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C&G 2922-34 Solar PV study materials
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C&G 2922-34 Solar PV practice questions

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Question 1Health, safety and regulatory requirements for small scale solar PV

Under Building Regulations Part P (England and Wales), which item of solar PV work is notifiable to a building control body?

  1. Adding a new DC circuit to the inverter Correct answer.
  2. Replacing a broken module with an identical one
  3. Swapping a faulty inverter for the same model
  4. Cleaning the module glass with a hosepipe

Explanation

Part P applies to electrical work in dwellings, and the installation of a new circuit is notifiable whether that circuit is AC or DC. Like-for-like replacement of accessories and routine maintenance such as cleaning are not notifiable.

Question 2Health, safety and regulatory requirements for small scale solar PV

A 3.6 kW single-phase domestic PV system is to be connected to the public network. Which body must be notified?

  1. The electricity billing supplier
  2. The distribution network operator Correct answer.
  3. The Health and Safety Executive
  4. The local building control body

Explanation

Any generating unit that operates in parallel with the public network requires the agreement of the distribution network operator. Household-scale single-phase systems are notified under the G98 process.

Question 3Health, safety and regulatory requirements for small scale solar PV

Which document sets out the UK requirements for the design, erection and verification of electrical installations, including solar PV?

  1. HSE Guidance Note GS38
  2. BS 7671, the IET Wiring Regulations Correct answer.
  3. The Electricity Safety, Quality and Continuity Regulations 2002
  4. MCS MIS 3002

Explanation

BS 7671 is the national standard for electrical installations, and Section 712 sets out the particular requirements for PV systems. Other documents support it but do not replace it as the installation standard.

Question 4Health, safety and regulatory requirements for small scale solar PV

Which instrument should be used to prove a circuit dead before touching conductors?

  1. An approved two-pole voltage indicator Correct answer.
  2. A multimeter set to its resistance range
  3. An insulation resistance tester
  4. A non-contact voltage detector pen

Explanation

A circuit may only be proved dead with an approved two-pole voltage indicator that has been checked on a known source before and after the test. Other instruments can give false readings and must not be relied on for safety.

Question 5Health, safety and regulatory requirements for small scale solar PV

To comply with HSE guidance GS38, what is the maximum length of exposed metal permitted at the tip of a test probe?

  1. 12 mm
  2. 4 mm Correct answer.
  3. 20 mm
  4. 8 mm

Explanation

GS38 requires test probes to have shrouded tips with no more than 4 mm of exposed metal, along with finger guards and fused leads. This limits the risk of short circuits and contact with live parts.

Question 6Health, safety and regulatory requirements for small scale solar PV

A team must reach a pitched roof to fit mounting hooks. Which approach follows the Work at Height Regulations 2005?

  1. Use a ladder because it is the quickest method available
  2. Rely on the installer's balance and experience on the roof
  3. Avoid access, or use edge protection or fall arrest Correct answer.
  4. Work from the ladder without securing it to the structure

Explanation

The Regulations set a hierarchy: avoid work at height where possible, then prevent falls using edge protection or similar, and only then minimise the consequences with fall arrest. Ladders may be used only for short-duration work assessed as low risk.

Question 7Health, safety and regulatory requirements for small scale solar PV

What does BS 7671 require on the DC side of a PV installation?

  1. A 30 mA RCD on the DC side
  2. A link removed only by the DNO
  3. A lockable isolator for the DC side Correct answer.
  4. A fuse in each string near the inverter

Explanation

Section 712 requires a switch-disconnector on the DC side of the array that can be secured or locked off, so that maintenance staff can be confident the array leads are isolated. It must be rated to break DC current safely.

Question 8Health, safety and regulatory requirements for small scale solar PV

Why is a DC arc from a PV array more hazardous than an AC arc?

  1. The arc does not self-extinguish at zero current Correct answer.
  2. The inverter shuts down too slowly to help
  3. Modules deliver only a few amps, so any arc is small
  4. DC arcs are cooled quickly by the module frame

Explanation

Direct current has no natural zero crossing, so once an arc is struck it continues until the circuit is physically broken, producing intense heat and molten metal. An AC arc is extinguished automatically at each current zero.

Question 9Health, safety and regulatory requirements for small scale solar PV

Which regulation of the Electricity at Work Regulations 1989 covers work on or near live conductors?

