9.3 Equipment Siting and Permissions

Quick Answer: Handbook outcome 4.1.5 requires all equipment to be sited taking into account applicable regulations, local authority requirements, applicable standards, and manufacturers’ instructions and guidance. That is four gates, not one. Building Regulations notification (structure, fire, weathertightness, electrical) is not the same as planning or listed-building consent. MCS 012 is the product standard for mounting kits. Where no certified kit is suitable, MCS 5.5.5 practice is an evidence trail: structure and wind, fire, weathertightness, and compatibility. Inverter location is previewed here (IP rating, ventilation, fireproof mounting) and detailed in a later chapter.

Four siting inputs, every device

Outcome 4.1.5 does not apply only to modules. Inverters, isolators, generation meters, batteries, distribution boards, DC combiners, and cable routes all have a location. A module layout that packed beautifully in section 9.1 still fails 4.1.5 if the inverter is in an unvented plasterboard cupboard beside a plastic oil tank on a listed wall.

Work the four inputs in order on every device:

1. Applicable regulations — in England and Wales that includes the Building Regulations (notably Part A structure, Part B fire, Part C moisture/weathertightness, Part P electrical in dwellings) and the Electricity at Work Regulations for safe isolation and equipment. Scotland and Northern Ireland use devolved building-control systems; the duty to site lawfully does not disappear at the border.
2. Local authority requirements — planning under the householder permitted development rules where they apply; listed-building consent; conservation-area and Article 4 restrictions; anything the authority having jurisdiction has published for that plot.
3. Applicable standards — BS 7671 (including Section 712 for PV), the IET Code of Practice for Grid Connected Solar Photovoltaic Systems, MCS installation practice (MIS 3002), MCS 012 for mounting products, and the ENA recommendations from section 9.2 for the connection.
4. Manufacturers’ instructions and guidance — rail spans, clamp zones, inverter mounting surface, IP rating, ventilation clearances, ambient temperature, orientation (some inverters must not lie flat), and forbidden locations (unvented cupboards, combustible surfaces, direct sun, saline spray). A competent-person certificate does not overrule a manufacturer ban.

Independent OpenExamPrep teaching keeps those four sources distinct. This guide does not describe OpenExamPrep as a City & Guilds, MCS, or ENA partner.

Building Regulations notification is not planning

Planning permission asks whether the development is acceptable in land-use and appearance terms. Most ordinary householder roof-mounted PV on a dwelling is permitted development if the published conditions are met (including projection and height limits, and typically not higher than the highest part of the roof excluding the chimney). Flats, listed buildings, some conservation-area frontages, Article 4 directions, and many ground mounts fall outside that easy path. Always check the local planning authority when any of those flags is present.

Building Regulations ask whether the work is safe and weathertight. Roof PV always has a Building Regulations story even when planning is permitted development:

• Structure (Part A): rails and modules add dead load and wind uplift. Clause 5.9.4-type MCS practice requires a competent check of the roof; unusual, distressed, or modified roofs need a structural engineer.
• Fire (Part B): the array must not wreck the roof’s fire performance. On a pitched roof, sitting above an existing non-combustible covering is the usual demonstration. In-roof kits need the fire classification that matches boundary distance. Approved Document B is the England and Wales fire guidance; devolved nations have their own approved documents.
• Weathertightness (Part C and the roofing system): flashings, hooks, and seals must leave the roof able to shed water for the life of the system.
• Electrical (Part P in dwellings, plus BS 7671): notifiable electrical work, certificates, and a route through a competent person scheme or a building-control application.

A competent person scheme notification (the installer self-certifies and the scheme tells building control) is still Building Regulations compliance. It is not listed-building consent and it is not a G99 offer.

Listed buildings typically do not enjoy the same permitted-development comfort. Listed-building consent is a local-authority process. Altering a listed building without the required consent is a criminal offence, not a paperwork delay. Black frames do not create a consent. Rear-elevation-only folklore does not create a consent. Ask the conservation officer before a surveyor’s chalk marks hit historic slates.

MCS 012 versus 5.5.5 evidence

MCS 012 is the product standard for solar mounting kits. A certified kit has been assessed as a product for structural performance, weathertightness, and related fire/safety behaviour on the roof types in its certificate. Specifying a live MCS 012 kit that matches the roof and the module is the clean siting route: the product already carries that evidence.

