Andehh Posted June 3, 2023 Share Posted June 3, 2023 Our electrician thinks we need a switch to divert the power between PV & mains into the fusebox. Ie when the day is sunny we switch the PV on to feed the fusebox, then at night switch it so that its 'off' and the mains power is 'on'. He says manual ones are cheap and automatic ones are £80 to £400. It's a old 13 year old system we are keeping due to the favourable FiT, and he dismantled it off our original roof 2 years ago (i know FiT rules have changed, but we dont have the funds to upgrade it). The system consists of a old Solarmax 4200s, couple of large isolation switches and a grey meter box. I couldnt get my head around this, as I have never heard of anyone needing to manual engage their solar system & switch back & forth from manual grid. He brought up a couple of google image search showing 'control boxes' connect to solar installs, but wasn't totally sure either way. I dont feel like he is up selling me & he is happy to connect it all in and see what happens. He is a good guy, albeit it bloody expensive! Any advice, or suggestions as to what he is referring to? Link to comment Share on other sites More sharing options...
SteamyTea Posted June 3, 2023 Share Posted June 3, 2023 Sounds like he does not have much experience with PV. You can get PV diverters that will switch on a load when there is excess PV generation to reduce exports, but that does not sound like what he is saying. In general a PV system has two isolators, one on the DC side from the roof modules, and other on the AC side after the consumer unit (fuse box). Between those two are the Inverter and the generation meter. The Inverter is what does all the magic in converting, conditioning and controlling the PV generation, the meter just shows a record of what it has delivered. 1 Link to comment Share on other sites More sharing options...
Andehh Posted June 3, 2023 Author Share Posted June 3, 2023 Thanks Steamy. Yes, he is not a solar expert, just a good electrician reconnecting the system up. So the Solarpanels feed just flows into the fusebox? As we have 3 phase, and this is a single phase inverter....he is just going to connect the Solar into our 1st Phase (which feeds the house)... is that all that is required? Link to comment Share on other sites More sharing options...
Marvin Posted June 3, 2023 Share Posted June 3, 2023 I think photos are required! 1 Link to comment Share on other sites More sharing options...
ProDave Posted June 3, 2023 Share Posted June 3, 2023 He is talking BS. AS you PV starts to generate power, it reduces what is imported from the grid, and when the power generated by the solar exceeds what is being used in the house it exports to the grid. Your inverter is "grid tied" so that means it has to be connected to the grid and it synchronises the waveform it generates to match the frequency and phase of the incoming mains. If you did switch it over as your guy is suggesting it would promptly switch off as it would not see the grid frequency to synchronise to. Just leave it as it is. You are getting paid a generous FIT rate, so it does not matter is a lot of it gets exported. But as @SteamyTea says you can get a solar PV diverter that sends any surplus to usually an immersion heater for water heating. Those are more important for recent installations that don't get a FIT so you want to self use as much as possible. 1 1 Link to comment Share on other sites More sharing options...
Andehh Posted June 3, 2023 Author Share Posted June 3, 2023 Best I have right now. We think the inverter packed up, so have replaced it with a new one due to be delivered today and fitted tomorrow... Hence it all looking messy. Link to comment Share on other sites More sharing options...
Marvin Posted June 3, 2023 Share Posted June 3, 2023 For your information our PV complements our mains power. That is to say when it produces an output this feeds into our mains and is either used to supplement our demand or heads to the grid. Ours does not turn on or off. 1 Link to comment Share on other sites More sharing options...
Andehh Posted June 3, 2023 Author Share Posted June 3, 2023 1 minute ago, ProDave said: He is talking BS. AS you PV starts to generate power, it reduces what is imported from the grid, and when the power generated by the solar exceeds what is being used in the house it exports to the grid. Your inverter is "grid tied" so that means it has to be connected to the grid and it synchronises the waveform it generates to match the frequency and phase of the incoming mains. If you did switch it over as your guy is suggesting it would promptly switch off as it would not see the grid frequency to synchronise to. Just leave it as it is. You are getting paid a generous FIT rate, so it does not matter is a lot of it gets exported. But as @SteamyTea says you can get a solar PV diverter that sends any surplus to usually an immersion heater for water heating. Those are more important for recent installations that don't get a FIT so you want to self use as much as possible. Hi Dave, thanks....now this sounds really interesting.... as the Inverter wouldn't switch on when he first connected it up, and we bought a replacement thinking it was broken. However, we never connected it into the Grid....so I wonder if the inverter never switched on because it didnt see a grid connection??? Link to comment Share on other sites More sharing options...
