UTILITY NIGHTMARE

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PE (done with training)

Senior Member
Location
Saint Louis
Occupation
Professional Engineer
I'm not sure where to begin on this story, this is a lot of information so bear with me and please let me know your thoughts.

8 months ago I started work on a pet hospital addition. The project involved reworking the main electrical service on the building. Electrical one-line attached for reference.

Before redesign, we meet with the utility contacts to establish what the new service will look like and eventually send a load sheet with our new loads shown (pretty standard for most utilities). For this project I followed the same procedure and sent the utility contact the new design as well as the entire electrical drawing set for reference.

Well 8 months later, after the install and after the utility contact even approved the design (also AHJ approved design as well), I get an email from the contractor saying that the utility came back saying the service is not in compliance with their standards.

For reference, our design involved a 120/240V single phase service with a 600 amp CT cabinet that then fed over to a wireway with fusible disconnects. On the wireway we had three disconnects, one 300 amp switch, one 400 amp switch, and one 200 amp switch. The main service feeder was sized for the demand load which was about 500 amps.

Below is the exact message that I received from the utility:

"Our concern is with the utility service manual which states that single phase 120V/240V services are limited to 800A maximum. You have 900A worth of disconnects, though current is much less, it still poses a risk that your load could one day exceed our rated maximum."

This design is seen everywhere and I'm not sure how the utility can ignore our NEC demand load calculations, but they seem to be making up rules on the fly...

Again, this design is NEC compliant per the code sections listed below:

Per NEC section 230.71 (Maximum Number of Disconnects)
There shall be not more than six sets of disconnects per service grouped in any location. We provided three disconnect switches.

Per NEC section 230.80 (Combined Rating of Disconnects)
This section says, "It is possible for the total of the six overcurrent devices to be greater than the rating of the service-entrance conductors. However, the size of the service entrance conductors is required to be adequate for the computed load only, and each individual service disconnecting means is required to be large enough for the individual load it supplies. See the commentary following 230.90(A), exception No. 3.

Per NEC section 230.90(A) exception No. 3

Two to six circuit breakers or sets of fuses shall be permitted as the overcurrent device to provide the over-load protection. The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors, provided the calculated load does not exceed the ampacity of the service conductors.

One final point, but the feeder from the utility transformer secondary to the service entrance is customer provided so I'm not sure why they are so concerned with our feeders.

I've worked with this utility hundreds of times and this is the first time I've ever dealt with a problem like this. Should I give up trying to argue my point with the utility even though I literally sent my utility contact all the info 8 months ago which he approved at one point. I'm at a loss on this one
 

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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Given that the total calculated load is 500A, I presume that the calculated load on each section (400A, 300A, 200A) is lower then the disconnect rating for that section.

This suggests that there is a path for complying with the utility in their assessment, no matter how asinine.

I'd suggest a 'nice' note stating compliance with NEC and good industry practice, exactly what you laid out in your post. Add to the note the utility prior approval. Then very nicely add that you would be very happy to do your part to help correct their error for a reasonable price. Could they confirm that they really made an error with the prior approval?

Jon
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I don't think it makes much difference what the national electrical code says. The reality is the utility gets to decide whether or not you're in compliance with their rules. I don't see any simple solution to your problem that does not involve the utility granting you a waiver. And probably they are not going to want to give you a waiver.

Is there some way that you can change the three disconnects into 200 amp disconnects? Would your load calculations for the downstream panel boards support doing that?

Would they accept you putting a 600 amp fused disconnect downstream of the CT cabinet?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Smile, say "my mkistake" and reduce your fuse size accordingly to match thier 800 amp max. :)
 
I have had some minor difficulties in the past when not using a single disconnect. I have also run into the issue Opie has when there is a limit to the service size and the multiple service disconnects exceed that value. In the end I have always gotten these connected, usually with just a little explanation or just hoping no one noticed which they didn't.
 
