Very Hot 60-amp Alternating Current Circuit Breaker

This is the breaker (Square D) on the feed from my 7.7kw Westerbeke. Yesterday, this breaker tripped twice with modest loads and was very hot to the touch. I opened the box this morning and could see nothing obviously wrong except the green line in from the generator is butt-spliced twice. The engine room was very hot but this is nothing new.

My thinking, my knowledge is very limited in this regard, is that the breaker has developed a high internal resistance over time. Am I on the right track or should I be looking elsewhere? We have used this generator extensively over the past two years but I have to admit that I never once felt the breaker box for heat so that this condition may have existed for a long time and is just now becoming acute.

Circuit breakers should not be hot to the touch. Replace it.

David

It is usually a symptom of a bad connection due to corrosion or looseness. Not always easy to see with a glance. Check all that thoroughly. Typically those sort of breakers are not very expensive, if that's where your investigation leads you.

Yes it is possible that the breaker has seen better days.
I used to work with manufacturing residential circuit breakers and they do wear out especially if they are cycled often with high load. The contact points can arc and get pitted then they heat up and trip.
I had a 30 amp breaker fail in my boat.

Is that generator 120 VAC or 240 VAC? Normally I would expect a boat of your size to be wired with two 30 amp or one 50 amp 240 volt shore power connection. So, typically the breaker on that generator would be a double pole 35 amp breaker. Seems odd that you have a 60 amp breaker.

Ted

CJ
Is the breaker in question the one mounted on the genset itself? If so the "book" should have an electrical diagram noting the OEM breaker specs.

Most of these breakers have two trips: One is thermal where a heating element in line with the load trips it if they get too hot. The other is magnetic that trips it rapidly on a very high overload. So some heat is normal. But if the thing is noticeably hotter than surroundings on modest load, contacts are in bad shape or connections have high resistance.

If connections are solid (snug them) and it is still hot, replace it.

Breakers go bad in normal use and from abnormal conditions. Check the loads with a clamp meter. Check voltages on both legs to neutral and ground, and to each other, loaded and no load.

Bad breakers can make a freak show of oddball electrical problems.


Be sure to get the right replacement. Don't just match the existing breaker.

Mostly, protect yourself while working with electrical issues. Ever see one of those hot dog cookers where the hot dog is the conductor? Don't be a hot dog.

I would certainly swap it out. If it is a Square D breaker it will be cheap and easy to swap so why not give it a try. If it still trips then look more closely at the system.

Circuit breakers do indeed fail.
However, do some checks first. If the fault is not the C.B. itself then a new one will repeat the problem.

Check the actual connections for ANY sign of oxidation which is darkening the lug and the wire .
Check the wire insulation for any sign of discolouring indicating heat buildup.
Check also for looseness as looseness will lead to oxidation .
Any looseness and resulting oxidation will create resistance which will create heat buildup which will discolour the wire itself, its insulation AND likely the C.B. terminal
THat heat buildup will also cause nuisance tripping.

I have had decent results with reterminating the wire back to bright wire or heavy wire brushing, SS wire brush, both the wire and the C.B. side terminals if discoloured and then applying some NoAlox or similar.

But if all are not tight and clean it will repeat.

Before I forget check the actual current flowing through the C.B. Maybe the draw is borderline and with a wee bit of oxidation it goes over the edge.

If the terminals are tight and clean now then the C.B. itself is the likely culprit.

Thanks guys for your ideas. I will replace the breaker and report back. This is a 50-amp boat.

Another thought. Why do I even have a circuit breaker? On board is another generator, a Perkins-powered Kohler 12.5kw. The output is wired directly to the panel, no circuit breaker.

Kohler genset is non-compliant as the wire run from the generator to the panel is unprotected by an overcurrent protection device (OCPD).

Ah, I always wondered about that. I will look into adding protection on that circuit. Question: how would over current occur coming from a generator that puts out a constant?

CharlieJ said:

Kohler genset is non-compliant as the wire run from the generator to the panel is unprotected by an overcurrent protection device (OCPD).

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Compromised insultation on the output cable.

Which Kohler 12.5kw genset do you have? What is the model, drawing, and/or build number? Some have over-current protection built into the unit rather than leaving it for one to wire up in a nearby electrical box.

The RATING you see is not a constant. That rating is the maximum current that it can produce safely without overheating and causing damage to itself.

Under a short circuit condition the amperage could climb greatly although the output voltage would falter.

