Moving electrical assembly work to the UK: notes for Japanese manufacturers

Do not connect a design made for Japan to a UK supply until you have checked every rating. In Great Britain the supply is 230 V between line and neutral, about 400 V between lines, at 50 Hz.¹ A PSE mark has no legal effect in the UK.

Two other rules are easy to miss. A machine moved from your Japanese factory can count as new to Great Britain, and you may then have the duties of its manufacturer.² Your engineers may visit to train and advise, but visitor rules limit what they can do.³ This is not legal advice. Check the legal points with a UK adviser.

Japan and the UK, point by point

Great Britain means England, Scotland and Wales. Northern Ireland has different product rules. The UK colours below are for installation wiring.

Which words differ?

What does a UK supply do to a design for Japan?

A resistive load designed for 100 V would take 5.29 times its power at 230 V, so it burns out or its protection trips. A three-phase part for 200 V receives 1.99 times its voltage at 398 V. Parts rated for a wide range, such as 100 to 240 V, may be acceptable.

Current falls: 1 kW takes 10 A at 100 V and 4.35 A at 230 V. But the insulation, connector and terminal must be rated for the higher voltage, so check them before you reduce any wire size.

For a 60 Hz design from western Japan, the synchronous speed of a 4-pole motor falls from 1,800 to 1,500 rpm, or 16.7%. At the same voltage, a transformer or AC coil has 20% more magnetic flux at 50 Hz, which can cause overheating.²⁷ We calculated these from standard equations.

This rule covers equipment intended for domestic use, with a lead and plug for a BS 1363 socket. UK law requires a correctly fitted standard plug. The other option is a non-UK plug that conforms to IEC 884-1, with a compatible conversion plug and a BS 1362 fuse rated to the manufacturer's instructions.²⁸ Do not assume a Japanese plug qualifies. For a factory panel or test bench, ask the site electrician which connection to use.

A control panel needs more than a voltage change. Start with which standard applies and short-circuit ratings.

Why you cannot buy the same wire size in the UK

The size series do not match. This table compares maximum resistance at 20 °C for Fujikura Dia's IV wire and a tri-rated panel wire sold in the UK.¹⁶¹⁷ The changes are our calculation.

Do not choose by nearest area. IV is rated for a 60 °C conductor, with current figures at 30 °C ambient.²⁹ This tri-rated wire is rated for 90 °C, with current figures at 45 °C ambient.¹⁷ Size the UK wire from its own current table, with grouping and ambient factors, the protective device, the terminal temperature limit and voltage drop.

The construction also differs. Fujikura's 2 mm² IV has 7 strands of 0.6 mm and a diameter of about 3.4 mm. The 2.5 mm² tri-rated wire has 50 strands of 0.25 mm and a nominal diameter of 3.75 mm. So check the terminal range and seal, then qualify the crimp again with a crimp height check and a pull test. This table covers panel wire only. Compare harness wire data sheets in the same way.

UK distributors use names such as H05V2-K, H07V2-K and BS 6231.¹⁷ "IV" is a Japanese name, from JIS C 3307.¹⁶

Can you use the same wire colours?

Not without checking. The same colour can have a different meaning.

• Black is usually line in Japanese single-phase building wiring.¹¹ Panasonic warns that on some wire and cable it is the other conductor.¹² In UK installation wiring today it is L2 in a three-phase circuit.¹³
• Older UK three-phase wiring used red, yellow and blue for the phases and black for neutral.¹⁵
• In the UK table for control circuits and extra-low voltage, white is an allowed line colour.¹³ A white wire in a UK control circuit may be a line conductor, not a neutral.

UK work starting after 31 March 2006 had to use the new colours, so an older factory can contain both sets. In 2005 the IEE reported that BS 7671 also allowed tape, sleeves, discs or letters for marking connections. Check the current edition.³⁰ Never identify a conductor by its colour alone. Isolate it and test it.

These UK colours come from the installation wiring rules. Inside a machine or control panel, do not assume brown, black and grey. Ask someone with a licensed copy of BS EN 60204-1 before you change a drawing. We read only the public listing of JIS C 0446, the Japanese standard on this subject.³¹

If you buy wire in Japan for UK use, check the colours. Fujikura's IV specification lists no brown or grey.¹⁶

Does a PSE mark count in the UK?

