Radian Posted July 15, 2022 Share Posted July 15, 2022 I think some inexperienced "weekend electricians" make a lot of false assumptions like this. Isolators are another example. DC isolators often present a number of poles that people think might be for separate strings when in fact they're designed to be linked in series to increase the breaking gap. IMO one essential bit of test kit is an insulation resistance checker. I wouldn't dream of installing PV without testing IR to module frame and to at least 1kV. Anything that's got wires and is outdoors is asking for trouble if there's more than 48V present. 3 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted July 15, 2022 Share Posted July 15, 2022 16 minutes ago, Radian said: It might surprise some people. As much as this does. https://en.wikipedia.org/wiki/Electrocuting_an_Elephant Link to comment Share on other sites More sharing options...
joe90 Posted July 15, 2022 Share Posted July 15, 2022 (edited) Wow, a very stark reminder @Radian Edited July 15, 2022 by joe90 Link to comment Share on other sites More sharing options...
Dillsue Posted July 15, 2022 Share Posted July 15, 2022 52 minutes ago, ProDave said: It is not so safe and fool proof now is it? Hopefully the OP can see that none of this relates to what he wants to do and can safely move his job forward and get the scaffold off hire. Link to comment Share on other sites More sharing options...
Onoff Posted July 15, 2022 Share Posted July 15, 2022 I've seen a few instances where AC rated isolators (as in good for 3P) have been used on DC battery systems. People wonder why they burn out 😂 Link to comment Share on other sites More sharing options...
LA3222 Posted July 15, 2022 Share Posted July 15, 2022 4 hours ago, ProDave said: It is not so safe and fool proof now is it? A bit smug for some reason. Why would anyone disconnect/connect MC4 connectors when under load? If someone tries to use an AC isolator for DC then I wouldn't give them advice at all in anything on here as they clearly fell at the first hurdle. Installing PV is no more dangerous than anything else in life, provided you are aware of and account for the specific risks associated with the task. Work safely and you will be fine. Cut corners and maybe you will, maybe you won't🤷♂️ The same principle applies to life in general. Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 15, 2022 Share Posted July 15, 2022 5 hours ago, Dillsue said: Hopefully the OP can see that none of this relates to what he wants to do and can safely move his job forward and get the scaffold off hire. Insulation resistance and other such basic tests are irrelevant to the OP then? Link to comment Share on other sites More sharing options...
SteamyTea Posted July 15, 2022 Share Posted July 15, 2022 2 hours ago, LA3222 said: Installing PV is no more dangerous than anything else in life Says, if I remember correctly, the man that drives without a seatbelt and refuses vaccinations. Link to comment Share on other sites More sharing options...
Dillsue Posted July 15, 2022 Share Posted July 15, 2022 44 minutes ago, Nickfromwales said: Insulation resistance and other such basic tests are irrelevant to the OP then? Nope. The OP wants to get the roof work done while he waits for a spark to come available. No mention of doing anything more than running DC cables to isolators. Link to comment Share on other sites More sharing options...
Marvin Posted July 15, 2022 Share Posted July 15, 2022 I read on one of the reports that I went through, months back, that the main cause of fires in PV setups in the UK was incorrectly fitted isolators. I assumed it was to do with the box poor fixing choices allowing water in but now I'm not so sure. Link to comment Share on other sites More sharing options...
LA3222 Posted July 15, 2022 Share Posted July 15, 2022 (edited) 2 hours ago, SteamyTea said: Says, if I remember correctly, the man that drives without a seatbelt and refuses vaccinations. Ha, think you may have your wires crossed there chief. I do wear seatbelts and do get vaccinated - not much choice with the vax, job means I have to be jabbed up. I think we get a bit hysterical on here sometimes. The OP was just talking about the roof work initially, it digressed into the electrical side and before you know it Bruce Willis is hitting a ride into space to blow up an asteroid that's about to wipe us out. Yes there are dangers, there are dangers with a lot of stuff in life. Let's be calm though, articulate the concerns/crocodiles that folk need to be aware of and move on with our lives🤷♂️ No need to blow this up into anything more than what it is. Edited July 15, 2022 by LA3222 Link to comment Share on other sites More sharing options...
LA3222 Posted July 15, 2022 Share Posted July 15, 2022 (edited) *Glitch in the matrix🥷 Edited July 15, 2022 by LA3222 Double post Link to comment Share on other sites More sharing options...