MCS 5.5.5 (in MIS 3002) is the installer-side clause for the awkward roof: where no MCS 012 certified mounting system is suitable for the given installation, a custom or otherwise uncertified arrangement may only be used with evidence. Current MCS practice expects the installer to be able to produce:

• completed structural and wind-loading calculations for the specific mounting system on that roof
• how fire performance has been maintained after installation
• how weathertightness has been maintained after installation
• that system components are compatible with one another
• confirmation that the installation follows manufacturer instructions

Those four evidence heads — structure, fire, weathertightness, compatibility — are exactly the siting questions 4.1.5 is pointing at when the roof is not a catalogue kit. MCS has tightened the wording of 5.5.5 so that a vague “it meets Building Regulations” sentence is not enough; keep the calculations and the written confirmations with the installation record. Present that as MCS installation practice a 2922 candidate should know, not as a City & Guilds exam-fee table.

If the kit is MCS 012 certified for that roof, you still follow the manufacturer’s laying pattern, clamp zones, and edge distances. Certification is not a licence to invent a layout.

Inverter location preview (detail in a later chapter)

Inverters fail from heat, water, dust, and being mounted on the wrong surface. Siting them is a 4.1.5 task even though the full AC/DC isolation chapter comes later.

• IP rating: the datasheet ingress protection must match the location. An indoor IP21 product in a wet alley is a manufacturer breach. An IP65 outdoor product still needs its glands, covers, and clearances; IP65 is not “install in a puddle.”
• Ventilation: manufacturers publish side, above, and below clearances because heat sinks need air. An unvented cupboard traps that heat. Loft spaces in summer can exceed the rated ambient. Batteries in the same volume add more heat and their own manufacturer rules.
• Fireproof mounting: many inverter instructions require a non-combustible mounting surface and specified clearances to combustible materials. Ordinary plasterboard on timber studs is not a fireproof mounting board. If the manufacturer requires a fireproof plate, fire-rated backboard, or masonry, that instruction is 4.1.5. Do not site inverters in unvented cupboards on plasterboard when the manufacturer requires fireproof, ventilated mounting.
• Access: DC and AC isolators must be reachable for maintenance and emergency isolation. A sealed loft hatch with no boarded walkway is not access.
• Environment: oil vapour, agricultural dust, ammonia, sea salt, and direct solar gain all sit in manufacturer limits. A plastic oil tank is not a heat sink and not a fire barrier.

Full gland, loop, and isolation detail belongs in the later equipment chapter. The siting decision is made before the first screw.

Constraint versus who owns it

Scenario: listed cottage, plastic oil tank adjacent, loft inverter idea

A Grade II cottage has a south roof the salesperson loves. A polyethylene oil tank sits against the rear wall under the eaves. The customer wants the inverter “hidden” in an unvented loft cupboard lined with plasterboard, reached by an unboarded hatch.

Stop the quote and split the gates.

Local authority: the building is listed. Roof PV, visible cabling, and often even discreet in-roof trays need listed-building consent (and planning if PD is withdrawn). Start with the conservation officer. Do not treat MCS registration as consent. Do not treat a competent-person electrical notice as consent.

Oil tank: OFTEC and Approved Document J practice keeps a plastic tank about 1.8 m from non-fire-rated eaves, openings, and combustible structures unless a qualifying 30-minute fire barrier is installed to the published details. The tank is already “adjacent.” Adding an inverter, battery, or DC isolator into that heat-and-fault neighbourhood does not create a fire barrier. It adds an ignition source next to stored fuel. Relocate the electrical plant, relocate or barrier-protect the tank through a competent oil specialist, or both. Do not invent a 200 mm “gap behind the tank” as compliance.

Loft cupboard: if the inverter manufacturer requires a ventilated, fireproof-mounted, IP-correct location with published clearances, an unvented plasterboard cupboard fails manufacturers’ instructions — which is an explicit 4.1.5 fail — before you even argue about summer loft temperature or safe isolation access. A later chapter will cover glands and isolator height. This chapter’s answer is do not site it there.

Mounting on historic slates: even if consent is granted, check whether an MCS 012 kit is certified for that covering. If it is not, 5.5.5 evidence (structure/wind, fire, weathertightness, compatibility) is required, and a conservation roof may also need a specialist slating detail. Capacity from section 9.1 still applies: listed roofs often have small planes, hips, and chimneys, so the kWp the customer saw on a new-build garage will not pack.

The competent 2922 answer on this site is a written constraints list with owners: conservation officer, building control/competent person, DNO, oil-tank rules, and the inverter datasheet. The incompetent answer is a single visit that promises 6 kWp, a cupboard inverter, and “it will be fine because it is at the back.”