Mastervolt Solar Inverter Faults and Repairs
Dutch company Mastervolt, founded in 1991, launched it's first photovoltaic inverter in 1993. Mastervolt are now part of power conversion and management equipment giants Power Products LLC. Mastervolt Sunmaster and the smaller Soladin ranges of solar inverters were widely installed in the UK between 2011 and 2014. Popular Sunmaster models being the Sunmaster XS2000, Sunmaster XS3200 and the Sunmaster XS4300.
Mastervolt are no longer manufacturing or supporting grid connected solar PV inverters and should they be needed, we are not able to source parts to fix these solar inverters. Mastervolt still enjoy a strong presence in the off-grid solar PV market.
Mastervolt Sunmaster solar inverters have an LCD display on the front of the chassis, which providing it's working, will highlight any errors with the solar inverter or the solar PV system that it runs. The Soladin range doesn't have a display, instead they communicate their status through different sequences of flashing lights. We have listed and described common faults with Mastervolt Sunmaster and Mastervolt Soladin solar inverters and what action to take to resolve them below:
All Solar Inverter Fault Codes, Warnings and Troubleshooting
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Mastervolt Sunmaster Solar Inverter Faults and Warnings:Some of the advice we give related to identifying, confirming and or resolving some of the faults detailed below, starts with safely shutting down and restarting the solar inverter and the solar PV system. This is something that nearly all solar PV systems installed in the UK would have been designed to be carried out safely by the solar PV system owner. However, paperwork, schematics and manuals are not always clear or available, so if you have any concerns about how to do this, Contact us and we will be pleased to talk you through the process over the telephone at no charge. |
How to Restart a Mastervolt Sunmaster Solar Inverter:
Leave everything near the supply meters turned on. At the solar inverter there will be an AC isolator, 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 correctly you will hear a clunk inside the machine and after a while a 'no-grid', 'missing grid' warning or similar on the LCD display.
 AC Isolator |
Near to as well as built into the solar inverter might 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/circuits, turn these 'off'. If there isn't a seperate DC isolation device, there is a way to isolate the DC supply built-in to the solar inverter itself, a rotary style yellow on/off switch underneath the chassis, also turn this one '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.
Mastervolt Sunmaster Solar Inverter: No lights, No Display
Mastervolt Sunmaster solar inverters are powered by the solar panels (the DC supply) and will startup at sunrise each day and shutdown at night. If you find the solar inverter with no lights or display working during the day, there is either a problem with the solar panels or with the solar inverter. Follow the shutdown and restart procedure outlined above and if the problem persists Contact us to discuss the next steps.
If you have the correct tools and are comfortable in doing so, isolate the AC and DC power supplies from the solar inverter and confirm that the incoming DC voltages are as expected by measuring between the positive and negative incoming terminals in DC isolators (if avalable) and or at the DC solar inverter inputs. Light conditions and the type of solar panel will affect voltages but as a rule of thumb anywhere from 30V-60V per panel x the number of panels connected in series in the string would be a reasonable voltage estimate.
No or very low DC voltage would suggest a problem with the solar panels, measuring the expected voltage at the isolator terminals and or the DC inputs, although additional testing should be carried out, would suggest a problem with the solar inverter. Contact us to discuss the next steps.
Mastervolt Sunmaster Solar Inverter Fault Codes and Explanations:
* VAC HIGH - The solar inverter is measuring a grid (mains) voltage that is too high in relation to the parameters that the solar inverter has been set to safely operate within. If this fault persists contact us to arrange for a solar engineer to visit to establish whether the fault lies with the solar inverter or with the grid.
* VAC LOW - The solar inverter is measuring a grid (mains) voltage that is too low in relation to the parameters that the solar inverter has been set to safely operate within. If this fault persists and mains power is available to other local circuits then check that all isolators, MCBs and RCDs on the AC side of the solar PV system are 'On' and carry out the procedures outlined for * NO GRID below. If everything on the grid/mains power supply side including the solar generation meter is switched 'on', this would be an indication that there is either an internal fault within the solar inverter or there's a problem with the grid/mains power supply. Contact us to arrange for a solar engineer to visit to establish whether the fault lies with the solar inverter or with the grid/mains power supply.
