Being an electrical dummy for the most part, all I can say is......YIKES!:eek: Glad you got it resolved. My 20 amp breaker on the DC panel got finicky last week and the Cabin lights/Nav/Running lights wouldn't work for a while, so I'm hunting for a replacement part as we speak.

Mike

Wally,

Unfortunately, there are several ways that can happen. All it takes is for the resistance to electrical flow to go up significantly in one localized area and it turns into a mini-toaster.

You are very fortunate that it occurred while you were present to quickly catch it. Thankfully, you could repair the damage and no major problems arose.

It should be mentioned that if a breaker is sized correctly for the wire and connectors involved the breaker should blow before the wire melts down.
in this case the breaker is suspect along with the connector.
Without trying to tell the whole story, the breaker or fuse is sized to the wire in the circuit, not the anticipated load. The breaker can be smaller than the load the wire would carry but never larger. In the older boats there is often added equipment which may have leads which are of a smaller wire size then the circuit to which they are connected. This smaller wire may be added to the circuit but should be separately fused with a fuse rated to the smaller wire size or less.
In all of this round trip lengh of wire runs, wire size, load, and voltage drop and any corosion in wiring or connectors should be looked at in new equipment and revisited on older boats where new stuff has been added over the years.
What I have just said is incomplete in the extreme but hopefully will encourage some to ramp up their knowledge or employ someone with the expertise to look at their wiring particularly in older boats.
Yup, all a lot of work but then a fire is no fun or just a piece of equipment failing on an extended cruise.
Fair weather, Neil Roach

Hi, Neil. Thanks for your contribution. I am not as savvy with electrical stuff as I would like to be, but here is a question.

If you have a damaged or corroded portion of the wire run or connection, isn't it possible for current (amps) below the rating of the circuit breaker or fuse to still cause a major overheating problem?

I guess my contention is that a properly sized fuse/circuit breaker will protect the wire from over-current in most cases, but not necessarily if there is damage.

I am happy to be educated if my contention is wrong.

I can't quote the technical details (see Ohm's Law), but think of this.

Look at the wires in a perfectly functioning toaster oven; bright orange and hot enough to set just about anything on fire. The are a highly resistive wire, but draw current (amps) well under what will trip a circuit breaker.

Any dirty/corroded/loose connection increases the resistance and can/will create heat while passing current that can be well under the point where a breaker will fail.

Hi Duane.
I'll preface my answer with a disclaimer: I'm not an electrical engeneer or a marine electrician. I have done a lot of electrical work in other fields, though most of my experience is on the job learning form others.
I'm pretty sure that the point of a breaker or fuse is to interupt any overload, before the wiring can be heated to the point of damage. That is the working theory anyway. I would like to hear from an electrical engeneer about breaker design and the effects of increased resistance caused by corrosion in a circuit. My impression has always been the the heat generated by the resistance in a corroded circuit is really just a short in slow motion; so perhaps the slowness of this fault would allow heating that a breaker will not fault. Some breakers are designed to allow a certain amount of overload for a fixed amount of time (slow blow) and perhaps these could allow a corroded point in a circuit to overheat to the point of a meltdown or outright fire.
I know that in my 1992 Cat 36 there were a number of points of corrosion in the wiring which I discovered while completely overhauling the wiring last winter. Some of this corrosion was just at the connector but where a connector was corroded, often the corrosion ran up the wire a considerable distance, in one case: several feet. The culpret: un-tinned wire which was widely used in my boat. I did find a number of loose connectors on my boat with another one surfacing just this last weekend on the propane solonoid circuit. Over time a properly made connection should not loosen up but there are a mumber of things which can effect the integrity of the connection, ie.: mechanical; vibration of strain,; corrosion and improper crimp on the connector and a poor quality to begin with. I stongly believe that we should only use marine grade connectors and hardware. Automotive quality connectors are for the most part just not up to snuff.
I realize that I could go on and on but maybe the real point is to suggest that those who want a good working knowledge of this stuff read one of the many good books written on the subject of marine wiring. Some of these are written in very simple language and are easily understood. When in doubt, consult an experienced marine electrician.
I will say that I never found any corrosion in the 110v wiring though the system ground was undersized (by a lot) based on the over-all equipment now installed on the boat.
I hope this helps, but fear that maybe it mnay just add to the confusion.
Anyway, fair winds to all, Neil Roach

Hi, Neil. You make a lot of good points; thanks.

It seems that we are all (so far) in agreement that having a properly sized fuse or circuit breaker (while extremely important) does not guarantee that no fire will result if there is some problem with the wiring/connectors.

I will echo your good advice about checking things for yourself and using a competent marine electrician if you are unsure. As with all things, and quite frequently in boat maintenance, not all who claim to be competent really are.

Cheers!

Neil's discussion was very good.