  1. Regulation 4
  2. Regulation 14 Correct answer.
  3. Regulation 16
  4. Regulation 8

Explanation

Regulation 14 prohibits work on or near live conductors unless it is unreasonable for the equipment to be dead and suitable precautions are taken. It is the regulation normally cited when justifying live working.

Question 10Health, safety and regulatory requirements for small scale solar PV

A fitter falls from a roof and fractures an arm. Under RIDDOR 2013, what is the reporting requirement?

  1. Reportable to the HSE without delay as a specified injury Correct answer.
  2. Not reportable because the injury was not fatal
  3. Reportable to the local authority building control team
  4. Reportable only if the fitter is off work for more than seven days

Explanation

RIDDOR 2013 lists specified injuries, including fractures other than to fingers, thumbs and toes, which must be reported to the HSE without delay. The seven-day rule applies to over-seven-day incapacitation, not to specified injuries.

Question 11Health, safety and regulatory requirements for small scale solar PV

An outdoor isolator enclosure is exposed to wind-driven rain. Which IP rating confirms protection against water splashing from any direction?

  1. IPX2
  2. IPX6
  3. IPX1
  4. IPX4 Correct answer.

Explanation

In the IP code the digit after the X indicates protection against water: X4 means splashing water from any direction. X1 and X2 cover dripping water at various angles, while X6 covers powerful jets.

Question 12Health, safety and regulatory requirements for small scale solar PV

BS 7671 requires a warning notice at the origin of a PV installation. What must the notice state?

  1. The date on which the modules were last cleaned
  2. The maximum output power of the inverter
  3. The name and phone number of the installing company
  4. That the PV supply remains live after isolation Correct answer.

Explanation

Section 712 requires a durable notice at the origin warning that the installation contains a PV supply and that parts remain live after the main switch has been opened. This protects anyone who assumes the installation is dead after isolating the AC side.

Question 13Health, safety and regulatory requirements for small scale solar PV

Under the Electricity at Work Regulations 1989, who is permitted to work on a PV installation?

  1. Only an employee of the DNO
  2. Only a graduate electrical engineer
  3. A person competent to prevent danger Correct answer.
  4. Anyone supervised by a qualified electrician

Explanation

The Regulations require work to be carried out only by persons who have the technical knowledge or experience necessary to prevent danger. Formal qualifications alone do not confer competence, and supervision does not make an incompetent person competent.

Question 14Health, safety and regulatory requirements for small scale solar PV

Before drilling into an older roof or soffit to fix PV mounting, what does the law require?

  1. Nothing, provided dust is swept up afterwards
  2. A structural engineer must witness the drilling
  3. Presume asbestos unless a survey says otherwise Correct answer.
  4. The HSE must be told 14 days before work starts

Explanation

The Control of Asbestos Regulations 2012 impose a duty to manage asbestos in premises. Until a survey demonstrates otherwise, materials in older buildings must be presumed to contain asbestos and must not be disturbed.

Question 15Health, safety and regulatory requirements for small scale solar PV

Which regulations govern the lifting and carrying of PV modules on site?

  1. The Provision and Use of Work Equipment Regulations 1998
  2. The Lifting Operations and Lifting Equipment Regulations 1998
  3. The Manual Handling Operations Regulations 1992 Correct answer.
  4. The Work at Height Regulations 2005

Explanation

The Manual Handling Operations Regulations 1992 require manual handling to be avoided so far as reasonably practicable, assessed where it cannot be avoided, and the risk reduced. Modules are heavy, awkward and easily caught by wind.

Question 16Health, safety and regulatory requirements for small scale solar PV

Which practice must be followed when working with MC4 connectors on a PV array?

  1. Disconnect connectors daily to check for corrosion
  2. Push the connectors together to test them under load
  3. Isolate the string first; never separate under load Correct answer.
  4. Use metal pliers to pull the locking clips apart

Explanation

A connector opened while current is flowing will draw a DC arc that does not self-extinguish, damaging the connector and endangering the worker. The string must be isolated and proved dead before any connector is separated.

Question 17Health, safety and regulatory requirements for small scale solar PV

Before a new domestic PV installation is energised for the first time, which requirement must be met?

  1. Satisfactory test results to BS 7671 Correct answer.
  2. A structural survey of the entire property
  3. A fire risk assessment of the whole building
  4. Written approval from the module manufacturer

Explanation

A new installation must be inspected and tested before being energised, and the results must be satisfactory, so that it can be shown to be safe to put into service. Energising an untested installation is not permitted.

