solarnovice
Member
Hi, no previous experience of electrics or pv but learning fast! Just looking for advice, comments or confirmation of problems i'm having.
15 solar panels in garden Oct 2018
Solis 4G inverter in unventilated shed eaves, two bits of 4x2 screwed onto plywood with inverter attached - bangs and rattles a bit as shed door banged to open and close, also gets very hot in there.
AC cable 51.7m from shed to house, 75% of it under ground with rest either in shed, along garden wall and about 5 metres through sofit to house. Installers recently confirmed cable is 4mm.
OV-G with inverter continuously shutting down and restarting which i noticed in May. Installer suggested perhaps squirrel or rabbit had chewed through cables.... Eventually Engineer came out Aug 2019 and measured incoming voltage at 242v, 252v then inverter reading 258v - his report as just received stated he had never seen ac voltage change before once inverter generating - surely this is how they work? No apparent calculations or considerations to solar rise/drop.
Installers said contact Manufacturer who said inverter working as should and contact DNO - UKPN metered for week and apart from 'up to' 253v max early morning and late at night, voltage remained relatively stable (for rural area) around the 240 mark. Back to installer who said, not our problem speak to DNO (think you can see where i'm going with this).
Finally got voltage drop calculations from installers as mV/A/m used is 9.5 as reference A & B enclosed in a conduit or trunking. Design Current Ib used 32amps Length of Run 30metres. Total VD 9.12.
However...... 4mm cable is below Manufacturers recommendation of minimum 6mm. A & B enclosed surely isn't correct for mostly underground cable? And when you change their incorrect cable length of 30m to the correct 51.7m gives VD= 15.72v and not inline with BS 7671. Neither is it inline with solar guidelines of 1-2% drop or 2.5-5v, which pushes the inverter over it's 260v threshold if the incoming voltage is anything over 244v.
I sent all information including dti guidelines, msc standards, BS 7671 etc to the installers who said they would increase ac cable to 6mm if i closed complaint (didn't know i'd made a complaint but just diagnosed what was wrong with their system). They have given new VD reading (again with cable rating A) as 9.12v - this again would push inverter over limits easily.
Yearly generation quote was 4035kw but as per last month (15 months after installation) it was only on 2600kw. The alarm function on inverter shows shut down in Sept 25 times in 50 mins and the last OV-G shut down was late October - the installers ignore my questions as to whether this would shorten the inverter lifespan bearing in mind it would have been worse during summer.
Not sure what sort of technical information to put here but basically i'm asking for help in confirming my 'diagnosis', someone who can check my calculations and advise really - this system was purchased by my 78yr old Mum so no way would she have been able to sort it but i am at a loss as to what to do next.
Many thanks in advance and hope i haven't sent you all to sleep with the above!
15 solar panels in garden Oct 2018
Solis 4G inverter in unventilated shed eaves, two bits of 4x2 screwed onto plywood with inverter attached - bangs and rattles a bit as shed door banged to open and close, also gets very hot in there.
AC cable 51.7m from shed to house, 75% of it under ground with rest either in shed, along garden wall and about 5 metres through sofit to house. Installers recently confirmed cable is 4mm.
OV-G with inverter continuously shutting down and restarting which i noticed in May. Installer suggested perhaps squirrel or rabbit had chewed through cables.... Eventually Engineer came out Aug 2019 and measured incoming voltage at 242v, 252v then inverter reading 258v - his report as just received stated he had never seen ac voltage change before once inverter generating - surely this is how they work? No apparent calculations or considerations to solar rise/drop.
Installers said contact Manufacturer who said inverter working as should and contact DNO - UKPN metered for week and apart from 'up to' 253v max early morning and late at night, voltage remained relatively stable (for rural area) around the 240 mark. Back to installer who said, not our problem speak to DNO (think you can see where i'm going with this).
Finally got voltage drop calculations from installers as mV/A/m used is 9.5 as reference A & B enclosed in a conduit or trunking. Design Current Ib used 32amps Length of Run 30metres. Total VD 9.12.
However...... 4mm cable is below Manufacturers recommendation of minimum 6mm. A & B enclosed surely isn't correct for mostly underground cable? And when you change their incorrect cable length of 30m to the correct 51.7m gives VD= 15.72v and not inline with BS 7671. Neither is it inline with solar guidelines of 1-2% drop or 2.5-5v, which pushes the inverter over it's 260v threshold if the incoming voltage is anything over 244v.
I sent all information including dti guidelines, msc standards, BS 7671 etc to the installers who said they would increase ac cable to 6mm if i closed complaint (didn't know i'd made a complaint but just diagnosed what was wrong with their system). They have given new VD reading (again with cable rating A) as 9.12v - this again would push inverter over limits easily.
Yearly generation quote was 4035kw but as per last month (15 months after installation) it was only on 2600kw. The alarm function on inverter shows shut down in Sept 25 times in 50 mins and the last OV-G shut down was late October - the installers ignore my questions as to whether this would shorten the inverter lifespan bearing in mind it would have been worse during summer.
Not sure what sort of technical information to put here but basically i'm asking for help in confirming my 'diagnosis', someone who can check my calculations and advise really - this system was purchased by my 78yr old Mum so no way would she have been able to sort it but i am at a loss as to what to do next.
Many thanks in advance and hope i haven't sent you all to sleep with the above!