In WA we have a state code rule that requires an engraved label for a case like this. I will try and post the language

042 Service conductor - Size and rating.
(6) For other than one- or two-family dwelling services rated up to 400 amperes, if the service conductors have a lesser ampacity than the overcurrent protection, permitted by NEC 230.90 or NEC 310.15, or the equipment rating that they terminate in or on, an identification plate showing the ampacity of the conductors stating: "Service conductor ampacity: _____" must be installed on the service equipment
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
Smile, say "my mkistake" and reduce your fuse size accordingly to match thier 800 amp max. :)

Could also say there will be a note inside the disconect that the reduced fuse size is the maximum to be used. This assumes that the reduced fuse size will be adequate for the loads.
 

PE (done with training)

Senior Member
Location
Saint Louis
Occupation
Professional Engineer
I let my anger get the best of me and argued with the utility. My blood was boiling, it was a bad mistake that is now costing me.

I showed them my design 8 months ago and they had everything in their hands. Now after the install, after the AHJ approved everything, and after the utility even approved everything, they change the rules on me for no apparent reason.

I have no choice but to comply and redesign accordingly as I'm at the mercy of the one that controls the power....
 
I let my anger get the best of me and argued with the utility. My blood was boiling, it was a bad mistake that is now costing me.

I showed them my design 8 months ago and they had everything in their hands. Now after the install, after the AHJ approved everything, and after the utility even approved everything, they change the rules on me for no apparent reason.

I have no choice but to comply and redesign accordingly as I'm at the mercy of the one that controls the power....
Can you just change the fuses to 200s and then swap them back when the utility planner field engineer guy whatever is done with the project? I'll be honest, I will cheat utility rules sometime if it's something stupid. In my experience the field planner might come by to approve everything, and then then that's the last you'll see of him. The line crew will show up and they usually won't care about something silly the planner came up with.
 

WA_Sparky

Electrical Engineer
Location
Vancouver, WA, Clark
Occupation
Electrical Engineer
I don't think it makes much difference what the national electrical code says. The reality is the utility gets to decide whether or not you're in compliance with their rules. I don't see any simple solution to your problem that does not involve the utility granting you a waiver. And probably they are not going to want to give you a waiver.

Is there some way that you can change the three disconnects into 200 amp disconnects? Would your load calculations for the downstream panel boards support doing that?

Would they accept you putting a 600 amp fused disconnect downstream of the CT cabinet?
Thats what i would do. Install a 600A disconnect between 600A wireway and 600A CT. Problem solved.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
How timely this post is for me as I just went through this with our city owned POCO. I proposed using 3, 150 amp service disconnects with a 320/400 direct meter socket. Calculated load was 250 amps. They claimed this violated their service standards and the NEC. I informed them that this was absolutely not an NEC violation and has been code compliant for many decades. The POCO, as it is city owned, called their counterparts at the city building department who confirmed that I was correct but they still refused to approve it anyway citing their service rules.
In all my years dealing with many POCOs I have never seen this. Since this is for my own house and I have lots of time, I told them that we may be going to the mat over this as I have a habit of not rolling over for things like this. I heard through the grapevine that I really stirred the pot and it is being discussed.
 

PE (done with training)

Senior Member
Location
Saint Louis
Occupation
Professional Engineer
How timely this post is for me as I just went through this with our city owned POCO. I proposed using 3, 150 amp service disconnects with a 320/400 direct meter socket. Calculated load was 250 amps. They claimed this violated their service standards and the NEC. I informed them that this was absolutely not an NEC violation and has been code compliant for many decades. The POCO, as it is city owned, called their counterparts at the city building department who confirmed that I was correct but they still refused to approve it anyway citing their service rules.
In all my years dealing with many POCOs I have never seen this. Since this is for my own house and I have lots of time, I told them that we may be going to the mat over this as I have a habit of not rolling over for things like this. I heard through the grapevine that I really stirred the pot and it is being discussed.
I'm sorry to hear you are going through the same issues. Since when are NEC demand loads not taken into factor. I hate that the utilities can just change the game up without any notification or responsibility...
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
I'm sorry to hear you are going through the same issues. Since when are NEC demand loads not taken into factor. I hate that the utilities can just change the game up without any notification or responsibility...
The fact that their service requirements handbook does not indicate that you must terminate in single OCPD rated for the service conductors or the sum total of the multiple disconnects was also an issue that I pointed out in my case. As I said previously, I'm not sure yet how far I'm going to take this. To me it's the principal.
 