Question 18Health, safety and regulatory requirements for small scale solar PV

A 50 kW three-phase PV system is proposed for a commercial unit. What must happen before it is connected?

  1. Only the local fire service needs to be informed
  2. Nothing, because commercial sites are exempt from notification
  3. The DNO must approve an application under G99 Correct answer.
  4. The installer must register the system under G98

Explanation

G98 covers only small single-phase connections of up to 16 A per phase. Larger installations require an application to the distribution network operator under G99, and connection must not take place until approval is given.

Question 19Health, safety and regulatory requirements for small scale solar PV

How is compliance with Part P demonstrated for a notifiable PV installation in England?

  1. By recording the test results in the installer's logbook
  2. By displaying a warning label at the consumer unit
  3. By sending a copy of the invoice to the local authority
  4. By a competent person scheme or building control Correct answer.

Explanation

Notifiable work must either be self-certified by an installer registered with a competent person scheme, or be notified to the local authority building control before work starts. The certificate or completion notice is then issued to the customer.

Question 20Health, safety and regulatory requirements for small scale solar PV

Where live DC work on a PV array cannot reasonably be avoided, which precaution is appropriate?

  1. Insulated gloves and tools rated for the voltage Correct answer.
  2. Leather rigger gloves worn on both hands at all times
  3. Cotton overalls and safety glasses
  4. Ordinary rubber gloves from the van

Explanation

Live working is a last resort and requires insulating gloves and insulated tools rated for the system voltage, together with barriers and a suitable rescue arrangement. Ordinary gloves give no electrical protection.

Question 21Health, safety and regulatory requirements for small scale solar PV

Where the metal mounting frame of a PV array is required to be earthed, how is this normally achieved?

  1. A separate earth rod driven in at the array
  2. Bonding to the nearest roof gutter system
  3. A protective conductor run back to the MET Correct answer.
  4. Reliance on the mounting clamps alone

Explanation

The frame is treated as an exposed-conductive-part and connected by a protective conductor to the main earthing terminal of the installation. This provides a low-impedance path so that protective devices operate under fault conditions.

Question 22Health, safety and regulatory requirements for small scale solar PV

What must be produced before work starts on a domestic PV installation?

  1. A risk assessment and method statement Correct answer.
  2. A letter of intent from the module supplier
  3. A copy of the client's home insurance policy
  4. A method statement only, with no risk assessment

Explanation

The Management of Health and Safety at Work Regulations 1999 require a suitable and sufficient risk assessment, and the significant findings should be recorded and turned into a method statement. Both must be specific to the site.

Question 23Health, safety and regulatory requirements for small scale solar PV

In what order should a PV system be isolated for maintenance?

  1. AC first, then DC at the array isolator Correct answer.
  2. Both sides simultaneously using one switch
  3. DC first, then AC, with the inverter left running
  4. DC only, because the AC side is always dead

Explanation

The AC side is switched off first so that the inverter stops exporting, and the DC side is then isolated at the array switch-disconnector. When reconnecting, the DC is restored first and the AC last.

Question 24Health, safety and regulatory requirements for small scale solar PV

Which set of documents should be handed to the customer at completion of a PV installation?

  1. A DNO application form and the G98 notification letter
  2. A risk assessment and a method statement for the site
  3. A sales invoice and the module manufacturer's brochure
  4. An EIC, test schedules and handover instructions Correct answer.

Explanation

On completion the installer must issue an Electrical Installation Certificate with the schedules of inspection and test results, and provide operating and maintenance instructions. These records show the installation was designed, installed and verified to BS 7671.

Question 25Health, safety and regulatory requirements for small scale solar PV

Why must the DC cables from a roof array always be treated as live during daylight?

  1. Stored energy in the modules leaks out slowly
  2. The array generates whenever it is lit Correct answer.
  3. The DNO requires the DC side to remain energised
  4. The inverter keeps the cables energised from the AC side

Explanation

A PV module is a current source: as soon as light falls on it, it produces a voltage at its terminals and there is no device at the module that can switch this off. Isolating the inverter or the AC side therefore does not make the array cables safe.

Question 26Health, safety and regulatory requirements for small scale solar PV

Which of the following is a duty placed directly on an employee by the Health and Safety at Work etc. Act 1974?