Not legally. PSE belongs to Japan's Electrical Appliances and Materials Safety Act, and Japanese law restricts the sale of listed items without the mark.¹⁸ We found no UK rule that accepts PSE. In our reading, a PSE test report does not replace UK or EU conformity. It may also not cover the Electromagnetic Compatibility Regulations 2016 or the RoHS Regulations 2012, so check those too.

As of 6 November 2026, Great Britain accepts UKCA or CE for electrical equipment, EMC, RoHS and machinery, with no end date in law.³²³³ On 20 January 2027 the EU Machinery Regulation applies and SI 2026/867 rewrites the Great Britain route for CE-marked machinery.³⁴ On our reading, a machine placed on the market or put into service in Great Britain on or after that date cannot rely on CE under the old Directive, unless it was already placed on the GB, NI or EU market before then. Read UKCA or CE for control panels before you buy or ship a machine.

The UK-Japan mutual recognition protocol covers conformity assessment for electrical products, but we found nothing that makes PSE valid in the UK.³⁵

If your UK company imports finished products, it usually has importer duties. These include putting its name and postal address on the product, or on the packaging or an accompanying document only if that is not possible. If it sells a product under its own name, or modifies it in a way that affects compliance, it takes on the manufacturer's duties.²⁰ Machinery is different: read the importer section of UKCA or CE for control panels. For parts imported for further manufacture, the GB manufacturer of the finished product has "the sole and ultimate responsibility". However, some components are products in their own right and may need their own marking. If a maker appoints an authorised representative for machinery on the GB market, that representative must be based in the UK.³⁶

What if you send a machine from your Japanese factory?

The Health and Safety Executive (HSE) regulates machines at work. It writes about second-hand equipment that is covered by product rules, such as the machinery rules, and is new to the UK. The person who first brings it into use takes responsibility for conformity, and that person "may be the importer or even the user". The duties include changing the design if needed, a technical file, a Declaration of Conformity and a conformity mark with your name as manufacturer. HSE warns that changing such a machine can be "very difficult and expensive".²

Before you ship anything, ask these questions about each press, test bench and automatic machine.

• Does it fall under the machinery rules? Does the maker offer a UKCA version, or a CE version under the new EU Regulation?
• What voltage and frequency does it need? Will a conversion or new control system be a substantial change?³⁷
• Is it safe under the work equipment rules (PUWER), whatever mark it has?²
• Would a new machine for the UK cost less?

What may your engineers do on a visit?

The GOV.UK rules, checked on 6 November 2026, allow a visitor to do these things, among others.³

• Advise, consult, trouble-shoot, train and share skills "on a specific internal project with UK employees of the same corporate group" (PA 5.1).
• Install, repair, service or advise on machinery, if there is a contract of purchase, supply or lease with a UK company, and their company is the maker or supplier, or has an after-sales arrangement agreed at the time of the sale or lease (PA 7).

PA 5.1 does not list installing machines. If your Japanese factory sends a machine to your UK company with no purchase, supply or lease contract, ask an adviser before your engineers install it.

Visitors must not do work that amounts to "filling a role or providing short-term cover for a role within a UK based organisation" (V 4.5). They must not receive payment from a UK source, apart from listed exceptions such as reasonable travel expenses (V 4.6). They must not "live in the UK for extended periods through frequent or successive visits" (V 4.2).³⁸ Do not plan a schedule of visiting engineers to cover production.

For longer stays, a sponsor licence and a certificate of sponsorship are usually needed. On 6 November 2026, the Senior or Specialist Worker and UK Expansion Worker routes required an eligible job and at least £52,500 or the going rate, whichever is higher.³⁹⁴⁰ The Graduate Trainee route has a lower figure.⁴¹ For the Global Business Mobility routes, the occupation list includes production managers, electrical engineers, production and process engineers and quality engineers. It excludes technicians, electricians, trades supervisors, testers, assemblers and panel wirers, and production supervisors.⁴² So a plan to send panel wirers or line supervisors on these routes will fail.

