Where to Ground?

rollo_cd26 · Post by **rollo_cd26** » Jun 6th, '11, 08:31

Despite the other setbacks that keep my boat from the water, I am boldly installing a fan in my CD-26D. I have run the lead wire to the 10 amp breaker and mounted the fan above the cabinet opposite the head. Now, where to find a suitable ground? Directly behind and above the cabinet is a set of ground wires from the port shroud base that would appear to do the job, but I am hesitant to break through the cover on the wire there and attach a copper lug grounding lug (it just doesn't seem right). The schematics for the CD-26D have a ground bar near the power panel. Should I go there, or the grounding strap connections in the bilge? Either of those are hard to get to.

bottomscraper · Post by **bottomscraper** » Jun 6th, '11, 09:14

rollo_cd26 wrote: The schematics for the CD-26D have a ground bar near the power panel. Should I go there,

Yes there.

Oswego John · Post by **Oswego John** » Jun 6th, '11, 11:26

Despite the other setbacks that keep my boat from the water, I am boldly installing a fan in my CD-26D. I have run the lead wire to the 10 amp breaker and mounted the fan above the cabinet opposite the head. Now, where to find a suitable ground?

When adding something new to your boat's electrical system, many owners, myself included, wire it by running a two wire cable from the electric panel to the new installation. The reason is twofold and without getting too deep into the subject, three or more fold.

It is good, but not absolutely necessary,to have the wiring color coded polaritywise. By having all of the circuit wiring originate and return to the electric panel, it makes it so much easier to troubleshoot the circuits. As Rich mentions, use the negative buss at the electric panel.

By the use of two, or more, conductors in a single cable, it eliminates the so-called rat's nest or bowl of spaghetti look so often found in some boats.

When installing something like a fan, you want it to run as efficiently as possible in the manner with which it was designed for. Too often, things are wired by using conductors that are too small. This is especially compounded by the fact that the source of power is low voltage 12 volts. And DC power doesn't help the cause.

Voltage drop is the culprit which causes much inefficiency. Look on the fan to determine its wattage.. Divide the wattage by 12 (volts) to know of the running amps. Measure the total distance of the path that the wiring will take. Double that distance (power to the fan and power return to the breaker). Look at the wiring chart in order to determine the minimum size copper conductors to be used in the installation.

Early on in the post I mentioned not to get too deep in the subject. If you decide not to use multi-wire cable but to use two single, separate conductors, it is best to lay the conductors of sufficient length on a flat surface and twist them spirally together.

There are uncountable, unseen thingies floating around (science fiction ??) close to the conductors when in service. When dealing with DC voltage especially, there is a phonema developed called magnetic lines of force, or flux. These forces are cumulative. When the supply wire (pos) is encased in close proximity with the return wire (neg), the lines of force ore nullified. The same thing happens when the supply and the return are twisted together. A sizable buildup of a magnetic field is, suffice to say, not desirable where near electronic devices.

Okay, I'm climbing down off the soap box.

Pet a dog, be nice to your mother-in-law.

O J

rollo_cd26 · Post by **rollo_cd26** » Jun 6th, '11, 12:04

OJ, thanks for that lesson on DC wiring. Just as I suspected, a cable tie attachment to a nearby ground is not the right thing to do. Amazing! BTW, what does the "ground bar" look like? There is a rat's nest left by the previous owner to dig through.

I soldier on through the other difficulties that spring forth from my beautiful boat in the dry. It is now high summer and the heat has dealt a blow to my ambitions to launch before fall.

Oswego John · Post by **Oswego John** » Jun 6th, '11, 13:28

Rollo,

I could get a lot of negative feed back (opportunity for a PUN?)

from some of the readers for this but....

....a ground bar is similar looking to a negative return buss bar but altogether different in purpose.

It is usually a length of copper bar, arbitrarily 4 or 5 inches in length up to maybe a foot long and 1/8" or 3/16" thick and maybe 3/4" wide. They can come in various sizes and dimensions according to use.

Many of them are drilled and tapped with 10-24 screw holes. In the holes are screwed short, maybe 3/8" long bronze RHMS, (round head machine screws) usually with a cup washer under the screw to contain stranded wire whiskers. It is better to use crimped terminals here.

Don't get overwhelmed. Remember, you are now a boatowner.

