Difference between DC grounding and DC - bus

clayhubler

What is the difference between the two bus bars on the back of this panel and what would be the most common reasons for these to be separate? It is a paneltronics circuit breaker panel.

Thanks

T.R. Bauer · Posted: Wed Jun 30, 2021 9:08 am Post subject:

Great question. I can't wait to hear the answer myself.

ssobol · Posted: Wed Jun 30, 2021 10:33 am Post subject:

Normally you would see that in a setup that a +DC and a -DC supplies (e.g. +15v, -15v). So you have the two voltages and a DC ground (which is used for shielding and if you only needed one or the other of the voltages on a load.

On a 12vdc boat, I don't know what it would be used for. I'll bet that both the DC ground and the -DC voltage gets tied back to the negative battery terminal somewhere.

thataway · Posted: Wed Jun 30, 2021 11:17 am Post subject:

A slight expansion on what ssobol commented. The "Green wire" in a boat is often DC ground (somewhat different than AC ground). It is for shielding of various electronics cabinets, and in some boats it also ties the thru hull fittings together.

For true RF shielding such as for an auto pilot when running high power SSB rigs, we use copper foil (about 1 mm thick and 2 to 3" wide. This gives far better RF shielding than just a wire.

As ssobol notes these all also go to the negative of the battery.

The only C-Dory I used this type of ground on was my Tom Cat 255, where I had a 100 watt SSB radio.

clayhubler · Posted: Wed Jun 30, 2021 11:19 am Post subject:

Thanks everybody. Should I just tie these together then for a larger negative bus?

thataway · Posted: Wed Jun 30, 2021 6:04 pm Post subject:

No reason to tie together unless you need more terminal posts.