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solarnovice

OV-G confirmation

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solarnovice

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!

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ProDave

The installer failed to make proper calculations. That is a long run of cable and the voltage drop (which actually manifests as voltage rise) is tripping the inverter.  For that length of cable you will need a much bigger cable than the current carrying capacity would suggest.

 

Your high mains voltage to start with is not helping.

 

You would be be a lot better off extending the DC cables and getting the inverter a lot closer to the house in a better environment.

Edited by ProDave

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solarnovice
1 hour ago, ProDave said:

The installer failed to make proper calculations. That is a long run of cable and the voltage drop (which actually manifests as voltage rise) is tripping the inverter.  For that length of cable you will need a much bigger cable than the current carrying capacity would suggest.

 

Your high mains voltage to start with is not helping.

 

You would be be a lot better off extending the DC cables and getting the inverter a lot closer to the house in a better environment.

Thank you ProDave, this confirms what i told the installer, they have come back with suggestion of 6mm steel wired armoured cable as it is the only one suitable for under ground (begs the question as to what sort of 4mm cable was laid initially) and voltage drop calculation as 3.942% (they have changed cable rating to D as i suggested). But surely that voltage drop is still way above the 'solar rise/drop' recommended of 1% and still likely to trip the inverter - the only thing 6mm will appear to do is bring the installer inline with BS7671?

 

Lately i found out about rural areas having unstable voltage and not much supply demand - something which should have been covered at sales/design/installation!

 

 

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kerching

I,would have said 10mm but what do I know?

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ProDave

If the voltage "drop" has been calculated as 4% then with your mains at 245V the inverter voltage will rise to 254V just above it's trip threshold of 253V

 

So as above, either 10mm, or shorten the cable length somehow.

 

Some inverters shut down if they exceed the maximum voltage.  Others just limit their output to not go above it.  Unfortunately yours is the former type.

Edited by ProDave

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solarnovice

Thanks again for replies, my thinking was 10mm too but it's whether or not the installers would agree.

 

ProDave mentioned moving the inverter closer to the house (generation meter) and extending the dc cables - would this cause problems with voltage drop on the DC side? I've only learnt about the AC side of things so far.

 

Another quick question - the system is registered with our DNO as G83/2, but the inverter setting is on G59/3 - does this matter? The installer said the solis inverters were only set to this standard but Solis mentioned in a previous email about checking the settings to see whether they were set to G83 or G59? All very contradictory and confusing!

 

Nothing written here will be quoted - i'm simply trying to find a workable solution - it's getting to the point where we are wondering if we should just get the installers to remove the whole thing, give full refund and start again with another installer!

 

 

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Murdoch

Hopefully @binky will be along shortly .....

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ProDave
2 hours ago, solarnovice said:

Thanks again for replies, my thinking was 10mm too but it's whether or not the installers would agree.

 

ProDave mentioned moving the inverter closer to the house (generation meter) and extending the dc cables - would this cause problems with voltage drop on the DC side? I've only learnt about the AC side of things so far.

 

Another quick question - the system is registered with our DNO as G83/2, but the inverter setting is on G59/3 - does this matter? The installer said the solis inverters were only set to this standard but Solis mentioned in a previous email about checking the settings to see whether they were set to G83 or G59? All very contradictory and confusing!

 

Nothing written here will be quoted - i'm simply trying to find a workable solution - it's getting to the point where we are wondering if we should just get the installers to remove the whole thing, give full refund and start again with another installer!

 

 

No. Volt drop on the DC side does not matter, the inverter will have a very wide range of acceptable input voltage levels.  It is only the output voltage that is very tightly controlled.  I set mine up with something like 30 metre long DC cables for that reason.

Edited by ProDave

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solarnovice
34 minutes ago, ProDave said:

No. Volt drop on the DC side does not matter, the inverter will have a very wide range of acceptable input voltage levels.  It is only the output voltage that is very tightly controlled.  I set mine up with something like 30 metre long DC cables for that reason.

Brilliant thank you - another option for the installers to consider :)

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binky

what a crock of horse droppings! 

 

1/ never heard of OV-G .

2/ requirement is 1% max volt drop, so 4mm cable on 50m run, ahem, nin-com-poop springs to mind

3/ so high resistance on the cable is pushing up voltages on AC cable, the inverter is seeing this as a high grid voltage and trying compensate for that by out-putting a higher voltage to push leccy down the cable. As a result it is boucing off its top limit and shutting down - NB this is normally around 260V max. Grid max is 253V, inverter should cope with that, but you may have a supply issue, but I suspect installation is more to blaim? 

4/ point 3, and comments about swa would suggest they have used a cable unsuitable for burial in the ground and the cable is failing.

5/ G59/3 is the old standard for systems over 4 kW, that changed about 18 months ago to G98 and 99 respectively, domestic/ commercial . Solis can be changed, but are normally supplied set correctly if you buy the right inverter from the right place.

