PV AC disconnects with multiple inverters

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philly

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I have seen some discussions in the other threads regarding the requirement of AC disconnects on a PV system and it sounds like this is something that is typically up to the AHJ. My question is based off of the assumption that the local AHJ will require and AC disconnect for a particular design.

So with the assumption that an AC disconnect is required I am wondering how many and the location of the disconnects required for a PV system with (3) inverters feeding into a panel. The PV system goes through three inverters which in turn have their AC side connected to circuit breakers in a panelboard. These inverters and panelboards are located remotely from the facilitys building with the utility entrance and system however this panelbaord is grid-tied to the system so is connected to the utility.

My main question here is if the utility required an AC disconnect for such an arrangement where would it need to be located? Would I simply need one disconnect on the output of the panelboard that is connected to the facilitys utility system, or would I need (3) disconnects one for each inverter that is connected on the branch breakers in the panelboard?
 
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From the Ac Combiner panel or main panel if your 120 percent rule works out you need an AC disconnect near the Inverter. You Also need a DC Disconnect before feeding the Inverter from the Array..... So I have used a handful of different inverters and they all provide a DC/AC Disconnect Combo that mounts the the bottom of the inverter and looks like it is part of the inverter resulting in a cleaner looking Job. Its also much more easy.
 
highvolts582 said:
From the Ac Combiner panel or main panel if your 120 percent rule works out you need an AC disconnect near the Inverter.
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You only need an additional AC disconnect if the local jurisdiction requires it, or if the AC combiner doesn't satisfy 690.14 (D) and 705.22.

So I have used a handful of different inverters and they all provide a DC/AC Disconnect Combo that mounts the the bottom of the inverter and looks like it is part of the inverter resulting in a cleaner looking Job. Its also much more easy.
Click to expand...

Are you sure those boxes disconnect the AC? Most of the ones I've seen only disconnect the DC.
 
highvolts582 said:
From the Ac Combiner panel or main panel if your 120 percent rule works out you need an AC disconnect near the Inverter. You Also need a DC Disconnect before feeding the Inverter from the Array..... So I have used a handful of different inverters and they all provide a DC/AC Disconnect Combo that mounts the the bottom of the inverter and looks like it is part of the inverter resulting in a cleaner looking Job. Its also much more easy.
Click to expand...

If these inverters are SMA Sunny Boys, the disco on the bottom only interrupts DC. It used to break both DC and AC connections, but they changed them in 2008 to DC only.

http://www.grosolar.com/dmdocuments/Advantages-of-the-New-SMA-disconnect.pdf
 
If you are interconnecting to an AC panel through a circuit breaker you already have an AC disconnect switch. Maybe the question is about the viewable blade and lockable AC disconnect requirement that many utilities impose on PV systems. This is typically a utility requirement and not from the local building department.

Utilities usually have the requirements for their AC disconnect in the documents you get from them when you apply for an interconnection. They can have very specific placement requirements and possibly even have a list of approved equipment that can be used. It's best to check directly with them before you go to far. It's no fun having the inspector sign off your system but then have the utility not allow it to be turned on.
 
jaggedben said:
You only need an additional AC disconnect if the local jurisdiction requires it, or if the AC combiner doesn't satisfy 690.14 (D) and 705.22.



Are you sure those boxes disconnect the AC? Most of the ones I've seen only disconnect the DC.
Click to expand...

damn your right I have I have done over 20 systems racking to module to ac and did not know that.
 
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