Solar Panel Faults

Solar panels are generally considered to be maintenance free.  It should be noted that whilst the potential problems listed below may arise they are relatively rare and the vast majority of panels will return many, many years of trouble free operation.  There are however rare occasions where individual panels or cells can become defective.  Listed below are some of the failings of Solar Panels:

Should your system have developed and faults and require any solar panel repair or maintenance don’t hesitate to contact C Gascoigne Limited.

Physical/Mechanical Damage

One of the most likely and certainly most visually noticeable faults is a cracked or broken glass.  The front glass serves as a self-cleaning protective layer for the delicate cells underneath which allows the sun’s rays to access the cells in the most efficient way possible.  If the glass is broken or damaged in any way this can affect yield and also potentially allow access to the dangerous voltage the panels operate at.  The glass is the first line of protection from the system voltage and should be treated in this regard.

If you have a panel with a broken glass then you should keep clear of the system and immediately report it to a competent person who has the knowledge and equipment to deal with the problem.

Damaged Backing Material

If your panel backing material has a defect of has been compromised at installation stage, then this may show up as moisture ingress on the front of the panel or an open circuit panel due to a damaged solder string.  This is almost impossible to spot without having visual access to the underside of the panel.

Bypass Diode Failure

Each solar panel has a number of bypass diodes in the rear connection box.  The bypass diodes minimise the effects of shading or reverse currents flowing in a panel under fault conditions.  A missing or defective diode can reduce the panels voltage by a third and depending upon how they fail could reduce the system efficiency even further.  These problems can be hard to identify and can go unrecognised for many years.

Connection/Diode Box Delamination

As described above.  On the back of each panel is a diode box.  These boxes are fixed to the panels using a compound and if poorly installed can become loose or delaminate from the backing material.  This in turn opens the box to the elements.  Again, very hard to identify in situ on a roof mounted array and again would probably go for many years without detection.

Trapped DC Cables/Insulation Faults

Each panel has two cables existing the diode box which have pre terminated connectors designed to connect it to its neighbouring panel which form the series wired string circuit in an array.  These cables are routinely 1 meter in length and can become trapped between the array frame and panel frame during installation.  Once the panel clips are tightened to secure the panels in place the cables can become crushed.  Whilst this compression fault may not show up at initial commissioning stage it may take several months or even years to be seen.  As the wind presses on the panels and the summer and winter temperatures expand and contract the frame, pressure on the trapped cable splits the insulation around the cable and starts to become more noticeable as the inverter trips out on insulation fault.  This can sometimes be more pronounced in wet conditions as the voltage tracks through the water.  This again has the hall marks of a disaster waiting to happen as the frame which the array is secured to can become live.  Most inverters have on board insulation monitoring circuits and will trip out in the event of such a fault occurring.  Whilst this stops the system from generating power and possibly brings it to the attention of a system operator it does not remove the fault.  Systems with insulation faults should be treated with great care and reported to a competent person for diagnosis at the earliest possible time.

The above fault can also be the result of a poor connection on a made up connector or water ingress to the same.


If you notice water ingress, (fogging), or mould growth under the panel glass then this is a sign of a panel frame seal failure.  If the panel has been stressed during installation, i.e. where the rails which the panels are fixed are not straight and the panel has been bent or forced onto the rails twisting the panel then the seals can be breached.  This in turn allows moisture to seep under the panel glass and allow mould growth or the backing material or glass to delaminate from the cells.  This will normally be evident via a visual inspection of the system.

Micro Cracks

Micro cracks can be traced back to three sources, manufacturing faults caused at soldering stage, transportation stage due to poor packaging and stacking and or installation/field stage by poor handing/incorrect installation/support.  Micro cracks can be seen under electroluminescence testing and can create yield loss by reduced cell performance area.  Micro cracks can be found in almost any panel, high end or otherwise and can have varying degrees of impact.  Micro cracks can also be a source of hot pots.

Hot Spots

Hot spots in a solar array can be created by poor or damaged soldered joints of internal strings or faulty solar cells.  Due to faults within the panel a panel current is allowed to back feed a particular cell or high resistance joint of a cell which can build up heat.  Hot spots can be seen on thermal imaging cameras in the right conditions or electroluminescence tests carried out at night.

Potential Induced Degradation – (PID)

PID is a complex fault which can arise in systems with no galvanic separation in the inverter, (transformerless/electronic inverters).   PID is where a solar array becomes bias towards either negative or positive with reference to ground.  This shift can cause up to and around 30% losses in a system.  The fault can be reversed by the use of an offset box.  PID can be tested for by the use of electroluminescence test equipment carried out at night.

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