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Open Roads Forum  >  Tech Issues

 > 12V 30Amp circuit breaker..

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BillyW

North ID

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Posted: 07/23/12 08:20am Link  |  Print  |  Notify Moderator

wcjeep wrote:

What caused the original problem? Try solving that before inviting more issues. How much amperage is it trying to draw? Any possibility a wire has shorted to ground? When I've looked in the past the electric fans could normally not keep up with a factory mechanical fan while towing heavy.

The melting seems confined to the fuse/holder. I've had the efans for about 6 years now. This is the first performance issue I've had with them. I think the fan controller may be malfunctioning. Perhaps that lead to this issue. At the same time, this fuse holder has been in the engine compartment that whole time and may have simply wore out from the extreme conditions. I also worried about them not keeping up, but they supposedly push more air than the factory fan. Most of my towing is in the mountains too.



'97 F150 4X4
'04 Pioneer 18T6



wa8yxm

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Posted: 07/23/12 10:38am Link  |  Print  |  Notify Moderator

The circuit breaker should work fine.

However why did the fuse melt? MY guess, and I stress GUESS! is that the blades got a bit dirty/corrorded/tranished and no longer made good contact with the socket. This caused overheat and the results you see. If this is the case it can bite the new plug in circuit breaker as well.. The kind of circuit breaker you hook up with a wrench however,, More robust in this area. But that will require wireing modifications .


Home is where I park it.
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MPD56

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Posted: 07/23/12 11:41am Link  |  Print  |  Notify Moderator

Just to add my opinion to the conversation. Auto resetting breakers of the type you’re talking about should be only as a main feed over current protection device. Meaning that any thing that is connected to the load side of these types of breakers should have another means of protecting from an over current fault that wouldn’t auto reset. If a fuse blows there is a problem (fault), if you have an Auto Resetting Breaker, it will keep trying to close on a fault till you notice it and what if you aren’t there to notice it. And if the fault is bad enough to damage the equipment or even start a fire. They have there place and there is a reason that they can’t be used in your house.

My guess is that the fuse holder was man made and that it was defective or a 30amp fuse in a 15 amp holder? Some fuse holders can dissipate heat better then others and maybe yours can. A fuse is a thermal activated device and is rated to melt open at certain amperage at a certain ambient temperature. When designing an Enclosed Fuse Holder like the OP’s, the designer also has to consider how to get rid of heat that builds up inside the enclosure. Again, the breakers in a house are designed to dissipate heat, if they didn’t, it would take a long time to reset them.

MEXICOWANDERER

las peñas, michoacan, mexico

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Posted: 07/23/12 12:04pm Link  |  Print  |  Notify Moderator

MPD56

Has a good point. I like to use type I bi metallic THERMAL breakers on a switched (in this case ignition) circuit to prevent them from cycling until the battery is drained.

But a crucial point has been either ignored or otherwise omitted here.

Thermal circuit breakers rely on heat to operate. They have a de-rate chart that should be consulted. I can guarantee you a thirty amp thermal breaker will fault at one heck of a lot higher amperage at 0C than it will at 110C.

I use a audible alarm inside. Connected to ignition on the + and connected to the downstream side of the fan circuit breaker (also ignition powered). If the fan power line goes dead (faulted breaker) the alarm will sound. This is less of a hassle and less expensive than a new engine and tow bill.

MPD56

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Posted: 07/23/12 01:15pm Link  |  Print  |  Notify Moderator

LittleBill wrote:

considering school buses use these for ALL fuses in their panels, close to 50 +. the comments above in my opinion are unfounded.

there are also different types of cb where they will stay tripped until the short is removed


Just my opinion. But school buses have fuse links before Auto Reset Breakers. And there are a lot of different types of Over Current Protection devices. I thought that I’d just give an opinion to why I wouldn’t replace a fuse with an Auto Reset circuit breaker. I don’t know where I found this information, but since I found it, it can’t be unfounded, or can it LOL.