  1. To provide a written risk assessment for each site
  2. To supply suitable personal protective equipment free of charge
  3. To cooperate with the employer on health and safety Correct answer.
  4. To report all site accidents to the Health and Safety Executive

Explanation

Section 7 of the Act places duties on employees, including cooperating with the employer so that the employer's statutory duties can be met. Providing PPE, producing risk assessments and making reports to the HSE are duties that fall on the employer.

Question 27Health, safety and regulatory requirements for small scale solar PV

A fitter has to handle live DC conductors from an array in daylight. Which item of personal protective equipment is appropriate for protection against electric shock?

  1. An antistatic wrist strap connected to the module frame
  2. Insulating gloves rated for the DC voltage of the system Correct answer.
  3. Leather rigger gloves for grip and abrasion resistance
  4. Cut-resistant sleeves worn over the forearms

Explanation

Gloves used on live DC work must be insulating and rated for the system voltage, and should be inspected before each use. Abrasion, static and cut protection gloves give no protection against electric shock.

Question 28Health, safety and regulatory requirements for small scale solar PV

A failed PV module has been removed during a service visit and will not be reused. What is the correct disposal route?

  1. Place it in the general commercial waste skip
  2. Use a licensed waste carrier to a WEEE recycler Correct answer.
  3. Store it on site permanently as it cannot be recycled
  4. Return it to the manufacturer as clinical waste

Explanation

Waste PV modules are electrical and electronic equipment and must be handled through the WEEE system using a licensed carrier. They cannot be treated as clinical or general waste, and the duty of care does not allow indefinite stockpiling.

Question 29Health, safety and regulatory requirements for small scale solar PV

During a two-day domestic installation the roof array and its DC cabling are left in place overnight. The roof is reachable from a shared garden. Which control is most appropriate?

  1. Ask the householder to watch the roof while the team is off site
  2. Rely on the fact that the array is out of easy reach from ground level
  3. Leave the DC isolator closed so the system is not left in a fault state
  4. Erect barriers and warning signs restricting access to the array and cabling Correct answer.

Explanation

Where live parts and their cabling remain in place, access must be controlled by physical means such as barriers plus warning signs. Verbal requests, deliberate energisation, or relying on height alone do not adequately control the hazard.

Question 30Health, safety and regulatory requirements for small scale solar PV

A PV company is installing a system on an occupied dwelling. Under CDM 2015, who takes on the client duties for this domestic project?

  1. The distribution network operator for the area
  2. The contractor carrying out the installation Correct answer.
  3. The local authority building control body
  4. The householder as the domestic client

Explanation

CDM 2015 provides that where the client is a domestic client, the client duties are carried out by the contractor (or principal contractor) doing the work. The householder therefore does not have to manage the construction phase, and neither building control nor the DNO takes on that role.

Question 31Health, safety and regulatory requirements for small scale solar PV

Which guidance sets out the safety requirements for test probes and leads used when testing a PV installation?

  1. HSE guidance note GS38 Correct answer.
  2. BS 7671 Part 7
  3. IEC 61215
  4. The MCS PV installation standard MIS 3002

Explanation

GS38 is the HSE guidance on electrical test equipment and specifies features such as fused, adequately rated leads, finger guards and short exposed probe tips. The other documents deal with installation requirements, module type approval and system installation quality respectively.

Question 32Health, safety and regulatory requirements for small scale solar PV

An installer plans to use a solvent-based sealant and a proprietary panel-cleaning agent on site. What does COSHH require before these are used?

  1. Assess the risks and apply suitable controls Correct answer.
  2. Display the manufacturer's safety data sheets in the van
  3. Restrict use to a well-ventilated roof space
  4. Obtain written consent from the householder before use

Explanation

COSHH requires the employer to assess the risk from hazardous substances and to apply suitable controls before they are used, together with providing information to those exposed. Safety data sheets inform the assessment but are not a control measure in themselves.

Question 33Health, safety and regulatory requirements for small scale solar PV

A colleague on a roof is being held by a shock while gripping a DC cable. What should you do first?

  1. Isolate the supply before touching the casualty Correct answer.
  2. Start CPR immediately while they are still in contact
  3. Pull the colleague clear of the cable by the arms
  4. Throw water over the cable to short out the supply

Explanation

The rescuer must first break the contact safely, isolating the supply where possible and otherwise using dry insulating material to separate the casualty from the conductor. Only when the casualty is clear of live parts should first aid or resuscitation begin.

Question 34Health, safety and regulatory requirements for small scale solar PV

Where should a lithium-ion battery storage unit forming part of a domestic PV system normally be located?

