Page 5
Loads that require “surge power” to start
Resistive types of loads (like incandescent lamps, toaster, coffee maker, electric range,
iron etc) do not require extra power to start. Their starting power is the same as their
running power.
Some loads like induction motors and high inertia motor driven devices will initially
require a very large starting or
“surge”
power to start from rest. Once they have
started moving and have attained their rated speed, their power requirement reduces
to their normal running power. The
surge
may last up to 5 seconds.
TVs and microwave ovens also require surge power for starting. The manufacturers’
specification of the appliances and devices indicates only the running power required.
The surge power required has to be guessed at best. See below under
“Sizing of
inverter for loads that require starting surge”
.
If an inverter cannot efficiently feed the surge power, it may simply shut down instead
of starting the device. If the inverter’s surge capacity is marginal, its output voltage
will dip during the surge. This can cause a dimming of the lights in the house, and will
sometimes crash a computer.
Any weakness in the battery and cabling to the inverter will further limit its ability to
start a motor. A battery bank that is undersized, in poor condition, or has corroded
connections, can be a weak link in the power chain. The inverter cables and the
battery interconnect cables must be sized properly. The spike of DC current through
these cables is many hundreds of amps at the instant of motor starting. Please follow
the instructions under
"Installation - DC side connections" on pages 20 & 21.
Sizing of inverter for loads that require starting surge
Observe the following guideline to determine the continuous wattage of the inverter
for powering loads that require starting surge. (Multiply the running watts of the
device/appliance by the Surge Factor)
*NOTE:
The surge power rating specified for this inverter is valid for duration
of less than 1 second. This very short duration may not be sufficient to
start motor based loads which may require up to 5 seconds to complete
starting process. Hence, for purposes of sizing the inverter, use only the
continuous power rating of this inverter.
Type of Device or Appliance
Surge Factor for Determining the Continuous x Wattage of the Inverter
(No. of times the running power rating of the device/appliance)
Refrigerator / Freezer
5
Air Compressors
4
Dishwasher
3
Automatic Washer
3
Sump pump
3
Furnace fans
3
Industrial motors
3
Portable kerosene / diesel fuel heater
2
Circular saw
3
Bench Grinder
3
