Grid-tie PV system

Status
Not open for further replies.
C

ccjking

Member
As a DIY guy I need some electrical code advice.

I am installing a grid-tie PV array for my house. I got everything installed and flunked my final electrical inspection due to an issue with my tie-in to the main breaker panel.

I have a 150 amp main panel, but if you add up all the breaker values in the box the total is about 680. This was pretty much the original configuration as I haven't really added any breakers since I bought the house many years ago. The inspector said that probably would be OK if you can show that not all the loads are being used simultaneously, but when you add a circuit for PV then this no longer applies. He?s saying that with the PV I now need a service panel rated so that my total breakers don?t add up to more than 120% which in this case would be a 560 amp panel. He?s saying there?s no other way around it. This doesn?t sound right to me.

I don?t think you can even get a residential panel for that much current can you? The most I?ve seen is usually about 250, so I?m thinking this guy must be wrong or else nobody would be able to get PV installed.

Can anyone clarify this for me. Thanks
 
Per forum rules we can not help tell you how to do your own wiring. Considering you have an inspector looking at your work we can comment on the codes.

The inspector is correct, check out 690.64(B) of the 2008 NEC.
 
I may have misspoke or you may have misunderstood what the inspector was saying.

The total of only the main breaker and the breaker for PV can not be more then 120% of the panels bus bar rating.

The branch circuit breakers do not figure into this at all.
 
Grid-Tie PV System

Grid-Tie PV System

The main breaker consists of two 50 amp breakers. The PV breaker is 20amp. That doesn't add up to 120% of the 150amp panel rating so I guess you are agreeing that he is mistaken?
 
ccjking said:
The main breaker consists of two 50 amp breakers.
Click to expand...

That does not make any sense to me at all.


The basic premise here is your supplying one set of bus bars from two sources, the utility and the PV system. The amount of current both sources could supply to the bus bar can not exceed 120% of the bus bars rating.
 
as an example if you had a 200 amp rated busbar, and you had a 200 amp main breaker you could have a max 40 amp PV breaker backfeeding that panel
 
OK I read Nec 2008 690.64 and I see what you guys are saying. I think he has miss-read line (2) where it specifies " The sum of the ampere ratings of overcurrent devices in circuits supplying power.... ".

One other thing he took issue with relates to this requirement: "(7) Inverter Output Connection. Unless the panelboard is rated not less than the sum of the ampere ratings of all overcurrent devices supplying it, a connection in a panelboard shall be positioned at the opposite (load) end from the input feeder location or main circuit location. "
He insisted my breaker needed to be located on the opposite end of the panel from the feeder end. The wording here is ackward (rated not less than) so I'm not sure how to interpret this requirement. I interpret this to mean that if the panel rating is greater than the main breaker plus PV breaker then it doesn't apply?
 
ccjking said:
One other thing he took issue with relates to this requirement: "(7) Inverter Output Connection. Unless the panelboard is rated not less than the sum of the ampere ratings of all overcurrent devices supplying it, a connection in a panelboard shall be positioned at the opposite (load) end from the input feeder location or main circuit location. "
He insisted my breaker needed to be located on the opposite end of the panel from the feeder end. The wording here is ackward (rated not less than) so I'm not sure how to interpret this requirement. I interpret this to mean that if the panel rating is greater than the main breaker plus PV breaker then it doesn't apply?
Click to expand...

if you had a 200 amp rated busbar, and a 200 amp main breaker, and a 40 amp PV breaker in that same panel, then the 40 amp PV breaker would have to be at the opposite end of the the panel, to prevent overloading the busbar, if the busbar is rated not less than the main & PV breaker it would not matter where you put the PV breaker, because you could not overload the busbar
 
Status
Not open for further replies.
Top