Any Drawbacks to Using Circuit Breaker instead of Fuse?

Not a subject that will be taught on a RV tech forum. But I’ve worked on many electrical devices that have breakers and fuses in parallel. The electrical code is clear when this configuration can be used.
Simply put, it has to be approved at the factory because we can’t expect all Electricians in the field to understand the electrical design theory or have access to specification to each type and make of breaker or fuse.
An interesting thing to note is, most high current fuses have multiple parallel elements which basically is paralleling fuses in one case. Not to be confused with timed delayed dual element fuses.
The design and use of an over current device is like everything in this world, is controlled by economics first. For example; I have fuses that cost over $10,000 and breakers that have to be re-condition for around $30,000 after so many times they are opened and closed and sooner if they trip under a fault condition. Every year I have to explain to a Company VP with a Business Degree why I need so much money in my budget.

I believe that the OP is trying to make a decision on using an auto resetting breaker, although he is thinking of safety first, he states that his electrical knowledge is limited. They’re reasons why one 40 amp over current device cost more then another, but putting expensive racing tires on my 4X4 doesn’t make it go faster or improve the ride. I believe that auto resetting over current devices are used in circuits that are prone to known momentary spikes in over current from a known electrical load (motors for one that is designed to take theses over currents). Or for safety reasons like a feed circuit to a hospital or power grid, can you imagine laying in a hospital bed and waiting for an Electrician to reset a breaker or change a fuse!!

The OP is thinking of putting an auto resetting breaker on an electrical device (Inverter) that doesn’t do well in over current events (electronics). If there is a fault, the breaker he posted will keep re-closing till something gives and if no one is there to possibly get hurt, the cost of repair will most likely be more then the price he would be saving on fuses.

liquidspaceman - The fuse you are referring to is there to protect the wiring in case of short more than protecting the inverter per say.

I would not be against using one of those HI-AMP by BUSS manual reset circuit breakers but they are alot more expensive than a BLUE SEA fuse block and fuse. I would not like to deal with an auto reset type circuit breaker as it will keep resetting until something burns up in this case.



This is the type of fuse block and fuse I always use. Haven't had one open up on me yet...


I am for using anything that has the same terminal lug connections as the battery cables...

just my thoughts
Roy Ken

When I was a kid I had a race between an Edison base fuse and a breaker. Screwed the 15a fuse into a lamp. Turned the lamp on.
20a breaker opened, 15a fuse was intact.


My preference is to stay away from self resetting breakers.

Class T fuse is slow to open so size it a little tight IMO.

GMT830 wrote:
If the breakers and associated wiring to split the load have equal resistance, each beaker will carry half the load.

I won't speak for electrical engineers, but most of the licensed electricians I've met couldn't even explain Ohm's law.

I'm essentially a visitor here so I'll bite my tongue.

I'll put you down for answering my question as to whether both breakers will assuredly be carrying the same current as "yes" because their resistances will be precisely the same.

Sorry to have butted in.

aruba5er wrote:
In all my years as an electrician, I preferred fuses. They are cheaper to buy and they will carry the load until they blow. Unlike a CB will degrade as it is loaded to full current. Each time it trips it gets a little weaker. Then it heats up internaly and starts tripping sooner and sooner. And you can get fast acting fuses or medium blowing fuses. or slow fuses. And like the poster ahead of me said. what happens if it resets when you are not around.

At one time... The code required fuses for some 120 volt and higher installations. I do not know if that is still the case but I once ask my boss why they had fuses AND circuit breakers. That was his answer.

In this case you are protecting electronics. In theory that fuse should never blow (Though I might have used a slightly larger fuse (perhaps 45-50 amp) but the self-resetting breaker ....

Well should something go wrong inside the inverter. that breaker will make it go wronger, and wronger, and wronger, and .. Bad things may happen. (Well worse things).

Oh, that time was like 45 years ago where I lived.

One other thing.. You need not worry about the fuse blowing, after all Murphy's Law for Electronics says that a $140.00 dollar transistor will blow in order to protect a $1.40 fuse.

There I was in the auto parts store looking for a 40 amp fuse to replace my main and they didn't have anything bigger than 35 amp. A six pack was going for $3.99. Got to looking around and noticed a 40 amp circuit breaker for $3.69 and that's what I bought and installed.

I can understand the argument not to use a breaker based on "what happens if it keeps resetting when you aren’t there" (even if I don't agree with it as a problem) but to not use one based on price? Really?

If the breakers and associated wiring to split the load have equal resistance, each beaker will carry half the load.

I won't speak for electrical engineers, but most of the licensed electricians I've met couldn't even explain Ohm's law.

GMT830 wrote:

...I might even argue two smaller breakers in parallel are better than a single. If the first breaker trips the second will go right behind it because you have instantly doubled the load.

I'd love to hear from an experienced EE that had any design experience to see if he/she agreed with that.

Of course if either breaker trips with say 55% of the desired trip load the other breaker will trip... so if you want 60 Amp protection and have a 33 amp draw, one breaker trips and the second follows. (Or are you insisting that each breaker will always carry half the load?)

I'd lovge to hear an input from a licensed Electrician id no EEs are out there.

MEXICOWANDERER wrote:
I love to for example have a breaker rated for the load, then have a fuse rated 10% greater for security. A breaker has a Jekyll & Hyde personality according to temperature. They will carry a substantially greater amperage load when cool.

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Very good post, an excellent idea. The breaker will reset for the occasional nuisance overload induced trip. But the fuse will prevent a major issue becoming a fire.

As for the parallel breakers, I agree it sounds a bit weird. But if they are sized properly, no issue. Two 30 amp breakers will provide 60 amps protection as well as a single 60 amp breaker. I might even argue two smaller breakers in parallel are better than a single. If the first breaker trips the second will go right behind it because you have instantly doubled the load.

SaltiDawg wrote:

No hassle intended, but everything I know screams never put breakers in parallel. Is this done commonly in RVs? (I'm not an RVer.)

My intuition screams the same thing. I'm even suspicious of paralleled fuses, but I see it done so often that I'm assuming somebody must have determined that it works ok.