230.72 Grouping of Disconnects

[goldsborough]

I recently failed a job by a contractor. A Service lateral terminates in a non-fused disconnect located about 5 feet from entry. All the grounding and bonding was completed at this non-fused disconnect. The non-fused disconnect then feeds two 4 gang Meter Stacks (OCPD at Each Meter) which brings the total services number to 8 for one building. There are other inspectors saying this is not a violation.

 

[jaggedben]

You described one service.

The violation I see is that relying on the 8 circuit breakers to be the overcurrent protection doesn't seem to meet the requirements in 230.90. Also the unfused disconnect may not be listed for use as service equipment, in which case the 8 meter OCPDs (I'm assuming they're breakers) is too many.

If there were only 6 OCPDs at the meters, or if the main disconnect were fused and suitable for use as service equipment, then there would be no problem.

It is not a problem that grounding is ahead of the meters. Bonding depends on how the rest of the situation would be resolved.

 

[Dennis Alwon]

The installation looks fine to me. As long as the disconnect is suitable as service equipment then I don't see any issues.

 

[jaggedben]

The installation looks fine to me. As long as the disconnect is suitable as service equipment then I don't see any issues.

How do 8 breakers in meter banks comply with 230.90?

 

[wwhitney]

There's a slight hole in the definition of "service conductors."

230.91 specifies that the "service overcurrent device" shall be integral to the "service disconnecting means" or located "immediately adjacent thereto." And the definition of "service equipment" covers both switches and circuit breakers at the service.

However, the definition of "service conductors" specifies "The conductors from the service point to the service disconnecting means." So when the service overcurrent device is not integral to the service disconnecting means, we have conductors from the service disconnecting means to the service overcurrent device, and they are not not technically service conductors.

It's unclear if those conductors are "feeders", as that definition refers to circuit conductors between "service equipment" and the branch circuit OCPD. So if you take that to mean downstream (away from the utility) of all the service equipment, feeders would only start on the load side of the service overcurrent device.

However, they are arguably "service entrance conductors," as that definition does not refer to the "service disconnecting means" but rather to "service equipment."

Anyway, this is clearly a flaw in the definition of "service conductors," which should read "The conductors from the service point to the service equipment."

Cheers, Wayne

 

[wwhitney]

How do 8 breakers in meter banks comply with 230.90?

With the above amendment to the definition of "service conductors," I don't see a 230.90 issue in the OP, you have 8 sets of service conductors, each has an overcurrent device.

But I do see an issue with 230.40, as you have 8 sets of service entrance conductors supplied by one service drop or lateral.

Basically Article 230 is written with an assumption or implicit requirement of a single overcurrent device per service disconnecting means, so attempting to provide 8 overcurrent devices with a single disconnecting means will break some of the requirements. I also question whether the meter centers count as "immediately adjacent thereto" for the purposes of complying with 230.91.

Cheers, Wayne

 

[jaggedben]

Okay...

If the unfused disco is supposed to be the service disconnect, then 230.91's requirement for overcurrent protection that is "an integral part of the service disconnecting means ... or located immediately adjacent thereto" is not fulfilled.

If the unfused disco is not supposed to be the service disconnect, then 8 service disconnects for normal loads violates 230.40 and/or 230.71's limits on the number of service disconnects.

 

[Elect117]

I am with Jaggedben.

You have more than one set of service conductors or a set of unprotected feeder conductors and noncompliance with exception 3 of 230.90. Unless your wires are oversized to the sum of the overcurrent devices. You have 8 OCPD. And most likely have one wire size from the service drop to the disconnect. Another wire size from the disconnects to the meter centers and another wire size tapped off in the meter centers.

 

[David Castor]

Non-fused disconnect switches have maximum short circuit rating of 10kA. If the available fault current is greater than this, it can't be used here. Anyway, I don't see how a non-fused disco can serve as a service disconnect.

 

[Dennis Alwon]

Non-fused disconnect switches have maximum short circuit rating of 10kA. If the available fault current is greater than this, it can't be used here. Anyway, I don't see how a non-fused disco can serve as a service disconnect.

I am confused. Is this not what you are talking about.

About This Product​

Heavy Duty Safety Switches are available in 30-1200A ratings and in Type 1, 3R, 12 and 4X enclosures. Both fusible and non-fusible versions are offered. They can be used on circuits that are rated through 200K when protected by or used with Class R or J fuses. They feature quick make and break operation and visible blade construction.

 

[wwhitney]

I am confused. Is this not what you are talking about.

Yes, note that it says "rated through 200K when protected by or used with Class R or J fuses." So the rating is lower when unfused, and while I haven't verified this, it is frequently commented here that the rating is only 10KA when unfused.

