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Solar PV System Repairs

Problems with a solar power system? Solar panels not working? Fault code oh a solar inverter? Faulty Solar Generation Meter? We can help.

Established in May 2007, we are one of the longest serving and most experienced solar PV companies around. We've carried out all sorts of solar repairs involving most types and size of solar PV system. So if there is a system fault or if there is any type of repair work to be carried out, Contact us and we will be pleased to help.

Below we highlight some common situations and faults found with solar PV systems and the steps required to resolve them.

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How do I know if the solar panels are working?

There are a couple of non technical ways to find out if the solar panels are working:

At the solar inverter: The solar inverter sits at the centre of a solar PV system and is the piece of equipment that converts the DC power generated by the solar panels into AC power for use in the home and export to the mains/grid.

Most solar inverters have LCD displays on the front which will show the status of the system. If the solar panels are working and the solar inverter has a display, it will likely show you here.

Most solar inverters have lights, they are all different but a solid green light suggests that the solar PV system and the solar inverter is in operation. A solid light of any other colour suggests a fault, further information will hopefully be available at the solar inverter's display.

Are my solar panels working?

Common measurements that are displayed on the LCD screens of solar inverters are:

  • The DC voltage (V) from the solar panels
  • The Current measured in Amps (A) from the panels
  • The overall power measured in Watts (W) being generated by the system
  • Mains/grid/feed-in voltage is sometimes also displayed

Solar inverters are usually around the size of a small TV or a microwave oven (there are pictures of solar inverters further down this page), if you can't find the solar inverter in the house, these are often installed in loft spaces and adjoining garages.

At the Solar PV generation / Feed in Tariff (FIT) meter: The solar generation meter is a small piece of equipment (picture further down this page) that counts all of the solar power that has been generated by a solar PV system in kWhrs.

Common places for these to be installed are:

If the solar panels are working, the solar generation meter will count the power that the solar PV system generates, this power is measured in kWhrs and counts all solar generation, you will see the numbers increase on the display and the red light will flash as it counts.

Solar Inverter Fault Codes, Warnings and Troubleshooting:

The solar inverter converts the DC power being supplied from the solar panels into AC power to be used by any local electrical loads within the property's electrical system, with any excess being exported to the grid/mains.

The solar inverter also controls the DC power being generated by the solar panels through it's use of MPPT trackers, it also actively monitors the grid/mains power supply conditions and is configured in accordance with engineering recomendation G83, replaced by G98, to only connect the solar PV system to the mains/grid supply when it's stable.

As part of a solar inverter's startup sequence it tests the integrity of all of the wiring connected to it, including the cabling between solar panels and it's own internal safety components before making the AC connection allowing the solar PV system to supply the property's electrical system and the grid/mains.

Solar inverters can stop working due to the presence of any number of faults. These could be faults within the solar inverter itself or as a result of the solar inverter safely shutting itself down after identifying a discrepancy elsewhere in the system such as from the solar panels, the mains or in the integrity of the wiring.

If the display on the solar inverter (assuming it has one) is still functioning, then the first place to look for a clue as to why the solar system isn't working correctly, can be found by looking at the solar inverter's LCD display.

Sometimes touching the screen or pressing a button on the solar inverter will iluminate the display. Note any warnings and or fault codes, if possible take pictures of the fault code and a wide picture showing the solar inverter and all the equipment connected to it.

Fronius IG Series Solar PV Inverter

Mastervolt Sunmaster Solar PV Inverter

SMA SunnyBoy HF Solar PV Inverter

If we have the solar inverter's manufacturer listed, you can find out more about the fault code including an explanation as to what's wrong by following the solar inverter manufacturer links below:

All Solar Inverter Fault Codes, Warnings and Troubleshooting

The make, model and the units serial number will be on a nameplate somewhere attached or built into the solar inverter, along with all the technical information, shipping information and barcode. If possible take a picture of the solar inverter's nameplate. The solar inverter's make, model and serial number is the key information to record.

