Question:

The CX7 KWIKstarter does not have a defeatable door interlock mechanism and isn’t that required by UL?

Answer:

The E-Combo KWIKstarter uses a screw-on cover (a cover is defined by UL 508 as not having a hinge). As such, it is not required to have the interlocking door mechanism.

UL 508 Section 39A.4: For a combination motor controller, a door shall be interlocked with the disconnecting means such that:

a. The door is not able to be opened unless the disconnecting means is in the open (OFF) position; and
b. The door is required to be latched before the disconnecting means is able to be switched to the closed (ON) position.

Exception: The door is not required to comply with this requirement when the interlocking means is intentionally defeated by means described in 39A.5.

39A.5: The interlocking means required by 39A.4 is able to have a defeat mechanism that requires the use of tools to open the door and that is self-restoring when the door is closed.

All of the above does seem to require an interlocking door mechanism for Combination Starters but reading UL definitions puts new light on the issue as follows:

2.8.1 Explains what a cover is: "COVER - An unhinged portion of an enclosure that covers an opening."
2.8.2 Explains what a door is: "DOOR – A hinged portion of an enclosure that covers an opening."

If we had a hinged door on the enclosure then we would need the interconnect device as defined by 39A. This E-Combo KWIKstarter uses a screw-on cover (a cover is defined by UL 508 as not having a hinge). As such, it is not required to have the interlocking door mechanism.

The E-Combo KWIKstarter has been approved by UL as an assembly and has a cUL file number assigned (E333251 for the enclosure only and E205542 for the complete assembly).

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