Derate Main Breaker for PV connection

I

ING23

Member
Location
Las Vegas
Occupation
Site Survey Tech
I just failed an inspection because the inspector did not see the Amps on my label
here is the label ,
(Some context PV system needed to de-rate main breaker in order to comply with 120% rule. Load calc allow it )
The new main breaker has the amps , the panel label has the Amps of the old Breaker .It is necessary to write down on the label ........" we de-rate from ___ Amps to _____ Amps?Derated Labels.jpeg
 
This isn't in the code at all so your inspector is just really making it up. Ok it's sort of reasonable to require a label but I think specifying the amps is going too far. The guy who comes afterward has been warned to do his due diligence, that's what matters.

Good luck.
 
Been downsizing main breakers for 20 years.
Never had to specify the amps on a label on the panel.


Your label is useful to inform future electricians......and I will order some myself.

Maybe you didnt specify the 175 Amps of the new breaker on your PLANS?
 
jaggedben said:
This isn't in the code at all so your inspector is just really making it up. Ok it's sort of reasonable to require a label but I think specifying the amps is going too far. The guy who comes afterward has been warned to do his due diligence, that's what matters.

Good luck.
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Agreed but only in reality if only ones doing any electrical work is fully qualified, this is not the case at all in upstate NY. Can't even find qualified cross trades that are engineering Geo systems don't or can't calculate the electrical loads related to the various motor and compressors for such installations. Even PV installers don't seem to know or understand aspects of the code requirements or restrictions. So to expect the layperson acting as an "unqualified electrician" to even understand the implication let alone calculate such limits is never going to happen, so yes lets label, not to "allow" for the "unqualified" but for own piece of mind or to CYB from "Winnebago" suits. This is why a toaster has a 50 page manual that will actually go as far as stating "Do Not Use Near or In a Shower or Tub".
 
Who said anything about unqualified laypersons? There's no accounting for people who don't even know there are rules.

Also what is hard to understand about "Don't upsize main breaker." Whatever you find it at, don't upsize it.
 
jaggedben said:
Who said anything about unqualified laypersons? There's no accounting for people who don't even know there are rules.

Also what is hard to understand about "Don't upsize main breaker." Whatever you find it at, don't upsize it.
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Not suggesting anything related to your work at all, but around my area that is like 80% of the work being done, including "Specialties". Not suggesting marking or labeling needs to be "in the rules" but I think it wouldn't hurt as majority of these "unqualified" here if there is a label don't know enough to think about making a change away from the warning limit. Just like they see a 20A breaker and just think they need a 12 wire or visa versa, this sometimes can bite them.
 
This question is not addressing the labeling requirement, but I was wondering if when someone derates a service like this do they explain the problems this may cause the owner in the future? The service is now 175A, so if the owner wants that new electric stove, EV charger, or heat pump water heater in the future the electrician will open this panel and may need to tell the owner too bad so sad but when the PV was installed they took away a good chunk of your available service capacity and now you can't add those things you want. I know if this happened to me on my house I would be an unhappy camper if I was not consulted about what it means to me to lose that capacity.
 
pv_n00b said:
This question is not addressing the labeling requirement, but I was wondering if when someone derates a service like this do they explain the problems this may cause the owner in the future? The service is now 175A, so if the owner wants that new electric stove, EV charger, or heat pump water heater in the future the electrician will open this panel and may need to tell the owner too bad so sad but when the PV was installed they took away a good chunk of your available service capacity and now you can't add those things you want. I know if this happened to me on my house I would be an unhappy camper if I was not consulted about what it means to me to lose that capacity.
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When I was designing resi PV systems we sometimes downsized main breakers from 200A to 175A or 175A to 150A to allow for 705.12 connectability as long as there were no obvious large loads that would suck up a lot of capacity. The only downside would have been nuisance trips of the main breaker, and I don't know of any cases of that on services we worked on.
 
pv_n00b said:
This question is not addressing the labeling requirement, but I was wondering if when someone derates a service like this do they explain the problems this may cause the owner in the future? The service is now 175A, so if the owner wants that new electric stove, EV charger, or heat pump water heater in the future the electrician will open this panel and may need to tell the owner too bad so sad but when the PV was installed they took away a good chunk of your available service capacity and now you can't add those things you want. I know if this happened to me on my house I would be an unhappy camper if I was not consulted about what it means to me to lose that capacity.
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Yes, we explain that it might be an issue in the future. Likely not for a while.
AND we just saved them $5-7k on a service upgrade. And made PV possible.
Although.... if they are even thinking of a service upgrade for other reasons (EV, or EVs, hot tub, all electric home renovation etc) i recommend doing it now as we can get them 30% off as we include it as part of the solar.
 
Zee said:
Yes, we explain that it might be an issue in the future. Likely not for a while.
AND we just saved them $5-7k on a service upgrade. And made PV possible.
Although.... if they are even thinking of a service upgrade for other reasons (EV, or EVs, hot tub, all electric home renovation etc) i recommend doing it now as we can get them 30% off as we include it as part of the solar.
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We would sometimes have customers who wanted solar now and who said that they would add batteries "later". We let them know that they would likely be paying a whole lot more for the battery upgrade "later" than they would for batteries as part of the initial project.
 
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pv_n00b said:
This question is not addressing the labeling requirement, but I was wondering if when someone derates a service like this do they explain the problems this may cause the owner in the future? The service is now 175A, so if the owner wants that new electric stove, EV charger, or heat pump water heater in the future the electrician will open this panel and may need to tell the owner too bad so sad but when the PV was installed they took away a good chunk of your available service capacity and now you can't add those things you want. I know if this happened to me on my house I would be an unhappy camper if I was not consulted about what it means to me to lose that capacity.
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Yes, we do explain. When necessary I will do a load calc with and without the potential new load and email the numbers. It's usually well under 100A without additional load and under 125A with additional load. 175A is 42kW and when you point that out to savier customers they usually realize they don't ever need that much; no normal home ever needs that much. Moreover often I have metering data from the utility or our system or both showing that the actual max draw is way under the NEC load calc. I've seen all electric 2000sq ft homes that never exceed 20kw over a 15min interval. Which is to say that for most normal homes anything over a 100A service is extra cushion, at least in my area. So, downsizing 200A service breakers to 175 or even 150 is essentially never a real issue. The ones that were a bit more borderline were 125 to 100A.

That all said, thank goodness for Enphase busbar control PCS. I hope I never have to downsize a main breaker again.
 
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