* ENS OFF - The solar inverter has detected a fault with the AC power supply, this could be due to damaged or faulty AC wiring or it might be picking up a disturbance on the grid/mains power supply power network. If this fault persists and mains power is available to other local circuits then check that all isolators, MCBs and RCDs on the AC side of the solar PV system are 'On'. If automatic safety devices such as MCBs or RCDs have switched 'Off' then leave them 'Off' and contact us to arrange for a solar engineer to visit to establish whether the fault lies with the solar inverter, the supply circuit or with the grid.
* G83 OFF - The solar inverter has detected a fault with the AC power supply, this could be due to damaged or faulty AC wiring or it might be picking up a disturbance on the grid/mains power supply power network. If this fault persists and mains power is available to other local circuits then check that all isolators, MCBs and RCDs on the AC side of the solar PV system are 'On'. If automatic safety devices such as MCBs or RCDs have switched 'Off' then leave them 'Off' and contact us to arrange for a solar engineer to visit to establish whether the fault lies with the solar inverter, the supply circuit or with the grid.
* FAC HIGH - The solar inverter is measuring a grid (mains) frequency that is too high in relation to the parameters that the solar inverter has been set to safely operate within. If this fault persists contact us to arrange for a solar engineer to visit to establish whether the fault lies with the solar inverter or with the grid.
* FAC LOW - The solar inverter is measuring a grid (mains) frequency that is too low in relation to the parameters that the solar inverter has been set to safely operate within. If this fault persists and mains power is available to other local circuits then check that all isolators, MCBs and RCDs on the AC side of the solar PV system are 'On' and carry out the procedures outlined for * NO GRID below. If everything on the grid/mains power supply side including the solar generation meter is switched 'on', this would be an indication that there is either an internal fault within the solar inverter or there's a problem with the grid/mains power supply. Contact us to arrange for a solar engineer to visit to establish whether the fault lies with the solar inverter or with the grid/mains power supply.
* NO GRID - The solar inverter is not measuring a grid (mains) voltage suggesting that mains power to the unit has been disconnected. If this fault persists and mains power is available to other local circuits then check that all isolators, MCBs and RCDs on the AC side of the solar PV system are 'On'.
Check fuses, isolators, Miniture Circuit Breakers (MCBs) and Residual Current Devices (RCDs) in and around consumer units, around the solar generation and mains/grid supply meters and see if anything marked 'solar PV' or you can see is related to the solar PV system is switched 'off'. The solar generation meter draws it's power from the mains so if this isn't on, this would be a strong indication that something heading toward the incoming grid/mains power supply has tripped off.
 RCD
 MCB |
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 somewhere on the circuit that it protects, this fault could be anywhere on the circuit and 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' and contact us to discuss the next steps. 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, connectors, solar panels and RCDs. Contact us to discuss the next steps. 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 and contact us to discuss the next steps. |
If the circuit breaker stays on, the solar PV inverter starts up and feeds power into the electrical system through the circuit breaker; although the circuit breaker will continue to protect the circuit, ideally a physical inspection and electrical test of the supply circuit including all isolators, circuit breakers, RCDs and electrical connections would also be carried out.
- Everything's 'on' but the error remains and the solar inverter won't start. If everything on the grid/mains power supply side including the solar generation meter is switched 'on', this would be an indication that there is either an internal fault within the solar inverter or there's a problem with the grid/mains power supply. Contact us to discuss the next steps.
* SOL1 HIGH - The solar inverter is measuring too much voltage from the solar panels. Assuming that this is an existing installation that has been specified correctly, hasn't recently been changed or added to and has operated before without problems. This could mean either a problem with the solar panels or with the solar inverter. We would advise that the DC side of the system is disconnected using either the built in DC isolator at the bottom of the solar inverter or the DC Isolator installed between the solar panels and the solar inverter (if available) and contact us to test the DC side of the system including and excluding the solar inverter.