 

I would contact whoever they claim to be registered with ie NICEIC / MCS  / other trade body, and trading standards and make  a formal complaint that this company is tango'd incompetent  and that the installation is potentially dangerous. 

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solarnovice
9 hours ago, binky said:

what a crock of horse droppings! 

 

1/ never heard of OV-G .

2/ requirement is 1% max volt drop, so 4mm cable on 50m run, ahem, nin-com-poop springs to mind

3/ so high resistance on the cable is pushing up voltages on AC cable, the inverter is seeing this as a high grid voltage and trying compensate for that by out-putting a higher voltage to push leccy down the cable. As a result it is boucing off its top limit and shutting down - NB this is normally around 260V max. Grid max is 253V, inverter should cope with that, but you may have a supply issue, but I suspect installation is more to blaim? 

4/ point 3, and comments about swa would suggest they have used a cable unsuitable for burial in the ground and the cable is failing.

5/ G59/3 is the old standard for systems over 4 kW, that changed about 18 months ago to G98 and 99 respectively, domestic/ commercial . Solis can be changed, but are normally supplied set correctly if you buy the right inverter from the right place.

 

I would contact whoever they claim to be registered with ie NICEIC / MCS  / other trade body, and trading standards and make  a formal complaint that this company is tango'd incompetent  and that the installation is potentially dangerous. 

Thank you binky - you have confirmed everything i suspected. The company is appalling - they appear to only specialise in 'passing the buck'. But yes, they are so far contravening every regulation i have checked so far. Neither myself or Mum knew anything about solar PV when it was installed but alarm bells rang when DC cable was laid from panels to shed along the bottom of the hedge with the warning 'careful when using hedge trimmers'...... I buried cable as i use a steel bladed strimmer!

 

Is it ok that the system is registered with UKPN as G83 but inverter set to G59 or is that another regulation breach? I have replied to UKPN as they wanted to know if system output which is 3.6kw but no reply yet.

 

Guessing this will have to go further now as the installer said they would change cable to 6mm but we have to close complaint! They fail to realise how much this has cost us in lost generation, FIT payments, time etc! Maybe they underestimated not only the design/installation but the term 'a woman scorned' as i refuse to give in to them! 

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binky

un-bury the DC cable - it will last about 5 ears buried, it needs armouring or alternative cable route.

 

Wouldn't worry too much about the G59 settings it doesn't really affect how it works, although strictly incorrect to regs. If your inverter is 3.6kW, ie 16A limited then it falls under the G83 (98) domestic settings which makes getting DNO approval automatic. If you go over 16A max output from the inverter, then DNO is suppossed to be notified for approval before installation. THe DNO can refuse connection and insist you turn the system off if over 16A without their permission..

 

Give them sh!t missus :slap

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ProDave
38 minutes ago, binky said:

un-bury the DC cable - it will last about 5 ears buried, it needs armouring or alternative cable route.

 

Wouldn't worry too much about the G59 settings it doesn't really affect how it works, although strictly incorrect to regs. If your inverter is 3.6kW, ie 16A limited then it falls under the G83 (98) domestic settings which makes getting DNO approval automatic. If you go over 16A max output from the inverter, then DNO is suppossed to be notified for approval before installation. THe DNO can refuse connection and insist you turn the system off if over 16A without their permission..

 

Give them sh!t missus :slap

They tried to tell me I cannot connect mine until they have given me a quote for upgrading the network, because they had seen "4000" in the model number of the inverter.  Only solved when I emailed them the manufacturers specifications that said the output was limited to 16A

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solarnovice
1 hour ago, binky said:

un-bury the DC cable - it will last about 5 ears buried, it needs armouring or alternative cable route.

 

Wouldn't worry too much about the G59 settings it doesn't really affect how it works, although strictly incorrect to regs. If your inverter is 3.6kW, ie 16A limited then it falls under the G83 (98) domestic settings which makes getting DNO approval automatic. If you go over 16A max output from the inverter, then DNO is suppossed to be notified for approval before installation. THe DNO can refuse connection and insist you turn the system off if over 16A without their permission..

 

Give them sh!t missus :slap

Thanks binky - the cable is in twinwall ducting (just looked it up) but no stickers or anything to say it's live electrical wire. The DC cable in the shed is bare and has a small white sticker on it which i thought was the sort of label you get with lamps that tell you what fuse to use etc..... I've been happily sharpening shears etc on a grinder thats next to the cable! If i'd known all this before i'd have sharpened a tomahawk, got my bow and arrows then laid in wait for them to ride over the hill on their horses ;) 

 

Finally got in touch with UKPN today who explained that even though we'd bought and paid for 3.9kw system, our inverter was derated to below 3.6kw. They're not interested in anything except what the company send in for approval..... So i'm guessing our cowboys (oops sorry, i meant installers) sent in G83 because G59 would never have been allowed with the installation they had planned and probably costs more... 

