National Grid AIC Ratings (Solar Line Side Tap)

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mkenney

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Syracuse, NY
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Solar Engineer
I'm trying to figure out how to determine the minimum AIC rating needed for a line side tap disconnect for a National Grid (NY) account. For all of our residential solar project that require a line side tap, we use a 2P, 60A, 240V, 22kAIC rated circuit breaker and have had no issues from inspectors on this. Recently, we had a NYSERDA inspection and they noticed that the main breaker of the homeowner's main panel was a 200A, 25kAIC rated breaker (Eaton BWH 200A, 25kAIC). Therefore they failed our inspection because our AC disconnect AIC rating didn't match that of the main panel's breaker. We are trying to contest this inspection but need to have something from National Grid stating what that AIC rating needs to be.

Does anyone know how to get this rating or calculation from National Grid? I have called several times, spoken with half a dozen different people, have emailed the distributed generation email, and left multiple questions and comments within the National Grid portal. I have either not gotten a response back or the person has never heard of an AIC rating.
 
That is lame. I expect more from NYSERDA. You could explain the CH load centers have 25kaic standard, which although is a bit higher than most other brands which are 22k, it's just the way Eaton is, highly unlikely they used 25k because they specifically needed the 25. Can you see the serving transformer and do you know how big it is? Unless it's a big transformer serving several places, there's no way the typical 25kVA will be anywhere near 22ka ( i can send you a data plate photo of grids typical 25KVA pole pig). You could try talking to Frank Mace at NYSERDA he should know all this.
 
electrofelon said:
That is lame. I expect more from NYSERDA. You could explain the CH load centers have 25kaic standard, which although is a bit higher than most other brands which are 22k, it's just the way Eaton is, highly unlikely they used 25k because they specifically needed the 25. Can you see the serving transformer and do you know how big it is? Unless it's a big transformer serving several places, there's no way the typical 25kVA will be anywhere near 22ka ( i can send you a data plate photo of grids typical 25KVA pole pig). You could try talking to Frank Mace at NYSERDA he should know all this.
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Frank Mace is the one that has rejected our contest on this issue. He says he needs something from the utility to prove the 22k is sufficient. I do know the transformer #, substation, and feeder name but I can't find any information on what size that transformer is, just the name and location.
 
mkenney said:
Frank Mace is the one that has rejected our contest on this issue. He says he needs something from the utility to prove the 22k is sufficient. I do know the transformer #, substation, and feeder name but I can't find any information on what size that transformer is, just the name and location.
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So you don't know where the serving transformer is? Is this an underground system?
 
Within the National Grid distributed generation portal, for this project it has the following listed for Power Supply Area:
Substation 1 - Harris Rd 235
Substation Transformer 1 - Harris Rd 235, Substation Transformer 2
Feeder 1 - 36_11_23551

I haven't been able to find any details about this transformer or feeder though
 
electrofelon said:
Might be worth $50 for a 42kaic breaker rather than a fight .....

www.pacificcoastbreaker.com

BRHH260 Cutler Hammer - New Circuit Breaker

120/240V42kAIC@240VPlug-In1 PhaseLong Time and Instantaneous Trip FunctionsThermal MagneticVery High Interrupting CapacityCurrent Model EATON Circuit BreakersResidential, Commercial, Industrial
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Thanks for you feedback and the link electrofelon. We might have to end up doing this, but we're really hoping we could get an answer from National Grid. NSYERDA is giving us a 2 out of 5 for this inspection because of this rating and even if we do correct this, our score won't improve.
 
mkenney said:
Within the National Grid distributed generation portal, for this project it has the following listed for Power Supply Area:
Substation 1 - Harris Rd 235
Substation Transformer 1 - Harris Rd 235, Substation Transformer 2
Feeder 1 - 36_11_23551

I haven't been able to find any details about this transformer or feeder though
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You don't care about the substation transformer, you want the transformer serving the customer. Do you not know where it is located?
 
mkenney said:
I have either not gotten a response back or the person has never heard of an AIC rating.
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You need to ask for the available short circuit current, often called SCA.
You then select protective devices with an AIC greater then the available SCA.

Some utilities will simply provide a minimum recommended AIC instead of a the available SCA.
 
mkenney said:
Does anyone know how to get this rating or calculation from National Grid? I have called several times, spoken with half a dozen different people, have emailed the distributed generation email, and left multiple questions and comments within the National Grid portal. I have either not gotten a response back or the person has never heard of an AIC rating.
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Ask for available fault current at the service point, or point of common coupling. If you can't get that, ask for the service transformer's KVA and impedance percentage. If it is labeled well enough, where you can see it, you may be able to see some of this information on the unit itself. The upper limit of available fault current, not accounting for on-site sources such as motor contribution, can be calculated from KVA and impedance. The short answer is that it is amps associated with kVA divided by impedance as a decimal.
 
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