* TEMP HI - The solar inverter is too hot. This could be due to a number of factors, for example 1) If the solar inverter is exposed to direct sunlight 2) If the solar inverter has been installed without adequate ventilation around the chassis which would allow excess heat to dissipate 3) The solar inverter's components are getting too hot due to an internal component fault. If the unit isn't running hot and if after the system has been safely shutdown and restarted this condition persists then contact us.
* INSULATION - This error is generated when during normal operation of the solar inverter, a leakage current to ground/earth is detected on the DC side of the system. Although it is also possible that the solar inverter generates this alarm message due to AC leakage currents connected to the capacitive nature of the solar panels compared to ground/earth or there could be a problem with the solar inverter itself.
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For as long as the situation persits then the solar inverter will not startup. Earth / Ground Faults (also called Insulation or Isolation Faults) often present themselves when it is raining or at times of high humidity when moisture can enter the solar PV system through damaged solar panels, connectors or cabling. These faults often clear when weather conditions improve but they will not get better by themselves, most often degrading and becoming more dangerous over time. We would advise that you book a solar repair engineer's visit in order to carry out a full solar system test, identify the source and rectify the fault. 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 |
* NTC FAIL - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* EF I2C FAIL - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* ENS FAIL - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* CB I2C FAIL - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* HW VAC FAC - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* HW RELAY - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* HW ERROR 1 - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* HW ERROR 2 - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* HW ERROR 3 - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* HW ERROR 4 - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* HW ERROR 5 - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* HW ERROR 6 - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* HW ERROR 7 - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* HW ERROR 8 - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
* HW ERROR 9 - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
Mastervolt Soladin Solar Inverter Faults and Warnings:
▬▬▬▬▬▬▬▬ Uninterrupted red light - No grid voltage - The solar inverter is not measuring a grid (mains) voltage suggesting that mains power to the unit has been disconnected. If this fault persists and mains power is available to other local circuits then check that all isolators, MCBs and RCDs on the AC side of the solar PV system are 'On'. If automatic safety devices such as MCBs or RCDs have switched 'Off' then leave them 'Off' and contact us to arrange for a solar engineer to visit to establish whether the fault lies with the solar inverter, the supply circuit or with the grid.
• • • • • Red blinking light - 1 time - The solar inverter is measuring low DC voltage. Assuming that this is an existing installation that has been specified correctly, there is sufficient irradiation (sunlight), no changes near the installation area have been carried out and the system has operated before without problems, then we would advise that you book a solar repair engineer to test the DC side of the system including and excluding the solar inverter.
•• •• •• •• Red blinking light - 2 times - The solar inverter is measuring too much voltage from the solar panels. Assuming that this is an existing installation that has been specified correctly, hasn't recently been changed or added to and has operated before without problems. This could mean either a problem with the solar panels or with the solar inverter. We would advise that you book a solar repair engineer to test the DC side of the system including and excluding the solar inverter.
••• ••• ••• Red blinking light - 3 times - The solar inverter is measuring a grid (mains) voltage that is too high in relation to the parameters that the solar inverter has been set to safely operate within. If this fault persists contact us to arrange for a solar engineer to visit to establish whether the fault lies with the solar inverter or with the grid.
•••• •••• Red blinking light - 4 times - The solar inverter is measuring a grid (mains) voltage that is too low in relation to the parameters that the solar inverter has been set to safely operate within. If this fault persists and mains power is available to other local circuits then check that all isolators, MCBs and RCDs on the AC side of the solar PV system are 'On'. If automatic safety devices such as MCBs or RCDs have switched 'Off' then leave them 'Off' and contact us to arrange for a solar engineer to visit to establish whether the fault lies with the solar inverter, the supply circuit or with the grid.
••••• ••••• Red blinking light - 5 times - The solar inverter is measuring a grid frequency that is either too low or too high in relation to the parameters that the solar inverter has been set to safely operate within. If this fault persists and mains power is available to other local circuits then check that all isolators, MCBs and RCDs on the AC side of the solar PV system are 'On'. If automatic safety devices such as MCBs or RCDs have switched 'Off' then leave them 'Off' and contact us to arrange for a solar engineer to visit to establish whether the fault lies with the solar inverter, the supply circuit or with the grid.
