AIC ratings on in-house custom built equipment

[Davebones]

We often build custom cabinets with controls and starters for heaters and up to 150 hp motors . These are all used in-house for testing of various parts that we manufacture . None of this equipment is ever sold . We mark the circuits, voltages , etc on the cabinets . We layout and build these in a maintenance shop without a engineer designing them .We make these up to meet the electrical code . Know a lot of plants build equipment like this without a engineer design . Do we need to have the AIC ratings marked on these ?

 

[jim dungar]

Do we need to have the AIC ratings marked on these ?

No.
But you do need to provide an SCCR (short circuit current rating), see 409.110(4).

 

[templdl]

No.
But you do need to provide an SCCR (short circuit current rating), see 409.110(4).

As I recall any in house built equipment will have a 5kaic rating by default unless it is UL listed and labeled in combination with other devices.
An example may be a combination starter that is tested as an assembly with a NEMA 1 enclosed disconnect (fused of breaker), contactor, and OLR. Then the enclosure itself would be listed and labeled with the KAIC.
The enclosure is an integral part of the testing as the enclosure must contain the spoils should the components go into a self distruct mode.
As such it's not as simple as putting together the same components as would be supplied as enclosed control and expecting that it would qualify for the same KAIC rating unless the manufacturer who supplies the components has a way to extent their UL listing to the OEM or the OEM does their own testing and gets it UL listed themselves.

 

[jim dungar]

As I recall any in house built equipment will have a 5kaic rating by default unless it is UL listed and labeled in combination with other devices.

AIC stands for Amps Interrupting Capacity. This is a term strictly for overcurrent protective devices that 'clear' fault currents. The AIC rating is determined by actual short circuit clearing tests. It is provided by the manufacturer of the device. The applicable NEC section is 110.9.

SCCR stands for Short Circuit Current Rating. This, and its related term withstand rating, are for devices that must carry or tolerate a fault current until some protective device operates.
The SCCR may be determined through testing or through design (i.e. determined per UL508A SB4.1). The applicable code section is 110.10.

Another important term is SCA, which is often used for either Short Circuit Amps or Short Circuit Availability. In either case this is the amount of current that can flow due to a fault.

The terms AIC and SCCR are not interchangeable, which is why they have separate definitions in the NEC Article 100.

But to specifically address your comment: The minimum rating of UL Listed branch circuit protective devices is 5kAIC. And the maximum rating of unmarked 480V devices used in control panels is assumed to be 5kA.

 

[Jraef]

Article 409 of the NEC addresses requirements for Industrial Control Panels, I suggest you read it thoroughly, right to the very end, i.e. 409.110. It lays out listing and labeling requirements for you.

Do you need to follow the NEC when you build in-house panels that are not going to be engineered or inspected by the local AHJ? And technically if you don't, who is going to know?

The answer is, nobody. That is UNTIL there is a problem, then EVERYBODY, including local AHJs and/or Fire Marshals and OSHA if anyone gets hurt, who may start looking for people to blame and fine after the fact. Also among the "everybody" will be insurance inspectors as well, and if they see something they can use to deny coverage, they often will. One of the advantages of using a UL 508 panel shop, in addition to the SCCR rating issue being properly done for you, is that UL stands for Underwriter's Laboratories, as in INSURANCE underwriters. If the panel has a UL label on it, the insurance inspectors will move on from that box.