Re: Ul certified equipment
kg said:
Is it ok to change the length of a 120v SJ cord installed on a piece of equipment or does this void the UL rating?
The UL mark applies to the equipment as it existed at the time it was labeled. You can no more "void" it than you can label it in the first place.
It is possible for you to modify, install, or even just use the item in such a way as to create a hazard regardless of the label.
You need to look at it in a more rational way. If you need to make the cord a foot longer to avoid the use of an extension cord that would otherwise be required, changing out the existing cord for a longer one reduces the hazard you might otherwise have introduced (the extension cord).
Keep in mind a plug and cord connected piece of equipment is probably not an installation as such, and thus probably not subject to the NEC, although I am sure any number of people will argue about this.