Building Wire Cross-Reference: GB/T vs H07V, THHN and BS 6004

This page is the building-wiring companion to our cable standard cross-reference hub, which maps the four standard systems as a whole. The hub page answers "which family does this belong to"; this page goes one level down and answers the question that actually reaches a quotation desk: the customer wrote H07V-R, or THHN, or BV — what do I quote, and what exactly does each letter mean?

The four systems do not sit on the same footing, and the difference matters before any table is read. The Chinese and European systems are both built on IEC 60227 — but the Chinese one adopts it identically while the European one harmonised it into its own EN document. The North American system never used IEC 60227 at all; it grew a separate letter alphabet that encodes ratings rather than materials. That single fact explains most of the mismatches in this article.

01What a building wire is, before the standards get involved

A building wire is the basic single-core conductor that runs inside conduit, trunking or a wall to feed lighting and power circuits. In every one of the three systems it is the same physical object: a copper conductor, one layer of PVC insulation, and no outer sheath. What changes between systems is how much detail the type code carries and what the code is anchored to.

• China: the code is a two-digit number after 60227 IEC, and it points at an IEC type; the familiar letters (BV, BVR, RV) are the older-generation names that the market still uses, now carried by the JB/T 8734 series.
• Europe / UK: the code is a harmonised designation of the form H + voltage + insulation letter + conductor-class letter, and it points at an EN 50525 part; the UK numeric names (6491X, 2491X) come from the superseded BS 6004.
• North America: the code is a string of rating letters (T, H, HH, W, N and a -2 suffix), and it points at a UL standard; the code says nothing about the conductor material, which has to be stated separately.

02China: GB/T 5023 and the two-digit code

The current Chinese standard for PVC-insulated cables up to 450/750 V is the GB/T 5023 series. Its Part 1 states the general rules, and Part 3 covers non-sheathed cables for fixed wiring. The standard's designation annex gives the naming rule in one line: every cable type is designated by a two-digit number placed after "60227 IEC", where the first digit is the basic classification and the second is the specific variant within it.

For fixed wiring, classification 0 covers the unsheathed types (01–08) and classification 1 the light sheathed type (10). The types you meet are:

Columns 1 and 4 are the two sides of the comparison table in the standard's informative Annex B, which pairs each current two-digit designation with the letter code used by the 1985/1986 editions. The first four fixed-wiring rows are shown; the remaining rows of Annex B cover cords, lift cables and screened types.

Why BV still shows up, and what it actually means

The letters did not disappear. BV, BVR, BLV and the rest are the 1985-edition names, and they remain the everyday market vocabulary. Two things follow, and both catch people out.

First, a Chinese supplier's own technical table often writes both at once — 60227 IEC 01(BV) — and cites GB/T 5023.3-2008 for that row. In this reading, BV is simply the colloquial name for the IEC 01 type, and the governing standard is GB/T 5023.3.

Second, the JB/T 8734 series (current edition 2016) also lists BV and BVR as its own types, with different voltage ratings: in that series BV is a 300/500 V wire and BVR is a 450/750 V flexible wire. So the same three letters, BV, can appear as a 450/750 V IEC-01 equivalent or as a 300/500 V JB/T 8734 type, depending on which standard the document is written to.

Decoding the letters, when letters are used

Where the older or the JB/T letter codes are used, the letters follow a fixed logic, grouped by function rather than by position:

• By use: B fixed wiring · R flexible cord / flexible conductor · A installation wire
• By conductor: copper is omitted; L marks an aluminium conductor
• By material: V PVC insulation or sheath · VY oil-resistant PVC sheath
• By construction: B flat (in the sheath families) · S twisted pair · P screened · R flexible stranding
• By heat rating: 70 °C is omitted; 90 marks the 90 °C version

So BV reads as fixed-wiring, PVC, copper (omitted letter); BVR adds flexible stranding; BLV swaps the conductor letter in for aluminium. The decoding is deliberately shallow — the letters only describe material and construction, never the electrical rating.

03Europe and the UK: the harmonised code and 6491X

Europe harmonises low-voltage cables through CENELEC, and the harmonised designation is what you read off the insulation. The current product standard for a single-core, unsheathed PVC building wire is BS EN 50525-2-31; its predecessor documents were BS 6004 in the UK and HD 21.3 at CENELEC level. A manufacturer's sheet may cite all three as historic lineage, as TEKIMA does when it prints "CEI EN 50525-2-31 and HD 21.3 S3" for its H07V2-K single core.

The designation is built from four fields:

The field order and meanings follow the harmonised designation system; because HD 361, the document that fixes the rules, was not obtained for this article, no clause number is cited. The field meanings are stated from multiple manufacturer datasheets that print the same construction.

So H07V-U is a 450/750 V PVC building wire with a solid conductor; H07V-R is the same with a stranded conductor; H07V-K is the flexible (Class 5) version used for panel and equipment wiring. Swap the 07 for 05 and the voltage drops to 300/500 V, which is the internal-wiring class.

