Model 2180A
7
• Large gauge wire (up to No. 14) should be used to prevent excessive voltage
drop, and the run should be as short as possible.
• Wiring runs should be as short as possible.
• Connect the positive supply to 24VDC (+) and the negative return 24VDC (-) on
the terminal block. An internal diode protects the system in the event of
inadvertent supply polarity reversal.
2.3 Battery Backup
An emergency battery backup can be used on a system normally operated by AC. The
battery rating (ampere-hour capacity) is dictated by the length of time power outages may
last. A Model 2180A Controller requires approximately 2 ampere (peak) at 24 VDC.
General Monitors recommends that a lead-acid type battery be used. This type of battery
can be expected to last for several years with minimum maintenance.
The customer furnished battery may be connected as shown. No manual or relay
switching is required. Note that in order to keep the 24V lead acid battery (whose voltage
is approximately 27VDC when fully charged) continuously charged through the series
diode, a regulated 28VDC power supply should be used. The cable lengths should be
kept as short as possible. Should AC power to the regulated DC power supply fail,
energy to run the system will be obtained from the fully charged lead acid battery. A 24
ampere-hour capacity battery should power one Model 2180A controller for at least 12
hours. DO NOT USE MORE THAN A 24-VOLT BATTERY.
Figure 2: Battery Backup Diagram
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