Temporary Solar Inverter Faults: Safe Shutdown and Restart

Most Solar PV Systems installed in the UK (and nearly all of those associated with a Feed in Tariff (FIT)) will have been installed to enable owners and operators of the system to safely shutdown the solar pv system and restart the solar inverter without a solar engineers assistance. If the solar inverter has been installed in an accessable location, the instructions below will help you safely restart the system.

Leave everything near the supply meters turned on. At the solar inverter there will be an AC isolator such as the one pictured; this is used to isolate the mains/grid supply from the solar inverter and to prevent the solar inverter from feeding solar power into the electrical system. Switch the AC isolator 'off', if the solar inverter is running you will hear a clunk inside the machine and after a while a 'no-grid', 'missing grid' warning or similar on the LCD display.

Solar PV System Restart

AC Isolator

Near to and or built into the solar inverter will be a method of isolating the solar (DC) supply from the solar inverter. Often these are black and grey and will be labelled 'DC isolator' or similar. There might be two or more of these if the system is fed by multiple strings. If there isn't a seperate DC isolation device, there will be a way to isolate the DC supply built-in to the solar inverter itself (often a rotary style switch underneath), turn this 'off'.

When all of the lights on the solar inverter have gone out, reintroduce the AC/mains power supply by turning the AC isolator 'on'. Introduce the DC supply by turning all DC isolators 'on'.

This will restart the solar inverter, on the display it might show you progress during it's startup procedure. During startup is when the solar inverter carries out all of the tests needed before being able to connect the solar supply to the electrical system. If errors are found during testing they will be displayed on the screen or an indication light might come on. Make a note of any warning messages, warning lights and fault codes.

If the restart is succesful a green light will come on, sometimes flashing at first but once connected to the mains/AC supply remaining permenantly on. The LCD display will show how much power the solar PV system is generating. The solar PV system can be verified as working at the solar generation / Feed in Tariff (FIT) meter which will count on the display, the red light will pulse as it counts.

Solar Inverter Identified Faults

Sometimes solar inverters shut themselves down as a safety measure after identifying a fault or finding itself in what it assesses to be an unsafe condition to operate in. This could be anything to do with the power system including integrating with the mains power network (the grid), the earthing system, batteries (if connected), related to the solar panels or if when tested, no fault condition exists, a faulty solar inverter.

Working with fault codes and the manuals will often give us a clue as to what to look for but faults like these if they persist will often require a solar engineer's site visit to diagnose and fix.

Solar Inverter Relay Faults

Solar Inverter Relay Faults

Relays are electronic switches that control the flow of power from the solar PV system into your local power system and the mains, they are either open or closed. Relays will not allow power through until the solar inverter deems it safe to do so. If a relay or series of relays is damaged or faulty the solar inverter won't be able to connect to the electrical system.

You may have heard the solar inverter 'clicking' when the sun comes up in the morning and the solar PV system turns on. If you have noticed this, then what you would have been hearing is these relays. Given that these relays open and close daily, relay faults are a reasonably common solar inverter fault. Unfortunately this often means that a replacement solar inverter will need to be installed to get the system working again.

Solar PV Inverter Repair

Solar Inverter Warranties:

If a fault is found to be within the solar inverter, most solar PV inverters are provided with a 5 year manufacturers warranty, occasionally longer and sometimes extended. The good news is that even if the original installer is no longer trading, the solar inverter hardware if purchased within the last 5 years or within it's manufacturer's warranty period, assuming that the manufacturer is still trading, is still likely to be covered by this warranty.

Warranty Claims: Some manufacturers use their own engineers to service warranty claims, some will ask clients to arrange for the testing of the unit to prove the fault and arrange for the return. We can provide as much or as little help as is needed in order to process a manufacturer warranty claim and will be happy to carry out any testing or commissioning work on your behalf.

Out of Warranty Solar Inverter Failures: If the solar inverter has failed and it is out of it's manufacturer's warranty period then it will either need to be replaced or repaired. We can help with either option and will provide all the information we can to help you decide the best way to proceed.

Can solar Inverters be repaired?

