Electrical panel

[Skywalker]

Hi guys, need some help.

Electrical issues are my weakness.

I purchased a new 8 breaker panel from Blue Sea.

The panel has two grounding buses, one "to DC grounding system" and the other "DC negative bus"

I checked conductivity, and the two buses are not linked.

My understanding is this. The grounding system is a boat wide system related to lightening strikes. The negative bus is used for the 12V system.

Right?

I do not have a grounding system, so I think I can ignore this.

Right?

Any thoughts?

Thanks

Chris
Skywalker

[ndutton]

The DC grounding system is for metal cased appliances and Radio Frequency shielding. This ground carries no current normally. In addition to RF shielding, you provide this ground to any DC component metal cases or parts that may become inadvertently energized. The ground provides a sufficient current path to force the circuit breaker to trip when a fault occurs.

[Skywalker]

Remember, you are speaking to the electrically impaired...

So, my stereo/mpg player has a metal case. I ground this to the DC bus.

The DC bus is grounded...where? I don't have a DC grounding system. The local thru hulls are Marelon. Do I ground it to the block?

Chris

[ndutton]

I would take this approach:

Go without case grounding for now. The risk of your stereo housing becoming inadvertently energized is close to zero. If you experience electrical interference noise, add the ground to both the stereo and whatever is causing the noise if you can chase it down. I'd say grounding to the engine block is the best you can hope for in your circumstance.

This way you're not doing a bunch of unnecessary work.

[joe_db]

The AC system on a boat is 3 wire - Hot, Neutral, and Ground.
The DC system is 2 wire - Positive and Negative. The Negative side will be connected to the ship's grounding system at ONE point. Blue Sea uses the same basic panels for AC and DC, so the DC version has this confusing "DC Ground" bus that really is intended for an AC three wire system. What I do with them is jumper them together and use them all for DC negative. The only way I could see ever having DC ground as separate is if you have an aluminum boat with a floating DC system including a third isolated ground wire. I have worked on a ton of boats back in the day and never saw anything like that though. You NEED this book to do boat wiring BTW (http://www.amazon.com/Boatowners-Mec...s=nigel+calder)

When I did my new panel I didn't use the negative bus on the Blue Sea panels for anything but grounding the LED lights to keep the wiring mess to a minimum.

Hi guys, need some help.

Electrical issues are my weakness.

I purchased a new 8 breaker panel from Blue Sea.

The panel has two grounding buses, one "to DC grounding system" and the other "DC negative bus"

I checked conductivity, and the two buses are not linked.

My understanding is this. The grounding system is a boat wide system related to lightening strikes. The negative bus is used for the 12V system.

Right?

I do not have a grounding system, so I think I can ignore this.

Right?

Any thoughts?

Thanks

Chris
Skywalker

[ndutton]

Chris (and Joe),

For your reading pleasure:

http://assets.bluesea.com/files/resources/instructions/9467.pdf

Installation item #7

According to the manufacturer of Chris' panel, the separate ground bus is there for a specific reason, not a vestige from a cloned AC panel. Jumpering between the current carrying negative buss and the optional ground defeats Blue Seas' original design and intention. I suspect they have a better idea of what they're doing than any of us.

[joe_db]

I wired boats for a living for some years and we never ever saw anything resembling a "DC GROUND" system run to the panel - ever. What would you connect to it
Likewise the ABYC classes we went to never mentioned anything like this. You sure as hell wouldn't want to run a bonding system that could end up carrying lightning discharge currents up through the panel

[ndutton]

I wired boats for a living for some years and we never ever saw anything resembling a "DC GROUND" system run to the panel - ever. What would you connect to it
Likewise the ABYC classes we went to never mentioned anything like this. You sure as hell wouldn't want to run a bonding system that could end up carrying lightning discharge currents up through the panel

I'd suggest taking it up with Blue Seas Systems. Until then, Chris has their product and their installation instructions.

[joe_db]

I bought TONS of their stuff for our installs. That is a relic of using the same panels for AC and DC. I have held them in my hands both at once. Can you point to anything on any boat that has separate DC grounding wiring and a 3 wire supply? The only things I have seen that even resemble that are SSB radios and LORAN sets with RF grounds and we took pains to keep DC currents OUT of the RF grounds.

I really think they added this stuff on to make use of the way the panels were being made anyway. Here is what they say:

[B]4. 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 Electrical Handbook, 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.
I have never - ever - never ever - seen a DC device with a SEPARATE case ground like this. This is how AC metal case devices are made. All you would be doing was looping back around to the DC negative anyway. This makes no sense at all.

2. Providing a low resistance return path for electrical current, preventing stray currents that may cause corrosion.
NO! Bad idea! Do NOT run your bonding system - if you have one - up through the panel. That system will carry lightning current if you get hit and RF current if you have a SSB. You do not want the junction for that in your panel. BAD IDEA!
3. Grounding metal electrical cases to prevent emission from inside or absorption from outside of radio frequency noise. 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 (RFI).
As stated in number 2, this is a BONDING system and does not belong in your panel.

If I were still going to the courses and seminars I would most certainly call them on this really bad advice.

I'd suggest taking it up with Blue Seas Systems. Until then, Chris has their product and their installation instructions.

[Ajax]

Chris (and Joe),

For your reading pleasure:

http://assets.bluesea.com/files/resources/instructions/9467.pdf

Installation item #7

According to the manufacturer of Chris' panel, the separate ground bus is there for a specific reason, not a vestige from a cloned AC panel. Jumpering between the current carrying negative buss and the optional ground defeats Blue Seas' original design and intention. I suspect they have a better idea of what they're doing than any of us.

You are correct, however you'll note that #7 states that the DC grounding wire (bare, green, or yellow-green) is "optional".

I definitely wouldn't tie these buses together, but on Toddster's (or any of our short-range pleasure boats), I wouldn't bother with the optional bus.

If I had high-power SSB radios for off-shore, or something that pumped a lot of power that could shock me through the equipment case, I'd use it, but I don't think it's applicable to most of us.

[ndutton]

My position is if the Blue Seas product is good enough to buy then their instructions are good enough to follow. Chris asked for a little help, I felt it was the best advice I could offer.

[ndutton]

You are correct, however you'll note that #7 states that the DC grounding wire (bare, green, or yellow-green) is "optional".

Yes, I noticed and referred to it as optional in my post. I tried to suggest Chris use his circumstances to determine if it was needed (if you have RF noise . . . )

[joe_db]

I did a lot of SSB work on boats and running RF grounds back up to the panel is the polar opposite of what works to minimize RF problems.

Yes, I noticed and referred to it as optional in my post. I tried to suggest Chris use his circumstances to determine if it was needed (if you have RF noise . . . )

[Ajax]

Yes, I noticed and referred to it as optional in my post. I tried to suggest Chris use his circumstances to determine if it was needed (if you have RF noise . . . )

Oops, sorry I missed that.

I enjoyed the discussion, because it's timely for me. I'm looking to upgrade to this very panel because I'm adding systems and my OEM Pearson panel has run out of breakers.

[joe_db]

Blue Sea stuff is excellent and usually can be found on FleaBay or Amazon for a good discount. Please do get the Nigel Calder book I mentioned a few posts back if you don't have it.

Generally, a boat can have a bonding system, AC grounding system, RF grounds, a DC negative bus, or some subset of that. It is important to have the interconnections between these done correctly.