  1. In a well-ventilated area away from escape routes Correct answer.
  2. In a sealed cupboard alongside the consumer unit
  3. In the loft directly above the bedrooms for short cable runs
  4. In the under-stair cupboard to keep it warm and secure

Explanation

Battery units must be installed to the manufacturer's instructions, which typically require a ventilated position away from escape routes, heat sources and sleeping accommodation. Enclosed or escape-route locations can trap heat and obstruct escape in the event of a fire.

Question 35Health, safety and regulatory requirements for small scale solar PV

Wind speeds on a roof are forecast to rise sharply while modules are being lifted into position. What is the correct response?

  1. Ask the customer to sign a waiver so the lift can continue
  2. Tie the modules to the scaffold with rope and carry on
  3. Continue working while holding each module flat on the roof
  4. Stop and secure loose materials until conditions improve Correct answer.

Explanation

Module lifting must stop when wind makes it unsafe, and any materials left in place must be secured before the team leaves them. Continuing the lift, lashing modules with rope, or obtaining a waiver does not remove either the physical risk or the legal duty.

Question 36Health, safety and regulatory requirements for small scale solar PV

A module slips from a stack on site and lands on the ground, but nobody is injured. What is the correct action?

  1. Report it to the HSE under RIDDOR within ten days
  2. Take no action because no one was injured at the time
  3. Record and investigate it under the firm's own procedures Correct answer.
  4. Report it to the distribution network operator as an incident

Explanation

An event with the potential to cause harm is a near miss; it is not reportable under RIDDOR but should be recorded and investigated so the cause can be corrected. Internal reporting supports the employer's general duty to manage health and safety.

Question 37Health, safety and regulatory requirements for small scale solar PV

Under the Management of Health and Safety at Work Regulations 1999, when must the significant findings of a risk assessment be recorded?

  1. Only when the client asks for a written copy
  2. Only when the work is notifiable to the HSE
  3. Only when more than one trade is working on site
  4. Whenever the employer employs five or more people Correct answer.

Explanation

Regulation 3 requires significant findings to be recorded where the employer employs five or more employees. Smaller employers must still assess risks, and a client or other legislation may separately require written records.

Question 38Health, safety and regulatory requirements for small scale solar PV

An inverter has been switched off at both its DC and its AC isolator. Why must the installer still wait before opening the inverter enclosure?

  1. The AC supply can backfeed through the neutral conductor
  2. The array will resume generating as soon as the cover is removed
  3. The inverter needs time to log the shutdown in its memory
  4. Capacitors inside can hold a dangerous charge after isolation Correct answer.

Explanation

Inverters contain capacitors that store energy, and the manufacturer states a discharge time that must elapse before the enclosure is safe to open. Isolation removes the supply but does not instantly remove stored charge.

Question 39Health, safety and regulatory requirements for small scale solar PV

PV modules and mounting rails are to be added to an existing domestic roof. Which regulatory requirement deals with the extra weight placed on the roof structure?

  1. Part P of the Building Regulations, covering electrical safety
  2. Part A of the Building Regulations, covering structural stability Correct answer.
  3. The Control of Asbestos Regulations, covering roof materials
  4. Part F of the Building Regulations, covering ventilation

Explanation

Part A requires the structure to remain stable and able to carry the loads imposed on it, and adding modules and rails increases the roof loading. The other named requirements address electrical safety, ventilation and hazardous materials rather than structural capacity.

Question 40Health, safety and regulatory requirements for small scale solar PV

Why should the presence and location of a roof-mounted PV array be made known to the local fire and rescue service?

  1. So that they can plan for DC cables that cannot be fully isolated Correct answer.
  2. So that they can switch the array off at the DC isolator during a fire
  3. So that they can remove the modules before tackling the fire
  4. So that they can charge the owner for any attendance at the property

Explanation

An array cannot be fully de-energised while daylight falls on it, so fire crews need to know that PV and its DC cabling are present in order to plan safe firefighting. The information does not make the array dead, and it has nothing to do with charging or removing modules.

Question 41Site survey, system design and component selection

In the UK, which roof orientation gives the highest annual energy yield from a PV array?

  1. West
  2. North
  3. South Correct answer.
  4. East

Explanation

A south-facing roof receives the highest annual irradiation in the UK, so a south azimuth produces the greatest annual yield for a given array. East and west aspects collect less overall, and north-facing roofs receive very little direct irradiance.

