Sea Frost DC 5000 - Manual (Page 46)

46
DC 5000 Low Voltage Protection Relay
The DC 5000 uses a Macromatic relay to monitor the voltage at the compressor motor.
The relay has an adjustable pick up voltage (reset). A red indicator lamp lights when
the relay is on. This lamp turns green when the relay senses low voltage and turns off.
This relay is designed to protect the compressor motor from low voltage damage as well
as protecting the batteries from deep discharge.
How It Works
As an example, if the pick up voltage is set at 12.2 volts and the drop out voltage is set
for 90 percent when the voltage drops 1.2 volts (10 percent of 12.2), the relay will turn
off the compressor. This would be at about 11 volts. The drop out voltage setting is
dependant upon the pickup voltage setting. The compressor will remain off until the
pickup voltage is restored to or above 12.2 volts by recharging the batteries.
About Battery Voltage
Battery voltage will drop as batteries are discharged. Resistance in the wiring and wire
size creates a lower voltage at the consumer than at the batteries. Battery voltage will
rise when the consumers are turned off. As a result of this spring back to at rest voltage
levels the voltage relay must be set for your particular installation.
Setting The Control
The control is mounted on the DC 5000 Electrical junction box. The relay has a two
knobs and an indicator lamp.
Initial stetting: Set the pick up point at about 3 o’clock this should be about 12 volts. Set
the drop out voltage at the 3 o’clock position as a starter. This should be about 90
percent of 12 volts or 10.8 volts. Use the 20-hour discharge rating of your battery bank
and calculate 30% as a safe discharge level in amp/hours. When properly set the
compressor drawing 40 amps per hour should be able to safely use this battery amount
without the protection relay switching off.
Target: Set dropout voltage as high as possible (toward 95 percent) without dropping
out when you know you have plenty of battery amp hours to go. Set pickup voltage at
greater than 12 volts.
Mark and log setting positions.
Vmkp012d71806