Connections in a CT cabinet.

Status
Not open for further replies.
M

marl2009

Member
Location
Iowa City,Iowa USA
I have a contractor wanting to tap out of the 800 amp CT cabinet with two 400 amp disconnects.
I'm not convinced you can do that if the utilities install a padlock on the CT cabinet door.
I would call that non-accessible. I believe taps and splices are required to be in a box that are accessible.
His taps will come off the load side of the meter, with listed lugs to match the qty. of wires
Is the contractor right in tapping off the CT Cabinet. Or is it a violation of the 2014 code
 
marl2009 said:
I have a contractor wanting to tap out of the 800 amp CT cabinet with two 400 amp disconnects.
I'm not convinced you can do that if the utilities install a padlock on the CT cabinet door.
I would call that non-accessible. I believe taps and splices are required to be in a box that are accessible.
His taps will come off the load side of the meter, with listed lugs to match the qty. of wires
Is the contractor right in tapping off the CT Cabinet. Or is it a violation of the 2014 code
Click to expand...

How would you ever use a CT cabinet if what you suggest is true?
 
marl2009 said:
That's my question...should one require a tap box after the CT cabinet or dump the paralleled wiring into a MLO panelboard with no more than six disconnecting means.
Click to expand...

I don't see any difference, the conductors supplying the splice box have the same rules as the conductors supplying disconnects.

By the way, none of what we are discussing are 'taps' they are simply service conductors.
 
marl2009 said:
I have a contractor wanting to tap out of the 800 amp CT cabinet with two 400 amp disconnects.
I'm not convinced you can do that if the utilities install a padlock on the CT cabinet door.
I would call that non-accessible. I believe taps and splices are required to be in a box that are accessible.
His taps will come off the load side of the meter, with listed lugs to match the qty. of wires
Is the contractor right in tapping off the CT Cabinet. Or is it a violation of the 2014 code
Click to expand...

Although many of the member's on this forum will have excellent insight and offer valuable advice; the fact remains each utility company has their own set of standards and requirements. I would consult them first on what they will allow or not allow.
 
marl2009 said:
Service point is at the transformer, Although the utilities want control of the CT's
Click to expand...

Huh???? Service point as I understand it is at the service disconnect. Of course the utility wants to control the CT section. It's the cash register. There is more than one way to "steal" power if the user has access to the CT's. Not to mention the available fault current ahead of any OCD's the customer supplies. I won't go into details, but the locks and seals are there for a reason. Any taps after the CT's and ahead of the service disconnect are very likely limited by the utility. After the service disconnect, the POCO is out of the loop and the AHJ takes over. Transformer is just part of the service, as is the primary, cutouts, service drop, etc. At least, that's the real world I live in.

Any taps after the CT's will not affect the CT metering, but there would still have to be service disconnects on each tap. The CT's would connect to a master meter and any taps would have to be sub-metered to differentiate load. Many, if not all, utilities do not want to get involved in "sub-metering". Definitely....check with the utility before you spend any money!
 
Last edited:
kingpb said:
Although many of the member's on this forum will have excellent insight and offer valuable advice; the fact remains each utility company has their own set of standards and requirements. I would consult them first on what they will allow or not allow.
Click to expand...

Talk about a gray area...utilities are going to put a padlock on the door of the CT cabinet. Definition of "accessible" is no locked doors.
230.33 Service conductors shall be permitted to be spliced or tapped in accordance with 110.14,300.5(E) AND 300.15
230.40 Exception 2 excepts 2- 6 service disconnecting means.

I'm just trying to find out how other electricians have approached the lock door when installing service entrance conductors (paralleled) off of a CT terminal(s) to feed 2-400 amp disconnects.
Or should I just accept it (locked door) and move on.
Thanks for your time.
 
marl2009 said:
Talk about a gray area...utilities are going to put a padlock on the door of the CT cabinet. Definition of "accessible" is no locked doors.
230.33 Service conductors shall be permitted to be spliced or tapped in accordance with 110.14,300.5(E) AND 300.15
230.40 Exception 2 excepts 2- 6 service disconnecting means.

I'm just trying to find out how other electricians have approached the lock door when installing service entrance conductors (paralleled) off of a CT terminal(s) to feed 2-400 amp disconnects.
Or should I just accept it (locked door) and move on.
Thanks for your time.
Click to expand...

You would not normally see a CT section ahead of taps and before the service disconnects. You'd have the taps, then a meter on each tap, then the service disconnects. If you want to have several smaller taps off of a larger CT service, they would normally be after the main service disconnect. If you're retrofitting an existing installation, check with the utility and save yourself some headaches later on. They may want you to bypass the CT metering and provide individual meters. We have some older installations where there is a master CT meter and downstream 100A sub-meters, because a hotel was converted into multiple ski condos. We actually subtract the sub-metering from the master and the difference is the "house" load. Major pain in the #$%@!
 
meternerd said:
Huh???? Service point as I understand it is at the service disconnect.
Click to expand...

Nope. There are two transitions to locate.

The first (usually) is the service point. That is a contractually agreed upon point where the POCO service conductors end and the customer's service conductors begin.
Upstream of that point the safety rules are entirely those adopted by that POCO, usually based on the NESC.
Downstream of that point the safety rules are entirely those of the NEC, although POCO may still impose additional conditions before they will provide service.