Where 6491X fits

6491X is the British numeric name that came from BS 6004, the older UK standard. It is not a second, parallel standard — it is the familiar name for a cable now built to BS EN 50525-2-31. The mapping is consistent across manufacturer datasheets:

• 6491X → H07V-U (solid) or H07V-R (stranded), 450/750 V
• 2491X → H05V-K (0.5–1.0 mm², 300/500 V) / H07V-K (1.5 mm² and above, 450/750 V) — the flexible, Class 5 version
• 6491XHR → H07V2-U / H07V2-R, the 90 °C heat-resistant version

Our own 6491X / H07V-R single-core building wire is quoted to BS EN 50525-2-31 and built around the H07V-R construction: Class 2 stranded copper to IEC 60228, 450/750 V, a 70 °C maximum conductor temperature, a 160 °C short-circuit limit, and a 2500 V finished-cable test voltage. The conductor class is the whole point of the R in the code — H07V-U, H07V-R and H07V-K are not interchangeable just because they share the H07V stem.

04North America: the THHN letter string

North American building wires do not use a material-based code. The letters encode ratings, and they stack up: each letter adds a property, and the code has to be read left to right as an accumulation. THHN is the most common building wire in the United States and the one most often compared against a Chinese or European type.

Read across a row, not down a column: a letter present in one type and absent in another is the whole difference between them. THHN therefore reads as thermoplastic, high-heat (90 °C dry), wet-rated, nylon-jacketed — a description of ratings, with no statement about the conductor material.

What the letters prove, and what they do not

THHN is defined by UL 83 (thermoplastic-insulated wires and cables); XHHW is defined by UL 44; USE by UL 854. A manufacturer's sheet for a THHN conductor, such as the Southwire SIMpull THHN/THWN-2 data, adds the ratings in plain terms: 600 V, PVC insulation with a nylon sheath, a 90 °C dry rating for the THHN/T90 marking, a 90 °C wet-or-dry rating for THWN-2, a 75 °C limit where exposed to oil, and VW-1 / FT-1 flame ratings. The jacket and insulation construction — PVC plus nylon — is what earns the N and the friction-reducing pull properties; it is not encoded as a material letter the way V is in the Chinese and European systems.

05The cross-reference table

This is the table to bookmark. It maps the four systems by the building-wire types you actually meet, and it deliberately leaves cells blank where no genuine equivalent exists. A blank is information: it tells you the comparison has to be made on construction and ratings rather than on names.

The empty North American cell in the first row is a genuine gap, not a missing lookup: UL 83 does not define an unsheathed PVC-only building wire equivalent to BV or H07V-U, because the American type carries the nylon jacket as part of its construction. Rows 2 and 4 show the nearest North American type with the caveat stated in the cell.

The two flexible-cord rows are developed elsewhere on this site: the sheathed-cord family is covered by the tray-and-cord standards comparison and the control-side equivalent sits with the RVV multi-core PVC cable.

06What does not translate

Four things survive a building-wire cross-reference as false friends. Each has a specific failure mode attached.

1. A bare letter does not carry a voltage

BV on its own does not fix the voltage: it is 450/750 V under GB/T 5023.3 and 300/500 V under JB/T 8734. H07V fixes 450/750 V only through its 07 field; drop to 05 and the class changes. THHN fixes 600 V by its UL 83 listing rather than by a digit. Never read a voltage off the letters alone — read it off the standard number or the digit field.

2. PVC in one system is not PVC in another

All three systems specify PVC insulation, but they specify it through different compound designations and test regimes. Europe names the compound (PVC Type TI1 for 70 °C, TI3 for 90 °C, to EN 50363-3). China specifies the compound performance in GB/T 5023.1. North America adds a nylon jacket on top, which is not an insulation change but does change the construction. The word "PVC" is common; the specification behind it is not identical.

3. Certification does not travel

CCC in China, CE/DoP in Europe and a UL listing in North America are separate schemes with separate scopes. A cable built to BS EN 50525-2-31 is not thereby acceptable on a project that requires CCC, and a UL listing for one construction does not cover a different build. Where a project turns on mutual recognition, that question belongs to the accepting authority, and we say so rather than answer it ourselves.

4. Conductor class and cross-section are separate decisions

The European letter (U/R/K) and the American construction (stranded or solid) both encode conductor class rather than size, and the metric-to-AWG step is a second, independent decision. Two wires with the same nominal area can differ in strand count and conductor class, which changes the bending radius and the termination. When a project specifies one class and the supply is in another system, convert on class and rating, not on area alone.

Reading the wire's own marking is the ground truth these tables are checked against, and the cable markings decoder works through what each layer of print does and does not prove.

07What this page publishes, and what it will not

The tables above are built from standard documents, standard records and manufacturer datasheets, and the adoption label on the Chinese side — identical adoption of IEC 60227 — is taken from the standard itself rather than inferred. Where a document was not available, the page says so and stops at the standard name: HD 361's text was not obtained, so the European table gives field meanings without clause numbers, and the North American row states the nylon-jacket caveat rather than pretending the types are equal.

What this page does not do is decide a project. It will not tell you that a particular BV wire satisfies a particular H07V or THHN requirement on your job, because that depends on the build, the certificate scope and the accepting authority. Bring us the two specifications and the site conditions, and we will work the comparison against what we actually manufacture.