[RE-wrenches] Code reference needed

[Peter Parrish]

I spent some time putting together information on the "2'-6" Lower Limit"
and the "6'-6" Upper Limit" for operable equipment; and then when I went to
send out the results of my efforts, the content in the email disappeared.
Since the information I thought would be helpful, I have re-assembled the
information. I also found the 6" depth of working space citation. Here goes.


First, there has been a pretty complete move to metric units in the NEC
a/k/a "SI or metric Units". In some places in the NEC, distances are defined
in terms of meters and decimal fractions of meters, in other places they are
defined in terms of millimeters, and in some others, they remain defined in
terms of feet and inches. So the oft mentioned 6'-6" (1.98 meter) limit has
occasionally been redefined to be 2.0 m (or 6'-6.7" and rounding up becomes
6'-7"). However, in many other sections of the NEC designates 2.0 m as 6-1/2
ft; go figure.

600 V or less: 

Height of working space (headroom) is 2.0 m (6-1/2 ft) or height of
equipment. Reference is 110.26(A)(3) "Height of Working Space", which in
turn refers to 110.26(E) "Headroom", with some exceptions. 

Depth of working space 150 mm (6 in.). Reference is 110.26(A)(3) "Height of
Working Space".

Overcurrent Protection needs to be "readily accessible" and the "center of
the grip of the operating handle" be no more than 2.0 m (6'-7"). Reference
is 240.24(A).

Switches: "center of the grip of the operating handle" be no more than 2.0 m
(6'-7") above floor or working platform. There are some exceptions for fused
switches and circuit breakers on busways, motor switches; and there is a
exception for "Hookstick operable switches".

Inverters. I have data on SMA, Xantrex and Fronius. 

SMA: The Sunny Boy must be mounted so that there is at least eight inches of
clearance around the Sunny Boy. The clearance between the inverter or the
SMA DC-Disconnect (if applicable) and the ground has to be at least 3 ft.
Sunny Boy Installation manual (Ver. 2.2, 2008) p. 26.

Xantrex: Table 2-2 Inverter Clearance Requirements Location Minimum
Clearance
Above 300 mm (12 inches) Below There is no clearance requirement between the
bottom of the inverter and the ground. Front 300 mm (12 inches) minimum. 910
mm (36 inches) are recommended for easy access for reading the display,
avoiding accidental contact with hot surfaces, and servicing the inverter.
Sides Units can be mounted side by side with no clearance between them, but
150 mm (6 inches) of clearance around the outside edges of the outermost two
units is recommended. In hot climates, some clearance between units may be
needed to prevent thermal derating. Xantrex Grid Tied Owner's Manual,
December 2009, Revision D, p. 2-7.

Fronius: To get the most out of your FRONUS IG unit, observe the following
rules... Only install it on a solid vertical wall at a minimum of 3 ft. (0.9
m) above
the ground and to a maximum of 6.5 ft. (2 m). Operating instructions
Grid-connected inverters for photovoltaic systems 02/2008.

I, too, can't find the 2'-6" lower limit specified anywhere in the NEC 2008.

Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com  
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885