Circuit Breaker Replacement and Question

[Christian Williams]

The interior panel of my 1984 E381 is salvageable, if I clean up the mess back there.

This model used original Wood Electric/AMC 112 series circuit breakers. They're robust switches with metal toggles, and I recognize them from aircraft I used to fly.

They're no longer manufactured, but replacements are available at www.cmsquick.com .

Here's a question: which side of these breakers takes the connector?

As you can see in the photo, one side has a hot bus bar. Somebody put several appliances on that side.

But the factory put all the connectors on the other side. Which is correct?

 

[toddster]

I might be wrong, but I think either side will work UNLESS there is a specific polarity marked on the device. For example, the 50-amp breakers I recently installed clearly had one terminal marked "BAT." It's maddening to imagine that for some devices, this might be something as ambiguous as a dot on one side.

Wait, what? There is a bar AND wires on that side? Was somebody "borrowing" a hot connection for some "extra" devices not protected by breakers? It looks like there are at least three or four things scabbed on to the hot side of breakers. (Besides the red wires that daisy-chain the bars.) The only thing I have like that is the "always on" wire to the stereo, and it has an in-line fuse.

 

[Christian Williams]

How to test?

Thanks, you gave me the key.

The PO apparently wanted a lot of stuff always on--when the batt switch was on. Radio and instruments for starters.

[added later: Nah, he was just bypassing inop circuit breakers]

He also added masthead running lights, with its own switch, and picked up juice for that from the hot side of the breaker.

He was then relying on in-line fuses in each case. No idea if that's wise.

Now, please--what's the best way to test a DC circuit breaker to see if it actually still trips? Not immediately answered elsewhere on the Web.

 

[Loren Beach]

I have experienced a trip of our boat's AC breakers and our main shore power breaker when I pulled too much current on a circuit. Usually this involves running a portable electric heater and then absently-mindedly powering up the vacuum cleaner.
Given that you might be able to find and ID various DC sources, I wonder if you could spec out some loads for each amperage of breaker and then overload them, one by one?
Perhaps borrow an inverter and plug a load into the output side?



Loren

 

[toddster]

^^ Maybe devices with volatile memories? The "always on" wire to the stereo is just for the presets memory and the clock - no detectable power drain until the switch is thrown, sending power to the "main" wire.

Of course you could always test a breaker by disconnecting its load and shorting to ground. Not sure how advisable that is - at least you'd need another breaker or fuse in the test circuit in case the unit under test doesn't trip. To actually test the amperage at which a breaker trips, you'd need some kind of expensive test rig with variable dummy loads. I wonder if you could make a poor-mans test-bed with something like a resistance heater or hot plate (non-thermostat) and an ammeter to dial up a current until a breaker trips? Not sure I'd ever get bored enough to do that...

 

[Tom Metzger]

Now, please--what's the best way to test a DC circuit breaker to see if it actually still trips?

If you just want to know if it will trip with a dead short put a ground on it and turn on the power. Generally, if it trips with a high current it will trip at the rated current, which is a multiple of the number written on the device. Typically, a breaker will carry 125% of nominal amperage forever, and will definitely trip at double the nominal.

It's not easy to give them a more accurate test.

 

[Christian Williams]

Replacement of these original breakers is $40 each, and I need five.

The appeal is the factory look, the matching toggles and the sturdy non-plastic feel under the finger.

But then, a simple two-pole switch also fits the panel hole, and looks and feels exactly the same. And under $10.

Why not just use them, with an in-line fuse?

Am I missing something here? Circuit breakers are just a convenience, no? And on boats they rarely trip anyhow, and if they do you'd have to scout the wiring anyhow.

Why not inline fuses instead of breakers?

 

[toddster]

Well, there is then the necessity to keep in stock a supply of all potentially required fuses. Which will blow when you are many hours from the nearest source. Considering the case of a motor experiencing over-current due to heavy demand. (e.g. a pump or something.) One might run through a small stock of fuses just when it's needed most... I think the only breaker I've had trip on the boat was a frozen-up macerator. And some zots from the tangled mess behind the engine control panel - which was not protected by either fuses or breakers at the time.

 

[Tom Metzger]

Adding an inline fuse is four more connections and a fuse to fail, and added clutter. Also a supply problem as Toddster said and the difficulty of reading the value on glass fuses at night in a seaway.

I would be inclined to call it "That much more hair in the scuppers".

That said, I prefer the automotive type fuses. There's nothing wrong with being frugal... cheap.

 

[Loren Beach]

Zap

One quibble I have about relying on conventional fuses is that you may need quite a lot of them when actually trouble-shooting problems away from the dock. (And, yes our boat does have some in-line fuses in secondary circuits, and several spares for each.)

The problem progression might be:
1) your electrical device/gadget stops working.
2) suspecting that the fuse blew because it is old, you replace it and flip the switch, and it blows.
3) initially checking over all of the connections and finding nothing "wrong" you try another fuse and flip the switch -- and the fuse blows.
4) you R&R the part after doing as much field-service maintenance as you can do, connect up all the wiring, and flip the switch -- and the fuse blows.

And, like, you know... etc....

I prefer circuit protection that is resettable, like a circuit breaker. If I were a better boat fixer, I might have a different viewpoint!

Also: "What Tom said!"


Cheers,
Loren

 

[Christian Williams]

Thank you all very much. I think. Anyhow, I ordered them.

I could have just cheaped out and nobody would know, probably not even me after a few months.

The source for replacements for the originals, no longer made, is www.cmsquick.com .

.

 

[TakeFive]

Thanks, you gave me the key.
The PO apparently wanted a lot of stuff always on--when the batt switch was on. Radio and instruments for starters.
[added later: Nah, he was just bypassing inop circuit breakers]
He also added masthead running lights, with its own switch, and picked up juice for that from the hot side of the breaker.

I would not be comfortable with so many hot leads coming off the bus bar.
It might be a good idea to install a Blue Sea blade fuse block and buy a large box of misc blade fuses from Amazon.
Much easier to dx a problem when fuses are located in one place.

-Gary

 

[GrandpaSteve]

Thank you all very much. I think. Anyhow, I ordered them.

I could have just cheaped out and nobody would know, probably not even me after a few months.

The source for replacements for the originals, no longer made, is www.cmsquick.com .

.

Failed breakers should fail open. These are high quality, I suspect replacement is going to give you a collection of very good spares. Sorry I did not see this thread earlier.

 

[Christian Williams]

I did read that in the research. These just don't complete a circuit. Multimeter readings are all over the place. The switches feel loose, as if a mechanical issue inside.

Former owner put five appliances on the common hot bus because these "failed closed." He added inline fuses.

Even so, I may well be missing something. I'll go at them again with the multimeter again tomorrow.

 

[GrandpaSteve]

I did read that in the research. These just don't complete a circuit. Multimeter readings are all over the place. The switches feel loose, as if a mechanical issue inside.

Former owner put five appliances on the common hot bus because these "failed closed." He added inline fuses.

Even so, I may well be missing something. I'll go at them again with the multimeter again tomorrow.

Of course you are right to be cautious if you suspect anything is wrong, and you certainly will improve the situation.