Of course that raises the question of whether you could install an oversized fuse to protected the safety switch against the AFC, but still consider the safety switch to be the disconnect only, with the separate service overcurrent protection located "immediately adjacent thereto".

Cheers, Wayne

 

[jaggedben]

I mean, maybe an unfused disco paired with a separate fuseblock for OCPD was considered normal in the 1930s, but I think nowadays it should be a fused disconnect if it's at the service. And we could further split the hairs on what's strictly allowed, but the OP saying it's an unfused disco calls into question whether the installer knew what they were doing. Certainly without seeing the label and knowing it's intended purpose it's impossible to say it's kosher from here.

 

[Dennis Alwon]

I found this and I know it is only 100 amps but I have seen others that are rated 600 amps non-fused at 200ka

Description

General Electric THN3363J Safety Switch​

The General Electric THN3363J is a 3 Pole safety switch with a current rating of 100 Amps and a voltage rating of 600VAC. It has an interrupting rating of 200kA@600V. The THN3363J has a surface mounting type and it is used for commercial and industrial applications.

 

[wwhitney]

I found this and I know it is only 100 amps but I have seen others that are rated 600 amps non-fused at 200ka

That information is misleading. Per https://electrification.us.abb.com/catalog/buylog/GE Products BuyLog 2019/04_GE Products BuyLog_SafetySwitches.pdf the ratings below apply to the Heavy Duty Type TH switches (excerpted from page 2). You can see that with no upstream fuse, the withstand rating is only 10kA.

Cheers, Wayne

 

[Dennis Alwon]

That information is misleading. Per https://electrification.us.abb.com/catalog/buylog/GE Products BuyLog 2019/04_GE Products BuyLog_SafetySwitches.pdf the ratings below apply to the Heavy Duty Type TH switches (excerpted from page 2). You can see that with no upstream fuse, the withstand rating is only 10kA.

Cheers, Wayne

View attachment 2573728

That is definitely misleading

 

[jaggedben]

That information is misleading. Per https://electrification.us.abb.com/catalog/buylog/GE Products BuyLog 2019/04_GE Products BuyLog_SafetySwitches.pdf the ratings below apply to the Heavy Duty Type TH switches (excerpted from page 2). You can see that with no upstream fuse, the withstand rating is only 10kA.

Notably that info is quite clear that the OCPD be 'upstream', while the standard construction (UL listing requirement, I assume) for fusible disconnects has the fuses downstream of the visible blades, so that the fuse holder components can be de-energized to replace the fuses. Which just cements my experience that the NEC's "located immediately adjacent thereto" language cannot actually be taken advantage of with any equipment listed for use as service equipment nowadays, at least below medium voltage.

 

[wwhitney]

Which just cements my experience that the NEC's "located immediately adjacent thereto" language cannot actually be taken advantage of with any equipment listed for use as service equipment nowadays, at least below medium voltage.

What about the scenario that I alluded to earlier. On, say, a 400A service you put a SUSE fused disconnect with 600A fuses, followed by an "immediately adjacent" SUSE 400A enclosed circuit breaker as the service overcurrent device.

Not sure why you'd do that, maybe the 400A fuses are out of stock or would cause some other problem.

Cheers, Wayne

 

[Elect117]

What about the scenario that I alluded to earlier. On, say, a 400A service you put a SUSE fused disconnect with 600A fuses, followed by an "immediately adjacent" SUSE 400A enclosed circuit breaker as the service overcurrent device.

Not sure why you'd do that, maybe the 400A fuses are out of stock or would cause some other problem.

Cheers, Wayne

I think you would need to fit into an exception for 230.90. So if the wire is sized to 600A, or where it can be rounded up to 600A, then I see no issue. But you have skipped a fuse size so I would call it non compliant with exception 2 without knowing the wire size.

 

[wwhitney]

I think you would need to fit into an exception for 230.90.

Why? I don't see how ignoring the 600A fuses for the purposes of 230.90/230.91 violates any of the text. And then the 400A breaker satisfies 230.90.

Cheers, Wayne

 

[Elect117]

Service conductor stops at the service disconnecting means. That would be your fused disconnect.

Service equipment is defined as having a circuit breaker or disconnect with fuses. That would also be your fused disconnect.

230.90 "Such protection shall be provided by an overcurrent device in series with each ungrounded service conductor that has a rating or setting not higher than the ampacity of the conductor."

Your fused disconnect has a higher rating than the conductor.

It also doesn't meet any of the exceptions.

The conductors after the switch would be a feeder. "All circuit conductors between the service equipment, the source of a separately derived system, or other power supply source and the final branch-circuit overcurrent device. (CMP-10)"