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Safely Retrofitting Roof Mounted Solar Photovoltaic (PV) Panels

You've decided how many solar panels you need, you know the size of the panels and you know how you want them to be laid out. Now you've got to work out how to get them safely up to the roof, secure them and be certain that they will stay there.

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Retrofitted Solar PV Panel System


This article describes some of the steps to take when carrying out a retrofit roof mounted solar PV installation and the typical equipment used to secure an on-roof (flat or pitched) solar PV system. We don't go into any detail about the electrical side, this article concentrates purely on the safety considerations and mechanical aspects of a typical retrofit PV installation.

Roof Assesment Survey

Asbestos Corrugated Sheeting

Assess the roof & Identify risks

This part should be carried out on first inspection and refered to throughout the system design stage. A record should be kept of what you find (ideally with pictures). Some of the key aspects relevant to roof mounting solar panels and the potential dangers, include:

  • Fragile roofing materials, including insecure, inadequate, corroded or broken roof fittings, anything that the installer or materials could potentially fall through if weight was applied.
  • Any protection at the roof edges to stop the installer, tools and or materials falling i.e something to stop a person or equipment sliding down the roof and over the edge.
  • The presence of asbestos, lead and other contaminates that could cause problems if cut, damaged or disturbed. Remember to also look at flashings, guttering, pipes and pipe insulation.
  • Insecure, inadequate, rotten or broken roof supports and rafters that may not be strong enough or big enough to handle the increased weight loading or provide a secure connection for the mounting feet.
  • Existing waterproofing and flashings, any damp, staining or corroded areas may be an indication of underlying instability.
  • External influences such as the proximity of power lines that may cause difficulties or dangers during the installation.
  • Moss, lichen or anything else that may be slippy when walked on.
Solar PV Panel Installation

Identify consequences (who and how might people be harmed)

Once you have this information think about and record the ways in which the issues that you have identified could affect the installation including:

  • The suitability of the equipment that will be installed in relation to the mounting area.
  • The suitability of the equipment that will be used for the installation.
  • The safety of the installation team.
  • The safety of others who may be using the building or be close to the building whilst the installation is taking place.
  • The long term effect of the increased weight loading on the structure.
  • Any uncovered problems that could be made worse because of the PV installation or spread to affect the installation at a later date.
Retrofit Solar PV Installation Planning

Identify suitable protections

Once you have considered these factors you are then likely to have a good idea of the best way to overcome these issues and progress, whilst reducing risks and selecting the most suitable equipment for the PV system itself and the equipment needed to carry out the installation.

Retrofit Solar PV Panel Installation

In many cases issues identified at this stage can be 'designed out' by using different equipment, changing the specification or making improvements to or changing the mounting area before the solar PV system is installed.

If there is any uncertainty, consult a building surveyor, a relevant specialist or the local building control department, this is likely to save time, money and effort later. If you are not sure, consulting a specialist and following their recomendations will give you the certainty to move forward confidently.

Scagffolding Tower

Access, Lifting & Safety Equipment

Depending on the nature of the installation and the potential risks you have identified, in conjunction with the heights you are working with, the size of solar PV system that is being installed and the stability of the roof; you may want to consider using a combination of the access, lifting and safety equipment below.

Access Equipment: General access scaffolding, tower scaffolds, stair scaffolds, trestles, ladders, roof ladders (crawling boards) could all be safely employed. You could also use Mobile Elevated Work Platforms (MEWPs) such as scissor lifts, cherry pickers and cranes.

Lifting Equipment: Gin Wheels, scaffold hoists, gantry hoists, scissor lifts, cherry pickers and cranes could all be used to safely raise the solar panels to the required height.

Commercial Flat Roof

Safety Equipment: Edge protection such as safety nets, guard rails and toe boards could be used to prevent equipment and people falling too far. Personal protection including harnesses (both to avoid a fall or reduce the consequences of a fall), could also be used but should be considered (when used in isolation) as a last resort if edge protection and other measures are not practicle.

Edge Protection for Commercial Flat Roof
The key points are to ensure that whichever installation equipment you choose it is right for the job and used correctly. Your primary aims should be to ensure that the risks involved in falling (people and materials) and the problems encountered when handling bulky and heavy solar equipment at height are reduced or ideally eliminated.

Solar Roof Mount Components (Retrofit)

There are mounting systems available to suit most types of installation and nearly all types of flat and or pitched roof. Some mounting system components common to many installation methods and the purpose of each is described below:

Solar PV Roof Mount: Foot


Mounting Feet / Roof Hooks: attach directly to the roof supports and are the main anchor points for the array. Mounting feet come in different sizes and can also incorporate extensions to raise the array depending on how far above the roof level you prefer the solar array to be (increased airflow) and the depth of the existing roof coverings (so the array rests on the rails not the roof). Mounting feet can also be used to increase the tilt of the array at an angle which is greater than the tilt of the roof if required to improve solar gain.

Solar PV Roof Mount: Extruded Rail
Extruded Rails: are secured to the mounting feet which in turn secures the rails to the roof. Extruded rails are usually made of high strength aluminium and are used to support the weight of the solar panels and provide a stable and flat surface onto which the solar panels can be individually secured. Individual rails can be supplied in spans up to 6m.
Solar PV Roof Mount: Internal Splice
Internal Splices: are used to extend the length of the extruded rails through slotting in the insides of the two rails that are to be joined. Internal splices lock into cavities built into each rail and are secured using self tapping screws.
Solar PV Roof Mount: End Clamp

Solar Panel Clamps

End Clamps: are used to secure the outside edges of the first and last solar panel in each row of the solar array to the rails.

Centre Clamps: are used to secure the inside edges of two solar panels to the extruded rails.

Useful external resources

Other documentation that may be useful for clients and installers in relation to installating solar photovoltaics safely onto roofs can be downloaded below.

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Mains/Grid Isolation and Surge Protection

Mains/AC Surge Protection Solar PV Systems

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.

Mains/Grid Isolation and Surge Protection


Solar PV Surge Protection (DC Surge Protection)

DC Surge Protection Solar PV Systems

DC surge protection devices (SPDs) are installed between the solar panels and the solar inverter to protect both the solar inverter and the downstream electrical equipment from transient overvoltages of an atmospheric origin impacting the electrical system via the DC side of the system / the solar panels.

DC Surge protectors are in compliance with the recently updated 18th edition amendment 2 of BS7671.

Solar PV Surge Protection (DC Surge Protection)

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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

Engineering Recommendation G98

Grid Connections for Micro-Generators including Solar PV Systems and Elecricity Storage Systems in the UK. Under 16Amps Per Phase, grid synchronised.

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.

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.

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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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