The UK Expansion Worker visa is for a business that has not started trading in the UK, and lasts at most 2 years. You must already work for the overseas business as a senior manager or specialist employee. The visa normally needs 12 months with the employer outside the UK, but GOV.UK makes an exception for "a Japanese national doing work for a Japanese company that is expanding to the UK".⁴⁰ The Senior or Specialist Worker visa is for existing employees of a business already trading in the UK. On 6 November 2026 it needed the 12 months unless pay was £73,900 or more.³⁹ JETRO's March 2025 guide gives an older salary figure.⁴³ Ask an immigration adviser before you plan any move.

Which employment rules can change the plan?

If you buy a business, or part of one, from another company, its employees usually transfer to you on their existing terms under TUPE, the UK rules on transfers of employment. GOV.UK says the identity of the employer must change, so we read a purchase of company shares as outside TUPE. Moving orders to a new goods supplier is also outside it.⁴⁴

We found no apprenticeship standard named for harness or panel wiring on the Skills England list for England. The closest are Engineering operative (ST0537, level 2, electrical and electronic option)⁴⁵ and the short unit Electrical fitting and assembly (AU0005, minimum 70 hours).⁴⁶

Your first 90 days: questions to answer

Days 1 to 30

1. Is the site in Great Britain or Northern Ireland?
2. For each product, who is the legal manufacturer and who is the importer?
3. What are the site's voltage, phases, capacity, earthing system and fault level (prospective short-circuit current)?
4. Which parts are rated only for 100 V, 200 V or 60 Hz? Which wires use Japanese sizes or colours?
5. Which machines will come from Japan, and which have CE or UKCA marking?
6. Who will visit, for how long, and does each activity fit the visitor rules? Does anyone need an ETA?⁴⁷

Days 31 to 60

7. Which standards does the customer require, and who holds licensed copies?
8. Have the drawings changed to mm², UK markings and UK voltages? Are work and machine instructions in English?⁴⁸
9. Can UK distributors supply the same connector and terminal part numbers? Who approves a change?
10. Are right-to-work checks and employers' liability insurance ready?⁴⁹⁵⁰

Days 61 to 90

11. Have you qualified crimps with UK wire and terminals, and tested a first article on a UK supply?
12. Who signs the declaration of conformity, and where is the technical file?
13. Who is competent for which electrical work, as UK law requires, and where is this recorded?⁵¹

Notes

1. The Electricity Safety, Quality and Continuity Regulations 2002, regulation 27. It extends to England, Wales and Scotland, and gives 230 V between phase and neutral. The 398 V is our calculation: 230 x the square root of 3. ↩ ↩² ↩³ ↩⁴

2. Health and Safety Executive, Second-hand (re-supplied) products. ↩ ↩² ↩³

3. GOV.UK, Appendix Visitor: Permitted Activities, read 6 November 2026. ↩ ↩²

4. 電気事業法施行規則 (Ordinance for Enforcement of the Electricity Business Act), article 38, e-Gov. 100 V: 101 V, plus or minus 6 V. 200 V: 202 V, plus or minus 20 V. ↩ ↩²

5. TEPCO Energy Partner, 低圧電力: standard voltage 200 V, three-phase three-wire, for shops and factories under 50 kW. Larger plants may differ. ↩

6. TEPCO, Substations. ↩

7. Fuji Electric, TT系統, glossary. Maker's guide. ↩

8. Earthing: your questions answered, IEE Wiring Matters, Autumn 2005. It says the distributor can tell you which system applies. An older article. ↩

9. Wikipedia, AC power plugs and sockets, accessed November 2026. We did not read JIS C 8303. ↩

10. The Plugs and Sockets etc. (Safety) Regulations 1994, definitions and regulation 6. ↩

11. Second-class electrician skills test, question No. 13, conditions of work, in the 2026 copy published by TAC. It sets white for the earthed side, black for the unearthed side and green for the earth wire. This shows practice in single-phase building wiring. It is not a panel standard. ↩ ↩² ↩³

