Insulating Glove AC vs DC Ratings: Why One Class Carries Two Voltages

Every IEC 60903 class carries two maximum use voltages — one AC, one DC — plus two proof test levels. Class 2 is 17,000 V AC and 25,500 V DC, tested at 20 kV and 50 kV. Read the column that matches your supply, or you order a class short.

Buying insulating gloves for a DC job usually goes wrong in the same place. The quotation says "20 kV", the buyer reads it as the working limit, and the glove that turns up is a Class 2: good to 17,000 V AC, and to 25,500 V DC. Correctly marked, properly tested — just not the glove that number implied.

The part people miss is that a class does not carry one voltage. It carries two maximum use voltages, one per current type, plus two proof test levels. Four figures behind a single class marking. Pick the wrong one and you are a class off, in one direction or the other.

1. One class, four numbers

IEC 60903 and EN 60903 sort insulating gloves into six classes. Colour, category letter, cuff length — all of it hangs off the class. But this is what one class row really holds:

Class 2, spelled out: 17,000 V AC to work on, 25,500 V DC to work on, tested at 20 kV AC, tested at 50 kV DC. Calling that "a 20 kV glove" throws away three of the four numbers and keeps the one that says least about where you may wear it.

If you want the wider selection picture — colour convention, category letters, Type I and Type II — that is in the Class 00–4 reference table. This page stays on the two voltage columns.

2. Use voltage and proof test voltage are different jobs

Maximum use voltage answers "what installation may I wear this on". Proof test voltage answers "what did it go through at the factory". They sit in the same row and they are not interchangeable.

Take the DC pair on Class 2: 25,500 V use, 50 kV test. Read 50 kV as the working limit and you will wear that glove on a 40 kV DC bus believing you have headroom. You do not — you are 14.5 kV past the limit, and the test certificate will still look perfectly in order.

The same confusion runs the other way on AC. Class 2 proves at 20 kV and works to 17 kV. Two numbers, one glove, and the bigger one is the one that is not the limit.

3. The DC limit is 1.5× the AC limit — do not do that maths yourself

Run down the table and the pattern is hard to miss. Every DC maximum use voltage is exactly 1.5 times its AC counterpart. 500 and 750. 1,000 and 1,500. 17,000 and 25,500. All six classes, no exceptions.

There is sound physics behind the gap. An AC figure is an RMS value, and its peak sits about 1.41 times higher than the number printed. A DC arc has no zero crossing to help it go out. Both push a DC limit above its AC twin.

But 1.5 is not 1.41. The relationship is published as a table, not as a formula, and the difference between the two is exactly the kind of rounding that turns into a wrong class on a purchase order. Read the DC column. Do not multiply.

4. The proof test pair does not scale the same way

This is where a careful reader still gets caught. The use voltages scale cleanly at 1.5. The proof test voltages do not:

Four, four, four, two and a half, two, one and three quarters. There is no single factor. So if all you have is an AC proof figure — which is what plenty of quotations carry — you cannot derive the DC test level from it, and you certainly cannot derive the DC use level.

Ask for the row, not a number.

5. Which column decides your class

One rule: compare the installation's maximum service voltage, for the current type you actually have, against the matching column.

If the system is DC, the AC column is irrelevant to the class decision. A 600 V DC battery string sits inside a Class 00 glove's 750 V DC limit — while 600 V AC would be outside the 500 V AC limit of that same glove and push you to Class 0. Same glove, same class, opposite answers, because the column changed.

If the system is AC, the DC column gives you nothing usable. It is not spare headroom. Do not bank it.

The constant across both: the maximum service voltage of the installation decides. Not the figure on the panel, not the room it sits in, not the class of gloves already in the store.

6. What the class label leaves out

Two gloves can share a class and behave very differently. What the marking does not tell you:

Service life. A Class 1–4 glove is compliant for up to 12 months from manufacture, and for 6 months from the date it is issued into service. Leave it in stores past twelve months and it needs re-testing before anyone wears it. Class 00 and Class 0 run on a different rule. Both clocks are set out in Insulating Gloves in Service.

Colour. Beige, red, white, yellow, green, orange — that is the ASTM D120 North American convention. It is not a class indicator, and a dual-certified glove sold outside North America may not follow it at all. Read the class marking on the glove.

Thickness. IEC 60903 sets a maximum per class; ASTM D120 sets its own, and the two do not match. Take the figure from the datasheet of the glove actually being supplied, not from a chart that pairs millimetres to kilovolts without naming a standard.

Protection. Wear the rubber glove without a leather protector over it and you go one class higher. Class 00 and Class 0 excepted.

Edition. IEC 60903:2014 is the edition in wide use. A 2025 revision is in draft and has not replaced it, so do not let a glove be sold to you on the strength of a standard that is not published yet.

Writing the order line for a DC job

Name the standard, the class, both use voltages, then the DC test level. Something like:

Two phrases do the work there: "maximum use" and "25,500 V DC". They are what stops a Class 2 arriving as "a 20 kV glove".

Gloves in the classes covered here are supplied as Rubber Insulating Gloves 10 kV – 35 kV and 35 kV Insulating Rubber Gloves for Live-Line Work, alongside Natural Rubber Insulating Gloves 3 kV Working / 10 kV Test.

Send us the installation's maximum service voltage and whether it is AC or DC. We will confirm the class against that column and return the type test report for the class quoted.