Solar inverters can sometimes be repaired; but the nature of the fault, the availablity of spare parts, the status of the original manufacturer and the overall build quality of the solar inverter will determine whether or not a lasting repair is viable.

NB: Residential solar inverters are rarely worth fixing, once all the typical repair costs are factored: 1) uninstall the unit: 2) deliver it to us in Swindon 3) make the repairs and or source and install any needed parts, 4) deliver the unit back to site, 5) reinstall the unit and recommission the solar PV system.

New solar inverter costs are just a fraction of what they once where and in general modern solar inverters (the ones we use anyway) are of a much better build quality than many of the older units. Investing in a good quality new solar inverter with a strong 10 year warranty and recycling the old one, is usually the best long term decision a homeowner can make when faced with the decision to repair or replace a faulty solar inverter.

Solar PV Generation / Feed in Tariff (FIT) Meter Not Working

No Display, No Lights: If the display on the solar generation meter has stopped working and there are no lights on the unit. The first thing to check is the mains power supply to the solar generation meter. The solar generation meter is powered from the grid/mains power supply, so lights should always be on or flashing on and off, with the display visible at all times.

Solar PV Generation / Feed in Tariff (FIT) Meter

Follow the cables out from the solar generation meter, one or two will be heading toward the solar PV system, one or two towards consumer units and the mains/grid supply meter.

Check fuses, circuit breakers and RCDs in consumer units around the solar generation and mains/grid supply meter and see if anything marked 'solar PV' or you can see is related to the solar PV system is turned 'off'.

An RCD has a test button and is twice the width or a circuit breaker. An RCD that's switched itself 'off' is an indication that it has picked up an earth fault on a circuit that it protects, this fault might have been temporary.

If an RCD has switched itself off it's ok to try to turn it back 'on' again. If you meet with instant and strong resistance to closing the switch, leave it off. If it stays on for a short while and switches off when the solar PV system has warmed up and begun to feed in power, there's most likely a problem with the solar PV system somewhere, leave the RCD turned 'off'.

If the RCD remains on for a few hours, weeks or days and then switches itself off, faults like these are often weather related. Damp cables and wet or windy conditions will often expose faults both physical and in design, with AC and DC cabling and RCDs.

If the RCD stays on, the solar inverter starts up and everything works fine in all conditions - all good.

If a circuit breaker has switched 'off' this is an indication of either a short circuit, most likely a serious failure either within the solar inverter or with the solar inverter supply cable. Or for some other reason the circuit breaker has picked up a fault and isolated the circuit to prevent the solar inverter supply cable from becoming overloaded.

Turn on circuit breakers at your own risk, there is the potential to cause damage and only do so when you are able to access and inspect the solar inverter and all isolation equipment whilst it's in operation. If you meet instant and strong resistance, leave the circuit breaker off and turn everything to do with the solar PV system 'off' remembering to also safely isolate the DC circuits.

If the circuit breakers stays on and then switches itself off after a few minutes, this is reasonably strong indication that the solar inverter has a serious internal fault. Turn off everything to do with the solar PV system including the DC isolators.

If the circuit breaker stays on, the solar PV inverter starts up and feeds power into the electrical system through the circuit breaker; ideally a physical inspection and test of the supply circuit including all isolators, circuit breakers, RCDs and electrical connections would be carried out.

We would advise to safely isolate the solar pv system at the supply and from the DC and physically inspect and ideally electrically test as much as you can. Finding burnt neutral conductors in poorly designed AC isolators and problems associated with earthing is something we see, ocassionally poorly terminated conductors in hard to reach and undersized AC isolators.

Solar PV Generation / Feed in Tariff (FIT) Meter

No Display, lights working as normal: If the display on the solar generation meter has stopped working, check if the lights are still working.

A solid red light suggests that the unit is connected to the grid/mains power supply but the solar supply is not in operation. This would be expected at night but the light on the solar generation meter should flash as it counts generation during daylight hours.

A flashing red light suggests that the solar generation meter is connected to the grid/mains power supply and the solar supply is in operation.

