R
roamwood
Five days without solar but guess I haven’t missed too much yet, thanks to the grotty weather.
I’ve had my solar installation since June 2011, SMA SB4000TL inverter and 16 sanyo HIT panels, total 3.67 kWp. We have been really pleased with the installation and the installer, recommending them many times. Last week we would have hit 10000kWh but the system stopped generating just 6kWh short! I have emailed the supplier to seek his advice of what to do but he hasn’t responded yet. The system is under guarantee for 5 years so perhaps he sees my email as a potential claim but I just want to get back up and running. I’m hoping some of the experts here will be able to guide me with what I suspect is a wiring issue rather than equipment failure.
The SB4000TL was selected as we have a shading issue first thing and last thing from a central chimney stack on our south roof slope. It’s clearly done its job as switching on the MPPT (which I did after a month when I discovered it was off) transformed our output readings from being crippled by the shading to hardly noticing. We hit our 3 year output “prediction” 7 months early, and the last reading I submitted to Scottish Power was initially refused by their system as being beyond what they would reasonably expect! That’s the good bit.
Not so good is the occasional trip outs we have been experiencing, perhaps every 2-6 months on average. We are on a TT system and I read on here that while permissible, the SB4000TL isn’t really ideal for such setups. I’m guessing this is tied up with the fact that this inverter is transformerless and therefore can trip the 30mA RCD protection I have covering all circuits. When the solar installers electrician first connected us up (he used a spare 16A MCB in our fairly old (guessing 20 years) consumer unit, it immediately tripped the 30mA RCD that feeds the CU from the meter. On the third attempt it latched and stayed that way, but he warned that it may cause issues in the future, but to see how we go.
When the RCD does trip it tends to be on damp or foggy days just as the sun breaks through. Normally after one or two attempts it latches. Looking back it has lasted up to 10 months between "trips". Mostly it isn't a huge problem, but the worst time was when we were on holiday in the summer and came back to a thawed out freezer. I’ve been daft leaving it. Last week after a foggy morning when it was generating it switched off about midday, just as the sun came out, and I haven’t been able to reconnect it since (apart from overnight). As soon as the panels start generating it trips the RCD. I’m hoping this is just a continuation of the old problem and not a new fault that might require the inverter to be replaced. If so perhaps my wiring could be reconfigured to include just 100mA Type B RCD protection feeding the consumer unit, and then replace all the MCB’s except the one to the solar with 30mA RCBO’s if there is space, or perhaps replace the whole CU and separate 30mA RCD with one high integrity board, suitably configured if not. I do have buried cables on my domestic circuits but the solar feed is just surface or within the floor void.
Can anyone spot any flaws in what I think may be required? If not and my original solar installer won’t help me, I could at least get that work put in hand by an electrician and see if sorts things. Is there any test that I could do to help diagnose whether anything else might be causing the problem (such as disconnecting each string in turn?) or get an electrician to do (such as checking the efficiency of the earth, or measuring the leakage current from the inverter?) Has anyone seen a SB4000TL inverter fail in a way that could cause this, or do people think it is most likely just the 30mA RCD being incompatible?
I guess what I’m really asking is what I should do next? I would be very grateful for any advice
Many Thanks, Mike
I’ve had my solar installation since June 2011, SMA SB4000TL inverter and 16 sanyo HIT panels, total 3.67 kWp. We have been really pleased with the installation and the installer, recommending them many times. Last week we would have hit 10000kWh but the system stopped generating just 6kWh short! I have emailed the supplier to seek his advice of what to do but he hasn’t responded yet. The system is under guarantee for 5 years so perhaps he sees my email as a potential claim but I just want to get back up and running. I’m hoping some of the experts here will be able to guide me with what I suspect is a wiring issue rather than equipment failure.
The SB4000TL was selected as we have a shading issue first thing and last thing from a central chimney stack on our south roof slope. It’s clearly done its job as switching on the MPPT (which I did after a month when I discovered it was off) transformed our output readings from being crippled by the shading to hardly noticing. We hit our 3 year output “prediction” 7 months early, and the last reading I submitted to Scottish Power was initially refused by their system as being beyond what they would reasonably expect! That’s the good bit.
Not so good is the occasional trip outs we have been experiencing, perhaps every 2-6 months on average. We are on a TT system and I read on here that while permissible, the SB4000TL isn’t really ideal for such setups. I’m guessing this is tied up with the fact that this inverter is transformerless and therefore can trip the 30mA RCD protection I have covering all circuits. When the solar installers electrician first connected us up (he used a spare 16A MCB in our fairly old (guessing 20 years) consumer unit, it immediately tripped the 30mA RCD that feeds the CU from the meter. On the third attempt it latched and stayed that way, but he warned that it may cause issues in the future, but to see how we go.
When the RCD does trip it tends to be on damp or foggy days just as the sun breaks through. Normally after one or two attempts it latches. Looking back it has lasted up to 10 months between "trips". Mostly it isn't a huge problem, but the worst time was when we were on holiday in the summer and came back to a thawed out freezer. I’ve been daft leaving it. Last week after a foggy morning when it was generating it switched off about midday, just as the sun came out, and I haven’t been able to reconnect it since (apart from overnight). As soon as the panels start generating it trips the RCD. I’m hoping this is just a continuation of the old problem and not a new fault that might require the inverter to be replaced. If so perhaps my wiring could be reconfigured to include just 100mA Type B RCD protection feeding the consumer unit, and then replace all the MCB’s except the one to the solar with 30mA RCBO’s if there is space, or perhaps replace the whole CU and separate 30mA RCD with one high integrity board, suitably configured if not. I do have buried cables on my domestic circuits but the solar feed is just surface or within the floor void.
Can anyone spot any flaws in what I think may be required? If not and my original solar installer won’t help me, I could at least get that work put in hand by an electrician and see if sorts things. Is there any test that I could do to help diagnose whether anything else might be causing the problem (such as disconnecting each string in turn?) or get an electrician to do (such as checking the efficiency of the earth, or measuring the leakage current from the inverter?) Has anyone seen a SB4000TL inverter fail in a way that could cause this, or do people think it is most likely just the 30mA RCD being incompatible?
I guess what I’m really asking is what I should do next? I would be very grateful for any advice
Many Thanks, Mike
