Posted February 15, 20223 yr Hi I recently had a solar installation done and the installer ran 4mm cable (see attached) to the inverter AC input, and also 4mm from inverter AC output back to the main DB earth leakage breaker. I had an electrician come out today for a CoC and he didn't approve it saying that you cannot run a house on 4mm (which I agree with) and he advised to change it to 10mm. I contacted the installer who doesn't want to take responsibility and change the cable to 10mm (which is max 20m to and from the main DB). They said if the electrician has a problem with the cable, then he can change it. My problem is I've already paid for the installation so don't think it's fair that I have to now pay an electrician to redo cabling. As a solar installer, minimum cable thickness should be elementary knowledge, and as a company, they should be liable for under-par work. Has anyone been in this situation before, and what would be the best route going forward? Thanks for any advice.
February 15, 20223 yr Not an electrician, but from what I googled, 4mm^2 cable is rated at around 30A, that would equate to 6-odd kW capacity, what size inverter have you got?
February 15, 20223 yr It all depends on the size of the inverter. I generally use 6mm2 on a 5kw inverter and 10mm2 on the 8kw inverter. Regards
February 16, 20223 yr Author Thanks, I have a RCT InfiniSolar 5.6kW inverter configured in grid-tied mode with battery backup. I also have a Eskom/inverter transfer switch where I can manually bypass the inverter if required, so won't that mean Eskom will run on the 4mm cable? I guess the inverter would have been fine on 4mm if it was connected off-grid as it would be a totally separate system?
February 16, 20223 yr How much will that inverter pull if loadshedding stops? Charge batteries - 120A - 6kw Running everything in the house that is connected. - 4kw. As now people start cooking and using the plugs. That is 10kw on a 20m 4mm2 cable.
February 16, 20223 yr 53 minutes ago, Luminous said: How much will that inverter pull if loadshedding stops? Charge batteries - 120A - 6kw Running everything in the house that is connected. - 4kw. As now people start cooking and using the plugs. That is 10kw on a 20m 4mm2 cable. How do you get to run 10kw load on 5kw inverter? 😂
February 16, 20223 yr 7 minutes ago, hoohloc said: How do you get to run 10kw load on 5kw inverter? 😂 Does your inverter stop suppling power to the plugs and lights when it charges the battery?
February 16, 20223 yr Nevermind the 4mm cable, but... am I correct that the breaker to the far left is you MAIN breaker coming from the grid ? Because it looks like the inverter is fed from BEFORE this breaker ? It also looks like you have a mix of essential and non-essential in the same board. And to make it worst circuit one is ESSENTIAL, then 2 and 3 is NON-ESSENTIAL (and not EL protected), then 3,5,6 ESSENTIAL again ?
February 16, 20223 yr 44 minutes ago, Luminous said: Does your inverter stop suppling power to the plugs and lights when it charges the battery? My inverter has a 40A breaker that automatically trips if I get over that. Again, you can not get 10kw out of a 5kw inverter, your inverter if off-grid, it will trip. both my 5kw inverters are supplied by a 4mm^2 twin flex, from a 32A each on the DB. My installation has CoC .
February 16, 20223 yr If you put a 30amp circuit breaker inside the DB on the 4mm cable feeding the inverter and a 30amp circuit breaker on the 4mm cable coming back from the inverter into the DB that will be to code. Provided that your inverter doesnt draw more than 30amps you will be ok. As it stands the 4mm cable supplying the inverter is connected before your homes main switch meaning that you are not able to switch it off via the mains (very dodgy) The 30amp circuit breaker feeding the inverter should be connected after the 60amp mains isolator switch. I'd suggest you have an electrician have a look at the other shortcuts they took as this is very concerning.
February 16, 20223 yr 5 minutes ago, hoohloc said: My inverter has a 40A breaker that automatically trips if I get over that. Again, you can not get 10kw out of a 5kw inverter, your inverter if off-grid, it will trip. both my 5kw inverters are supplied by a 4mm^2 twin flex, from a 32A each on the DB. My installation has CoC . The problem is not about getting 10KW out of the inverter. The problem is 10kw into the inverter. The inverter above have a 120A AC charger for the battery. That is 120 x 54v for charging is already 6.5kw. The inverter has a maximum AC Input Current of 40 A . 40 x 240 which is 10kw. So 40 is above the rating for a 4mm2 cable
February 16, 20223 yr 2 minutes ago, Luminous said: The problem is not about getting 10KW out of the inverter. The problem is 10kw into the inverter. The inverter above have a 120A AC charger for the battery. That is 120 x 54v for charging is already 6.5kw. The inverter has a maximum AC Input Current of 40 A . 40 x 240 which is 10kw. So 40 is above the rating for a 4mm2 cable If the OP can supply his inverter through a 30A breaker and set his AC charge current to 30Amax, he will be ok with 4mm^2 cable. His installation will pass CoC with those small corrections
February 16, 20223 yr I think the installer was in the wrong here to install 4mm2 cable. Thus limiting the inverter and any future upgrades to save R700 on the cable costs. I agree not to pass the COC on this but for the installer to fix. From the quotes I have seen a lot of installers asks design costs but in this case there was no design done.
