The local power company where I inspect now mandates that commercial services are required to have a unfused disconnect before the meter. I ran into this for the first time today. It was a 200 amp, 480 volt service 3Ph. 4W. Am I correct at assuming this is now the main disconnect and requires the main bonding jumper and all associated grounding to be done at this point? Which now means a 5 wire feeder will now enter building to the main distribution panel which should have a 200 amp overcurrent device and split buss for grounds and neutrals?? Anything I missed? Thanks.
Disconnect before meter
- Thread starter bar714
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RichB
Senior Member
- Location
- Tacoma, Wa
- Occupation
- Electrician/Electrical Inspector
I believe the intent is just a non-fused disconnect so the meter guys can do thier thing without having voltage present on the line. It does not change your grounding/bonding requirements. We just mount a 3 phase switch to the outside of our cabinets or put a breaker in the cabinet that only the POCO can access.
- Location
- Illinois
- Occupation
- retired electrician
I agree with Rich for the most part. The only issue is that most non-fusible switches are only suitable for use on systems with 10,000 amps or less of available fault current. 230.82(3) permits this line side meter disconnect.
K8MHZ
Senior Member
- Occupation
- Electrician
Are the meters rated for more than that?
How would it be safer to pull an energized meter under a load than it would be to operate a switch ahead of it and pull it with no power present?
So, to clarify for me, the disconnect outside before the meter does not get the main bonding jumper and "normal" grounds run to it? The cold water ground and main bond still go to main disconnect inside the building? I believe thats what 230.82 (3) states in the handbook that this disconnect is not the service disconnecting means. Correct? Thanks for everyones input.
Locally, all we do is install a bonding jumper to that disconnect to comply with 250.92. We do not consider it a "service disconnect" as it is usually locked by POCO. All the system bonding is still done at the "actual" service disconnect.
- Location
- Illinois
- Occupation
- retired electrician
I didn't say it was safer to pull the meter, but the code clearly requires that the meter disconnect have a rating suitable for the available current. The locations where the utilities require meter disconnects are often locations where the fault current exceeds 10,000 amps. That would effectively prevent the use of a non-fusible disconnect.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
I disagree with "The locations where the utilities require meter disconnects are often locations where the fault current exceeds 10,000 amps". Not saying it will never happen but let me explain my reasoning here.
Most places where I have seen this disconnect required was for 200 amp or less self contained metering.
200 amp @ 480 three phase = 166.3 kVA. unless supplied by a 500 kVA or larger transformer, the fault current available if the disconnect were installed right at transformer terminals likely would still be below 10kA.
If you have a transformer of 225kVA or larger supplying a single customer chances are it is CT metering and not self contained. If you have a mall or someplace with multiple customers and individual meters all close to transformer is the most likely situation where this may be more of a concern.
Most places where I have seen this disconnect required was for 200 amp or less self contained metering.
200 amp @ 480 three phase = 166.3 kVA. unless supplied by a 500 kVA or larger transformer, the fault current available if the disconnect were installed right at transformer terminals likely would still be below 10kA.
If you have a transformer of 225kVA or larger supplying a single customer chances are it is CT metering and not self contained. If you have a mall or someplace with multiple customers and individual meters all close to transformer is the most likely situation where this may be more of a concern.
The 10k has come under discussion more than once here.
I do see them on 400 amp 480v services.... plus some of the 200 amp services that have them are fed from
large pads which feed multiple service disconnects.
I do see them on 400 amp 480v services.... plus some of the 200 amp services that have them are fed from
large pads which feed multiple service disconnects.
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- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
I didn't think it was a NEC matter until load side of the meter, except a few conditions, ie; overhead clearance to ground.
Does that mean the conductors you install in your riser are not subject to the NEC since they are on the "line" side ??
I do, however, see your point. The fact that it's a POCO "required" switch enters into our 10k discussions, however, the switch is installed by the contractor as well as the conductors and are considered to be regulated by the NEC by local AHJs.
It's currently a "sticky" situation here.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
Does that mean the conductors you install in your riser are not subject to the NEC since they are on the "line" side ??
I do, however, see your point. The fact that it's a POCO "required" switch enters into our 10k discussions, however, the switch is installed by the contractor as well as the conductors and are considered to be regulated by the NEC by local AHJs.
It's currently a "sticky" situation here.