Question 42Site survey, system design and component selection

For a grid-connected array in the UK, which tilt angle is generally chosen to give close to the maximum annual yield?

  1. 90° (vertical)
  2. 30° to 40° Correct answer.
  3. 0° (laid flat)
  4. 60° to 70°

Explanation

In the UK a tilt of roughly 30° to 40° gives close to the maximum annual energy yield, balancing the high summer sun and the low winter sun. Flatter or steeper angles favour one season at the expense of the other.

Question 43Site survey, system design and component selection

Where should the DC isolator for a roof-mounted PV array normally be installed?

  1. At the consumer unit beside the AC isolator
  2. At the point of entry, in an accessible position Correct answer.
  3. Inside the inverter enclosure only
  4. At the incoming supply meter position

Explanation

The DC isolator must be reachable so the array can be isolated for maintenance or emergency, and is typically fitted where the DC cables enter the building or adjacent to the array. It must be rated for DC and for the string voltage and current.

Question 44Site survey, system design and component selection

Which location is most suitable for a wall-mounted string inverter?

  1. A bedroom wardrobe
  2. A shaded, ventilated plant room or garage Correct answer.
  3. A south-facing wall in direct sunlight
  4. A sealed cupboard with no ventilation

Explanation

Inverters shed heat and derate or trip when they overheat, so they need a shaded position with free air circulation around the case. Manufacturers specify minimum clearances and a maximum ambient temperature that must be respected.

Question 45Site survey, system design and component selection

Which survey measurement directly determines the maximum number of modules that can be fitted on a roof?

  1. The usable shade-free roof area Correct answer.
  2. The cable route to the consumer unit
  3. The height of the building above ground
  4. The pitch of the roof covering

Explanation

The number of modules is limited by the usable, shade-free area after allowing for edges, obstructions and access gaps, divided by the module dimensions and fixing clearances. Height, covering type and cable route affect access, fixing method and cable sizing but not the module count directly.

Question 46Site survey, system design and component selection

A survey finds a large south-facing roof but the consumer unit is at the opposite end of the property. What is the main design consequence?

  1. Voltage drop increases, so a larger cable size is needed Correct answer.
  2. The array must be reduced to four modules
  3. The array must be split into two strings
  4. The inverter must be mounted on the roof

Explanation

A long DC run increases resistance and therefore voltage drop, which wastes energy and can push the string voltage outside the inverter window. The cable cross-sectional area must be increased, or the inverter relocated, to keep losses within the design limit.

Question 47Site survey, system design and component selection

How should the metal frames and mounting rails of a roof-mounted PV array be treated electrically?

  1. Bonded to the main earthing terminal Correct answer.
  2. Earthed only through the mounting rail
  3. Left isolated from earth
  4. Connected to the DC positive conductor

Explanation

Exposed metalwork of the array must be connected to the installation earthing system by a protective conductor so that a fault cannot leave the frame at a dangerous potential. This equipotential bonding is required by the wiring regulations and by most inverter manufacturers.

Question 48Site survey, system design and component selection

Why is a gap normally left between the underside of the modules and the roof covering?

  1. To make the modules easier to detach
  2. To allow rainwater to drain into the roof space
  3. To let air circulate and cool the modules Correct answer.
  4. To reduce the wind load on the roof

Explanation

Module output falls as cell temperature rises, so an air gap behind the array allows convective cooling and keeps operating temperature down. The gap also lets rainwater and debris pass beneath the array.

Question 49Site survey, system design and component selection

A 4.0 kWp array is being matched to a grid-connected string inverter. Which AC output rating is most typical?

  1. 3.6 kW Correct answer.
  2. 8.0 kW
  3. 12 kW
  4. 1.5 kW

Explanation

In the UK it is normal to size the inverter AC rating slightly below the array peak rating, typically around 0.8 to 1.0 times the kWp, because the array rarely reaches full output. This improves low-light efficiency and reduces cost without significant clipping.

Question 50Site survey, system design and component selection

A module has a Voc of 41.5 V at 25 °C and a Voc temperature coefficient of −0.29 %/°C. What is the approximate module Voc at a cell temperature of −10 °C?

  1. About 38.2 V
  2. About 52.0 V
  3. About 45.7 V Correct answer.
  4. About 41.5 V

Explanation

The temperature difference is 35 K, so the voltage rises by 0.29 % × 35 = 10.15 %. Applying this to 41.5 V gives approximately 45.7 V, which is the value that must be used when checking the string against the inverter maximum input voltage.