Use of GFCI breakers in a Solar System Question

[tsuru]

Have 4 each 200 Watt Solar Panels wired 2S2P in to my 60 Amp MPPT (SCC?)

Do you use GFCI breakers for this, and where would you place them, and IF I can ask one more question Please how do you know what amperage to use?

Thank you so very much for your help. I'm guessing this is a super easy question but for me I have no idea!

 

[12VoltInstalls]

how do you know what amperage to use

You would use a breaker that is 100%-125% of the wire rating.

My preference:
I always oversize these cables, so if you are transferring 18A I’d fuse/breaker it at 20A even if using 10awg (which is 30A) but 12ga is 20A and it would function for that, too. Typically you would fuse or breaker based on wire size.

 

[Mattb4]

GFCI are for AC and not DC usage. They are problematic for use after a mobile inverter. Likely will trip due to lack of proper NG bond. Not familar with Bouge inverters and if they allow the use of a GFCI rated breaker.

 

[robbob2112]

GFCI are for AC and not DC usage. They are problematic for use after a mobile inverter. Likely will trip due to lack of proper NG bond. Not familar with Bouge inverters and if they allow the use of a GFCI rated breaker.

There are GFIC outlets for use in RVs and there are ones that are specific for DC. Of course you have to special order them and they cost a lot. The DC ones are usually a breaker style setup verse outlet...

 

[Mattb4]

There are GFIC outlets for use in RVs and there are ones that are specific for DC. Of course you have to special order them and they cost a lot. The DC ones are usually a breaker style setup verse outlet...

Never heard of a DC GFCI rated breaker. Learn something new.

 

[robbob2112]

MidNite Solar MNDC-GFP80 80 amp 125VDC DC Ground Fault Protector

80 amp 125VDC DC Ground Fault Protector

www.solar-electric.com

 

[Hedges]

The GFCI outlets/breakers you all know and may or may not love trip if difference between current in Line and Neutral of AC circuit exceeds 5 mA. Any current going out through Line and not returning through Neutral might be flowing through your body and into ground.

European whole house RSD (GFCI) have 30 mA threshold. 30 mA is about the level where your muscles tighten and you can't let go.

https://www.solar-electric.com/lib/wind-sun/Ground-Fault.pdf

This PV GFCI doesn't trip until 0.5A, some designs actually tripping due to current through an 0.5A breaker. Rather than measuring difference between PV+ and PV- current, they make the ground bond through a breaker. Not for human safety, rather an attempt at fire prevention.

 

[mikefitz]

GFCI breakers for this, and where would you place them

At the output of the inverter, but your inverter may not be suitable, it needs a neutral to earth bond for a GFCI to function correctly.
Because you have multiple outlets and appliances connected to the inverter there is a higher risk of electric shock that a correctly installed GFCI would prevent. Check with Bouge that this bond is possible.
Additional comments of your instalation.
Inverter cables seem under sized for a 3000 watt unit.
The breakers on the inverter and controller feed cables are low cost junk. They have high volt drops, don't protect correctly, melt at high current. Either replace with fuses or Bussmann type breakers.
The batteries, assuming lithium, idealy each need a suitable fuse as close as practical to the positive battery post. Suggest a MRBF fuse in Bluesea holder, rated at 125% of BMS maxinum current.

 

[12VoltInstalls]

GFCI are for AC and not DC usage. They are problematic for use after a mobile inverter. Likely will trip due to lack of proper NG bond

needs a neutral to earth bond for a GFCI to function correctly

I didn’t finish my post because I got a phone call and exited mid thought

Some 120VAC breakers do work fine on inverters. (Pass&Seymour or Leviton 20A; can’t recall)
Actually probably most do.
The problem that comes up is that many will not reset if G is not zero potential with N.

I have my inverter output connected to the breaker panel via GFCI outlets that DO reset without N-G bonding. They have tripped on occasion when welding. When first installed the GFCI tripped a couple random times but I found no reason, but that hasn’t happened in (four?) years now.

With bigger inverters (due to 20A max GFCI outlet availability) you would need GFCI breakers.

Check with Bouge that this bond is possible

Post 18 here:
https://diysolarforum.com/threads/inverter-grounding.60720/

 

[tsuru]

You would use a breaker that is 100%-125% of the wire rating.

