TM 9-6115-647-14&P
Section II. DESCRIPTION AND DATA
1-9. Description. Power Unit PU-789/M (figures 1-1 and 1-2) is made up of one Tactical Precise Generator
Set, DOD model MEP-114A, mounted on a modified M353 trailer. The generator set is a liquid-cooled diesel
engine-driven unit with a load capacity of 30 KW at 400 HZ. The trailer is a two-wheeled, two-tire unit with a 3-
½ -ton carrying capacity. The modifications to the basic trailer provide stowage for the accessories and all
equipment necessary for mobile operation, work platforms and access steps for the operator and maintenance
personnel, and a 93-gallon fuel tank. A low fuel sensor is activated and supplies a low fuel signal to the Patriot
Information Coordination Central (ICC) and the Communications Relay Group (CRG) when the fuel level drops
below 13.5 gallons (51.1 liters). The PU-789/M provides a generator on-line signal to the ICC/CRG and
provides for power disconnect from the ICC/CRG. Since the PU-789/M is exclusively used for supplying power
to the ICC and its Antenna Mast Group (AMG) or to the CRG and its Antenna Mast Group, the power unit is
equipped with a Patriot application kit. This kit consists of a power distribution unit (PDU) mounted on the
trailer, an adapter plate assembly mounted on the generator set to provide an interconnection point for
generator set and PDU cabling, and the related cables and wiring harnesses. In the field, two PU-789/M power
units are used interconnected as shown in figure 1-3, where one power unit is designated the primary power
source and the second unit serves as a standby unit in the field configuration, the PDU provides an
interconnection point for the primary and standby power units and the ICC or CRG, allowing either unit to
supply 120/208 VAC 400 HZ power to the equipment.
1-10. Tabulated Data. The tabulated data provides operator and unit level personnel with the dimensions and
weights for Power Unit PU-789/M. These specifications are computed from the combined dimensions and
weights of the generator set and trailer as modified for use with the power unit. Specifications of the individual
components can be found in their respective technical publications. For additional information concerning
Generator Set DOD Model MEP-114A, refer to TM 5-6115-465-12, -24P and -34. For additional information on
the M353 trailer, refer to TM 9-2330-247-14&P. The tabulated data also includes the location and content of all
data plates unique to the power unit.
a.
Identification and Instruction Plates.
(1)
Identification plate.
(a)
Location. This plate is located on the front curbside trailer frame.
(b)
Content.
US ARMY
ELECTRIC POWER UNIT
PU-789/M
LG 188 19 IN./W 96 00 IN./HGT 84.50 IN.
NSN 6115-01-208-9827
PART NO. 97403-13227E5850
MFD BY:
CONTRACT NO.
DATE MFD:
SERIAL NO.
DRY WT 6800 LBS
REGISTRATION NO. VB01FY
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