Micro inverters with multiple strings - how to set up the safety cutoff?

Proteus

New Member
Joined
Oct 19, 2020
Messages
3
I'm relatively new to the whole world of solar and have educated as much as I can but I'm getting conflicting information so I figured I'd turn here for some help. Here's my steup:

20 400 watt panels
5 QS1 micro inverters
Unirac racking

Since the max panels in a QS1 string is 12, I have two strings. This means 2 AC lines of 20A each.

My original plan was to terminate both strings in a junction box and then make two runs from the junction, through conduit, to my service panel where I'd put two 240V 20A breakers for inputs. I have to have a safety cutoff to be code compliant and for the life of me I can't find a solution. One "expert" has told me I need a combiner for AC that has its own breakers and that will have a single output to run through the cutoff, then to the service panel. I'd obviously have to have a larger breaker at the panel since there would be two 20A feeds combining. This seems expensive and completely unnecessary. The second expert has told me there's no real cheap way to do it but the most effective would be to just put two small knife safety cutoffs - one for each string - and run each to the service panel with a 20A breaker for each. What I'd prefer to do is find a cost effective cutoff with more connections inside to accommodate two AC runs but there doesn't seem to be an inexpensive solution. What am I missing here?
 

schmism

Solar Addict
Joined
Jul 13, 2020
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Location
Central IL, USA
you got like $5k + of equipment listed. and your hand wringing over a couple hundred dollars worth of shuttoff panels?

It also seems like the QS1 are single phase 240v output which suggests your location is not in NA. If thats the case I defer to the people that know the standards for your area.
 

Proteus

New Member
Joined
Oct 19, 2020
Messages
3
It's not the cost it is the elegance of install. I'd prefer a single cutoff but if not an option, I'll just do two.
 

ArthurEld

Photon Sorcerer
Joined
Aug 3, 2020
Messages
2,069
Location
Palm Harbor, Florida
My DC system was designed without disconnects between the solar panels and my inverter.
The inverter has a disconnect and rapid shutdown is required in my area.
So, I don't think I need disconnects but the passthrough box for going from PV wire to conduit in my system design costs $200.
I have been thinking about replacing the pass through box with isolators from this company - https://www.factorymation.com/
They sell AC disconnects too and they have live chat. Maybe they can help you out.
Someone else will probably come along with more ideas
 

texskeet

Solar Enthusiast
Joined
Nov 11, 2020
Messages
74
Every state or for that matter city have there laws. My system is very close to yours. Where I am you would have to come down to a combined box and then to a single cutoff. Then to your panel . I don't know about where you are. He has micro inverters.
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
8,428
One 40A or larger DPST switch. One side goes to 40A breaker in your panel. Other side goes to four touch-safe fuse holders or two 2-pole breakers on a DIN rail inside the switch enclosure.

Not sure if either of these has the space inside. I did it with a 100A switch with fuse holder. It was tight, would have been easy without fuse holder.


 

texskeet

Solar Enthusiast
Joined
Nov 11, 2020
Messages
74
My switch was a blade type with a fuss in it. But again different rules in different places. For that mater Three sets of rules I had to meet State, city, and utility.
 
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