps.

http://www.marathonsp.com/PDFs/135PB flyer.pdf
Click to expand...

Thank you for the link. If I hear back from Burndy I will post that info.

MarkyMarkNC said:
So what would the SCCR rating of a split bolt covered in rubber tape be? Does wire have an SCCR rating?
Click to expand...
When this thread was started, a Chief Electrical Inspector in our area asked the same interesting question.
 
K

K2X

Senior Member
Location
Colorado Springs
Thanks for the replies. We got our bus gutter in. Quite a monster.

Apparantly the problem was the engineer's note on the one line that states
"Equipment shall be series rated at 42,000 AIC minimum"
I guess there was some talk of changing the rating but then they decided to just go with the bus gutter. The boss got an extra/change order on that.

I tried to get the guys to explain "series rated" but I'm really not getting that. Could it be parallel rated??

Also the inspector had us bond the neutral and the ground in the bus gutter in addition to bonding in the disconnects. There was some grumbling about bonding in the bus gutter from the journeymen. ??

Thanks..again.
 
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kwired

kwired

Electron manager
Location
NE Nebraska
K2X said:
Thanks for the replies. We got our bus gutter in. Quite a monster.

Apparantly the problem was the engineer's note on the one line that states
"Equipment shall be series rated at 42,000 AIC minimum"
I guess there was some talk of changing the rating but then they decided to just go with the bus gutter. The boss got an extra/change order on that.

I tried to get the guys to explain "series rated" but I'm really not getting that. Could it be parallel rated??

Also the inspector had us bond the neutral and the ground in the bus gutter in addition to bonding in the disconnects. There was some grumbling about bonding in the bus gutter from the journeymen. ??

Thanks..again.
Click to expand...

It is supposed to be bonded if it is service equipment
 
V

Volta

Senior Member
Location
Columbus, Ohio
K2X said:
Also the inspector had us bond the neutral and the ground in the bus gutter in addition to bonding in the disconnects. There was some grumbling about bonding in the bus gutter from the journeymen. ??

Thanks..again.
Click to expand...

They might have been grumbling because the grounding conductor wasn't needed in the splice box at all, bonding the neutral to the enclusure would have been sufficient. The extra wire was not needed.

kwired said:
It is supposed to be bonded if it is service equipment
Click to expand...

Exactly, for the grounded conductor. The grounding conductors could have been derived in the disconnects though.
 
V

Volta

Senior Member
Location
Columbus, Ohio
buck33k said:
The photo makes me wonder when we can and can not tap the secondary conductors of a transformer.

If a transformer is after the service disconnect we could not tap the secondary conductors in this fashion?
Click to expand...

I don't think so. A set of conductors or each set of conductors is allowed to be connected to the transformer secondary without OCP as specified in the following sub-sections 240.21(C). Not connected to a wire 5 feet away from the secondary, but 'to the secondary'.

And then there is the fact that you cannot supply a tap through a tap 240.21.
 
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