My preference:
I always oversize these cables, so if you are transferring 18A I’d fuse/breaker it at 20A even if using 10awg (which is 30A) but 12ga is 20A and it would function for that, too. Typically you would fuse or breaker based on wire size.

Thank you so much for your response. I will go back over what gauges of wire I installed and make sure to have that fused properly. And 100%-125% makes good sense, thanks.

 

[tsuru]

GFCI are for AC and not DC usage. They are problematic for use after a mobile inverter. Likely will trip due to lack of proper NG bond. Not familar with Bouge inverters and if they allow the use of a GFCI rated breaker.

Thanks for answering. I will send Bouge an email and see what they say about their 3000 Watt Inverter. Appreciate your time to answer, thanks.

 

[tsuru]

There are GFIC outlets for use in RVs and there are ones that are specific for DC. Of course you have to special order them and they cost a lot. The DC ones are usually a breaker style setup verse outlet...

Thanks so much for the answer here. I'm not too affluent on a SS check so probably might skip this if too expensive.

 

[tsuru]

MidNite Solar MNDC-GFP80 80 amp 125VDC DC Ground Fault Protector

80 amp 125VDC DC Ground Fault Protector

www.solar-electric.com

Thanks for the link. Says connects between negative battery and earth ground. That helps explain more for my lack of knowledge on all this too.

 

[tsuru]

The GFCI outlets/breakers you all know and may or may not love trip if difference between current in Line and Neutral of AC circuit exceeds 5 mA. Any current going out through Line and not returning through Neutral might be flowing through your body and into ground.

European whole house RSD (GFCI) have 30 mA threshold. 30 mA is about the level where your muscles tighten and you can't let go.

https://www.solar-electric.com/lib/wind-sun/Ground-Fault.pdf

This PV GFCI doesn't trip until 0.5A, some designs actually tripping due to current through an 0.5A breaker. Rather than measuring difference between PV+ and PV- current, they make the ground bond through a breaker. Not for human safety, rather an attempt at fire prevention.

Thank you for your answer. Enlightening. More I think about all this maybe might forego this whole idea. I'm really learning more with all the great responses and information - so thankful for so many people helping!

 

[hwy17]

I'd put a 120v GFCI outlet on the output of the inverter here. If I wanted GFCI.

 

[12VoltInstalls]

I'd put a 120v GFCI outlet on the output of the inverter here. If I wanted GFCI.

I do/did that.
My ‘complication’ developed when I jumped from 2000W inverter to 3000W inverter: ‘standard’ “5-15” outlet GFCI’s are only available up to 20A
Simple solution is to find a GFCI breaker that fits the (old) sylvania breaker box or much better: replace it with a safe, modern panel.
I let myself ‘get away with it’ because the 20A GFCI outlet I’m using feeds outlets on 20A breakers; that still leaves a potential overload if actually pulling 20A in the shop and the fridge starts. Unlikely scenario but I do need to fix that.

 

[tsuru]

I do/did that.
My ‘complication’ developed when I jumped from 2000W inverter to 3000W inverter: ‘standard’ “5-15” outlet GFCI’s are only available up to 20A
Simple solution is to find a GFCI breaker that fits the (old) sylvania breaker box or much better: replace it with a safe, modern panel.
I let myself ‘get away with it’ because the 20A GFCI outlet I’m using feeds outlets on 20A breakers; that still leaves a potential overload if actually pulling 20A in the shop and the fridge starts. Unlikely scenario but I do need to fix that.

Thanks. Makes sense too.

 

[tsuru]

I do/did that.
My ‘complication’ developed when I jumped from 2000W inverter to 3000W inverter: ‘standard’ “5-15” outlet GFCI’s are only available up to 20A
Simple solution is to find a GFCI breaker that fits the (old) sylvania breaker box or much better: replace it with a safe, modern panel.
I let myself ‘get away with it’ because the 20A GFCI outlet I’m using feeds outlets on 20A breakers; that still leaves a potential overload if actually pulling 20A in the shop and the fridge starts. Unlikely scenario but I do need to fix that.

Good info. Thinking might do this.

 

[tsuru]

I'd put a 120v GFCI outlet on the output of the inverter here. If I wanted GFCI.

Thanks for that.

 

[DPC]

Backing away slowly.....