Zippy, further to my last post: Do not connect negative leads together at the equipment
and run one wire back to a negative bus. This is a dangerous situation and can lead to fire. Your negative wires are not fused and by connecting them together at the equipment you run the risk of overloading and so overheating
You must make sure that when adding equipment that all of the wire is protected by the breaker/fuse.
Another good reason (perhaps the best of reasons) to run duplex wire back to your panel.
PS: I know of at least one fire that was caused when a yard installed a larger alternator
to an engine. The old alternator
had an internal negative path (through the case) but the new alternator had a separate, isolated negative. The yard didn't install a new negative cable and so the only negative path back to the batteries was through the regulator
. When the batteries reached a discharge level where the alternator started putting out more than the negative lead could handle there was a fire which resulted in the total loss of the alternator. Luckily the boat and people were okay, however the alternator had been installed in a rush to start an offshore
trip and so resulted in a very uncomfortable trip to the Azores
and to having no engine on arrival. Besides, fire extinguishers can cause a lot of corrosive damage.
PPS: did I mention that they had counted on a watermaker
which of course they couldn't use?