[RE-wrenches] Code reference needed

[Exeltech]

Hello all,

I may be able to shed some light on this.  

The perceived minimum height requirement isn't mandated
in the context being discussed, but instead but likely
has its roots in UL1741 Section 61.3.2, which outlines
the requirements for the "Sprinkler test".  Text excerpted
below:


61.3 Sprinkler test

61.3.1 A unit required to be subjected to a sprinkler test
is to be tested as described in 61.3.2 and 61.3.3.

61.3.2 An outdoor ground-mounted unit is to be turned about
its vertical axis to each of four positions 90 degrees from
each other, each for 30 minutes during the 2-hour portion of
of the test described in 61.1.3, with adjustable parts arranged
for maximum vulnerability to the water spray. Wall-mounted units
intended for mounting within 914 mm (3 feet) of the ground, are
to be similarly tested in the most vulnerable normal mounting
position.

61.3.3 The unit is to be positioned as shown in Figure 61.3 in
front of a standard water spray head of the type shown in Figure
61.2, to which the water pressure is maintained at a gage pressure
of 138 kPa (20 psi).



The key aspect of Section 61.3 is found in 61.3.2:
"Wall-mounted units intended for mounting within 914 mm (3 feet)
of the ground are to be similarly tested in the most vulnerable
normal mounting position."

... "intended for mounting within 914 mm (3 feet) of the ground..."


If a manufacturer states in their installation instructions
a unit is to be mounted *more* than 3 feet above the ground,
this relaxes the sprinkler test requirements as noted above.

This in turn decreases testing time, reduces testing costs,
and reduces the possibility of a test unit failing (in this
case by getting water inside).  All it takes are a few words
in the installation manual requiring the unit be mounted more
than 3 feet above the ground.



Dan
Sr. Engineer
Exeltech

--- On Sun, 12/5/10, Dave Click <daveclick at fsec.ucf.edu> wrote:

> From: Dave Click <daveclick at fsec.ucf.edu>
> Subject: Re: [RE-wrenches] Code reference needed
> To: re-wrenches at lists.re-wrenches.org
> Date: Sunday, December 5, 2010, 7:49 PM
> At a Xantrex training once upon a time, they explained
> that the three foot minimum height was to keep the unit
> out of reach of a typical lawn sprinkler. I don't know
> of an NEC reference for any minimum height required.
> 
> > Peter Parrish wrote:
> > 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 2.0m (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 300mm (12 inches) minimum. 910mm (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. (0.9m) 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