SE Stephens Engineering Group
Electrical & Building Services Consultancy

Electrical design and delivery for commercial buildings.

One technical authority from concept through to certification. South Wales, Bristol and UK wide.

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Coverage
South Wales · Bristol · UK Wide
Established
2024
Scope
Design → Delivery → Certification
Direct
07478 269752
What we do

Design authority held from concept to certification.

Electrical & Building Services Design

Feasibility and load assessment, LV distribution and small power, Part L and decarbonisation strategy, RIBA Stage 0–3 packages.

Installation & Delivery

Works delivered under contract to SEG. Installation is carried out by an approved electrical contractor; SEG holds the design, supervises the works and signs the design section of the Electrical Installation Certificate.

Lighting Design

Architectural and functional lighting, emergency lighting strategy, LED upgrade and energy comparison, Dialux modelling.

PV & EV Design

Array layout and yield calculations, charge point design and load management, DNO coordination, cable sizing and protection.

Compliance & Technical Review

Condition and compliance review, asset registers and evidence packs, prioritised remedial plans, contractor scope and quote review.

Handover & Assurance

Certificate tracking, as-built checks, O&M review, final compliance summaries.

How we can be engaged

Design only

Drawings, specification and schedules issued for tender. You appoint the contractor.

Design and delivery

Single point of responsibility. SEG designs, appoints and supervises the installer, and issues the completed certification.

Delivery against an existing design

We price and deliver another consultant’s design, with a buildability and compliance review before works start.

Selected work

Design output, drawn properly.