Radian Posted July 15, 2022 Share Posted July 15, 2022 Risk is a funny thing. Imagine a huge flat salt lake like the sort people break speed records on. Now paint a thin straight line several miles long on it and head off close to left of that line at 70MPH while another car is doing the same from the opposite side/end. Seems incredibly risky to me. But no different to driving on a regular A road. Link to comment Share on other sites More sharing options...
SteamyTea Posted July 15, 2022 Share Posted July 15, 2022 3 hours ago, Radian said: Now paint a thin straight line several miles long on it and head off close to left of that line at 70MPH while another car is doing the same from the opposite side/end. Except for the trillions that have been spent on engineering and education. And it still kills on a regular basis. Link to comment Share on other sites More sharing options...
Dillsue Posted July 16, 2022 Share Posted July 16, 2022 15 hours ago, Radian said: Seems incredibly risky to me. But no different to driving on a regular A road. Its massively different to driving on an A road as on the salt flat theres the option for both cars to move a long way from the line and virtually eliminate the risk. Going back to the OPs level of risk and hes already got a spark on site that could megger the cables even if not taking responsibility for the full PV. The OPs questions are well written and list all the things that need doing to complete the roof work......hes just looking for confirmation. All suggests low risk to me Link to comment Share on other sites More sharing options...
ProDave Posted July 16, 2022 Share Posted July 16, 2022 1 minute ago, Dillsue said: Going back to the OPs level of risk and hes already got a spark on site that could megger the cables even if not taking responsibility for the full PV. The OPs questions are well written and list all the things that need doing to complete the roof work......hes just looking for confirmation. All suggests low risk to me What is needed is that spark to read this thread, grow a pair, and connect the DC cables from panels to DC isolator after testing with his megger (other brands available) 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 16, 2022 Share Posted July 16, 2022 (edited) 23 hours ago, Dillsue said: Nope. The OP wants to get the roof work done while he waits for a spark to come available. No mention of doing anything more than running DC cables to isolators. Crikey....... You need to get the cables tested BEFORE any other works progress / get covered over. I'm out. Edited July 16, 2022 by Nickfromwales Link to comment Share on other sites More sharing options...
Dillsue Posted July 18, 2022 Share Posted July 18, 2022 On 16/07/2022 at 15:00, Nickfromwales said: Crikey....... You need to get the cables tested BEFORE any other works progress / get covered over. I'm out. Read on a bit and.... On 16/07/2022 at 09:45, Dillsue said: hes already got a spark on site that could megger the cables even if not taking responsibility for the full PV. Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 18, 2022 Share Posted July 18, 2022 No mention of that from the OP though, which is my whole point. Link to comment Share on other sites More sharing options...
Dillsue Posted July 19, 2022 Share Posted July 19, 2022 18 hours ago, Nickfromwales said: No mention of that from the OP though, which is my whole point. I think the OP sensibly came looking for clarification/advice about something he already seemed clued up on. If he already knew exactly what to do hes not likely to have posted?? Link to comment Share on other sites More sharing options...
DragsterDriver Posted July 19, 2022 Share Posted July 19, 2022 I may be missing the point a bit but- i linked all my panels together on the roof with the roofer and left the final tails each end in the loft space with the factory connectors on so the scaffold could be struck? Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 19, 2022 Share Posted July 19, 2022 2 hours ago, DragsterDriver said: I may be missing the point a bit but- i linked all my panels together on the roof with the roofer and left the final tails each end in the loft space with the factory connectors on so the scaffold could be struck? If it wasn’t optimised that was a lethal cocktail. 1 Link to comment Share on other sites More sharing options...
Onoff Posted July 19, 2022 Share Posted July 19, 2022 7 minutes ago, Nickfromwales said: If it wasn’t optimised that was a lethal cocktail. Why? 1 Link to comment Share on other sites More sharing options...
Radian Posted July 19, 2022 Share Posted July 19, 2022 3 hours ago, Onoff said: Why? Optimisers typically have a built-in safety function that reduces the output to 1 Volt DC when unloaded. So if disconnected or isolated or even if the AC is removed from the string inverter, the big scary DC voltage (should) drop to a few 10's of volts - depending on how many optimisers are in the string. 1 Link to comment Share on other sites More sharing options...
Dillsue Posted July 19, 2022 Share Posted July 19, 2022 3 hours ago, Radian said: Optimisers typically have a built-in safety function that reduces the output to 1 Volt DC when unloaded. Solaredge do as standard but I dont think Tigo do. The Solaredge safe 1 volt output can be overriden with a Solaredge tool and then give full output in the same way Tigo units do. Best to check with a meter if you dont know the spec of the optimised system youre working on. Link to comment Share on other sites More sharing options...
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