Measuring ground integrity

[HeadedToTexas]

Virtually all of my electrical experience prior to boat life had been 120 and 480 VAC, or very low current DC control voltage. That has left me somewhat unsure of using what seems like a vague ground to complete DC circuits on things like 12 VDC water pumps. While I appreciate that a given circuit can be completed with a convoluted path back to the negative terminal of the DC electrical system, how does one judge the need to provide a new and direct wire from the load to the ground buss?

 

[DavidM]

Well, one way to test the integrity of ground connections on DC devices is to measure the voltage at the devices negative terminal WHILE IT IS RUNNING relative to a solid ground like a battery buss bar. It should be near zero. Any significant voltage is reason to be concerned and can be traced back by doing the same measurement at each connection going back to the ground buss.

That is a precise way. A quick indication is to feel for heat at those connections.

David

 

[Comodave]

I usually end up adding ground bus bars in several different locations around the boat with heavy cables back to the main ground bar. That way I don’t have to run the ground wire all the way back. I use Blue Sea tinned bus bars. Also usually end up replacing the original ground bars since they are not usually tinned. Corrosion adds up at each connection and will cause some voltage drop.