UL 248 and IEC 60269 both describe low-voltage fuses, but they do not use the same language. This page explains the practical difference between North American fuse classes, IEC utilisation categories and BS88-style UK practice without treating one label as a direct substitute for another.
The standards overlap in purpose, not in naming.
UL 248 is the fuse standard family most often met in North American equipment. It uses class names such as Class J, Class CC, Class L, Class R and Class T. Those names carry practical meaning: dimensions, rejection features, current-limiting performance, interrupting rating and how the fuse is accepted in a listed assembly.
IEC 60269 takes a different route. It describes low-voltage fuse-links through application categories such as gG, aM, aR, gR and gPV. Those letters tell you what kind of protection the fuse is intended to provide, such as general cable protection, motor backup, semiconductor protection or photovoltaic string protection.
BS88 sits close to the IEC-style world and is familiar in UK industrial panels, switchgear and HRC fuse work. It adds its own practical body sizes, tag styles and holder arrangements. That helps in UK replacement work, but it still does not make a BS88 fuse the same thing as a UL class fuse.
Use this table to understand the language before looking at a proposed replacement.
| Point | UL 248 side | IEC 60269 / BS88 side | What it means in practice |
|---|---|---|---|
| How fuses are named | By class names and product families used in North American equipment. | By utilisation categories, body formats and national or regional practice. | The label tells you which system you are reading, not whether another system is equivalent. |
| Typical labels | Class J, CC, L, R, RK1, RK5, T, G and supplementary fuse types. | gG, aM, aR, gR, gPV, NH, cylindrical and BS88 fuse-links. | The same current rating can belong to very different fuse designs. |
| Approval context | Common in UL-listed equipment and North American code environments. | Common in IEC, EN and UK industrial equipment. | A technically similar fuse can still be unacceptable if it changes the equipment approval path. |
| Fault rating language | Often described as interrupting rating. | Often described as breaking capacity. | The wording differs, but the question is the same: can the fuse safely clear the available fault current? |
| Holder system | Class-specific and rejection holders are common. | BS88, NH, cylindrical and other holder forms are common. | A fuse that fits loosely, bypasses a rejection feature or changes heat rise is not a proper replacement. |
| Best replacement approach | Use the original class, series, voltage, interrupting rating and holder data. | Use the category, voltage, breaking capacity, dimensions and holder data. | Compare the whole protection point, not one marking. |
This is a reading guide, not a substitution table. The final choice belongs to the equipment data, the fuse data sheet, the holder and the rules for the installation.
UL class names bundle together several North American assumptions: the fuse class, holder type, rejection feature, current-limiting behaviour, marking and acceptance in equipment. IEC categories describe the job the fuse performs in the circuit. That is why a class name from one side cannot simply be turned into a category name from the other.
Motor protection is a good example. IEC aM fuses are normally used as backup short-circuit protection with a separate overload device. They are not general overload fuses. Semiconductor protection is another example: aR and gR fuses are selected around high-speed operation and let-through energy, not just around the printed current rating.
For a replacement, the useful question is not “which code sounds similar?” The useful question is whether the new fuse preserves the same electrical behaviour, mechanical fit, fault rating and approval basis as the original part.
UL 248 class names help define the fuse's physical system, interrupting rating, current-limiting role and the holder arrangement used with it. In replacement work, the class marking is a strong clue, but the exact product series and equipment listing still matter.
IEC 60269 categories help describe the intended protection job. gG, aM, aR, gR and gPV are not decorative letters. They point to very different behaviour under overload, short circuit, inrush, semiconductor fault or PV string conditions.
BS88 fuses are widely used in UK industrial work and often appear in HRC fuse replacement. They should be checked by their own body form, tags, holder, voltage, breaking capacity and circuit role rather than compared loosely with a UL class.