SteamyTea Posted June 3, 2023 Share Posted June 3, 2023 The left hand side switch (black) is the DC isolator, right hand side one (red) is the AC isolator, yellow box is the inverter and the little grey box with the LED display is the generation meter. 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted June 3, 2023 Share Posted June 3, 2023 2 minutes ago, Andehh said: as the Inverter wouldn't switch on when he first connected it up, and we bought a replacement thinking it was broken. Oh dear. Link to comment Share on other sites More sharing options...
Andehh Posted June 3, 2023 Author Share Posted June 3, 2023 Could you expand on that please? Neither of us are solar experts, and I feel may have made a mistake here.... Link to comment Share on other sites More sharing options...
Marvin Posted June 3, 2023 Share Posted June 3, 2023 Proceed with caution! Our system has to be turned off by the panels first and then off by the mains, and reverse when turning on. Link to comment Share on other sites More sharing options...
SteamyTea Posted June 3, 2023 Share Posted June 3, 2023 Just now, Andehh said: Could you expand on that please An inverter not only turns DC to AC, it also synchronises the AC waveform to the grid waveform. But much more importantly it is a safety device that disconnects your system from the grid if there is a power cut. This is to stop 230V flowing down the line to where people may be working. Link to comment Share on other sites More sharing options...
SteamyTea Posted June 3, 2023 Share Posted June 3, 2023 2 minutes ago, Marvin said: Proceed with caution! Our system has to be turned off by the panels first and then off by the mains, and reverse when turning on. That is odd as most systems are turned off on the AC side first. The DC side can be delivering quite a high current to the inverter and arcing can occur. Turning the AC side off first and the inverter will automatically shut down safely ass it mimics a power cut. 1 Link to comment Share on other sites More sharing options...
Andehh Posted June 3, 2023 Author Share Posted June 3, 2023 Oh bugger! So had we plugged the inverter into the fuse box, the system would probably have worked.. DAMN! 2 weeks of stress and £275 on a spare inverter. Link to comment Share on other sites More sharing options...
JohnMo Posted June 3, 2023 Share Posted June 3, 2023 Get someone who knows what they are doing with solar, it is not something you mess about with and hope for the best Link to comment Share on other sites More sharing options...
SteamyTea Posted June 3, 2023 Share Posted June 3, 2023 1 minute ago, Andehh said: DAMN! 2 weeks of stress and £275 on a spare inverter. And two weeks of very sunny weather and the associated loss of FiT payments. Link to comment Share on other sites More sharing options...
SteamyTea Posted June 3, 2023 Share Posted June 3, 2023 2 minutes ago, JohnMo said: Get someone who knows what they are doing with solar, it is not something you mess about with and hope for the best Yes. I hate seeing this. It may well be totally safe as disconnected at the other end, but one never knows at first sight. Link to comment Share on other sites More sharing options...
Andehh Posted June 3, 2023 Author Share Posted June 3, 2023 Thanks guys, hopefully get this resolved on Monday. Link to comment Share on other sites More sharing options...
ProDave Posted June 3, 2023 Share Posted June 3, 2023 Since you have novices working on this, it is far to warn you the DC side will still be live even without an inverter. The black wired coming from the panels and entering that grey DC isolator switch will be live. So pest screw the switch back into it's box ans ensure that switch remains OFF until you connect your inveter. And yes the inverter needs to be connected to the mains otherwise it will not work. Find an electrician who understands solar. Link to comment Share on other sites More sharing options...
TonyT Posted June 3, 2023 Share Posted June 3, 2023 And sell me the new inverter 😁 Link to comment Share on other sites More sharing options...
TonyT Posted June 3, 2023 Share Posted June 3, 2023 And the cables under the meter need sorted too Link to comment Share on other sites More sharing options...
Dillsue Posted June 3, 2023 Share Posted June 3, 2023 Take note of the Danger sign on the front of the grey and black isolator hanging loose. If its connected to the panels there could be several hundred volts on the isolator. If your electrician left the isolator like that and doesnt understand solar, then get a new electrician! Link to comment Share on other sites More sharing options...
Andehh Posted June 8, 2023 Author Share Posted June 8, 2023 Worked like a treat, thanks all! Link to comment Share on other sites More sharing options...
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