Lawson Fuse Types, Sizes and References
How Lawson fuse references are organised
Lawson uses several product families rather than one universal fuse format. A code such as NIT32, TIA20 or TIS63 belongs to the Type N&T industrial bolted range. A reference beginning with SSA, SSB or SSC points to the higher-voltage Type SS range. Compact Clipfit links use the SS, NS and MES families, while Type J, LSC, MD and other product groups serve different applications and holder systems.
The useful reading order is manufacturer series → BS or IEC system → current rating → voltage → utilisation category → physical format. This avoids the common error of seeing a familiar current value and assuming the body or operating duty is interchangeable.
For bolted industrial links, the BS88 size code is especially useful because it connects the fuse reference to a standard body and fixing pattern. It is a mechanical reference point, not a complete replacement specification.
| Read this | What it tells you |
|---|---|
| Series code | Which Lawson product family and body system you are looking at. |
| Current rating | The nominal fuse-link current, but not the whole replacement specification. |
| BS88 size | A standardised mechanical size or fuse system reference for many industrial links. |
| Voltage | Whether the fuse belongs to a 240V, 415V, 500V, 690V or another rated family. |
| gG / gM / aR | The protection duty and operating behaviour. |
Main Lawson fuse families at a glance
Lawson Type N&T: 400/415V BS88 size map
| Lawson series | BS88 size | Typical rating span | Fixing centres | Format |
|---|---|---|---|---|
| NIT | A1 | 2–32A | 44.5 mm | Offset tag |
| TIA | A2 | 2–32A | 73 mm | Offset tag |
| TIS | A3 | 35–125A | 73 mm | Offset tag |
| TCP / CTFP / TFP | A4 | 6–200A across variants | 94 mm | Offset tag |
| TC / TBC | B1 | 2–100A across variants | 111 mm | Central tag |
| TF / CTF | B2 | 125–200A | 111 mm | Central tag |
| TKF | B3 | 250–315A | 111 mm | Central tag |
| TMF | B4 | 355–400A | 111 mm | Central tag |
| TM | C1 | 355–400A | 133 / 184 mm | Large central tag |
| TTM | C2 | 450–630A | 133 / 184 mm | Large central tag |
| TLM | C3 | 670–800A | 133 / 184 mm | Large central tag |
| Example | Read it as |
|---|---|
| NIT32 | NIT family, BS88 A1 body system, 32A rating. |
| TIA20 | TIA family, BS88 A2 body system, 20A rating. |
| TIS63 | TIS family, BS88 A3 body system, 63A rating. |
| TF160 | TF family, BS88 B2 central-tag system, 160A rating. |
How to decode a Lawson fuse reference
A reference such as NIT32 is more useful than the isolated marking “32A”. The NIT prefix places the fuse in the Type N&T industrial bolted family and links it to the A1 mechanical system. The current value then narrows the exact rating within that family.
Motor-duty references can add an M element, so a code may show both the fuse-link rating and a higher motor circuit rating. Those references should be checked against motor-starting data rather than interpreted as ordinary gG replacements.
Older stock, non-standard variants and different voltage families can use related-looking codes. If a printed reference is incomplete, use the body, fixing centres, holder and remaining electrical markings to establish the family before ordering a replacement.
Lawson Type SS: the 690V industrial family
Lawson Type SS covers industrial bolted fuse-links rated for 690V a.c. applications. The family extends across BS88 sizes A1 to C3 and includes both offset-tag and central-tag forms. Because the same BS88 size concept can appear in the 415V and 690V ranges, a mechanical match does not make the voltage families interchangeable.
The most useful quick comparison is A1 SSA1, A2 SSA2, A3 SSA3 and A4 SSA4 or related A4 variants. Larger central-tag positions move through SSB and SSC families. Additional non-standard fixing-centre variants also exist.