While I am not a trained electrician, ever since we got our boat in 1998 I have been learning as much as I could.

In addition to the two major issues Neil mentioned: buying a book and learning that MOST if not all electrical issues are the connections (!) there are two things I would add:

1. Open up your electrical panel and start to make friends with the rats nest back there

2. Start to develop your own wiring diagrams by learning how to read them and draw them

I said to myself: "I dunno about any of this stuff." In terms of safety, it's pretty important to know. So just start, step-by-step. Start by disconnecting the shorepower cord, and checking all the AC connections, for example. If you draw diagrams and LABEL THE WIRES it'll start to make sense to you.

Eventually, you'll get it.

Heck, if I could do it...:eek:

In order to accurately asses we need to know;

A) The load on the circuit
B) The wire gauges (pos & negative)
C) The circuit breaker rating
D) The distance round trip

A weak or bad connection will generally only cause heat at the connection itself. If the wire literally fell out of the connector, that's how I read it, it is likely that it grounded to something behind the panel and that is what caused the melting down.

It can, on occasion, melt insulation an inch or two from the connection, if there's enough heat generated, but I have seen this only once or twice and I know the wire was right up against its limit when this happened and it had a weak connection. I have seen LOTS of bad connections and the melting is usually right there and no further.

A bad termination won't melt the insulation in the middle of the wire or the whole length. If this wire was over heating from a bad connection it is a SLOW process and you would have very likely smelled it long before it got real bad or the power cut off. it sounds like it happened quickly which is indicative of a dead short.

You probably have an under rated wire, circuit breaker to big, a short or a failed breaker and over loaded circuit. You also have some bad connections but this won't cause what has been described if the wire is typical of what Catalina uses.

A breaker will trip, if working properly, before the jacket melts over it's entire length as that is the whole intent.....

Oh, I am an ABYC certified marine electrician and I slept at a Holiday Inn Express last night......;):D

Good article in 48(degrees) North, Aug. Issue which deals with much of this stuff.

Hi, all. I just had a similar electrical meltdown, in the wire running from the shore power plug to the main ac circuit breaker. The melt (and smoke) started when I turned on the space heaters plus the dehumidifier, such that the total amps was close to 30.

The melt was near the connector, back to about 1.5 inches down the wire.

We noted a couple of oddities:

1. The wire leading from the shore power connector (30 amp) was 12 gauge! which everyone at West Marine is telling us is too thin.

2. The main ac circuit breaker is 50 amp, which everyone at West Marine is telling us is too big.

...so my first question is: Is that normal? Is that what came from the factory in 1984 when the boat was new? or did someone perhaps replace wires and circuit breakers with whatever they had laying around?

Second question: What SHOULD we put it there. We're thinking a 30 amp main ac breaker (since that's what the shore power plug is rated for) and 6 gauge 3-wire marine grade.

Thoughts?

according to a couple links found with a google search, 12AWG is undersized for 30 amps. I'm not an electrician, so take your own conclusions.

Also, where is the 'main breaker'? On my '97, it's in the lazarette, about a foot from the shore power connector. If you are referring to a breaker on the electrical panel in the cabin, I'd consider that dangerous, as the wire running from the shore power connector to the panel is not protected.

[url]http://www.pinsandsockets.nl/awg%20info/awg%20info.html[/url]

[url]http://www.rowand.net/Shop/Tech/WireCapacityChart.htm[/url]

[url]http://www.homedepot.com/webapp/catalog/servlet/ContentView?pn=Wire[/url]

Thanks, all.

Catalina Direct confirms 30 amp and installation of a 30amp breaker at the shore plug, in addition to the 30 amp breaker in the master electrical panel:

[url]http://www.catalinadirect.com/index.cfm?fuseaction=product.display&produ...

When I had my survey, one of the required items was to upgrade the line from the shore power connection to the panel from 12 gauge to 10 gauge. There was a connection on the panel where you could see that there had previously been a problem and the wire had arced. The surveyor indicated that this was a "look for" item on his check list for Catalinas.

Have a look in the C36IA Technical - Maintenance library (accessable from the C36IA home page) for my article called 'Shore Power Inlet Replacement'. You'll see other potential problems with your shore power connection, such as a corroded wire at the connector itself. It sounds like you're going to have to rewire/modernize your AC system, so beginning with a new connector might be something to consider.

one of the things on my "Important" list of things to do, is to convert my 14 year old shore power connector to this newer type. Everything about it looks like an improvement.

http://www.defender.com/product.jsp?path=-1|328|299260|319691&id=1723187

I keep an eye on both the connector and the cable end, and both are reaching the end of their service lives. So I should be replacing both anyway.

