Question 1

What is arc resistant switchgear?

Accepted Answer

Arc resistant switchgear is switchgear designed, tested, and labeled to contain and vent an internal arcing fault so that personnel standing in front of (or alongside, or behind) the closed and latched lineup are protected. It is governed by IEEE C37.20.7, the Guide for Testing Metal-Enclosed Switchgear for Internal Arcing Faults. The rating is earned through a physical type test on the exact configuration: a real arc is initiated inside the compartment, and the lineup is verified to contain and vent it without releasing hot gas, debris, or door fragments at the personnel-protection surfaces.

Question 2

What are Type 1, Type 2, 2B, and 2C ratings?

Accepted Answer

They describe which surfaces of the lineup are protected when the doors are closed and latched. Type 1 protects only the front. Type 2 protects the front, sides, and rear (the entire enclosure). Type 2B adds protection with the low-voltage instrument compartment door open, which is how operators most often interact with the gear during routine work. Type 2C adds protection between adjacent compartments inside the lineup, so a fault in one cell does not propagate to its neighbors. Type 2B is the most common rating we engineer to because it reflects real operator workflow.

Question 3

Is arc resistant switchgear the same as arc flash mitigation?

Accepted Answer

No, and the distinction matters. Arc resistant construction contains and vents the fault if one occurs. Arc flash mitigation reduces the probability and magnitude of the fault in the first place, through fast clearing, optical detection, zone-selective interlocking, and current-limiting devices. The two are complementary, not interchangeable. The best protected lineups have both: arc resistant construction as the last line of defense, fast mitigation as the first.

Question 4

Can existing switchgear be made arc resistant after the fact?

Accepted Answer

Not by retrofit alone. Arc resistance is a tested rating for a specific structural configuration: doors, walls, vent paths, hinges, latches. You cannot bolt arc resistance onto a lineup that was not designed and type-tested for it. What you can do is add fast clearing (optical arc flash relays, zone-selective interlocking, fast bus protection) that reduces incident energy substantially, even without an arc resistant rating. That is often the right call when the structural lineup is sound but personnel exposure has crept above acceptable thresholds.

Question 5

Can we retrofit our arc resistant switchgear without losing the rating?

Accepted Answer

Yes, but it requires engineering. Any modification to the type-tested configuration invalidates the rating until the new configuration is revalidated through engineering analysis (equivalence to the original test) or, in some cases, a new type test. We are one of the few engineering firms that takes on arc resistant retrofits, and we deliver the qualification documentation that proves the rating is preserved at the end. Most field failures we see come from undocumented modifications that quietly lost the rating years before anyone noticed.

Question 6

How much does arc resistant switchgear cost compared to standard switchgear?

Accepted Answer

Arc resistant construction typically adds 20 to 40 percent to the cost of an equivalent non-arc-resistant lineup, with significant variance based on voltage class, accessibility type, and the complexity of the venting path. For mission-critical facilities, the cost is usually trivial relative to the value of the personnel protection. For non-critical applications, fast clearing alone may be the right tradeoff.

Question 7

Will arc resistant switchgear satisfy our insurance carrier and AHJ?

Accepted Answer

When properly documented, yes. The carrier and the AHJ want to see the type test report (or qualifying configuration analysis), the IEEE C37.20.7 compliance basis, the arc flash study with NFPA 70E labels, and the PE-stamped engineering. We deliver all four. Where the rating is being preserved through a retrofit, we deliver the revalidation analysis as well. Undocumented arc resistant equipment is functionally the same as non-arc-resistant equipment for insurance and code purposes.

Question 8

Do you do both low voltage and medium voltage arc resistant switchgear?

Accepted Answer

Yes. Low voltage (208V through 600V) in UL 1558 listed assemblies with IEEE C37.20.7 arc resistance, and medium voltage (4.16kV through 15kV class) in IEEE C37.20.2 metal-clad assemblies with IEEE C37.20.7 arc resistance. The standards and the testing protocols differ between LV and MV, but the engineering discipline is the same.

Arc resistant switchgear, Built to the test report, not the marketing

Arc resistance is a tested rating, not a feature you can claim.

Which surfaces and conditions the rating actually covers.

Six engineered elements every arc resistant lineup includes.

The technical envelope.

Modifying arc resistant switchgear is harder than modifying anything else.

From application review to documented commissioning.

Application review

Engineering and qualification

Build, test, install

Commission and document

What an arc resistant lineup looks like installed.

Built for the places personnel work on energized gear.

Healthcare

Data Centers

Utilities & Generation

Industrial & Process

Deeper reading and adjacent work.

Low voltage switchgear

Paralleling switchgear

Custom switchgear

Switchgear retrofit guide

Switchgear retrofitting service

Answers from our engineering team.

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