Fishbrain

Member
Location
Continental US
Occupation
EC/EE
The fact that their service requirements handbook does not indicate that you must terminate in single OCPD rated for the service conductors or the sum total of the multiple disconnects was also an issue that I pointed

out in my case. As I said previously, I'm not sure yet how far I'm going to take this. To me it's the principal.
PRINCIPLE or PRINCIPAL?

Must be nice owning a sizable share of POCO.
Just like MUSK owning Twitter.
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
For reference, our design involved a 120/240V single phase service with a 600 amp CT cabinet that then fed over to a wireway with fusible disconnects. On the wireway we had three disconnects, one 300 amp switch, one 400 amp switch, and one 200 amp switch. The main service feeder was sized for the demand load which was about 500 amps.

Below is the exact message that I received from the utility:

"Our concern is with the utility service manual which states that single phase 120V/240V services are limited to 800A maximum. You have 900A worth of disconnects, though current is much less, it still poses a risk that your load could one day exceed our rated maximum."

This design is seen everywhere and I'm not sure how the utility can ignore our NEC demand load calculations, but they seem to be making up rules on the fly...
That’s probably the most asinine statement I’ve read from a utility, and I’ve read plenty of them..
So a 200 amp main with 400 amps worth of breakers behind it is violation?
what size transformer are they feeding this service with??
Its probably going to be smaller than “calculations” so is the wire feeding your service.
A 100kVA won’t do 600A @100% loading. A 167.5 is over 600 amps.

quite simply, the EASIEST thing to do physically would be to have the utility fuse the XF on the primary side to limit secondary current to 600A.
Convincing the utility may be another issue…
 

Todd0x1

Senior Member
Location
CA
That’s probably the most asinine statement I’ve read from a utility, and I’ve read plenty of them..
So a 200 amp main with 400 amps worth of breakers behind it is violation?
what size transformer are they feeding this service with??
Its probably going to be smaller than “calculations” so is the wire feeding your service.
A 100kVA won’t do 600A @100% loading. A 167.5 is over 600 amps.

quite simply, the EASIEST thing to do physically would be to have the utility fuse the XF on the primary side to limit secondary current to 600A.
Convincing the utility may be another issue…
I interpret this mess as when there is no main disconnect the utility adds up the size of the disconnects to determine the service size. I don't feel like theyre wrong. Your 200 amp main with 400 amps of breakers behind it example is different because you have the one 200 amp main making it a 200 amp service. Service size is determined my main ocpd no?
 
I interpret this mess as when there is no main disconnect the utility adds up the size of the disconnects to determine the service size. I don't feel like theyre wrong. Your 200 amp main with 400 amps of breakers behind it example is different because you have the one 200 amp main making it a 200 amp service. Service size is determined my main ocpd no?
I don't think there is a specific definition of or process to compute service size in the NEC. Where there are multiple service disconnects I always take the service size to be the ampacity of the service entrance conductors. Once I did a 2-200A service with two sets of 250 AL in a common riser, so 368 amps of conductor. This area had a plan review requirements for equipment including and over 400 amps. I figured it didn't need plan review so I just got an over the counter permit, but they kicked it back to me said it needed plan review. So yeah the multiple disconnect thing can be a little tricky without very specific definitions.
 
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