If the solar PV system is operating as normal and the light on the solar generation meter flashes as it counts generation but it doesn't show the figures on the display then it's reasonable to assume that the LCD display on the solar generation meter has failed and that the solar generation meter should be replaced.

Display Works but Doesn't Count, Red light on solid: A solid red light suggests that the solar generation meter is connected to the grid/mains power supply but the solar supply isn't in operation, a flashing red light suggests that both the grid/mains power supply and the solar supply are in operation.

A red light on the solar generation meter is what would be expected whilst the solar PV system was shutdown at night but if the red light stays on permenantly during the day this is a strong indication that the solar PV system isn't in operation for some reason.

Check the solar inverter: The solar inverter will usually show its status on the LCD display, sometimes touching the screen or pushing a button will illuminate the display. A solid green light on the solar inverter would also suggest that the solar inverter is in operation and that the solar PV system supply is working. A solid light of any other colour suggests a fault, further information will hopefully be available at the solar inverter's display.

If the solar generation meter doesn't count when the solar PV system is in operation, then there is a fault with the solar generation meter which should be replaced.

Solar PV Generation Meter Replacement

Solar generation meter replacements are a relatively inexpensive and common repair but sometimes what appears to be a faulty solar generation meter can be an indication of faulty or damaged wiring elsewhere.

If in doubt, book a solar repair engineer to carry out a fault finding visit. The solar engineer will inspect and test both the AC and DC sides of the solar power system as well as the solar generation meter. We keep single phase solar generation meters in stock, so let us know when you book the solar engineer that you might have a suspect solar generation meter and we will make sure to bring one with us. Wherever possible we try to get fault finding visits that result in solar generation meter replacements done in the same visit.

Solar PV Generation Meter Replacement

Solar Ground Faults, Earth Faults, Isolation (ISO) Faults, Insulation Resistance faults and Riso Low Faults

These errors are picked up by solar inverters or through testing when during normal operation of a solar inverter, a leakage current to ground/earth is detected from within the solar PV system.

Solar PV Earth Faults

This could be originating from the AC or the DC side of the system, it's also possible that the solar inverter generates an alarm message due to AC leakage currents connected to the capacitive nature of the photovoltaic generator compared to ground/earth.

For as long as the situation persits then the solar inverter will not startup. Earth / Ground Faults (also called Iso, RISO low, insulation resistance or Isolation (ISO) Faults) often present themselves when it is raining or at times of high humidity when moisture can enter the system.

These faults can clear when weather conditions improve but they will not get better by themselves, potentially becoming more dangerous over time. If the solar inverter picks up these faults we would advise that you book a solar repair engineer to carry out a full system test, identify the source and rectify the fault as soon as possible.

We've written more about how to identify and repair ground faults here: Ground Faults, Isolation (ISO) Faults, RISO Low Faults and Insulation Resistance Faults with Solar PV Systems

Solar Panels Trip RCD, Nuisuance RCD tripping, RCD trips at solar system startup, RCD trips when it's raining and the solar PV system gets wet

This situation can come about from a number of different possible faults, as well as from errors made during the initial installation. Often this fault presents itself a number of years after the system was initially installed. So what's going on? There are a few possibilities:

Solar Panels Trip RCD
  • There is a genuine fault to earth, either from the DC side of the solar PV system including the solar panels, cables, connectors and any junction boxes, from the solar inverter or from the supply cable to the solar inverter that is finding it's way back to the RCD and causing it to trip.
  • There is a minor fault somewhere else on the main electrical system that in combination with the sometimes expected capacitive discharge current from the panels (enhanced in wet conditions) going to earth that in combination are enough to cause a shared or sensitive RCD to trip.
  • There is a problem with the incoming grid/mains power supply that is causing the RCD to trip.
  • The RCD is faulty or of a low quality i.e. tripping at a value lower than it's rating.

