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A fuse size chart is really a table of two numbers. Cylindrical fuse sizes are written as diameter × length in millimetres — 10×38 mm, 14×51 mm, 22×58 mm and 14×85 mm are the four you will meet most often in low-voltage distribution and photovoltaic work. Fuse size tells you what fits where, and it is the first thing to confirm when replacing a fuse or specifying a holder.
It is also the most over-trusted number on the fuse. Two fuses with identical dimensions can carry different voltage ratings, different operating classes and different breaking capacities, and swapping one for the other on the basis of size alone is how protection systems quietly stop protecting anything. This chart gives the dimensions and the typical pairings for each size, then sets out what the size does not tell you.
The size designation is diameter × length in millimetres. It refers to the cylindrical body, and the diameter is a nominal figure rather than an exact one. Measure a 10×38 mm fuse across the end cap with a caliper and you will typically read around 10.3 mm, not exactly 10 mm; a 22×58 mm fuse usually measures close to 22.2 mm. This is normal manufacturing tolerance on the cap, and it is the reason a holder designed for one size will not accept the next one up even when the numbers look close.
To measure a fuse you are trying to replace:
Modern cylindrical fuse links carry their ratings on the body or on the metal end caps. Those markings are the authoritative source; a size measurement only tells you what will physically fit.
The table below covers the four common cylindrical sizes, the current ranges typically available in each, and the standard pairings used in AC distribution and solar PV work. Ratings shown are typical for these formats rather than a limit on what any particular series offers.
| Size (Ø × L) | Typical current range | AC fuse link + holder | PV fuse link + holder | Typical voltage | Uso habitual |
|---|---|---|---|---|---|
| 10×38 mm | Up to 32 A | RO15 + RT18-32 / GD18-32 | GD-10PV / GD-12PV + GDPV-32L | 500 V AC · 1000 V DC | Control circuits, small distribution, PV strings |
| 14×51 mm | Up to 63 A | RO16 + RT18-63 | GD-14PV + GDPV-50B | 500 V AC · 1000 V DC | Distribution and control panels, PV combiner boxes |
| 22×58 mm | Up to 125 A | RO17 + RT18-125 | GD-15PV series + GDPV-22B | 500 V AC · 1000 V DC | AC main distribution, 1000 V DC array feeds |
| 14×85 mm | Typically 8–50 A in gPV | — | GD-13PV + GDPV-50 series | 1500 V CC | High-voltage solar PV strings and combiners |
Notice the pattern: the first three sizes appear on both the AC and the PV side, and the fourth is a PV-only format. That overlap is exactly where mismatched substitutions happen, so read the next section carefully.
At 38 mm long and roughly 10 mm across, this is the most widely used small cylindrical format. In AC work it pairs with RO15 fuse links rated 32 A at 500 V AC in gG class, held in RT18-32 or GD18-32 holders. On the PV side the same body size carries GD-10PV and GD-12PV links rated up to 32 A at 1000 V DC in gPV class, held in a GDPV-32L base.
The 10×38 mm format fits comfortably into dense control panels, which is both its advantage and its risk. Because the holders are small and look similar, an AC holder and a DC holder of the same physical size can sit side by side in the same cabinet and be swapped by someone reading only the size.
The longer 51 mm body gives more arc-quenching volume, which supports higher current ratings. In AC service, RO16 links reach 63 A at 500 V AC in gG class, using RT18-63 holders. For PV, GD-14PV links cover 15–50 A at 1000 V DC in gPV class with a GDPV-50B base, and this pairing is common on PV combiner boxes where several strings are grouped.
The jump from 32 A to 63 A between the 10×38 mm and 14×51 mm formats is one of the few places where fuse size correlates strongly with current capability. It is still not a rule you can rely on for voltage.
The largest of the three AC-side formats, 22×58 mm carries RO17 links up to 125 A at 500 V AC in gG class on RT18-125 holders, and it is the size you find on AC main distribution feeders. On the PV side, GD-15PV series links in 30–50 A at 1000 V DC are listed in this format with the GDPV-22B base for 1000 V DC solar protection.
