A question concerning DC ground

[grahamdouglass]

The question I have is specific to grounding a Blue Seas Panel PN 8380 but first the preamble.

I am replacing an old Perko DC panel, circa 1980, that has positive in Red and Negative in Black. The leads off of the positive side of the panel to the circuits are a rainbow of colours depending on the circuit. Its a bit of a rats nest of spaghetti wiring on the verge of bursting into flame.

On a boat there are a lot of grounds, there is AC ground usually green but sometimes brown.

There is DC ground usually green but sometimes brown and sometimes black and recently yellow? Are DC ground and negative return circuit different or can they end up going to the same place.

Then there is bonding, usually green but sometimes just a bare copper wire.

In the wiring of my new panel there is a DC Ground and also a DC negative return. My old panel just had a ground that served as a negative return.

I can figure out that the DC negative return goes to the DC negative bus in my engine room which connects to my house bank negative terminal.

The DC negative ground is supposed to connect to the engine which connects to the water via the propeller shaft or to a grounding place on the keel. I think my boat probably never had a DC ground but just a floating ground that connected to my negative . The engine is connected via the starter and alternator so there is ground going to my engine.

Am I over thinking this and all I have to do it run a grounding wire to my DC negative bus from my new DC panel ground connection?

Share your thoughts on this.

 

[Comodave]

Your boat most likely doesn’t have a DC grounding bar. Most likely just a DC return bar. The panel has both but the DC grounding is optional. If your devices don’t have the DC grounding wire then there isn’t anything to connect to the DC grounding bar.

This is from the 8380 instructions;

Optional - install grounding system wire
The grounding wire (bare, green or green with yellow stripe and normally non-current carrying) should not be confused with the negative ground wire (black or yellow and normally current carrying).
In Boatowner’s Illustrated Handbook of Wiring, Charlie Wing identifies three purposes of DC Grounding:
1. Holding conductive housings of low voltage (under 50 volts) DC devices at ground potential by providing a low resistance return path for currents accidentally contacting the device cases.
2. Providing a low resistance return path for electrical current, preventing stray currents that may cause corrosion.
3. Grounding metal electrical cases to prevent emission from inside or absorption from outside of radio frequency noise (RFI).
ABYC requires that grounding wires be sized no smaller than one wire size under that required for current carrying conductors supplying the device to which the grounding wire is connected.

 

[grahamdouglass]

I kind of figured I had no ground since all I have had to deal with over the years is the DC negative return. So this makes the job a little easier. Thanks for the confirmation and input.