Our Installation Standards

Roof works

The roof was weathertight before we arrived and it has to be weathertight when we leave. Everything else on this page is secondary to that.

• The covering and the structure are inspected from the scaffold before the first tile is lifted. Rafter size, span and centres are established at survey and confirmed on site; assumptions taken from aerial imagery are not carried into the fixing layout.
• Tiles and slates are lifted, not broken. Where a tile has to be cut to clear a bracket it is cut cleanly and dressed, and any cut edge is left supported. Slates are refixed with hooks or tingles rather than face-nailed through the middle.
• Cracked, delaminating or perished tiles found during the works are photographed and reported to you before an array goes over them. We do not cover defective covering and leave you to find it later.
• Ridge, hip, valley and verge details are left as found or better. Mortar disturbed during the works is made good.
• Array setting-out respects the roof: minimum edge distances are maintained from verge, eaves, ridge and abutments so wind uplift at the perimeter is not carried by the outermost fixings alone, and so a roofer can still get to the details later.
• Flat roof and membrane work is either fully ballasted or mechanically fixed with penetrations detailed by someone competent to work on that membrane. Nothing is fixed through a single-ply membrane without a proper detail and, where the roof is under warranty, without the covering manufacturer’s method.
• Loft insulation is lifted and reinstated, not compressed or left in the working area. Roof voids are left clear of offcuts, cable ends and packaging.

Fixings and structural interface

This is where poor installations fail first, usually two or three winters after handover, and always expensively.

• Roof anchors are fixed into rafters, never into battens. A batten is a tile-carrying member. It is not a structural fixing point for an array carrying wind uplift, and any array fixed to battens is a defect regardless of how it looks on the day.
• Where a rafter cannot be reached at the required position, the fixing is moved to a rafter that can be reached, or a properly designed spanning member is installed. Fixings are not placed where they miss.
• Anchor spacing and rail span are taken from the mounting manufacturer’s structural tables for the actual site: wind zone, terrain category, building height, roof pitch and position of the array on the roof. Standard spacing is not applied to an exposed site because it worked on a sheltered one.
• Screw type, diameter and embedment depth follow the mounting system specification. Pilot holes are drilled where the specification requires them so the rafter is not split.
• Every penetration is sealed by the method the mounting system specifies for that covering — a flashing, an anchor with an integral seal, a lead or proprietary soaker — not by a bead of sealant applied over a hole.
• Rails are levelled and aligned, thermal expansion gaps are left where the system requires them, and rail ends are finished with end caps rather than left as an open cut section.
• Module clamps are placed only in the manufacturer’s permitted clamping zones and tightened to the stated torque with a calibrated tool. Over-tightening a frame is as much a warranty problem as leaving it loose.
• In-roof systems are installed as a roof covering in their own right, with the tray, flashings and underlay laid to shed water outward and downward at every lap.

Electrical works

The installation is a generating set connected to a domestic supply. It is designed and tested as one, to BS 7671 and the relevant guidance for solar PV and electrical energy storage systems.

• The existing installation is assessed before anything is added: main earthing conductor and main protective bonding sizes, the earthing arrangement, the condition and rating of the consumer unit, available ways, and the supply capacity. Where the existing arrangement will not support the addition, that work is priced in the quotation rather than raised as a variation.
• String design is checked against the inverter’s operating window using the panel’s temperature coefficients, so open-circuit voltage at the lowest expected cell temperature stays inside the inverter’s maximum input voltage and the array still operates at the highest expected temperature.
• DC cable is sized for current-carrying capacity and for voltage drop over the actual route, using double-insulated solar cable rated for the temperature and UV exposure it will see.
• DC connectors are of one type and one manufacturer within a connection. Mating different makes of connector is not permitted, even where they appear to fit — it is a known cause of overheating and roof fires.
• AC circuits are protected and sized correctly for the inverter output, with the correct type of RCD for the equipment. Where the inverter or battery system requires a particular RCD type, that type is fitted.
• Surge protection is provided where required by the risk assessment for the installation, and earthing and bonding of the array frame is carried out where the system design calls for it.
• Battery systems are installed to the manufacturer’s instructions and the applicable code of practice: correct location, ventilation, clearances, fire separation where required, and the specified protection and isolation on both the battery and inverter sides.
• EV charge point work follows the same discipline, including the correct earthing arrangement for the supply type. Our page on EV charger installation sets out what that involves.

Isolation

Anyone who arrives after us — an electrician, a roofer, a firefighter — must be able to make the installation safe without guessing.

• A DC isolator is provided in the position the design requires so the array can be separated from the inverter, and an AC isolator is provided adjacent to the inverter so the inverter can be separated from the supply.
• Isolators are readily accessible, not buried behind the array, above a hatch that needs a ladder, or inside a locked cupboard nobody mentions at handover.
• Battery systems have their own means of isolation, clearly identified, in addition to the PV DC and AC isolation.
• The full shutdown sequence — the order in which isolators are operated to make the system dead — is proved at commissioning and written on a label at the point where someone will look for it.
• Where a firefighter switch or a rapid shutdown device forms part of the design, it is installed, labelled and demonstrated at handover.

