Help!

[oldsalty]

Hi,

Had panels installed in November last on a rented house. Very quickly realised I had no way of monitoring if the array was even working, without knocking and asking the tenant to let me in. Very quickly concluded that was unacceptable and looked for alternatives. Found, considered and discarded wi-fi because there is none in the house - the Polish tenants don't have a landline so no ADSL options, generation meter was located under the stairs so no mobile signal nor wi-fi. Tried Ileos4You but no signal.

Decided to move gen meter to DNO meter box on outside wall, other side of house. Installer couldn't do it 'for a few months' and failed to find another MCS to do it in any sort of reasonable amount of time. Tenant went on holiday giving me access to the house so decided to get a retired industrial electrician to move the meter following the principle of doing the wiring in exactly the same way but powering the inverter and gen meter from a sub-main powered through a henley block on the DNO meter DB.

The attached (appalling) hand drawing shows the system as it currently is connected. The gen meter flashes and is recording generation (just on 500Kwh since installed on 12 Nov) but I need reassurance that the henley block connection to power the inverter/generation meter is correct to ensure that generated power is used in the property before any surplus is sent off down the grid. I will be grateful if somebody could have a look at the drawing and put my mind at rest that everything is in order. (I was prepared to pay well for an MCS to have the job done at short notice - rented property so put it against tax anyway - but just COULD NOT get anybody to do a quick job

Thanking you in advance.

 

[Gavin A]

layout is fine, but the cable is probably undersized for a 20m run - that's about the maximum for a 6mm2 cable on a 4kWp system, not sure what size system you have though.

 

[oldsalty]

layout is fine, but the cable is probably undersized for a 20m run - that's about the maximum for a 6mm2 cable on a 4kWp system, not sure what size system you have though.

Thanks for that. 3.25Kw is the registered capacity. Measured precise length of cable was about 17m but treated it as 20 for safety. We went through all the diversity and tables in the OSG and came out with 4mm T&E as fittiing because of where it is run without being covered anywhere etc, etc.

 

[Gavin A]

OSG doesn't apply, the volt drop limit for solar PV is 1%, so it requires a bigger cable than standard.

Check the manufacturers instructions, they'll probably specifiy 6mm2 for that size system at that length of cable run.

 

[Worcester]

PV works on a permitted voltage drop of only 1% else there are challenges with the inverter disconnecting when the grid voltage to high (your average sparks wouldn't know this, so no criticism on him)

The OSG probably refers to 3%, which is ok on a distribution circuit when sending power the other way - with the Inverter the voltage RISES at the inverter end, so it can then push the voltage over the top of the permissible figure - hence only 1%

17m is right on the limit for 4mm2 (20m is too far )- Just keep an eye open, as we start to get some great sunny days in march that the system isn't disconnecting (Grid Voltage too high) if it is then increase the cable size to 6mm2

 

[oldsalty]

Very many thanks for that information and advice, guys. Gonna go out today to get some 6mm T&E and will have my guy in to rip out the 4mm at the earliest opportunity.