A C.B. or fuse is needed to protect against shorts. Are you sure there is not one installed as part of the gen set itself?

Report - The breaker had to be pried out with a screwdriver. The spring contacts were highly encrusted. Much resistance right there. The plastic housing near the contacts was melted from the heat. The box is being replaced as well. Now, take a look at the picture. Notice the corroded, breaking and broken strands in one of the wires (after I removed the electrical tape) that were connected in an unacceptable manner. Frightening, isn't it? Needless to say, the wiring and connections will be updated properly. There are three black wires that were connected together. Two come from the generator head. The third is the run to my electrical panel along with a white wire and a green wire, all 6 AWG.

That is some great electrical work there... I would replace the wiring if it is damaged and instead of using a nut and bolt put them on a terminal block. Maybe do an electrical survey of the boat. If they did this, what else have they done? Glad you found the problem.

Before you get too far into your remediation plan, flex the cables where accessible between the breaker and the main boat panel. The cable should be bendable. I would want to check for stiff sections from compromised insulation or strands fusing together. Might be worth disconnecting the wires at both ends and doing a resistance test with an ohm meter.

Ted

Comodave said:

That is some great electrical work there... I would replace the wiring if it is damaged and instead of using a nut and bolt put them on a terminal block. Maybe do an electrical survey of the boat. If they did this, what else have they done? Glad you found the problem.

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Terminal block already ordered. I will try finding good wire from which to butt splice. As I do not like butt splices I would rather replace that bad wire all the way back to the generator head but that would mean lots more work in my particular case.

As for an electrical survey, I don't think it would be very revealing. When we bought the boat, I had all of the chargers and inverter chargers ripped out, a Magnum 2812 installed, batteries relocated near the Magnum, and all new switches and ACRs. But, that nut and bolt terminal, idiotic. At the end of the day, I will not be taking any shortcuts. I am really glad I opened up that box rather than just installing a new breaker box and using the existing wire ends.

By the way, the old charging system was downright scary. The feed to the failed Xantrex was through an old, dumb ferro-something charger. The picture is of the new setup.

catalinajack said:

Report - The breaker had to be pried out with a screwdriver. The spring contacts were highly encrusted. Much resistance right there. The plastic housing near the contacts was melted from the heat. The box is being replaced as well. Now, take a look at the picture. Notice the corroded, breaking and broken strands in one of the wires (after I removed the electrical tape) that were connected in an unacceptable manner. Frightening, isn't it? Needless to say, the wiring and connections will be updated properly. There are three black wires that were connected together. Two come from the generator head. The third is the run to my electrical panel along with a white wire and a green wire, all 6 AWG.

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Bad news for me. The two black wires in that hokey, non-compliant connection that go to the generator head are seriously corroded probably all the way back to the generator head. I cut them both way back and found the same that you see in the picture. So, I do not have any good wire with which I can retrofit. That means I need to remove the generator head cover to run new wire. The problem is I will have to remove my water heater in order to get the head cover off, a major project in itself. Fortunately, we have two generators aboard this boat so the smaller Westerbeke is out of commission until I either commit to a major project or I have the Westerbeke removed. My preference is to remove the Westerbeke to capture engine room space.

Anyone is welcome to this generator for free if it is removed at no cost to me. Except for the bad wires, it has performed as designed. We are berthed in Galesville, MD.

Congratulations. A boat owner who is alert to anything out of the ordinary will usually have the fewest cruise interruptions and emergencies.

Time for a new breaker sq D is a household breaker and gets tired quickly in a marine environment

Comodave said:

That is some great electrical work there... I would replace the wiring if it is damaged and instead of using a nut and bolt put them on a terminal block. Maybe do an electrical survey of the boat. If they did this, what else have they done? Glad you found the problem.

Click to expand...

Update on generator wiring. The two leads pictured are the hot lines from the brushes to the feed wire to the circuit breaker. I replaced these with 8 AWG wire to a bus bar which I installed in the generator connections box. Looking at the other two wires coming from the brushes which are ganged together along with the neutral and safety wires, I did not like the looks of the original (37 years old) nylon crimps so I cut them off and bared new wire to take a look. Well, those two wires were also corroded all the way back to the brushes but they were not heat damaged or brittle. These two wires were also replaced. Today, I fired up the generator and all is well. I also installed a new 60-amp breaker box.

Glad you got it all fixed. Amazing what some POs do with electrical work...