February 16, 20223 yr Author 3 hours ago, Mier said: Nevermind the 4mm cable, but... am I correct that the breaker to the far left is you MAIN breaker coming from the grid ? Because it looks like the inverter is fed from BEFORE this breaker ? It also looks like you have a mix of essential and non-essential in the same board. And to make it worst circuit one is ESSENTIAL, then 2 and 3 is NON-ESSENTIAL (and not EL protected), then 3,5,6 ESSENTIAL again ? Hi. Yes, the main breaker is to the far left. Yes, the inverter is fed from before, but it has it's own 63A breaker in the garage. I told them to exclude the geyser and stove from being powered by the inverter, so those 2 would be the non-essential. I have a GeyserWise conversion with the dual AC/DC element for the geyser, and the AC part is powered by Eskom by default. I also have an induction stove which runs from the plug, but it's about 1kw when in use.
February 16, 20223 yr Author 3 hours ago, hoohloc said: If the OP can supply his inverter through a 30A breaker and set his AC charge current to 30Amax, he will be ok with 4mm^2 cable. His installation will pass CoC with those small corrections Cool thanks for this. I think this would be the cheapest option for me, while also sticking to the cable current rating. I have the AC input to the inverter permanently switched off, so it doesn't charge the battery with AC. My inverter charges the battery using only solar. On the output side I haven't gone above the 5600W inverter max. Edited February 16, 20223 yr by opteron47
February 16, 20223 yr Author 1 hour ago, Luminous said: I think the installer was in the wrong here to install 4mm2 cable. Thus limiting the inverter and any future upgrades to save R700 on the cable costs. I agree not to pass the COC on this but for the installer to fix. From the quotes I have seen a lot of installers asks design costs but in this case there was no design done. Yes agree, it does limit upgrades if I want to install an 8kW inverter in future.
February 16, 20223 yr 1 hour ago, opteron47 said: Yes agree, it does limit upgrades if I want to install an 8kW inverter in future. It is not really a limit, you already have 4mm^2 from the DB to the inverter and another one from the inverter to the DB. When you upgrade, double them up and use them to supply your inverter and then run 10mm^2 from inverter to the DB.
February 18, 20223 yr Wire size is determent by the amount of current running through it. This can be limited by a breaker. If it exceeds the breakers rating it will trip. Even if the load is 100A the breaker will only allow its rated current. My 5kw inverter is also fed by 4mm wire and has a 30Amp breaker feeding it. My Ac charging current is set at 2Amps. If I forget and set it to 50A the breaker will protect die 4mm wire.
February 18, 20223 yr you have to remember that a 30 amp circuit breaker will not instantaneously trip if current exceeds 30 amps, it can ( depending on the current ) take a while .
February 18, 20223 yr 9 minutes ago, Tariq said: you have to remember that a 30 amp circuit breaker will not instantaneously trip if current exceeds 30 amps, it can ( depending on the current ) take a while . Yes, but the wire will also take a while to heat up...
February 18, 20223 yr 53 minutes ago, Tariq said: you have to remember that a 30 amp circuit breaker will not instantaneously trip if current exceeds 30 amps, it can ( depending on the current ) take a while . Correct but 4mm can handle 32amp continuously up to a certain length. It can handle more for short periods.
February 21, 20223 yr Author Thanks. Does anyone know any electricians that will approve the CoC once the 30A breaker is installed? I'm in Weltevreden Park, Roodepoort. The electrician I initially contacted said he still won't approve it, so it's clear he's trying to make a quick buck.
February 21, 20223 yr 1 hour ago, opteron47 said: Thanks. Does anyone know any electricians that will approve the CoC once the 30A breaker is installed? I'm in Weltevreden Park, Roodepoort. The electrician I initially contacted said he still won't approve it, so it's clear he's trying to make a quick buck. You are not far from my place, I used these guys for my CoC Mr Titan Electric Sunburst Electric www.sunburstelectric.co.za [email protected] Tel: 087 55 11 000
February 21, 20223 yr Author 36 minutes ago, hoohloc said: You are not far from my place, I used these guys for my CoC Mr Titan Electric Sunburst Electric www.sunburstelectric.co.za [email protected] Tel: 087 55 11 000 Thank a mil
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