12. Panasonic, TERASU dictionary: 中性線. Maker's guide. ↩ ↩²

13. Paul Cook, Harmonised colours and alphanumeric marking, IEE Wiring Matters, Spring 2004. Installation rules from a 2004 article. ↩ ↩² ↩³ ↩⁴

14. Fujikura Dia Cable, IV (G/Y) specification SES-00056B. Maker's document. ↩

15. IET Wiring Matters, The history of colour identification of conductors, March 2021. ↩ ↩²

16. Fujikura Dia Cable, IV specification SES-00040B. Maker's document. ↩ ↩² ↩³ ↩⁴

17. Farnell, Tri-Rated Flexible PVC Equipment Wire. Distributor data sheet for one product range. ↩ ↩² ↩³ ↩⁴

18. 電気用品安全法 (Electrical Appliances and Materials Safety Act), articles 10 and 27, e-Gov. METI's own pages refused our automated request, so we used the law and JETRO. ↩ ↩²

19. JETRO, 家電製品の輸入手続き：日本. ↩

20. GOV.UK, Placing UKCA or CE marked products on the market in Great Britain, read 6 November 2026. ↩ ↩²

21. Wikipedia, Cable harness, accessed November 2026. ↩

22. Wiktionary, earth, accessed November 2026. ↩

23. The Electricity at Work Regulations 1989, regulation 8. ↩

24. Wikipedia, List of gairaigo and wasei-eigo terms, accessed November 2026. ↩

25. Mitsubishi Electric, MCBとMCCBとの違い. Maker's guide. ↩

26. Amphenol Japan, A.W.G. and mm² table. Maker's document. ↩

27. Wikipedia, Transformer, EMF equation, accessed November 2026. ↩

28. The Electrical Equipment (Safety) Regulations 2016, regulation 35. ↩

29. Fujikura Dia Cable, IV, HIV, KIV and KIP catalogue. Maker's document. ↩

30. New cable colours: deadline approaches, IEE Wiring Matters, Winter 2005. Installation rules from a 2005 article. ↩

31. Standards listing, JIS C 0446:1999. Sales page only. ↩

32. GOV.UK, Product regulations by sector, read 6 November 2026. ↩

33. Product Safety and Metrology etc. (Amendment) Regulations 2024, SI 2024/696, explanatory note. ↩

34. SI 2026/867, regulation 2 (new regulation 12A) and regulation 3. In force 20 January 2027. ↩

35. GOV.UK, Trade with Japan, section on the mutual recognition protocol, read 6 November 2026. ↩

36. GOV.UK, Supply of Machinery (Safety) Regulations 2008: Great Britain. ↩

37. Health and Safety Executive, Refurbished and modified machinery. ↩

38. GOV.UK, Appendix V: Visitor, read 6 November 2026. ↩

39. GOV.UK, Senior or Specialist Worker visa: eligibility, read 6 November 2026. ↩ ↩²

40. GOV.UK, UK Expansion Worker visa and eligibility, read 6 November 2026. ↩ ↩²

41. GOV.UK, Graduate Trainee visa: eligibility, read 6 November 2026. ↩

42. GOV.UK, Appendix Skilled Occupations, read 6 November 2026. Listed: 1121, 2123, 2125, 2481 (table 2). Not eligible: 3112, 3116, 5241, 5250, 8143 (table 2aa) and 8141, 8160 (table 6). ↩

43. JETRO London, 英国事業拠点設立ガイドブック, March 2025, in Japanese. ↩

44. GOV.UK, Business transfers, takeovers and TUPE. ↩

45. Skills England, Engineering operative, ST0537. ↩

46. Skills England, Electrical fitting and assembly, AU0005. ↩

47. GOV.UK, Electronic travel authorisation, £20 when read on 6 November 2026, and Appendix ETA National List, which lists Japan. ↩

48. Health and Safety Executive, Buying new machinery, INDG271. Its dates for CE marking are out of date. ↩

49. GOV.UK, Checking a job applicant's right to work. ↩

50. GOV.UK, Employers' liability insurance. ↩

51. The Electricity at Work Regulations 1989, regulation 16: knowledge, experience or supervision. It does not name a licence. ↩