LittleBill

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Posted: 07/23/12 12:48pm Link  |  Print  |  Notify Moderator

considering school buses use these for ALL fuses in their panels, close to 50 +. the comments above in my opinion are unfounded.

there are also different types of cb where they will stay tripped until the short is removed





LittleBill

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Posted: 07/23/12 01:19pm Link  |  Print  |  Notify Moderator

MPD56 wrote:

LittleBill wrote:

considering school buses use these for ALL fuses in their panels, close to 50 +. the comments above in my opinion are unfounded.

there are also different types of cb where they will stay tripped until the short is removed


Just my opinion. But school buses have fuse links before Auto Reset Breakers. And there are a lot of different types of Over Current Protection devices. I thought that I’d just give an opinion to why I wouldn’t replace a fuse with an Auto Reset circuit breaker. I don’t know where I found this information, but since I found it, it can’t be unfounded, or can it LOL.


well when i ripped off the running lights on a school bus, after grabbing a low lying telephone line. the only breaker tripping was an auto reset circuit breaker

also i have NEVER seen a fusible link, have any other type of protection on its line, there would be no point. Just my opinion

MPD56

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Posted: 07/23/12 02:42pm Link  |  Print  |  Notify Moderator

LittleBill wrote:

MPD56 wrote:

LittleBill wrote:

considering school buses use these for ALL fuses in their panels, close to 50 +. the comments above in my opinion are unfounded.

there are also different types of cb where they will stay tripped until the short is removed


Just my opinion. But school buses have fuse links before Auto Reset Breakers. And there are a lot of different types of Over Current Protection devices. I thought that I’d just give an opinion to why I wouldn’t replace a fuse with an Auto Reset circuit breaker. I don’t know where I found this information, but since I found it, it can’t be unfounded, or can it LOL.


well when i ripped off the running lights on a school bus, after grabbing a low lying telephone line. the only breaker tripping was an auto reset circuit breaker

also i have NEVER seen a fusible link, have any other type of protection on its line, there would be no point. Just my opinion


A perfect use of an auto reset breaker, can you imaging a Bus loosing all its lights because of an intermittent fault, of course not. By Law the makers of the bus can’t use auto re-settable CB on certain circuits. But if the fault doesn’t clear and auto breaker keeps closing and causes a fire!! In my opinion a fire on the bus would be more of a safety concern.

Just my opinion but I don’t see the air I that I breathe and I would think that there would be no point to have an opinion why. I do know that there are wiring regulations on vehicles that is not what the OP asked.

wa8yxm

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Posted: 07/23/12 07:33pm Link  |  Print  |  Notify Moderator

LittleBill wrote:

considering school buses use these for ALL fuses in their panels, close to 50 +. the comments above in my opinion are unfounded.

there are also different types of cb where they will stay tripped until the short is removed


I have those in my rig (The kind that do not reset till power or the short is removed)

Drove me batty cause the contacts got dirty and it would trip at low current. .. I will re-clean the contacts soon but for now.. REPLACMENT works great.

BillyW

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Posted: 07/23/12 07:57pm Link  |  Print  |  Notify Moderator

It sounds like a lot of knowledgeable noggins have chimed in. So here's an update with more questions; I installed the auto resetting breaker and it is functioning properly and remaining cool to the touch so far. However, I also added a 40 amp relay into the circuit to prevent the fans from running when the ignition is off, since the fan controller seems to think it needs to do that periodically. The relay does get pretty warm. Is this a worry? Maybe I was mistaken to assume a relay could handle the amperage long term. By the way, the original fuse and fuse holder were chosen carefully for the application. Why would someone spend hundreds on a system only to skimp on the power and safety features. With that said, the fuse holder experienced high heat and melting on one leg all the way out to the wire. Maybe I'll reconsider the auto resetting cb and go back to some kind of a fuse.

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