Many facility engineers, plant engineers, and plant managers believe there should be 3 ft of clear space in front of electrical panels. A quick look at Table 110.26(A)(1) of the National Electrical Code (NEC) confirms this to be the minimum working clearance for 480V panels with exposed parts on one side of the working space and no live or grounded parts on the other side. It’s also true if there are exposed parts on both sides of the working space but they are effectively guarded by insulating materials.
If you change this just a tiny bit, the minimum distance is greater. For example, if a 480V panel with exposed parts on one side of the working space also has grounded parts on the other side, the distance increases to 3 ft - 6 in.
Similarly, if a 480V panel with exposed parts on one side of the working space also has a concrete wall on the other side, the distance increases to 4 ft.
OSHA’s tables are taken directly from the NEC, so if you look there, you will find the same minimum distances. What you won’t find in the tables in either place is how much working space is enough?
A clue to the answer, however, is found in the text of 110.26: “Access and working space shall be provided and maintained about all electrical equipment to permit ready and safe operation and maintenance of such equipment.”
Most maintenance workers (electricians and mechanics) are male, and the average waist circumference of the American male is over 40 in. today. For females, it’s a few inches smaller. If a maintenance procedure requires two people, is it safe to provide them only 3 ft of space in which to perform that maintenance?
That’s one consideration. Another is the type of maintenance expected to be performed in a given window of time. For a given production line, it often makes sense to perform all of the electrical and mechanical PMs for that line in one time window rather than interrupt production multiple times.
It can be costly to production if you PM the motors one day, the VFDs the next, the motor controls the next, the terminations the next, and so on, while the mechanics take a similar approach.
If the work is planned properly, you could have three or four maintenance carts (with one or two techs each) competing for space along that line. Some of the test and maintenance equipment may be bulky, further complicating the space issue.
You won’t find the correct numerical answer to this question in OSHA regulations or in the NEC because it simply is not possible for the code-making panel members to anticipate the exact circumstances of every facility and publish a 900-plus-page chart to cover the various possibilities.
In the event of a lethal shock incident, one of the key determinations in a lawsuit is whether enough working space was provided for the intended work to be safely performed. If the defendant used the tables but gave no consideration to other factors that may call for increased working space, that could be ruled as negligence.
So, are those tables useless? No, they will cover most applications, but not cover every application. Be sure to assess your application for issues that may require greater working space requirements than the tables call for. If the needed space is going to be a battle to secure, there may be a technical fix that reduces how much space you need.
For example, you can install a thermography window to eliminate cover removal. You could mount a camera permanently, thereby eliminating the need to have a thermographer also walking around that equipment and competing for working space. You can also buy DMMs with remote display functionality or install test ports where there is already more space. Even if your space is adequate already, these measures are worth looking into for other reasons including safety and productivity.
