I would just tell them I put an amp meter and used the worst case scenerio
How about both scenarios ?
When should you ask utility if there is enough power available?
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I would just tell them I put an amp meter and used the worst case scenerio
12 month demand will give you the basis for your NEC calc , that covers that, then you can see if you realistically have a problem with the utility transformer size , if you know the Kva.
I’ve gathered a bunch of data and Guidelines from various utilities so I can can guess the size they will select for the purposes of preliminary fault current calculations and planning purposes. One I have shows data they use like percentages of actual usage of design load. Regardless your past the point now and if you get a utility bill and your lucky enough to get good demand numbers then you should have a good idea if they have a problem you should notify them about.
This is the answer ^^
This is good to know
Yea but what about NYC? What’s the kW cutoff to inform utilities?
It’s in ours also.
In all the others I’ve read too.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Only place I work where you need AIC/AFC to pull a permit is projects within the city of Seattle that require plan review. Even then they don't seem to look too close and the reviewer almost always just does a mark up for the field inspector to verify AIC ratings. As far as inspectors, yes I recently had one agree with me that AFC wasn't an issue just by looking at it. I have enough experience to have a pretty good idea when an inspector will be concerned about fault duty, and also to know when I need to do an exact calculation or not. There just isn't a black and white answer, just like the original question in this thread. Do I add load without doing a calc or contacting the power company? Yes all the time. Does that mean I NEVER get demand readings or contact the power company? No.
- Location
- Illinois
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- retired electrician
Since that load is not required to be included in the original calculation, no new calculation is required.
NewtonLaw
Senior Member
- Location
- Honesdale, PA USA
The answer depends. If this is an addition to your existing load and it will be a demand of 15 kVA, I.e., no diversity, then I suggest you let you local utility know of your intentions. Why? In PA and specially in PPL Electric Utility Corp. territory, three tariff rules filed with the PAPUC requires the customer inform them of any load increase. This is so the Utility can address the need for larger transformers and or secondary cables run from pole to pole for both load and voltage considerations. Example of a problem where the customer did not inform the Utility was, the customer replaced a 3 ton heat pump with a 5 ton unit and said nothing to the Utility. The customer experienced voltage drops during start that caused light flicker and general low voltage conditions for him. When he went to the Utility for an upgrade to his service he was told he had to pay for any changes to the transformer size or service conductor replacement since he was required to inform the Utility first, before he made the load addition. The PA Public Utility Commission supported the Utility since it was part of their tariff. It was not cheap. It would have cost him nothing if he had informed the Utility first.
So when is it required and when is it not required? ... Is that a judgement call?
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Those things aren't really what OP was about. They will (should) come up if POCO ends up increasing the transformer size though.
Another C10
Electrical Contractor 1987 - present
- Location
- Southern Cal
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- Electrician NEC 2020
This note here basically sounds like the main will not be upgraded therefore Id say no worries on the load calcs. If you were adding a larger Main Breaker then yes the utilities should be informed normally through the city inspector after approval. that way the utilities can determine if the transformer they provide will still be sufficient.
kwired
Electron manager
- Location
- NE Nebraska
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- EC
Again, many services out there that don't have corresponding POCO transformer to supply the full service capacity, simply because the load isn't there.
I upgraded service in a school building a few years back when they installed new HVAC system. Went to a 1200 amp main @ 208/120. If full 1200 amps were needed the transformer likely would need to be about a 500 kVA. Based on previous demand plus however POCO figured the additional HVAC, they put in a 225 kVA - rated amps is about 625. I had a 600 amp feeder to the HVAC alone, though it was maybe a little oversized but definitely needed to be over 400 amps. The existing building load still on top of that but they figured 225 was what they needed. But for HVAC to draw full rated load it needed to be a really hot summer day, otherwise actual demand was going to be much lower most of the time. But one could easily add another ~600 amps of load to that service and not trip the main, yet the 225 kVA transformer maybe won't handle it so well.
Another C10
Electrical Contractor 1987 - present
- Location
- Southern Cal
- Occupation
- Electrician NEC 2020
In that case I would think the liability would fall on the Utility for not accommodating a designed and approved main switch gear. My argument would be to the utility, hey.. I have the right to utilize 100% of my gears capacity or until it trips, why didn't the utility grid engineers prepare for my maximum consumption.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
No, they don't care about your NEC service size, they generally go off the loads you told them at the initial design. They do sometimes have standards for how much they will "undersize" their equipment. For example, I just talked to Seattle city light about upgrading a 400A high leg (fed open delta) to 600. Service lateral is 500 AL, bank is not that big, maybe 125kva total. They said I could go up to 600 A service and they would not change anything.
For a bank that big we would definitely close the delta, unless the three phase portion happens to be under ~50kVA
Fred B
Senior Member
- Location
- Upstate, NY
- Occupation
- Electrician
I've had when change of occupancy that required rewire and new loads that permitting and POCO wanted loads calculations. Also POCO wanted me to calculate loads and provide to them, then they'll determine whether they will change to meet my new loads on remodels.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
It could well be smaller, maybe a 50 and a 25, probably original to when the building was build in the 80's. Not sure what the original use or loads of the building were.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Many cases, particularly when you go over maybe the 100kVA range, you start to get into demand charges applying and need to be in more closer contact with POCO involving loading anyway. If you suddenly decide to add load without changing your billing agreements you will pay penalties for being over demand that will likely cost you more than had you informed them of the changes.
There is also minimum demand charges, fees you pay whether you use the energy or not, why subscribe for high usage if you are not going to use it? If your load changes then you talk to POCO about new minimum demand charge to better suit your load and they can at that time decide if they need to upgrade anything as well.
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