Above this size, cylindrical formats give way to blade-type fuse systems for higher currents. If you are working in that range, the different fuse base types and what currents they cover covers the alternatives.
The 85 mm body is noticeably longer than the other three, and that extra length is functional rather than cosmetic. A 1500 V DC arc needs more distance and more arc-quenching fill to extinguish than a 500 V AC arc, so high-voltage PV formats are longer. The GD-13PV 25A 1500 V DC fuse link uses this format in gPV class with a 20 kA breaking capacity, and the series spans 8–50 A.
The 14×85 mm body pairs with the GDPV-50 series of PV fuse bases, which accept both 10×85 mm and 14×85 mm links depending on model and support both 1000 V and 1500 V DC systems. Because two compatible formats exist in the 85 mm length, confirm the diameter as well as the current rating when ordering a replacement.
This is the part of the chart that matters most. Size is a mechanical fact; the four values below are electrical, and none of them can be inferred from the dimensions.
| Parámetro | Why size cannot substitute for it |
|---|---|
| Voltage rating | A 10×38 mm link exists in 500 V AC gG and 1000 V DC gPV versions. The bodies are the same; the ratings are not interchangeable. |
| Operating class | gG, aM and gPV classes share body sizes but interrupt different fault profiles. Using a gG link in a PV string leaves the circuit protected by a device never tested for that duty. |
| Capacidad de frenado | Two links of the same size can differ substantially in the fault current they can safely interrupt. |
| Holder rating | A holder of the correct size may still be rated below the fuse link’s current or voltage. The assembled pair performs to the lower of the two. |
For the values printed on the body and how to check them, how to read fuse datasheet parameters goes through each field in order. If the fuse is marked but the marking is unfamiliar, current, voltage and interrupting capacity ratings explains what each number refers to.
The four sizes above are the cylindrical family. Two other groups show up regularly in distribution work and should not be confused with them:
There is also an 8.5×31.5 mm format that predates the 10×38 mm standard and still appears in older equipment. It is shorter than the 10×38 mm body and will not seat correctly in a 10×38 mm holder without modification, which is never an acceptable solution.
When the body marking is illegible or absent, work through the following before ordering a replacement:
Where the fuse protects a solar string, note that AC and DC links of similar appearance are built differently internally even when the body dimensions match — the reasons are set out in our comparison of AC and DC fuse construction.
The first number is the nominal diameter and the second is the body length, both in millimetres. A 10×38 mm fuse is nominally 10 mm across and 38 mm long between the end caps.
They are the same size, but that does not make them a valid pair. The holder must also be rated at or above the fuse link’s voltage and current, and must be intended for the fuse link’s operating class. An AC holder of the right size is not suitable for a 1000 V DC gPV link.
Around 32 A is the practical limit for this format in both AC gG and PV gPV versions. Higher currents move up to the 14×51 mm or 22×58 mm formats, which provide more body volume for arc quenching.
A DC arc has no natural current zero to help extinguish it, and the higher the DC voltage the longer the arc can sustain itself. The extra length gives the fuse more arc-quenching fill and greater separation to interrupt the arc reliably.
No. The contact geometry differs, so the smaller link will not seat properly and will make poor contact in the holder. Poor contact creates localised heating, which is a common cause of premature fuse failure.
The marking on the body or end cap states VAC or VDC along with the value and, for photovoltaic parts, the gPV classification. If the marking cannot be read, treat the fuse as unknown rather than assuming it matches the holder.
Fuse size gets you to the right shelf. It does not confirm that the fuse will carry the load, interrupt the fault or survive the system voltage. Measure carefully, read the markings, and check the holder, then verify voltage, current and class against the circuit before you install anything.
The full range of matched fuse links, holders and bases across all four cylindrical sizes — including the 1000 V and 1500 V DC photovoltaic formats — is listed on the GA&DA fuse and fuse holder range. If you need a size that is not listed, send the diameter, length, voltage, current and estimated quantity and the team will confirm availability.