O J

gpb102030 · Post by **gpb102030** » Jun 6th, '11, 17:08

My 1987 cd26d did not have a negative bus bar. It only had a piece of # 8 wire striped with all the negative wires wrapped around it and wrapped in electrical tape. it was located behind the fuse panel / over the fuel tank you could acess it from over the fuel tank. it was pushed up in the head liner. I installed a new bus bar and connected all my grounds to it. nice and neat. behind the fuse panel. Greg.

bottomscraper · Post by **bottomscraper** » Jun 6th, '11, 19:46

My 1987 cd26d did not have a negative bus bar. It only had a piece of # 8 wire striped with all the negative wires wrapped around it and wrapped in electrical tape.

I wonder if that was original or some PO's "improvement". It seems very odd to me that CD would have done that. (Not saying that all CD electrical work was great but...)

Steve Laume · Post by **Steve Laume** » Jun 6th, '11, 22:12

All my grounds were run to one of the nuts on the voltage meter in the panel. Mine looked much more like an octopus than a typical rat's nest. There were a lot of wires on there. I believe there were also a few soldered together so don't put anything beyond Cape Dorys possibility in the wiring realm.

I also installed a ground buss and ran everything to it. Lots and lots or various sized wire ties did a great deal to neaten things up as well.

It is a very good thing to get familiar with the back of your electrical panel, Steve.

Maine Sail · Post by **Maine Sail** » Jun 7th, '11, 07:23

Rule #1 for DC negatives is to keep them separated from DC Bonding wires or DC lightning grounds. You should not use DC bonding or lightning grounds as DC negative returns. This = BAD...

This is perhaps the most common grounding issue I see on boats. The bonding or lightning system should never carry any DC current. DC negatives should be tied to a buss then back to the battery, then one wire the same size as your battery cables runs to your ships earth ground. The Earth ground on most boats is the engine.

If you have an engine that is non-isolated ground that wire will carry the current of the starter and alternator back to the battery as well as any other engine circuits that are grounded to the engine.

Bonding is for Earth potential and should be 0.0V...

rollo_cd26 · Post by **rollo_cd26** » Jun 7th, '11, 08:03

This is getting really interesting. There is no such "negative buss bar" behind my electrical panel, but there is an aluminium horseshoe device bracketing the back of the volt meter with a large green ground wire attached to it and no other wiring sharing the connection. I will search the other locations for this mystical "ground bar".

I am surprised by the lack of detail in the CD manual on this issue (and others). Mixing the electrical load grounds with the lightning arrest system sure did seem wrong to me when I was searching around. It also seems strange that there are no go routing channels or holes to get to the power panel. I guess they decided no one would want to add or reroute wiring.

tpq · Post by **tpq** » Jun 7th, '11, 09:19

Look at the diagrams and notice there is a "GND BAR" noted near the DC Panel. I don't own a Cape Dory but this should be your negative distribution bus because the diagram shows it eventually connects to the house battery negative terminal. That negative distribution bus is where you want to connect your negative wire for your new load. The positive should be connected to a properly protected feed from the DC Panel.
If the panel has no open breakers there are other options.

Steve Laume · Post by **Steve Laume** » Jun 7th, '11, 09:58

rollo_cd26 wrote:This is getting really interesting. There is no such "negative buss bar" behind my electrical panel, but there is an aluminium horseshoe device bracketing the back of the volt meter with a large green ground wire attached to it and no other wiring sharing the connection. I will search the other locations for this mystical "ground bar".

You might want to follow that green wire. All my circuits were connected to where your green wire is going, so someone might have took off the spaghetti and run it all somewhere else with the large green wire.

If you are lucky they installed a nice ground buss. If you are not lucky you might find a household wire nut, twisted and taped wires or a soldered mess.

If any of the latter scenarios are present you will have a story to tell and a good place to install that ground buss. I had a couple of circuits wired with cheap speaker wire on Raven. Fortunately the guy who did that didn't appear to do any other wiring modifications, Steve.

M. R. Bober · Post by **M. R. Bober** » Jun 7th, '11, 13:41

The electrical system is an embarrassment. Removing the panel can take your breath away. I have cleaned up a few circuits, but never did the right thing (i.e. rewiring the entire boat). Maybe this time.

Mitchell Bober
Sunny Lancaster, (Where the little minus signs hit the ground) VA

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