[QUOTE=plaineolde;11778]one of the things on my "Important" list of things to do, is to convert my 14 year old shore power connector to this newer type. Everything about it looks like an improvement.

http://www.defender.com/product.jsp?path=-1|328|299260|319691&id=1723187

I keep an eye on both the connector and the cable end, and both are reaching the end of their service lives. So I should be replacing both anyway.[/QUOTE]

I added the Smart Plug last summer. Very happy with all aspects, including the fact that the old pieces were just that, old and worn. Make sure you buy the Smart Plug cord as well as the inlet. The cord has a power indicator that is not available if you buy the kit and add the female end to your existing cord. They also make the Smart Plug cord in 25' lengths, which I like since I prefer to stern tie and it makes for less cord to keep off the dock.

Bruce, did the boat side unit fit in the stock hole without needing to cut and did it cover up where the original plug fit? Are there any cosmetic issues after changing to this plug?

[QUOTE=bstreet;11790]Bruce, did the boat side unit fit in the stock hole without needing to cut and did it cover up where the original plug fit? Are there any cosmetic issues after changing to this plug?[/QUOTE]

They did a great job designing the boat side unit. It fits the hole exactly and the wiring was a snap. No issues with cosmetics and the design means that the inlet is well protected from weather when not in use. They even include a cover that goes on the Smart Plug end of the cord to protect it from corrosion when not in use.

I particularly like the fact that I don't spend time hanging over the transom trying to line up the prongs when I get in late at night :).

[QUOTE=pmeyers;11775]When I had my survey, one of the required items was to upgrade the line from the shore power connection to the panel from 12 gauge to 10 gauge. There was a connection on the panel where you could see that there had previously been a problem and the wire had arced. The surveyor indicated that this was a "look for" item on his check list for Catalinas.[/QUOTE]

If these boats have 12 GA wire for the AC panel feed the largest main AC breaker that should be installed is a 20A breaker. Go to 10GA wire and you can install a 30A breaker.

[QUOTE=benethridge;11770]

We noted a couple of oddities:

1. [COLOR="DarkRed"]The wire leading from the shore power connector (30 amp) was 12 gauge![/COLOR] which everyone at West Marine is telling us is too thin.

2. [COLOR="DarkRed"]The main ac circuit breaker is 50 amp, which everyone at West Marine is telling us is too big.
[/COLOR]
[/QUOTE]

There should NEVER be a 50A 120V breaker on a 12GA or 10GA wire feed. Doing this you can melt it down and start a fire.

Depending upon the 30A or 50A dock breaker to protect you is like going to Vegas you're probably the one who's going to lose..

Also any wire run between the AC shore power inlet receptacle and the AC panel should not be more than 10' of total WIRE length, this is raw wire footage not as the crow flies...

If it is longer than 10 wire feet then a second AC breaker should be installed at the shore inlet. Many Catalina's come with this extra breaker, our 2005 did, and she had 10GA wire and a 30A breaker as it should have been for a safe AC installation.

[QUOTE=Maine Sail;11793]
Also any wire run between the AC shore power inlet receptacle and the AC panel should not be more than 10' of total WIRE length, this is raw wire footage not as the crow flies...

If it is longer than 10 wire feet then a second AC breaker should be installed at the shore inlet. Many Catalina's come with this extra breaker, our 2005 did, and she had 10GA wire and a 30A breaker as it should have been for a safe AC installation.[/QUOTE]

This is the breaker Maine Sail is referring to, or at least it's the one that's on my '97. It's in the stbd lazarette, so a very short wire run from the shore power inlet. This protects all of the wire between the breaker and the main panel. That run has to be well over 10 feet, even 'as the crow flies', which wire never does on a boat.

[url]http://www.catalinadirect.com/index.cfm?fuseaction=product.display&produ...

[QUOTE=Maine Sail;11793]
Also any wire run between the AC shore power inlet receptacle and the AC panel should not be more than 10' of total WIRE length, this is raw wire footage not as the crow flies...
[/QUOTE]

Unless someone gives me a good reason not to, I am going to cut a 2 3/4 hole in the starboard deck (vertical section just about where the "Catalina 36" plastic plate is) and move the shore plug over there.

That will cut down the length of this wire to about 4 feet (from the shore plug to the electrical panel). This will solve many problems:

1. It will conform to the (relatively new?) ABYC standard 10' max.

2. It will allow me to use the 10 gauge wire (instead of the recommended 6 gauge if I keep the shore plug on the port side, which is about a 25' run).

3. It will eliminate the need for the second 30amp breaker at the shore plug.

4. It will cause less voltage drop from the shore plug to the electrical panel (since the wire will now be MUCH shorter.)

...and hopefully will not create any new problems. :-)

Except for the caulking (required coz we couldn't locate a 2-7/8" hole saw and had to use a 3"), this job is complete. Total wire length from the plug to the AC power circuit breaker is about 5'. Much safer, simpler setup, I believe.

See attached photos.