Automatic Charging Relays (ACRs) are connected to engine and house battery banks through large conductors. In the unlikely event that there is a fault in the ACR internal circuitry that allows fault current to flow from the high powered positive leads to the negative reference wire, the negative reference wire may have to carry more current than it is capable of and can overheat. The wire is typically rated for 20A; the normal current in this wire is less than 1 ampere.
A 10-15A fuse in the negative wire can prevent excessive current from flowing in the wire leading to overheating or possible fire. In-line AGC or Blade fuses are suitable. Place the fuse in a location not subject to flammable gas and use a sealed fuseholder.
All ACRs are vulnerable to ground faults flowing through the negative connection. This includes ACRs from other manufacturers. Refer to the wiring diagram for the location of the negative wire and install an in-line fuse in it.
Follow these specific instructions for each Blue Sea Systems' ACR:
7610/7650
Connect the quick connect terminal marked GND (ground) through a 10-15A in-line fuse to the main negative bus or negative terminal of the nearest battery.