I-R Guy... welcome to ECN. Thanks for the post.
As you are probably aware, the requirements for working space is found in Article 110.26 of the NEC. Based on this, your generalization that only "switches" require clearance is incorrect.
110.26 Spaces About Electrical Equipment.
Sufficient access and working space shall be provided and maintained about all electric equipment to permit ready and safe operation and maintenance of such equipment. Enclosures housing electrical apparatus that are controlled by lock and key shall be considered accessible to qualified persons.
The NEC Handbook offers the following additional guidance.
Key to understanding 110.26 is the division of requirements for spaces about electrical equipment in two separate and distinct categories: working space and dedicated equipment space. Working space generally applies to the protection of the worker, and dedicated equipment space applies to the space reserved for future access to electrical equipment and to protection of the equipment from intrusion by nonelectrical equipment. The performance requirements for all spaces about electrical equipment are set forth in the first sentence. Storage of materials that blocks access or prevents safe work practices must be avoided at all times.
Also, you need to consider the specifics of 110.26(A).
(A) 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), (2), and (3) or as required or permitted elsewhere in this Code.
Again, the Handbook offers additional guidance.
The intent of 110.26(A) is to provide enough space for personnel to perform any of the operations listed without jeopardizing worker safety. These operations include examination, adjustment, servicing, and maintenance of equipment. Examples of such equipment include panelboards, switches, circuit breakers, controllers, and controls on heating and air-conditioning equipment. It is important to understand that the word examination, as used in 110.26(A), includes such tasks as checking for the presence of voltage using a portable voltmeter.
Minimum working clearances are not required if the equipment is such that it is not likely to require examination, adjustment, servicing, or maintenance while energized. However, â€śsufficientâ€ť access and working space are still required by the opening paragraph of 110.26.
There are very few pieces of equipment that do not require this access space.
BTW. There is parallel OSHA standard, 29 CFR 1910.303(g)(1)(i). Since you seem to be talking about existing equipment, you are unlikely to have an "electrical" inspection on this issue. But, you are playing "russian roulette" with a potential OSHA citation if the clearance is not maintained. http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_i d=9880#1910.303(g)(1)(i)
Hope this helps.
Edited to correct coding error.
[This message has been edited by safetygem (edited 02-04-2005).]