Northern Lights AC breaker tripping to much

[HKTim]

I have a Northern Lights 7kW genset. Yesterday afternoon the AC power breaker tripped several times while running two air cons with soft start installed and my battery charger (outdoor ambient temp was plus 35 degrees C). Since the breaker is inside the genset frame, it was obvious from my frequent resets that the temperature was quite warm around it. After taking the sound shield off and back on three times to reset the breaker, I finally left it off and also kept the genset locker door open. No more tripping. The night before I was running three air cons, battery charger and microwave with no problem. Is there a temperature limit for the AC circuit breaker? Would a fix be to install a fan inside the genset enclosure?

The genset coolant temp by the way was normal at 180 F.

Thanks


Sent from my iPad using Cruisers Sailing Forum

[meridian28]

Circuit breakers will fail with age, especially if in a hot environment and what sounds like a heavy load. I would just replace it.


Sent from my iPhone using Cruisers Sailing Forum

[Cruisingscotts]

Before you change anything you should verify that it is not doing what its supposed to do. Circuit breaker operate via a bimetallic trip that is using the line amperage as the heat source. Once it gets hot enough to trip it may need to cool down some to reset and stay that way. On the breaker it should list the max ambient temp it can safely operate in. It is more than likely higher than the environment it is in but you never know. The very first thing to verify is that you are indeed not pulling excess amperage at the breaker. A loose connection or bad soft start could both be spiking current causing the breaker to trip, you could also be seeing excessive in rush current from the air conditioning units starting. A good AC clamp amp meter like a fluke will be able to read in rush current.

[GordMay]

➥ How hot can circuit breakers get? What is the temperature of a molded case breaker?

➥ What are the allowable temperature rise limits for circuit breaker parts? Customer is doing thermal imaging.

[seasick]

I run the same gen set. It is my understanding and experience that every time a circuit breaker blows, it becomes weaker and will pop below its rating, progressively getting weaker by the pop.

My suggestion is to replace the breaker with an identical one.

[a64pilot]

Not sure about Gords links as I have a slow connection, but yeas there are temp limits for a CB, in fact heat is what makes them trip, heat from electrical load, but if the ambient heat is high enough, they will trip with a low or no electric load.
Since yours works fine with the cover removed, I'd bet Lunch that your not getting enough cooling airflow with the cover on.


Sent from my iPad Pro using Cruisers Sailing Forum

[J Clark H356]

I agree with A64 Pilot. Heat increases resistance and acts like load in an electrical circuit. It sounds like a combination of a weak breaker, high head loads from the compressors, charger load, and the heat of the enclosure all simultaneously causing peak loads that combined to increase beyond your limits. Since it worked when cooled off, it was most likely due to temperature. 35C is 95F so pretty warm, but within the enclosure much hotter. Did you have any other loads like HWH and computers, IPads, etc. charging? 7000 watts or 2 HVAC units and a charger should have been plenty.

I have a 5kw Northern Lights but only 1 AC unit and run HWH and Microwave plus charging, tv, and miscellaneous loads and have never tripped my main breaker on the Northern Lights, but almost always do if I am at the dock using one 30 amp cord and have the simultaneous loads as above, but I trip the 30 Amp boat breaker, not the Northern Lights.


33.00Sent from my iPad using Cruisers Sailing Forum

[a64pilot]

Even my little 3.5 KW will not trip before the boats 30 amp breaker will, but making 30 amps plus is more than its rating or right at max. But a 5 KW or larger shouldn't be breathing hard at 30 amps. 5KW at 120 V is a little over 41 amps I think.
I did when I first installed it have a problem with the 30 amp breaker inside of the gen enclosure tripping, turned out to be inadequate cooling. Nexgen supplied a bilge blower hose for the blower, but the blower is actually a sucker and the cheap flimsy hose would try to suck in, and that along with ripples from the wire in it caused enough drag so that airflow suffered, I replaced the bilge blower hose with Aircraft Scat hose and that increased airflow rather dramatically, much cooler in the enclosure now, and no more tripping breaker.


Sent from my iPad Pro using Cruisers Sailing Forum

[Cruisingscotts]

Took a look in the panel behind my desk, a 2000kw switchboard, every breaker in it is rated for 40c ambiant, which would appear to be a standard. It certainly sounds like its too hot where its located, but as I said before, the 1st step is verifying load. Myopia is not your friend on a boat.

[HKTim]

Thanks everyone. Helpful guidance. I did not mention the genset is only 1 year old and it's probably tripped no more then 10-15 times in its life. So I'll start off with the assumption the breaker is not worn out yet and just see if I can improve air circulation within the sound enclosure. Ambient outdoor temp was 35 C. But when reaching in to flip the breaker back on, I'd say the temp was much higher then this around the electronics of the genset. I'll put my infrared thermometer on it when running on the next hot day. Thanks again.


Sent from my iPad using Cruisers Sailing Forum

[a64pilot]

If a breaker trips twice, the circuit needs investigating. Once could be some kind of an anomaly.
Ten to fifteen times, you definitely have a problem, remember these things are sometimes the only thing between us and a fire, and a fire scares me worse than anything that can happen on a boat, I consider an explosion a type of fire before anyone points out propane explosion

It could be as simple as a loose connection


Sent from my iPad Pro using Cruisers Sailing Forum

[boatbod]

Something to consider is whether your genset is configured to put out 110 only or 110/240 and whether the boat is set up for single or twin 30A shore inlets. All affect how the load it's presented to the genset, and whether the breaker is sized appropriately for the expected load.

[liveaboard60]

Originally Posted by a64pilot

<snip>
...a fire scares me worse than anything that can happen on a boat, I consider an explosion a type of fire before anyone points out propane explosion

<snip>

Yep, an explosion is nothing more than a very, very fast burning fire <grin>.. flk k

[HKTim]

Did some more investigating yesterday afternoon using an infrared thermometer.

Deck of genset locker was 43C
Sound enclosure of genset was 48C
Circuit breaker switch was 66C

After two hours of running 3 air cons, 2 hot water heaters and 1 battery charger, could not encourage the system to trip.

I opened up the deck locker and sound enclosure and ran everything for another 30 minutes. At 2.5 hours, the temp on circuit breaker had fallen to 55 C

The northern lights manual says the max temp for the AVR is 60C. But I was above this for two hours. I think my problem the other day was ambient temperature only. I am still going to try to measure current flowing to each device to confirm no problems there.


Sent from my iPad using Cruisers Sailing Forum

[transmitterdan]

The circuit breaker probably has wires attached at the back with nuts holding the crimp lugs. Or possibly the breaker has compression fittings with screws that tighten a plate against the bare copper wire. Either way a new install should have the connections checked for tightness within the first 6 months of installation. A generator vibrates a lot and can easily loosen wiring connections. This will in turn cause the breaker to get hot and trip. Check the connections visually looking for signs of overheating of the wire. Dark insulation is a good warning sign. Mechanically check the nuts or screws to be sure they are still tight. Obviously do this with all AC power switched off and the boat disconnected from shore power.