If an old fuse is marked 600V or 690V, treat that as a decisive clue. Do not replace it from the 415V N&T family simply because the current and BS88 size appear similar.
| BS88 size | 400/415V example | 690V example |
|---|---|---|
| A1 | NIT | SSA1 |
| A2 | TIA | SSA2 |
| A3 | TIS | SSA3 |
| A4 | TCP / related variants | SSA4 / SSFP |
| B2 | TF / CTF | SSB2 / related variants |
| C2 | TTM | SSC2 / related variants |
Compact Lawson fuse sizes: SS, NS and MES
The Type CDS range uses Clipfit holders and compact blade-contact fuse-links. The three common compact families are SS for size E1, NS for size F1 and MES for size F2. These short reference codes can otherwise be confused with larger industrial or legacy Lawson fuse families.
The compatible Clipfit holder family is Type LCF. The 20A holder position is associated with SS/E1, the 32A position with NS/F1 and the 63A position with MES/F2. A compact fuse should therefore be identified from the blade/body system and holder, not by comparing its amp rating with a bolted NIT or TIA link.
| Lawson family | Compact size | Holder position |
|---|---|---|
| SS | E1 | LCF 20 |
| NS | F1 | LCF 32 |
| MES | F2 | LCF 63 |
Which Lawson fuse family matches the application?
Lawson fuse size is not the same as Lawson fuse rating
- BS88 size or other system reference.
- Offset tag, central tag, blade or cartridge body.
- Fixing centres and tag geometry.
- Body dimensions and holder/carrier type.
- Rated current and system voltage.
- AC or DC duty where relevant.
- Breaking capacity.
- gG, gM, aR or another utilisation category.
Quick identification workflow
Common questions about Lawson fuse types
What are the main Lawson industrial fuse types?
The main industrial families include Type N&T for 400/415V bolted BS88 fuse-links, Type SS for 690V bolted industrial fuse-links, Type CDS for compact Clipfit fuse-links, Type MD cylindrical general-purpose links, and specialist families such as Type J, LSC, ABB and LGP for particular systems or applications.
What does NIT mean on a Lawson fuse?
NIT is a Lawson Type N&T offset-tag industrial fuse reference associated with BS88 size A1. The standard NIT range uses 44.5 mm fixing centres and is part of the 400/415V industrial family.
What BS88 size is a Lawson TIA fuse?
TIA is associated with BS88 size A2. Standard TIA fuse-links use 73 mm fixing centres and sit within the Lawson Type N&T 400/415V industrial range.
What BS88 size is a Lawson TIS fuse?
TIS is associated with BS88 size A3 and uses 73 mm fixing centres. The series covers higher current ratings than the standard TIA A2 range.
What is the difference between Lawson N&T and Type SS fuses?
Type N&T is the principal 400/415V industrial bolted range, while Type SS is the 690V industrial bolted range. Similar BS88 size references can appear in both families, so voltage rating and exact series must be checked rather than matching size alone.
Are Lawson fuse references interchangeable if the BS88 size matches?
Not automatically. The BS88 size helps identify the mechanical system, but the current rating, voltage, breaking capacity, utilisation category, fixing centres, holder and circuit duty must also be compatible.
What are Lawson SS, NS and MES fuses?
SS, NS and MES are compact-dimension Lawson fuse-links used with the Clipfit system. They correspond to compact sizes E1, F1 and F2 respectively and are distinct from the larger bolted N&T industrial series.
How should an old Lawson fuse reference be identified?
Record the complete printed reference, rated current and voltage, utilisation category if shown, body shape, tag or blade arrangement, fixing centres and holder type. The complete combination is more reliable than identifying the fuse from amp rating or appearance alone.
Bottom line
A Lawson fuse is easiest to identify from the complete series code, not from the amp rating alone. For industrial bolted links, NIT, TIA, TIS, TCP and the larger TF/TKF/TMF/TM/TTM/TLM families map into recognisable BS88 size systems. Type SS covers higher-voltage industrial positions, while compact CDS, Type J, LSC, MD and other families use different mechanical or application logic.
Use the series to establish the family, the size and fixing centres to establish the mechanical system, and the electrical markings to confirm the protection duty. That sequence is much more reliable than choosing a replacement from appearance or current rating alone.