photovoltaic inverters with neutral

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I am using PV inverters that require a neutral. They are mounted on an out-building not attached to biulding where the main service is. I am installing a sub-panel for the inverters. I need to run a neutral to the sub-panel right? I know since the building is not attached I need to bond the sub-panel. But my question is I NEED to run a neutral right?
 

ty

Senior Member
For the most part, you would always run a neutral to a sub panel in a detached structure, anyway. Depending on what Code cycle you're on, the 4th wire (ground) could be optional depending on the circumstances.
 
I agree the sub panel has to have a neutral. I have seen one brand of inverter that doesn't require a neutral. Which inverter are you using?

In my experience most of the PV systems I see that connect via a sub-panel violate 690.64 (B)2 at the main or on the feeder between sub and main.
 
inverters

inverters

Its a sunny boy inverter. Yes, ive used PV power inverters that do not require a neutral. Sunny boys do.

I'm just confused about grounding as well since the subpanel goes to a disconnect, then straight to 400 amp CT cabinet. So there is no ground to sub panel right? Also if I run the neutral to sub panel doesn't it have to be the same size as the service neutral or can I greatly downsize it? Where do i get my ground from at subpanel?
 

zbang

Senior Member
So it's CT can -> disconnect -> cable to outbuilding? Yes, run a neutral. As mentioned, might need to run a ground lead, too. Since it's a separate structure, you'll need a grounding system (rods/etc). Bonding N and G at the outbuilding depends on whether or not you ran a ground lead from the service.
 
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reply

yes, that is correct. does the neutral need to be sized according to the 400 amp service or a neutral load calculation for the inverters?
 

ty

Senior Member
I would like to know a couple things for my own info.
What State are you in?
What is your electrical background?
It states in your profile that you are a photovoltaic installer, and I would just like a bit more info on who I'm helping out, before I go any farther.
 
info

info

I am in Pennsylvania. I have been a commercial/industrial electrician for over 5 years. I recently got hired to do PV systems.
 

ty

Senior Member
I see. Typically I don't ask, but since you were asking electrical questions, not PV, I was curious.
Did you go to school for PV? We do PV across the entire state of PA. As well as MD, and DE.

Last post says '400amp service'
Where is this? From previous posts, I concluded - CT can > Disconnect > service to Detached Structure. But now, I am unsure this is your set-up.

Where does your service to detached structure start exactly?
Is your disconnect fused, or unfused?
If fused, what size is it?
Have you drawn any riser diagram to show how you are doing this install?
Are there any loads (other than PV) being fed from this 'sub-panel'?
 
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