SOLAR PV ARRAY Single line diagram 46.35 kWp 40 kW inverter / 7 strings / 4 MPPT MPPT 1 : 1.1 STRING OF 18 x TRINA 450W (TSM-450NEG9R.28) MPPT 1 : 1.2 STRING OF 18 x TRINA 450W (TSM-450NEG9R.28) MPPT 2 : 2.1 STRING OF 10 x TRINA 450W (TSM-450NEG9R.28) MPPT 2 : 2.2 STRING OF 10 x TRINA 450W (TSM-450NEG9R.28) MPPT 3 : 3.1 STRING OF 16 x TRINA 450W (TSM-450NEG9R.28) MPPT 3 : 3.2 STRING OF 19 x TRINA 450W (TSM-450NEG9R.28) MPPT 4 : 4.1 STRING OF 12 x TRINA 450W (TSM-450NEG9R.28) SOLIS 40K 5G 3P QUAD MPPT INVERTER AC ISO AC ISOLATOR kWh GENERATION METER EXISTING LV BOARD CAT5 CT LINK PV ARRAY TABLE STRING MODULES KWP 1.1 18 8.10 1.2 18 8.10 2.1 10 4.50 2.2 10 4.50 3.1 16 7.20 3.2 19 8.55 4.1 12 5.40 TOTAL 103 46.35 SYSTEM DESIGN PARAMETER VALUE Peak power 46.35 kWp Inverter power 40 kW Modules 103 x Trina Solar 450W Module type TSM-450NEG9R.28 Inverter Solis 40K 5G, 3P quad MPPT Standards BS 7671 / BS EN 62446 / G99
Solar PV · Single line diagram 46.35 kWp rooftop array, 103 modules, 40 kW inverter. Seven strings across four MPPT inputs, metered generation into the existing LV board.
SEG-SLD-DALI-001 DALI-2 LIGHTING CONTROL ARCHITECTURE STAGE 2 CONCEPT - NOT FOR CONSTRUCTION SYSTEM ARCHITECTURE BMS HEAD END BACnet/IP [1] IP BACKBONE AC-GF Ground floor DALI-2 application controller AC-01 Level 1 DALI-2 application controller AC-02 Level 2 DALI-2 application controller AC-RF Roof and external DALI-2 application controller TYPICAL FLOOR - LINE ARCHITECTURE (AC-01 shown, AC-GF and AC-02 identical) AC-01 2 x 4-line router 8 lines fitted, 6 used 25% spare per I-17 [2] PSU 250mA D1 Open plan - perimeter zone A 56 luminaires | 6 sensors | 0 panels | 62 addresses | 124mA PSU 250mA D2 Open plan - perimeter zone B 56 luminaires | 6 sensors | 0 panels | 62 addresses | 124mA PSU 250mA D3 Open plan - interior zone 55 luminaires | 6 sensors | 2 panels | 63 addresses | 126mA PSU 250mA D4 Cellular and meeting rooms 43 luminaires | 10 sensors | 8 panels | 61 addresses | 122mA PSU 250mA D5 Circulation and stairs 57 luminaires | 6 sensors | 0 panels | 63 addresses | 126mA PSU 250mA D6 WC, tea point, plant, store 30 luminaires | 8 sensors | 4 panels | 42 addresses | 84mA TYPICAL LINE DETAIL - D1 DALI bus LUM L1 x 56 LUM SEN presence + SEN daylight x 6 EM L7 self-test EM PNL wall panel LUM Bus is polarity free, 2-core 1.5mm2 rated 300/500V, max 300m per line, 2V max drop. It may share a multicore with the mains supply because it is mains-rated - but it is NOT SELV and must never be treated as Band I [3]. CONTROL STRATEGY Ref Space Detection Daylight Standby Off K-01 Open plan - perimeter Presence Closed loop dimming Dim to 10% 20 min K-02 Open plan - interior Presence None Dim to 10% 20 min K-03 Cellular and meeting Absence Closed loop dimming Off 15 min K-04 Circulation Presence Open loop where glazed Dim to 20% 10 min K-05 Stairs Presence None Dim to 20% 10 min K-06 WC Presence None Off 10 min K-07 Plant and store Presence None Off 15 min K-08 External and EV area Photocell Dusk to dawn Dim to 30% after 23:00 - Absence detection in cellular rooms is deliberate - manual on, auto off. LINE LOADING Line Addr Max Spare mA Chk D1 62 64 3% 124 PASS D2 62 64 3% 124 PASS D3 63 64 2% 126 PASS D4 61 64 5% 122 PASS D5 63 64 2% 126 PASS D6 42 64 34% 84 PASS KEYNOTES [1] BMS interface is BACnet/IP at the application controller, not at device level. Exposing 350 DALI addresses to the BMS creates a maintenance problem nobody wants to own. [2] Two 4-line routers per floor gives 8 lines against 6 used. Spare lines matter more than spare addresses - a line at 63 of 64 addresses is effectively full. [3] The DALI bus is mains-rated and may share containment with the supply, but it is not SELV. Treating it as Band I is a common and expensive error at installation. [4] Emergency luminaires are DALI-2 Part 202 self-test on the same lines as general lighting. Monthly function and annual duration tests are logged automatically to BS EN 50172:2024. [5] Commissioning is where DALI projects fail. Addressing, grouping and scene setting must be a named deliverable with a witnessed handover, not something the installer does on the last Friday. [6] Sensor current is taken as 2mA. Some multi-sensors draw considerably more - verify against actual device data before the line allocation is frozen. STEPHENS ENGINEERING GROUP SEG DALI-2 lighting control architecture Reference building, LV distribution design standard DRG No SEG-SLD-DALI-001 REV P01 SCALE NTS @ A3 STATUS STAGE 2 CONCEPT - NOT FOR CONSTRUCTION Do not scale. Read with SEG-SCH-LVD-001 sheet 13 and SEG-REF-LTG-002.
Lighting control · DALI-2 architecture Reference design standard. Four application controllers on a BACnet/IP backbone, six DALI-2 lines per floor with addressing, sensor counts and line current checked against the 64-address limit.
Who we work with

Technical input with a defined scope.

  • Architects and developers
  • Building surveyors
  • Electrical and main contractors
  • Landlords and property owners
Understand→Define→Coordinate→Review→Close out
About

Senior engineering input from the first conversation.

Stephens Engineering Group is an electrical and building services consultancy based in South Wales, working across Cardiff, Newport, Bristol and the wider UK.

Founded by Aaron Stephens MIET. Every instruction is handled at senior level, with Part L, decarbonisation and renewable integration considered from the outset rather than added later.

Contact

Discuss a project.

Drawings, a brief, an existing building or an idea. We are happy to have an early conversation.