meetyg
Solar Enthusiast
- Joined
- Jun 4, 2021
- Messages
- 1,093
Hi there.
I have a small (but a bit complicated) grid-tie DIY solar setup.
I have been playing around with solar a bit, just to learn, but now am trying to make my DIY setup as safe as possible, given some constraints.
Basically I am using those cheap no-name Chinese micro-inverters (I have two, one is a GTB-600W and the other is a GTB-1200W).
They both have anti-islanding, and will only produce AC power if the grid is live.
Other than that their specs are fairly unknown/unclear to me...
I have two 450w glass panels connected to the GTB-1200, and four 100w flexible panels connected to the GTB-600.
The micro inverters are connected to an AC wall socket. Yes, I know that this is not ideal, but please don't criticize me for this. I really have no other choice, as my main AC panel is far away, and I would have to drill holes in concrete to get a line straight to the main panel. I'm also trying to keep this setup as cheap as possible, in order to make it cost effective and offset some if my electrical bill.
But I am willing to invest a little in some safety measures.
The micro inverters are not installed under the panels (although they are IP65 rated) but rather placed in a box (with fans for cooling) about 5 meters away from the panels.
The reason for this is to increase the life of the inverters, making them run cooler and not exposed to the elements.
Anyways, I'm pretty confused as how to make this as safe as possible. Currently I only have a DC isolator switch between the panels and the micro inverters, and a 16A MCB between the inverters and the AC socket.
After lots of reading online I have some questions, as there are mixed statements around:
1. Grounding:
Do I need to ground the inverters?
Both of them have a ground hole on their metallic casing. But from doing a continuity test, it seems both do NOT have continuity from the DC terminals to the metallic housing.
One of them (only the GTB-1200) has continuity from the housing to the AC ground wire.
Does this mean that the GTB-1200 is DC isolated and does not need additional grounding?
Can I just bond the GTB-600 to the GTB-1200 so that it will also be grounded?
Also, is it safe to ground the PV panels (frames and rails) to the AC ground wire coming from the wall socket (just like the GTB-1200 does), or do I need a dedicated ground wire and grounding rod for the panels ?
2. Fuses, MCBs and SPDs:
DC SIDE:
Assuming I get proper grounding sorted out as above, do I really need fuses and MCBs between my panels and the micro-inverters ?
Will this help protect my micro-inverters or is this redundant? (they have no external fuses on them).
Should I also use an SPD on the DC side?
If so, again how should I ground it properly?
AC SIDE:
Should I install an RCD between the inverters and the wall socket?
I am trying to protect the line and other loads (wall sockets, lights, etc...) and of course people in the house from possible short-circuits, ground/isolation faults.
If I need an RCD, how many milli-amps should it be rated for, given that the main RCD is rated 30ma (type AC).
I have read that it is recommended to get a 100ma RCD for some installations, but they were for a direct line, not a wall socket connection like mine is.
From my understanding, the danger here is that if a fault should occur, the main RCD could trip, but the micro inverter might still supply AC current to the line, untill it detects the the grid is disconnected (could take a few seconds I suppose). This means that someone could still get electrocuted until the micro inverter responds and cuts out the AC current it's producing.
Am I correct?
Sorry for the lengthy post, and thanks in advance for your answers and advice.
Just one last thing, as for local code and regulations, I am aware that my setup might be in the grey area of legality/regulations.
But, as I have seen similar setups being done by companies such as Legion Solar I guess that it might not be that bad.
They don't really explain how you should handle all these issues, so I am.just trying to do my best to understand and make my setup as safe as possible...
I have a small (but a bit complicated) grid-tie DIY solar setup.
I have been playing around with solar a bit, just to learn, but now am trying to make my DIY setup as safe as possible, given some constraints.
Basically I am using those cheap no-name Chinese micro-inverters (I have two, one is a GTB-600W and the other is a GTB-1200W).
They both have anti-islanding, and will only produce AC power if the grid is live.
Other than that their specs are fairly unknown/unclear to me...
I have two 450w glass panels connected to the GTB-1200, and four 100w flexible panels connected to the GTB-600.
The micro inverters are connected to an AC wall socket. Yes, I know that this is not ideal, but please don't criticize me for this. I really have no other choice, as my main AC panel is far away, and I would have to drill holes in concrete to get a line straight to the main panel. I'm also trying to keep this setup as cheap as possible, in order to make it cost effective and offset some if my electrical bill.
But I am willing to invest a little in some safety measures.
The micro inverters are not installed under the panels (although they are IP65 rated) but rather placed in a box (with fans for cooling) about 5 meters away from the panels.
The reason for this is to increase the life of the inverters, making them run cooler and not exposed to the elements.
Anyways, I'm pretty confused as how to make this as safe as possible. Currently I only have a DC isolator switch between the panels and the micro inverters, and a 16A MCB between the inverters and the AC socket.
After lots of reading online I have some questions, as there are mixed statements around:
1. Grounding:
Do I need to ground the inverters?
Both of them have a ground hole on their metallic casing. But from doing a continuity test, it seems both do NOT have continuity from the DC terminals to the metallic housing.
One of them (only the GTB-1200) has continuity from the housing to the AC ground wire.
Does this mean that the GTB-1200 is DC isolated and does not need additional grounding?
Can I just bond the GTB-600 to the GTB-1200 so that it will also be grounded?
Also, is it safe to ground the PV panels (frames and rails) to the AC ground wire coming from the wall socket (just like the GTB-1200 does), or do I need a dedicated ground wire and grounding rod for the panels ?
2. Fuses, MCBs and SPDs:
DC SIDE:
Assuming I get proper grounding sorted out as above, do I really need fuses and MCBs between my panels and the micro-inverters ?
Will this help protect my micro-inverters or is this redundant? (they have no external fuses on them).
Should I also use an SPD on the DC side?
If so, again how should I ground it properly?
AC SIDE:
Should I install an RCD between the inverters and the wall socket?
I am trying to protect the line and other loads (wall sockets, lights, etc...) and of course people in the house from possible short-circuits, ground/isolation faults.
If I need an RCD, how many milli-amps should it be rated for, given that the main RCD is rated 30ma (type AC).
I have read that it is recommended to get a 100ma RCD for some installations, but they were for a direct line, not a wall socket connection like mine is.
From my understanding, the danger here is that if a fault should occur, the main RCD could trip, but the micro inverter might still supply AC current to the line, untill it detects the the grid is disconnected (could take a few seconds I suppose). This means that someone could still get electrocuted until the micro inverter responds and cuts out the AC current it's producing.
Am I correct?
Sorry for the lengthy post, and thanks in advance for your answers and advice.
Just one last thing, as for local code and regulations, I am aware that my setup might be in the grey area of legality/regulations.
But, as I have seen similar setups being done by companies such as Legion Solar I guess that it might not be that bad.
They don't really explain how you should handle all these issues, so I am.just trying to do my best to understand and make my setup as safe as possible...