PS Magazine - TB 43-PS-613

PS, The Preventative Maintenance Monthly

ISSUE 613

DECEMBER 2003
PS Magazine - TB 43-PS-613 - Page 23 of 33
PS 613
DEC 03
43
M934-Series Expansible Van…
Conductor
The conductor should be at least 6 AWG copper or copper-clad aluminum. Flat
straps meeting these requirements work best because they have low impedance.
The conductor should not be spliced and should go continuously from the rod to
the generator trailer as straight and short as possible. It also must run downhill from
the trailer to the rod. Don’t loop it up and over any other equipment.
Connections
The ground connection for the
trailer is a ground stud above the
curbside front step. The surface
immediately around the stud must
be free from corrosion, paint,
grease and dirt. The stud should
be clean and corrosion free.
The connection at the ground
rod should be tight and the con-
ductor pressed against the ground
rod by the arms of the clamp and
not the tightening bolt.
Don’t twist or tie the conductor
to the rod. The connection is poor
and it could work free entirely.
From the same connection point, run a conductor strap to the ground stud locat-
ed on the circuit breaker side of the switch box.
Your generator and its trailer are now grounded.
The Van: Outside
The surface wire ground system (SWGS) kit, MK-2551A/U, NSN 5820-01-263-
1760, is a good system to use for the M934 expansible van.
The Generator and Trailer: Ground Rod
Effective grounding of the 60-KW generator starts with the ground rod.
There are two ground rods
available. NSN 5975-00-224-
5260 brings a single-section 6-ft
brings a 9-ft rod in three 3-foot
sections.
For the 9-ft, 1-in thick ground
rod, you’ll need clamp, NSN
5975-01-034-8882, to hold the
grounding strap to the rod.
The 6-ft rod comes with a thumb screw for holding the strap. If you need to
replace it, you can use a nut, bolt and washer, or order clamp, NSN 5999-00-496-
5834. Since this rod is thicker than the 9-ft rod, you cannot use the same clamp.
To install the 6-ft rod, use sledgehammer,
NSN 5120-00-243-2957. To install the 9-ft,
sectional rod, use slide hammer, NSN 5120-
01-013-1676.
The ground rod needs to be driven down to
the water table so it pierces the moisture line.
The top of the ground rod should be at least
an inch below the ground surface. Too many
are left sticking up from ground level and
become a walking hazard as well as decreas-
ing the effectiveness of the ground.
The immediate area around the top of the ground rod should be dug out and the
soil prepared with chemicals and water, as necessary.
T
he M934 expansible van, the equipment inside it, the 60-KW generator it is pulling
and the trailer that generator is riding on are all one system.
A system requires a system ground. It’s not enough to ground just one or two
pieces of the system. They all need to be grounded.
Without a good system ground, there is potential damage to your equipment, your
health and the health of those around you.
Here’s some advice on how to ground:
M
O
R
E
The
SWGS
comes
with…
Couplings
Drive/head stud
For 9-ft rod
Clamp
a carrying case
3-pound
sledge
hammer
and
75 feet of steel
grounding cable
(not shown)
2 10-ft long steel
connector cables with
crimped 75-amp
copper clips
15 10-in long steel grounding pegs
613. 42-43 (C)
10/28/03
11:40 AM
Page 1
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