The recent focus on NFPA70E requirements is good, but it’s not enough. That standard, though excellent, doesn’t address all the safety issues that arise when accessing a panel. Here are some more:
- Removing a panel cover is a two-person job. So is putting it back.
- Before removing a panel cover, carefully note which, if any, branch circuit breakers are open.
- Especially note breakers that indicate a trip. If you don’t know the reason for the trip, investigate before proceeding.
- If you accidentally open a breaker, don’t reclose it because it may be under load; remove the load, then reclose it. Same applies in reverse if you accidentally open one.
And obviously, NFPA70E isn’t intended to address breaker replacement. To avoid disaster:
- Determine if the breaker you’re installing is suitable for that panelboard. Is it of a rating and type the panelboard will accept?
- Always look at the interrupt rating (expressed in Kilo-Amperes Interrupting Capacity or KAIC) of each new breaker before installing. This value must exceed the available fault current at the panelboard or you’ll be installing a time bomb.
If you don’t know the available fault current at the location, and are just adding to an existing panel of breakers look at the KAIC of the other breakers. Install one of the same or higher rating. This assumes the original installer didn’t err in breaker selection and won’t make the situation worse if he did. Verify soon.
Source: Mark Lamendola | Mindconnection