The solution will be found after a complete test and inspection of the whole solar PV and electrical system has been carried out. Problem DC cabling and connectors that have corroded are quite a common reason for RCDs to trip like this (particularly when wet), ageing solar inverters and sensitive RCDs that protect both the house circuits and the PV supply cable are also common causes for this fault.

No DC Power

If the solar inverter appears to be working correctly but is not registering any DC power then make sure all DC Isolators (often grey, rotary style isolators are used) are switched 'On'.

Low Solar DC Power

Some solar inverters have built in DC Isolator switches, look around and on the underside of the chassis and make sure anything labelled DC Isolator is switched 'On'.

If the system has two DC circuits/strings with seperate isolators, try one circuit at a time and see if the fault can be isolated to a circuit.

If the solar inverter recognises the AC side of the system but not the DC and everything is turned on, then there could be a problem with either the solar inverter, the solar panels, the DC cables or their connectors. Best advice would be to turn any available isolators (AC and DC) 'Off' and book a solar repair engineer to test the solar PV system.

Solar Systems not generating enough power

There may be an issue on the DC side of the system which might include solar inverters, isolators, circuit breakers, combiner boxes, the solar panels and the associated cabling and connectors between them.

Check that everything related to the DC side solar PV system is turned 'On'. If automatic safety devices such as circuit breakers or RCDs have switched 'Off', then there is likely a safety reason or a temporary fault. Leave them 'Off' until you know more about the fault or the system has been tested.

Mastervolt Sunmaster Inverter Faults

There may be an issue on the AC side of the system which includes the solar inverter, any DC and AC isolators, the solar generation meter, any consumer units/distribution boards connected to the solar power system, RCDs and circuit breakers and the associated cabling between them.

Check visually if everything that you would expect to be is turned 'On. NB: If you find automatic safety devices such as circuit breakers or RCDs are 'Off' then there is likely a very good safety reason for this, leave them 'Off' until the system has been tested.

There could be an environmental issue, has there been any changes to the installation area? Has there been any building work carried out nearby? Have trees grown taller and increased the level of shading on the panels? Are the panels excessively dirty?

Assuming a succesful safe shutdown and restart had been carried out, the solar inverter was not showing any errors and all safety devices such as MCBs and RCD were in operation we would need to provide a solar engineer to fully test both the AC and DC sides of the solar power system before making any recomendations.

Damaged and Faulty Solar Panels - Solar Panel Replacement

If any solar panel is damaged or faulty then in most systems (those where panels are wired together in strings) there is a good chance that the solar PV system will see a significant reduction in overall power generation.

A damaged or faulty solar panel can't always be seen but it can be identified through testing. The ideal fix is to replace the panel with a correctly specified and well sized new one or to rewire in order to exclude the damaged panel.

Solar Panel Replacement

Can solar panels be repaired? If the glass has been broken then the panel is no longer viable and should be safely removed and recycled.

If the damage is to cabling or a faulty junction box then there is a good chance that these could be replaced/repaired and the panel recommissioned.

The information we are going to need to be able to quote for this work is the make and model of the damaged panel, this will often be with the solar PV system paperwork and always listed on any MCS certificate; and if possible, a wide angle picture of the location, that shows the damaged panel in situ, and also how the panel might be reached.

Please email any relevant pictures and documents along with your enquiry to:

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Solar Power System Testing, Servicing & Maintenance

Regular solar PV system testing, servicing and maintenance will extend the life of a solar PV system and ensure that solar panels are always operating safely and at their best, whilst maximising yields.

We offer complete safety and performance testing for solar PV power systems of any size. Includes solar panels, cables, solar inverters, isolators and mains connections.

We provide solar power system testing and maintenance services for residential, commercial, industrial and agricultural clients across Southern, South West England and the West Midlands, with specialist experience working with farmers, developers and commercial and industrial buildings owners.

Solar Power System Testing, Servicing & Maintenance


Solar PV Inverter Replacement

If you have a faulty solar inverter, we offer an efficient, value for money, hassle free solar inverter replacement service. We offer good advice and install quality equipment with comprehensive warranty and support options. We will test the rest of the system as part of the service, take care of all hardware deliveries, record the new unit's serial number and confirm the warranty details with the manufacturer.

