Installer Requirements

Steve PesterPrincipal Consultant

BRE

Scope of MCS Installer scheme

MCS Installer Technical Standards (e.g. MIS3002 for PV):

“specifies the requirements of the MCS for contractors undertaking the– supply– design– installation– set to work– commissioning and – handover

of Photovoltaic microgeneration systems for permanent buildings”

MCS Installer scheme stands on 3 pillars

MCS

QualityManagement

SystemMCS 001

Consumer Code(OFT*-approved)

e.g. REAL Code

PV TechnicalStandardMIS 3002

*OFT = Office of Fair Trading

Documented Quality Management System – why?

• Consistent quality of installations – there’s a lot to remember if you want to be a good installer!

• Business interruption due to illness/injury

• Staff training and new staff induction

• Auditable and accountable (esp. when things go wrong, can’t blame rogue engineer)

Consumer Code of Conduct

• Members of the REAL Assurance Scheme agree to abideby the REAL Assurance Scheme Consumer Code.

• Covers contractual elements of installation…

REAL Assurance Scheme cont..

• Acceptable sales and marketing techniques • Details of the conditions of business that apply • Guarantees, and any maintenance and after-sales

services needed • What action will be taken to deal with any problems

MCS Technical Standards (MIS 3xxx)

MCS Tech. standard

MIS3xxx

Existing Industry Guides and Standards

BuildingRegulations

MCS-specificrequirements

Regulations & Guides called up in PV technical standard

Stages of an MCS Installer Assessment

Assessment:• Quality Management System (QMS) assessment• System Design and Technical documentation of installation(s)• Technical assessment of physical installation(s)

All Non-Conformances must be rectified before an installer is certificated

BRE certificated installers are listed on the BRE green products sourcing site: www.greenbooklive.com

Typical small PV systems in the UK -practicalities

Typical Domestic Installation - schematic

Inverters

Inverters transform the DC electricity produced by your PV modules into the alternating current (AC) electricity

commonly used in most homes (they do other things too!)

DC Disconnect Requirements

Ø Double Pole

Ø Rated for DC

Ø Rated in excess of the expected current

Ø Labelled

AC Disconnect Requirements

Ø Double Pole

Ø Lockable in OFF position

Ø Rated in excess of the expected current

Ø Labelled

The Consumer Unit - AC Disconnect & Labelling

Commercial Buildings use 3-Phase Power

Micro-inverters

• DC – AC conversion on roof

• No high DC voltages

• Possible control & monitoring of individual modules

• Over-temperature shutdown

Photo: Enecsys

Safety – Why PV has Special Safety Issues:

• Beware High Voltage DC Electricity – Dangerous!

• The PV modules cannot be switched off (upstream of the DC isolator)

• Fuses are not likely to blow under short circuit conditions

• PV modules produce DC electricity – few electricians familiar

• For installers: combination of hazards: Working at height with high voltages and heavy modules

Earthing – Array Frame

Earthing of the array is NOT mandatory1) Must be earthed if:§ Any part of the frame is touchable from a window, attic

space, etc§ Also if positioned close to a solar thermal system

2) AC Side is normally earthed

Lightning Protection

Lightning protection of the array is only required if:

• there is a particular risk of lightning or• the array is near to a lightning protection system on the

same building

Protection can consist of:• Lightning conductors to earth• Surge Arrestors (usually small electronic components in

the junction box) • Spark gaps (unusual on small systems)

Array Mountings vary widely

• Installers must demonstrate static and dynamic load calculations and roof structure assessment

• Further info on mountings– New NHBC Guide

– DG495 - Mechanical installationof roof-mounted photovoltaicsystems

Common PV Installation issues:

• Some Installers have limited knowledge leading to poor design or installation

• Manuals, warranties, test certificates, grid connection docs not supplied to owner/operator

• Labelling not present or incorrect

• Earthing requirements often misunderstood

• Most operators have limited knowledge!

Fortunately poor DC connections are not very common!

Food for thought….• In daylight, there are high voltage DC electrics power on

roof and inside building• Not possible to completely isolate the DC electrics with

standard systems. Panels down to DC isolator remain live• DC is more dangerous than AC at the same voltage• 200-600V DC is common• Under fault conditions, shorts can occur, producing very

hot arcs, both inside panels and between shorting conductors

• Glass can fall from PV panels when broken

However, fires caused by PV appear to be rare at present!

Summary

• Installers - MCS requirements are tightening but still some way to go

• Safe practices and products are well-understood thanks to early German market and a few pioneers in UK

• DC high voltages and arcs are main dangers• Micro-inverters may offer some higher level of safety,

although they do not yet have much track record

• Questions?