 

More fuel for the fire though...... :)

 

 

 

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binky
17 hours ago, ProDave said:

They tried to tell me I cannot connect mine until they have given me a quote for upgrading the network, because they had seen "4000" in the model number of the inverter.  Only solved when I emailed them the manufacturers specifications that said the output was limited to 16A

 

this is the biggest issue, you can frequently go over 16A, but if you don't ask first they can get shirty and try to land you  a large bill for upgrading transfomers etc etc. Usually I put an application in before going over 16A and ask what they can allow for that property. Sometimes I get mr jobsworth who says "nothing" but normally I get a decent response that means I can export more than standard. YOu can install 16A whether they like it or not, and if there is an ugrading issue it's their problem along with any costs.

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binky
16 hours ago, solarnovice said:

Thanks binky - the cable is in twinwall ducting (just looked it up) but no stickers or anything to say it's live electrical wire. The DC cable in the shed is bare and has a small white sticker on it which i thought was the sort of label you get with lamps that tell you what fuse to use etc..... I've been happily sharpening shears etc on a grinder thats next to the cable! If i'd known all this before i'd have sharpened a tomahawk, got my bow and arrows then laid in wait for them to ride over the hill on their horses ;) 

 

 Twin wall ducting should be fine provided it's dry inside, the cable can't take constant contact with water. The DC cable is pretty tough stuff, so just go easy with the shears. 

 

remind me never to argue with you....:^O

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solarnovice
4 hours ago, binky said:

 Twin wall ducting should be fine provided it's dry inside, the cable can't take constant contact with water. The DC cable is pretty tough stuff, so just go easy with the shears. 

 

remind me never to argue with you....:^O

Thanks again binky. I’ll be extra careful when sharpening my talons.... 
 

knowledgeable and wise 😂
 

Email almost ready - listing installers breaches (both legal and contractual) - fingers crossed 🤞🏼 

 

Hopefully it’ll all be done and sorted soon then I can post some pics for you all to shake your heads at 😳

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solarnovice

Quick question- to change ac cable from inverter to house. Does it have to be done by solar installer or can qualified electrician do it?

 

Need to change 4mm twin core to minimum (haven’t checked ratings and voltage drop yet) 10mm SWA ! 

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Sharpend

I believe that it may be an electrician. It will be classed as a fixed radial supply. 

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solarnovice

So far we've been offered 6mm SWA with volt drop of 9.12v which has been rejected, now the installers 'electrical safety officer' has said 10mm cable as anything above is overkill. The rough calculations for this are 7v drop so still too high for solar 1% or 2.5v - am hanging on for 16mm hopefully!

 

We have 15 solar world real value panels (invoice says bisol pv's) which i think are 265 each?? The DC cables are both 4mm over a run from back of array (nearest point) to shed/inverter at 32.5m, can anyone say yes or no to this or is it something i need to be looking at and learning about too???

 

Many thanks in advance.

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binky

32 m is a long run, but the cable is capable of nearer 100m in 4mm with no problems.

 

I would push for 16mm, but (and I haven't checked the numbers) I had a customer with a long AC feed in undersized, for PV, cable to his barn. When I checked the calculations from basics it only worked at a few watts energy lost, certainly npt enough to cause issues. I that installation, we were  on 16mm SWA but with 10kWp of panels and a run of 130m.  

 

"Electrical Safety Officer"  sounds like an unqualified sparky to me :slap

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solarnovice
11 hours ago, binky said:

32 m is a long run, but the cable is capable of nearer 100m in 4mm with no problems.

 

I would push for 16mm, but (and I haven't checked the numbers) I had a customer with a long AC feed in undersized, for PV, cable to his barn. When I checked the calculations from basics it only worked at a few watts energy lost, certainly npt enough to cause issues. I that installation, we were  on 16mm SWA but with 10kWp of panels and a run of 130m.  

 

"Electrical Safety Officer"  sounds like an unqualified sparky to me :slap

Thanks again nimbly. Will leave the dc cable alone and hold out for 16mm ac cable. Installers are now asking me To confirm the qualifications of the info I’ve quoted.... sure the dti, UKPN and NICEIC would be happy to provide this 😳 

 

wonder if I could apply as electrical safety officer if no qualifications needed 😂

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Sharpend

You’d stand a chance given your understanding is better than theirs?!

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binky
20 hours ago, solarnovice said:

Thanks again nimbly. Will leave the dc cable alone and hold out for 16mm ac cable. Installers are now asking me To confirm the qualifications of the info I’ve quoted.... sure the dti, UKPN and NICEIC would be happy to provide this 😳 

 

wonder if I could apply as electrical safety officer if no qualifications needed 😂

  

Fully qualified Electrician and Solar installer with nearly 1 miilion kWs of solar installed. 

 

all you need to know is not to lick your finger and stick it whre it will hurt :slap.

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