The label helps you understand the fuse family. It does not approve a substitute.
| Label | System | Plain meaning | Replacement caution |
|---|---|---|---|
| Class J | UL | Current-limiting branch-circuit fuse class used in many industrial panels. | Keep the holder, rejection feature, voltage and interrupting rating intact. |
| Class CC | UL | Compact current-limiting class often used in control circuits. | Do not confuse compact size with an IEC cylindrical fuse. |
| Class L | UL | Large current-limiting class for high-current feeders and service equipment. | Panel rating and approved holder system are central. |
| Class R / RK | UL | Rejection-type fuse classes intended to prevent unsuitable substitutions. | Bypassing the rejection system defeats part of the safety design. |
| Class T | UL | Compact high-interrupting fuse class used in specific designs. | Its small size makes poor substitutions tempting. |
| gG | IEC | General full-range protection, often used for cable and line protection. | Not a North American branch-circuit class by itself. |
| aM | IEC | Motor-circuit backup protection, normally paired with overload protection. | Do not use it as a general overload fuse unless the circuit design requires it. |
| aR / gR | IEC | High-speed protection for semiconductor devices. | Compare time-current curves, I²t and the protected device data. |
| gPV | IEC | Fuse category for photovoltaic string and array protection. | PV DC voltage and fault behaviour need specific data. |
Do not begin with a cross-reference table. Begin with the installed protection point.
Record the marking on the existing fuse, then record the holder marking. Look at the equipment label or drawing if it is available. The holder can be just as important as the fuse because it controls fit, heat rise, rejection features and contact pressure.
Next, read the circuit. Is it AC or DC? What is the system voltage? What fault current is available at that point? Is the fuse protecting a cable, a motor starter, a transformer, a semiconductor device, a PV string, a battery circuit or a control circuit?
Only after those facts are clear should a proposed replacement be compared. The comparison should include current, voltage, fault rating, time-current behaviour, body format, holder fit and any approval or listing requirement. For a wider process, see the fuse cross-reference guide, breaking capacity guide and fuse holder guide.
A table can help, but it should not make the decision for you.
| Check | What to confirm | Why it matters |
|---|---|---|
| Original system | Whether the installed part is being read through UL, IEC, BS88 or another local standard. | The replacement has to preserve the design basis, not just a rating number. |
| Current and voltage | Rated current and the correct AC or DC voltage. | DC applications and higher voltages can make a familiar fuse unsuitable. |
| Fault rating | Interrupting rating or breaking capacity against the available short-circuit current. | The fuse must safely clear the worst expected fault at that position. |
| Time-current behaviour | Curve shape, delay, current limitation and coordination with other devices. | The wrong behaviour can cause nuisance operation or fail to protect the intended component. |
| Holder and heat path | Body style, tags, clips, rejection features, contact pressure and derating. | A poor mechanical match can overheat or defeat the original holder design. |
| Application | Cable, motor, transformer, semiconductor, PV, battery, UPS, EV or control circuit. | Different applications need different fuse behaviour. |
| Approval context | Equipment listing, local code, manufacturer instructions and maintenance records. | An electrically similar part may still be unacceptable in approved equipment. |
Drives, inverters, EV chargers, battery systems and PV combiners make fuse comparison more demanding. In these circuits, the fuse may need to limit energy quickly enough to protect semiconductors or clear DC faults safely. A broad class or category name is not enough.
For semiconductor protection, compare pre-arcing I²t, total clearing I²t, peak let-through current and the manufacturer's device coordination data. For DC systems, check the DC voltage rating, the expected fault current, polarity or series requirements where relevant, and the holder's suitability for the same duty.
These applications are expensive when the comparison is wrong. Use product data and equipment documentation, not a generic equivalence list.
Use these pages to connect the standards question with rating, holder and application checks.
Short answers for common UL, IEC and BS88 comparison questions.
No. They are different low-voltage fuse standard families. They cover similar protection ideas, but their class names, approval systems and application categories do not translate directly.
Not by class name alone. The circuit, holder, voltage, fault rating, time-current behaviour and equipment approval all need to be checked before any substitution is considered.
BS88 is common in UK low-voltage industrial fuse practice and is close to the IEC-style world. Its body forms and tags should still be checked against the holder and equipment data.
A fuse can fit a holder while still having the wrong approval, breaking capacity, time-current behaviour, rejection feature, thermal performance or DC rating.
No. gG and aM are IEC-style utilisation categories. gG is used for general protection, while aM is normally backup protection for motor circuits with separate overload protection.
No. A table can help narrow the search, but the final decision needs the equipment documentation, fuse data, holder data and the applicable local rules.