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Section 4. Power Center
4.1 Overview
The power center PCB is the true brain of the system. The micro-controller on the PCB is constantly sending signals
through the communication wires to the control panel and polling the system to determine which circuits should be on
and which should be off.
4.1.1 Driver Chips
The driver chips can be thought of as a series of small relays. When one of the driver chips receives a signal, it closes
a contact which passes 24 to 32 VDC to the appropriate relay coil socket, in this case AUX 1. Each relay driver chip
activates a specifi c set of relay coil sockets (see the chart below). If a driver chip fails, it is usually caused by either
shorted relay coil wires, a shorted relay coil, or a relay not designed for the 24 VDC coil voltage (i.e., 24 VAC rather
than 24 VDC). The relay coil provides resistance (approximately 300 Ohms); if there is no resistance, the driver chip
circuit will be damaged.
4.1.2 Reset Button
Pressing the reset button, located in the upper left hand corner of the power center bezel, resets the power center
micro-controller. This also changes the time and date to the default settings for PCBs prior to Rev N. Pressing this
button will not remove any programming, AUX labels, etc.
4.1.3 EEPROM
All programming, labeling, temperature settings, etc., are stored within an EEPROM (Electronically Erasable Pro-
grammable Read Only Memory) chip. This chip is located on the PCB and will retain all settings indefi nitely, even if
power is lost for an extended period. If the Power Center PCB is prior to Rev N, a 9-volt battery will keep the clock
running during power outages.
4.1.4 Battery
If the power is off for more than 34 hours, the battery will drain below 6.3 volts. This is insuffi cent to keep the clock
running, therefore, the date and time will be lost. If the PCB is Rev N or newer, a three (3) volt lithium battery will
keep the clock running during a power outage. If the line power is off for more than three (3) years, this battery may
drain to the point where it will no longer keep the clock running. Even if the battery is dead, the user inputs (Pro-
grams, Labels, Temperature Settings, etc.) will never be lost.
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