•••••• •••••• Red blinking light - 6 times - The solar inverter is too hot. This could be due to a number of factors, for example 1) If the solar inverter is exposed to direct sunlight 2) If the solar inverter has been installed without adequate ventilation around the chassis which would allow excess heat to dissipate 3) The solar inverter's components are getting too hot due to an internal component fault. If the unit isn't running hot and if after the system has been safely shutdown and restarted this condition persists then contact us.
••••••• ••••••• Red blinking light - 7 times - If after the system has been safely shutdown and restarted this condition persists the inverter has a fatal error and should be replaced. There are a few ways that we can help with this: Solar Inverter Replacement
Solar Inverter Recycling: - Recycling Mastervolt Solar Inverters
Mastervolt solar inverters contain valuable materials such as copper and aluminium, these materials are in high demand and recycling them is significantly less energy intensive than extracting them from ore.
If you find yourself with a damaged or faulty Mastervolt solar inverter, we will be pleased to help you recycle it.
- There is no charge for this service but all costs involved with decommissioning and transportation are covered by you.
- If you're delivering an inverter to us in person, although it's usually no trouble to arrange other days, the most convenient time for us is between 9am and 2pm on a Saturday, please let us know of your visit with an approximate time in advance.
- We do not buy or sell used solar inverters or used solar inverter parts. For UK buyers and sellers, we've found ebay to be the best place for buying used solar inverters and inverter parts.
- We can accept deliveries by courier at all times throughout the week but please contact us before you arrange this.
- We can also help to recycle solar panels, solar batteries and solar mounting equipment.
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.
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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 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 your new unit's serial number and confirm the warranty details with the manufacturer.
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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 Systems & Equipment, including Electrical & Roofing Systems
Grid-tie inverters, Hybrid Inverters, AC Coupled Inverters, Battery Storage Inverters, Off-Grid Inverters, Charge Controllers, Transfer Switches, Hot Water Controllers, Optimisers, Lithium Batteries, Lead Acid Batteries, Solar Panels, Mounting Systems, Test Equipment, Earthing Equipment, Electrical Distribution Equipment, Cable and Accessories
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Deliveries to anywhere in the UK are quick, tracked and accurate, technical support (by phone and on site if needed) and design/product advice is available before, during and after installation. The recording and collating of serial numbers, factory and other test results, manuals any other information required for equipment warranties, add ons and extensions is included. Trade, DIY and Retail Clients Welcome. |
Bespoke system design, equipment testing and integration support as well as on-site technical support and job/equipment specific training is available for off-grid, hybrid, larger and or more complex systems.
Mains/Grid Isolation and Surge Protection
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A whole house surge protector is installed to provide protection from transient overvoltages originating from the mains/grid. A whole house surge protector is installed directly inline and as close as possible to the incoming mains/grid supply meter, this allows for surge protection for all circuits and equipment including solar inverters, routers, stereos and other sensitive electrical equipment within the network. The addition of a 100Amp lockable isolator also allows for safe and convenient isolation of all electrical equipment within the network including consumer units, solar inverters, battery storage units and EV chargers from the mains/grid in one place. Surge protectors are in compliance with the recently updated 18th edition amendment 2 of BS7671. |
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.
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How to provide backup power to a house using a portable generatorIn this article we show you how to provide backup power to your home using a portable diesel, petrol or LPG backup generator. We look at changeover switches, the importance of earthing, backup generator loadings, how to isolate non essential loads. We ask where to locate the backup generator when it's in operation, how best to safely isolate the grid/mains power supply and switch to a backup generator supply. BSI - PAS 63100:2024 - Protection Against Fire of Battery Energy Storage Systems for use in DwellingsThis Publically Available Specification (PAS) from the British Standards Institution (BSI) was sponsored by The Department for Energy Security and Net Zero. Although not yet a British Standard, this guidance was developed in response to an urgent demand for clarity as to good practice across the industry including product, service and process standards. Solar PV, Safety & The Building RegulationsResidential PV systems notifiable under Part P. Special consideration needed for Part A. A combination of serious risks for solar PV installers. Ground Faults, Isolation (ISO) Faults, RISO Low Faults and Insulation Resistance Faults with Solar PV SystemsAfter 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. |
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.
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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