The second is the point where the service conductors end and the branch and feeder wiring begins. That is, by Code, the first disconnect with OCPD on the customer side of the service point. POCO protection on their transformer primary or secondary is not considered to be protecting the service conductors. At best it will protect the transformer. This is one reason that the NEC puts limits on how far service conductors can run within a building.
 
meternerd said:
You would not normally see a CT section ahead of taps and before the service disconnects. You'd have the taps, then a meter on each tap, then the service disconnects. If you want to have several smaller taps off of a larger CT service, they would normally be after the main service disconnect. If you're retrofitting an existing installation, check with the utility and save yourself some headaches later on. They may want you to bypass the CT metering and provide individual meters. We have some older installations where there is a master CT meter and downstream 100A sub-meters, because a hotel was converted into multiple ski condos. We actually subtract the sub-metering from the master and the difference is the "house" load. Major pain in the #$%@!
Click to expand...

Sorry, it wouldn't let me edit my reply....If you want to use one CT metering setup for multiple loads, you could tap ahead of the MSD in the CT cabinet, but it would still be sealed or locked, and anything ahead of the individual service disconnects (up to six grouped) would be sealed and under the jurisdiction of the utility. More than six, you'd install one service disconnect, but it would be sealed by the utility. Utilities are pretty picky about access to metering equipment, for obvious reasons.
 
GoldDigger said:
Nope. There are two transitions to locate.

The first (usually) is the service point. That is a contractually agreed upon point where the POCO service conductors end and the customer's service conductors begin.
Upstream of that point the safety rules are entirely those adopted by that POCO, usually based on the NESC.
Downstream of that point the safety rules are entirely those of the NEC, although POCO may still impose additional conditions before they will provide service.

The second is the point where the service conductors end and the branch and feeder wiring begins. That is, by Code, the first disconnect with OCPD on the customer side of the service point. POCO protection on their transformer primary or secondary is not considered to be protecting the service conductors. At best it will protect the transformer. This is one reason that the NEC puts limits on how far service conductors can run within a building.
Click to expand...

So, you're saying that as a utility, we supply the service drop wires and connect to the customer's service wiring, so we stop at the weatherhead? Nope...we seal the meter section and any associated wiring that is not past the meter. It's considered "unmetered" and we restrict access and do not allow customer wiring to "pass through or terminate in" any section containing unmetered conductors. Simple...right?:lol: That's why I never claimed to be a Code expert.

Maybe we're just talking definitions, but to me as a POCO guy, the service is anything ahead of the meter (or metering equipment). That's why it's sealed. I agree that any protection ahead of the service disconnect is for protection of the transformer, not the service. Code also does not apply to the meter manufacturer wiring, since bend radius, conductor size, clearances, etc. are under the jurisdiction of other agencies. Even though the customer may supply and wire the service equipment, it still seems to be "service" and our responsibility.
 
Last edited:
You are certainly free to think of the boundary between POCO and building wiring in any way you want.

And my point is that each POCO is free to define the service point any way they want to apply to any particular type of service (OH, UG, etc.)

But the NEC determines the boundary of its scope on the service side by the formal service point that the particular POCO in question defines.
And again, by virtue of its commercial right to deliver or not deliver power, POCO is able to force particular wiring arrangements even past the service point, thus muddying the waters considerably.

One example is the fact that some POCOs will allow a line side connection of a PV system to the service, downstream of the meter but upstream of the main disconnect, while others will not.
The line side connection is permitted by the NEC and the safety parameters associated with it are well defined. But the POCO can still reject it, even without having to move its service point definition to the downstream side of the service disconnect.
 
Kinda off the subject, but a good example. Manufacturers are desperately trying to sort out that very question. Should they build meter panels with a PV breaker ahead of the Main and avoid the 80% rule, or build it with a designated PV breaker at the end of the bus, rated appropriately. Hope those who come after me (being retired and all:D) can get it sorted out, because consistency usually leads to cost savings.
 
iwire said:
That depends on the utility, most of the utilities near me require cold sequence metering on services over 250 to ground.
Click to expand...

Really....most here on the left coast don't allow cold sequence because doing a disconnect by locking off the main (which is pretty convenient when you have multiple meters off of one service) would kill power to the the Smart Meter and produce a read failure. Even disconnected services are still read each month to insure there's no usage (power theft). Plus, the service disconnect being ahead of the metering would require the breaker wiring to be inaccessible to the customer, since it contains unmetered conductors, and would have to be sealed. I can see why they don't like >250V at the meter, but when working metering, it's pretty common to kill it at the transformer anyway before working it. I have seen the aftermath of 277/480 metering faults and they ain't pretty. Maybe your way is better.
 
Last edited:
meternerd said:
Really....
Click to expand...

Really. :)


Plus, the service disconnect being ahead of the metering would require the breaker to be inaccessible to the customer, since it contains unmetered conductors. .
Click to expand...

Typically they don't seal the disconnect.

I can see why they don't like >250V at the meter, but when working metering, it's pretty common to kill it at the transformer anyway before working it.
Click to expand...

Here it is rare to see them kill the transformer.
 
No seal, huh. Must have honest folks where you are. Power theft is becoming epidemic here. Lots of folks secretly advertising on the web their services when you need to "modify" your service for big savings. Working metering hot is sometimes a necessity, but with the fact that clearances are small, lighting is terrible and being ahead of the main means huge fault arcs, we prefer de-energized and a 40 cal flash suit if we have to to live line testing. Guess it's just what you get used to.
 
Status
Not open for further replies.
Top