Fine, pull rank on me and use the inspector card.
Actually it was more of a question than a statement and I did say with a few exceptions. I've not had to deal with this, maybe it's a commercial or industrial application as I haven't seen it required on residential installs by the 2 or 3 POCOs I deal with.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Fine, pull rank on me and use the inspector card.
Only times I have seen it are on 480 volt services. POCO's don't want their personell pulling or installing those meters live, yet a 400 amp 240 volt meter with higher avaliable fault current is ok to pull/install live.:happysad:
The other thing is the 480 service is often the only service on the transformer so the transformer could be killed and not affect other customers, but with 240, the transformer often serves other customers and can't be shut down without affecting the other customers.
- Location
- Illinois
- Occupation
- retired electrician
The NEC starts at the service point. The meter is normally on the load side of the service point. In our area the service point for commercial services is the secondary side of the transformer for most services.
- Location
- Illinois
- Occupation
- retired electrician
You have a point there. The disconnect is most often used on meters without CTs so it is on smaller services. Our utility requires the meter disconnect for 480 volt services of less than 201 amps, but they also require that the disconnect be a breaker or a fused disconnect.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
How do you comply with these rules when using a fused disconnect? It is not all that practical to provide user access to overcurrent devices yet prevent access for unmetered conductors in the enclosure. At least not with most typical "Safety Switches".
Most of the time when I run into this it was a transformer that fed a single meter anyway and my thoughts were why can't they just kill the transformer when working on this. We have hundreds of 200 amp or less services feeding irrigation wells around here and the rural power companies do exactly that - kill the transformer when working on almost anything secondary related - including metering.
- Location
- Massachusetts
The metering has little to do with where the 'service point' is located.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
That kind of depends on the POCO.
We have some POCO that for typical service lateral on dwellings or smaller non dwelling services (usually 400 amp and less) they require owner to be responsible for installing (or having their contractor install) raceway and meter socket. They specify raceway size, raceway path, types of fittings, specifications for the meter socket and things like that. They will install the lateral conductors themselves and will not use NEC to size them. They also have in their contracts with the owner that they assume ownership of all this equipment, and will provide maintenance of it in the future.
Where is the service point in this situation? Around here it is the load terminals of the meter even though the contractor installed everything but the conductors all the way to the pad or pole.
I guess that metering still doesn't determine where the service point is, but it is really where POCO determines that their ownership and or maintenance ends.
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K8MHZ
Senior Member
- Occupation
- Electrician
Almost the same here but the HO who owns and is responsible for the mast, weatherhead, flange and the wiring in the mast. The meter and socket is installed by the HO or and EC, but is owned by the POCO. (They supply the materials for free here). Below the meter is owned by the HO.
Where it gets funky is the connection of the wire inside the meter socket. The POCO owns the socket and all that came with it and the HO owns the wire. Who is responsible for a bad connection inside the meter socket? The rules here say I can't remove the meter but I am responsible for the wire. So if there is a bad connection that needs more than a screw tightened, the POCO can't do it. Also, working hot in a meter socket is a no-no, so the power has to be cut. The rules also say that in order for the POCO to re-connect, there has to be a permit and an inspection.
I just went through this with our POCO. I had a bad neutral connection at my house inside the meter socket. When I told the linesmen that came out about it, the politics started to fly. All I wanted was for them to snip me for 5 minutes so I could fix the connection. I had to remove the clamp, brush clean the wire and clamp, ad some noalox and put it back together and I really didn't want to do it hot, but would as I was jeopardizing electrical stuff in my house due to high voltages.
I showed the linesmen my license and told them if they didn't snip me, I was ripping the meter hot and fixing the thing and that was going to happen before I went back into the house.
One linesman looked up at the drop and told his buddy, 'Those connections look bad, we better change them'. He looked at me and asked if I could do what I had to in less than 10 minutes. I said sure, and did the job while they were 'fixing' the bad connectors.
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- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Exactly. We've had to install disconnects ahead of the meter since 1985 and its a disconnect for the POCO so they don't have to replace the meter hot. Our POCO specs state - switch fuse meter but they will allow a non fused switch if the available fault current is less than the AIC of the switch, 10,000 amps typically. The bonus is we have had to use the meter disconnect many times to work on the main disconnect, some of ours overheat due to motor loads, many amps, running 24x7X months.
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