TP-5594 5/95 Installation 6-3
Motor Loads
When figuring generator set capacity requirements for
installation involving motor loads, do not overlook the
highcurrentdemandedbythemotorduringstartup. The
in-rush or starting current may be 2-5 times higher than
that required when the motor reaches normal operating
speed. Allowreserve capacityforin-rush demandsplus
other loads which could be on the line as the motor
starts.
Air conditioning units are perhaps the most common
type of motor load for generator sets in recreational
vehicles. The starting characteristics of the different
makes of air conditioners vary greatly—one particular
13,500 Btu unit has, for example, lower starting
requirements than an 11,000 Btu unit of another make.
When only one unit is involved, there is usually no
starting problem, provided of course, the lighting and
appliance load is not too high when the unit is started.
The trend seems to be toward larger capacity air
conditioners and the use of more than one unit in larger
vehicles. Simultaneousstartingoftwounitscanpresent
problems if the capacity is marginal. Because of the
variationin starting characteristics of the variousmakes
of air conditioners, no definite statements are made in
this publication regarding multiple motor-starting
capabilities of the mobile generator sets covered.
Consider delayed starting or use of easy-starting
devices on air conditionerunits wheneversimultaneous
startingof morethanone motoris involved. Thestarting
andrunningrequirementsofsomemotorloadscommon
to mobile applications are listed in Figure 6-1. Use this
as a guide when selecting generator set capacity
requirements involving motor loads. See Figure 6-2 for
generator set capabilities regarding air conditioners.
Capabilities will vary according to kilowatt derating
(following). For specific information regarding
simultaneous starting of twoor more motors, contact an
authorized Kohler dealer/distributor.
1/4 HP
Motor
1/3 HP
Motor
1/2 HP
Motor
3/4 HP
Motor
1 HP
Motor
2 HP
Motor
3 HP
Motor
Starting (In-Rush) Watts
Running Watts
750 1000 1500 2000 3300 4000 5000
350 400 600 750 1100 2000 3000
Figure 6-1. Single-Phase Motor Requirements
Kohler Model
Wattage
Capacity
Will Operate
Air Conditioner(s)
of Sizes Indicated
Power To Spare
for Lighting, Appliance, Tools, etc.
7 kW 7,000 Two 13,500 Btu 2800 Watts
10 kW 10,000 Two 13,500 Btu N/A
Figure 6-2. Air Conditioner Ratings (60 Hz)
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