Cable management

Cable routed carelessly is the fault that turns up in year four, when nobody remembers what runs where.

• No cable carries its own weight on a connector. Runs are supported at intervals with UV-stable fixings, and cable is never left resting on tiles, hanging in a loop under an array, or in contact with a sharp roof edge.
• Exposed external runs are in UV-resistant containment, fixed straight and level, and kept off the roof surface so debris and water can pass beneath them.
• Roof and wall penetrations are sleeved and sealed on the weather side, and made good internally.
• DC and AC cabling are segregated and identified. Inside the loft, cable is clipped and contained, run alongside structure rather than diagonally across a void, and kept clear of downlighters and flues.
• Cable is not run where it will be walked on, stored against, or crushed by a board someone lays across the joists.
• Enough slack is left at the inverter, battery and consumer unit for a future service or replacement, and no more.

Labelling

The test of the labelling is simple: an electrician who has never seen the property should be able to understand the installation from the labels alone.

• A dual supply warning label at the origin of the installation and at the meter position, so nobody assumes the consumer unit is the only source of energy.
• The PV array, DC isolator, AC isolator, generation meter position and battery isolation each labelled with what they are and what they do.
• Circuit identification at the consumer unit updated so the new circuits appear on the schedule, not written in pen on the inside of the lid.
• A shutdown procedure label listing the isolation sequence in the order it must be carried out.
• Warning labels on any enclosure or accessory that remains live after the main switch is opened.
• Battery installations labelled with the chemistry, the isolation points and the manufacturer’s required safety information.
• Labels of a durable material, machine-produced, fixed where they can be read without dismantling anything, and legible in years to come rather than a handwritten sticker that fades.

Scaffolding and access

Nobody works from a ladder on a roof through Solar Fx. Access is designed for the elevation, not improvised on the morning.

• Scaffolding is designed and erected for the elevation, the roof pitch and the loads involved, by a scaffold contractor competent for that work.
• It is handed over in writing as fit for use before anyone works from it, inspected before first use and re-inspected at the required intervals and after anything that could affect its stability.
• Edge protection, a safe means of access, and a working platform at the correct height relative to the eaves are provided as standard rather than on request.
• Where a scaffold stands on a neighbour’s land, a shared drive, a public footway or a highway, the permission or licence is arranged before the installation date is confirmed.
• Public and household access routes beneath and around the scaffold are protected, and debris nets or sheeting are used where materials could fall.
• Roof-mounted work stops in wind, ice or conditions in which it cannot be done safely, and the date is moved rather than the standard.

Commissioning and testing

Commissioning is a set of measurements written down, not a look at the inverter screen.

• Before energising: DC string polarity, open-circuit voltage against the calculated value, and insulation resistance on each string.
• On the AC side: continuity of protective conductors, insulation resistance, polarity, earth fault loop impedance and RCD operating time and current.
• On energising: operating current per string compared against expected values for the irradiance at the time, inverter start-up sequence, and confirmation that the inverter’s grid protection settings match the required national settings.
• Loss-of-mains and reconnection behaviour confirmed, and the isolation and shutdown sequence physically proved rather than assumed.
• Battery systems commissioned to the manufacturer’s procedure, with charge and discharge proved, the operating mode set to what was agreed with you, and firmware brought up to the current release.
• Monitoring configured, the portal registered in the customer’s name, and generation, consumption and battery data all confirmed as reporting before anyone leaves site.
• All results recorded on the electrical installation certificate and the schedule of test results, and issued as part of the documentation pack.

Handover

The job is finished when you can operate the system and you hold the paperwork, not when the scaffold comes down.

• An in-person walkthrough covering isolator locations, safe shutdown and restart, what the display and app are showing, how any battery schedule or tariff setting has been configured, and what normal performance looks like across a year.
• The documentation pack handed over: electrical installation certificate and test results, as-installed specification and layout, manufacturer manuals and datasheets, warranty registrations, and the network notification or connection agreement.
• The certification for the installation provided so you can apply to a Smart Export Guarantee licensee for an export tariff.
• The property left clean: working routes cleared, protection removed, packaging and offcuts taken away, and the loft left as it was found.
• A named route for aftercare — what to check yourself, what needs a visit, and how to raise a fault or a warranty claim. Our maintenance service and warranty pages set out both.
• Anything outstanding recorded in writing with a date, rather than left as an understanding between you and whoever was on site that day.

What these standards are measured against

Nothing above is invented in-house. Each item traces back to a standard, a manufacturer’s instruction or a network requirement.

Common questions

Related reading

The standards above in context — the survey they come out of, the products they apply to and the cover that follows.

• How Solar Fx worksThe seven stages from enquiry to commissioning, and where each standard applies.
• Warranties and guaranteesProduct, performance, inverter, battery and workmanship cover, and how a claim is made.
• Mounting systemsRails, anchors, in-roof trays and ballasted frames, and how each interfaces with a roof.
• What happens during a solar surveyThe inspection that determines rafter centres, fixing layout and cable routes.
• Scaffolding and access for solarWhy scaffolding is specified, who erects it, and what the permissions involve.
• Solar panel repairsPutting right installations that were not carried out to these standards.