"Working Space. Working space for equipment operating at 600 volts, nominal, or less to ground and likely to require examination, adjustment, servicing, or maintenance while energized shall comply with the dimensions of 110.26(A)(1), (A)(2), and (A)(3) or as required or permitted elsewhere in this Code"
Opines needed.
What in a transformer needs examination, adjustment, servicing, or maintenance while energized? If the windings short you can either see the smoke, smell the smoke, or see smoke stains. Adjustments are made in a de-energized state, try to change taps while energized damages equipment fed from the xfmer. What is to serviced and what is to be maintained inside a transformer? If voltage readings are needed, they can be made either at the OCPD upstream or downstream. So, other than the practacality of installation, why would the dimensions in Table 110.26(A)(1) be needed?

I guess the real life issue would be examination.
Just like a panelboard or switchboard. You remove the cover to inspect the interior while energized, due to a problem. The same would hold true with a transformer.
Sometimes you find items such as a animal, burning connections, lost a leg because a lug broke off. visually check what tap connections were used, thermal imaging test, ETC.
I for one would not want to tell a customer with say a intermittent ocpd tripping that I need to turn the store off just to look.

I would agree with Ruben as far as examination. But also terminals could be checked for torque and tightened if need be. Xformers do vibrate. I have seen where lugs became burned and/or discolored due to a loose connection. And then subsequently that had to be fixed.

I think the issue stated is why a working clearance is required when a external disconnect is installed.
I still stand by the requirement regardless of the situation.

I have never been a big fan of the language in this section. In fact, I submitted a proposal a code cycle back to eliminate the words "likely to require" & "while energized" form the section.

To start with, "likely to require" is too vague and uneforceable & I feel working space is needed about equipment regardless if it is energized or not.

So, I do not feel it is a good policy to require some equipment to have the required working space and allow others to not. In my book, ALL equipment, except for devices, utilization equipment, and luminaires are required to have the required working & dedicated equipment space as identifed in 110.26.

PERIOD.

Once I heard Charlie Minnick say that you need the working space for the transformer even if only for a maintenance person to come in and dust it off, or paint it, or whatever. I always enforce 110.26 and I also enforce the required venting space (distance away from walls) that always seems to be compromised when it comes to xformer installations.

Bryan, how do you deal with air handler disconnects in closets and attics? That always seemed to be the tough one.

I know how I deal with it. I go by 110.26. And unit breaker can serve as the disconnect in many cases.

No problem.

I agree with Nick. Since the FBC-R & FBC-M both require appliance access when installed in these locations (M1305 / 306), I don't see why the electrical equipment associated with these appliances would not be requred to meet required working space & access as well...

I agree with the sentoment but I see plenty of them that you can't push Jim Pauley''s "refrigerator box" (a rough approximation of working space) up to. It certainly is not happening in a typical Florida 3:12 or 4:12 attic, unless the trusses are 50' wide.

There is no doubt appliances located in closets, attic spaces, & attics make it extremely difficult for compliance with the NEC requirement for working & dedicated equipment space.

That being said, the installer has several options to come into compliance. If space is not provided for an actual disconnecting means, the a "unit swtich" can be installed. If there are no provisions for a "unit switch", a breaker lock-out device can be installed.

I will admit I have approved disconnecting means located with one or more working space dimensions NOT in full compliance, but where I was readily & easily able to approach, examine, operate, and inspect the equipment without resorting to acrobatics or other unsafe practices.

But those are exceptions to the rule, not the rule...

Several good thought provoking opinions given. Odd how a string can take a life of it's own. Going from 110.26 working space for a transformer to equipment located in closets, attics, and such. How maybe it shouldn't really apply to receptacles and switches, to judgement calls, to absolutely applied in all cases. Would someone actually try to verify the torque of transformer lugs while it was still energized? If you have a transformer that is being supplied correctly yet the output is incorrect, ie single phase rather than three phase, would you really have to remove the cover to realize that there was a bad connection or an open winding? Going back to the original question, and from your opinions, the working clearance as outlined in 110.26 would be required.
Again some good opinions. Thanks.