ECN Forum Forums General Topics of the Trade General Discussion Area I believe that fuses are far superior than circuit breakers!

My comments regarding single phasing, was the instance when only one (or two) of three fuses (three phase) will blow.
Most older engineers also don't trust those fancy multifunction MV relays (ie Multilin) or fancy smancy PLC's, and still require electromechanical relays. Some are set in their ways.

Is there any reason (other than _cost_) not to simply put a fuse in series with a circuit breaker, coordinated so that the circuit breaker will trip in normal circumstances, but the fuse will blow if the breaker fails?

-Jon

I like breakers. I find them to be reliable.

removing a breaker is easier than removing a fuse when working on circuits.

Rather than stepping backwards, why don't we improve the standards for circuit breakers? There are some circuit breakers currently on the market that we know are prone to fail (GE, Siemens, Cutler Hammer BR series, Square D Homeline) and others we know do a very good job (Square D QO and Cutler Hammer CH series). The lower quality ones need to have the standards boosted.

I had a job with a Cutler Hammer CH 200 amp main disco and Siemens 200 sub panel. A 20 amp circuit had a dead short on it that would trip the 200 amp main, but not the 20 amp Siemens breaker. Makes you wonder what good the Siemens breakers are doing.

I'm with CharlieE, where's the AFCI and GFCI fuses? From someone who has been a champion of the AFCI, the fuse statement in Joe's initial post suprises me a little. Does the undeniable superiority of the fuse in an over-current situation outweigh the AFCI's bennefits? Or the GFCI's? In my own opinion, fuses are superior to circuit breakers in some applications and inferior in others. Unless all aspects of an application are factored in I don't think you can make a blanket statement such as "always use circuit breakers" or "always use fuses".

I used to prefer breakers.

Then I got a job as the electrician for a maintenance dept.

If a breaker trips, someone might reset it dozens of times before they let me know. And it could be dozens of different people.

When a fuse blows they come to me because I keep them in my shop. If they come back a second time, they do not get a second fuse untill I check it out.

Another thing, we have a few situations where if theres a short the 20 amp branch AND the 3000 amp main trip. Never had a main breaker trip when a branch fuse blew yet.

There are of course problems with fuses such as the no blow pipe type.

Joe,
A long time ago, ( I think you heard this story before ) I had a problem with one of my customers. It seemed after a thunder and ligtning storm the customer complained that they didn't have any power in their house. I went out and saw a 200 amp single phase service. There were 2 200 amp main service fuses and the rest of the panel had 40 Zinsco circuit breakers. All of the breakers tripped but the 2 main 20 amp fuses were good. I checked around, and reset all of the breakers and everthing worked OK. About a month or two later the same thing happened. This time it was a nice sunny dry day. The fuses were OK but all 40 circuit breakers tripped. I couldn't find anything. I knew the head lineman at the power company (POCO) and I asked him the check his transformer on the pole. ( Which was at the bottom of the driveway of my customer.) The POCO said that everything was OK. I think that after several months and a lot of phone calls, the POCO changed the transformer and everything was OK after that. My thoughts would be that there was a spike our surge that would trip the magnetic part of the circuit breaker but not affect the fuses.

Low-voltage molded-case circuit breakers have a tendency to “vent” during fault interruption—similarly rated fuses do not.

As for me, it all depends on the load characteristics and the Customer.

Fuses introduce the problems of Single Phasing when loads such as Motors and Transformers are conserned, but the problem may go beyond that.

Circuit Breakers may fail to open under excessive Fault conditions - like an improper AIR situation (installing a device with an AIC that is lower than what's available), or the device fails in the closed position.
Other Circuit breaker issues come from when they have been setup in a non-selective fashion - with either a "Fuse / Breaker Combination" or simply all OCPDs are Circuit Breakers.

Single Phasing issues may be brought on from a failed Breaker protecting a 20 Amp Branch Circuit (Fault on the Branch Circuit), and a Fused Main Switch with one-time / fast acting type Fuses. Seen it several times (troubleshoot calls).

As I said, it all depends on the installation. The decision to be made will reflect the hazards vs the consequences of each type OCPD.

Each type device has good and bad points. Each one has a "Better Place" in the design of the systems at a given project.
Each one has its own drawbacks from failure or worse - replacement by unqualified persons.

Incorrect fault ratings on either type will have bad effects.

For breakers, it's obvious about an excessive SCA through the device than it can handle...
"BANG!!!"..."SMOKE!!!"..."FLAMES!!!"

Same for a fuse with improper Arc quenching ability. Arc inside the fuse will be sustained until something finally gives.

Then again, the 3/4" All-Copper Fuse Replacements don't offer much help either!

No way to outguess the most determined idiots, as they just keep turning out bigger, better idiots!
(had to include the typical disclaimer!).

For a Fuse type Main, these could easily incorporate an extended protection device - like AFCI or GFCI. It would be setup like a GFPE protected main switch (480Y/277 VAc 3Ø 4W 1000 Amps or more).
There are both types - Circuit Breaker and Fuse types. The Fault sensing device trips a multipole switch (looks like a breaker - but has no overcurrent protection elements).

Scott35

a properly sized fuse is better then a fpe or Zinsco NO-Trip Breakers