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Trace Engineering DR Series Owner's Manual - Version 3.2 - 9/7/98 - Page 5
Search Mode Watts
The SEARCH MODE WATTS control is used for adjusting the sensitivity of the search mode circuit.
The DR Series inverters feature a circuit that minimizes power drain by reducing the inverter's output
to small test pulses when there is no load connected to the inverter. These pulses are used to detect
the presence of a load. When a load is detected the inverter's output goes to full voltage. The
sensitivity of the detection threshold is adjustable. Turning the SEARCH MODE WATTS control
clockwise decreases the sensitivity. Turning the control full counterclockwise increases sensitivity and
at the full counterclockwise position, defeats the search mode feature.
Example: With the SEARCH MODE WATTS control set to detect a 40 watt load, a 50 watt load will
bring the unit to full output voltage. However, a 30 watt load will leave the inverter in its energy saving
search mode state. If the sensitivity is increased by setting the control to 10, a 20 watt load will bring
the inverter out of the search mode, while a 5 watt load will not.
When in the search mode, the green power LED will blink and the inverter will make a ticking sound.
At full output voltage, the green power LED will remain lit and the inverter will make a steady buzzing
sound. When the inverter is used as an uninterruptable power supply, the search mode function
should be defeated by turning the control completely to the left (counter clockwise).
A neon type nightlite can also be used as a good indicator to determine if the inverter is in search
mode. Simply plug the light into any AC outlet that is connected to the inverter's output. When the
inverter is in the search mode the light will blink. If the inverter is running a load, the light will be on
continuously.
Exceptions: (Murphy's Law) Unfortunately, things don't always work the way the manual says they
will.
Example A: If the SEARCH MODE WATTS control is set to detect a 40 watt load and a 30 watt
incandescent light is turned on, the inverter will detect the light. The light is a bigger load than 40 watts
when its filaments are cold. When the light gets hot it becomes a 30 watt load. Since this is below the
control setting of 40, the inverter will not detect it and the light will go out. This will cause the light to
cycle repeatedly.
Example B: If the SEARCH MODE WATTS control is set to detect a 30 watt load and a 40 watt
fluorescent light is turned on, the inverter will not detect the light. The light presents a smaller load than
30 watts until the gas in the fluorescent tube ionizes.
Example C: There are some appliances that draw power even though they are turned off. TVs with
instant on circuits, microwave ovens with digital displays and VCRs are examples. These loads
present a dilemma. If the sensitivity is set higher than the combination of these loads, then an auxiliary
load must be used to bring the inverter out of the search mode before the appliances can be turned
on. If the sensitivity is set lower than this combination of loads, the loads will be left on and will put an
additional drain on the batteries. (Three such 15 watt loads would amount to an additional 90
amp/hours per 24 hours in a 12 VDC system.)
One solution is to turn these items off at the wall. Use an extension cord with a rocker switch, a switch
at the outlet, or the appropriate circuit breaker. Another solution might be to place all these phantom
loads on a separate circuit with its own disconnect.
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