Our solar electricians work cleanly and will dispose of any unwanted boxes, faulty equipment and packaging.

Many modern solar inverters can now use wireless home networks to transmit solar generation data to PCs, tablets and smartphones, so if you would like something like this, let us know and we will be happy to set it up as part of the installation.

Solar PV Inverter Replacement

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Articles: Further Information, Calculators & Solar Inverter Fault Codes

Lots of articles, calculators and technical information including links for further reading. Covering a range of topics related to the installation and maintenance of solar photovoltaic and electrical systems in the UK.

Solar PV Information Articles

Surge Protection for UK Solar PV Systems

Recent changes to the BS7671 UK Wiring Regulations 18th Edition in the form of amendment 2 have introduced requirements and considerations for surge protection on both the AC and DC side of a solar PV System. In this article we take a look at surge protection, particularly in the context of the updated UK wiring regulations and how surge protection could best be incorporated into new and existing solar PV systems installed in the UK

Ground Faults, Isolation (ISO) Faults, RISO Low Faults and Insulation Resistance Faults with Solar PV Systems

After a number of years exposed to wind, rain, snow, ice and sometimes animals; solar panel systems can start to develop faults. The most common faults we find related to exposure are ground faults, isolation (ISO) faults, RISO low faults and insulation resistance faults. In this article we take a look at what these faults are, the possible causes and what steps are taken to identify and resolve them.

How to provide power to a house using a portable generator

In this article we show you how to power your home using a portable diesel, petrol or LPG generator. We look at changeover switches, the importance of earthing, generator loadings, how to isolate non essential loads. We ask where to locate the generator when it's in operation, how best to safely isolate the grid/mains power supply and switch to a generator supply.

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What Our Customers Say:

"We had been let down by a failure on our system,and the manufacturer of the part was no longer trading. We called Glen during the afternoon and he was there in the evening. He examined the system and recommended a replacement manufacterer, promising to come back and fit in the new part once it arrived. We informed Glen of the arrival on a Friday PM, he was there fitting the new part by 10:30 on the following Monday. Of course it worked. That is what you call service, and guess who is looking after all our requirements in the future. Highly recommend this company." - Gill Spencer, Newbury

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Case Studies

We've carried out Solar PV System design, installation, testing, repair and maintenance work on solar PV systems of all shapes and sizes all across the UK.

All case studies

Areas Served:

We are located in Wanborough, very close to Swindon in Wiltshire, Southern England, UK. From here we service clients within a 90 minute driving radius including the towns, cities and regions below:

Swindon: Abingdon, Aldbourne, Amesbury, Andover, Banbury, Basingstoke, Bath, Berkshire, Bicester, Blunsdon, Box, Bracknell, Bradford on Avon, Bridgwater, Bristol, Buckingham, Burford, Burnham on Sea, Calne, Camberley, Cardiff, Carterton, Cheltenham, Chippenham, Chipping Norton, Chipping Sodbury, Cirencester, Corsham, Cricklade, Devizes, Didcot, Evesham, Eynsham, Faringdon, Frome, Fleet, Glastonbury, Gloucester, Gloucestershire, Hampshire, Henley-on-Thames, Highclere, Highworth, Hook, Hungerford, Keynsham, Kingsclere, Lambourn, Lechlade, Ledbury, Ludgershall, Lyneham, Maidenhead, Malmesbury, Marlborough, Marshfield, Melksham, Minety, Newbury, Newport, Oxford, Oxfordshire, Pewsey, Purton, Ramsbury, Reading, Ross on Wye, Royal Wootton Bassett, Salisbury, Shaftesbury, Shalbourne, Slough, Southampton, Stow, Stratford upon Avon, Stroud, Swindon, Tewkesbury, Thatcham, Tidworth, Trowbridge, Wanborough, Wantage, Warminster, Weston Super Mare, Wiltshire, Winchester, Windsor, Witney, Wokingham, Worcester, Wroughton and Yate.

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