ERC-12-35 Emergency Relay

The Emergency Relay/Charger is a device for assuring immediate backup power to communications equipment in the event AC power is temporarily lost to the power supply or the supply fails. In addition, it will allow the power supply to act as a “trickle” battery charger without any additional modification.

When the ERC senses a loss of DC voltage, it employs a fast-acting S.P.D.T. relay to automatically switch the equipment’s DC input over to a standby battery to allow continued operation. When the power supply is returned to service, the ERC disengages the battery and puts the supply back online to provide DC voltage. While the power supply is operating normally, a small portion of the output current is directed to the battery to trickle-charge and maintain it at full voltage. (Note: Battery float voltage will be maintained at .7 volts lower than the power supply voltage.)

Note: If the power supply is down for an extended period, the backup battery may become significantly discharged while powering the radio. When the supply returns to service, the trickle charge rate of the ERC may be insufficient to restore the battery to full charge promptly. In the event this occurs, a supplemental charger may be necessary to bring the battery to full charge.

Installation

Select a suitable location as close to the battery as possible where there is no likelihood of accidental contact and shorting of the terminals. The ERC may be mounted vertically, horizontally, or even upside-down, if necessary, without affecting its operation. Two # 10 sheet metal or wood screws will be needed. Mounting on a metal surface is acceptable as the inputs and outputs are isolated from the mounting bracket.

Note: If the battery is stored in an unventilated enclosure, users are not recommended to mount the ERC within the same enclosure. As with any relay, it should not be in an area where there may be battery gases or any other potentially explosive gases present.

Wiring

The wiring should be as direct as possible. Ensure that the battery posts are free from corrosion. Determine the correct gauge wire using the information below. The wire length is the total length of the run (ERC-to-Radio + Power Supply-to-ERC) or (ERC-to-Radio + Battery-to-ERC), whichever is longer.

• 5 ft. wire length = #8 AWG
• 10 ft. wire length = #6 AWG
• 15 ft. wire length = #4 AWG
• 20 ft. wire length = #4 AWG

Use the provided crimp ring lug connectors to secure wiring to the ERC. Models ERC-12-15 and ERC-24-15 have yellow plastic terminal covers, which must be reinstalled after wiring to prevent accidental shorting.

Specifications:

• Input Range: 10.0-14.5 VDC (12V)
• Relay Rating: 30 amps continuous & 35 amps intermittent
• Float Trickle (typical): 0.1 amps
• Dimensions (inch): 5-1/8" x 2-7/8" x 3-5/8"
• Weight: 1.15 lbs

Owner's Manual (pdf)