Polarity For Negative And Positive Ground Sites configuration

Wireless communications sites and network devices typically operate on 12, 24 or 48 volts DC. For 12 and 24 volt sites, the polarity of these devices is typically either +12 volts DC or +24 volts DC. This is also often referred to as negative ground, i.e. the negative line is used as the ground – also referred to as return or common – and the positive line is the “hot” line which carries the +12 or +24 volt potential.

For 48-volt sites, these typically operate with a positive-ground configuration, or occasionally with a negative-ground configuration. Positive-ground systems supply –48 volts (the positive line is grounded and is used as the return or common); negative-ground systems supply +48 volts (the negative line is grounded and used as the return or common).

When incorporating batteries into sites, it is very important to be aware of which configuration the site is using. For positive-ground systems (–48 volts DC), the positive (+) line of the battery is referenced to ground and the negative (–) line of the battery is the “hot” conductor. The opposite is true for negative-ground systems: the negative (–) line of the battery is referenced to ground and the positive (+) line of the battery is the “hot” conductor.

It is very important to understand the configuration of the site, as failure to note the polarity can result in short circuit conditions which can represent a safety hazard or other negative conditions such as ground loops.