Fuses vs Circuit Breakers
- Thread starter bwyllie
- Start date
- Status
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: Fuses vs Circuit Breakers
What will happen on a sunday at 2am when the fuse blows and there is no replacement ?
What will happen on a sunday at 2am when the fuse blows and there is no replacement ?
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
Re: Fuses vs Circuit Breakers
The only time I uses fuses instead of a breaker is when I need them for series rating of equipment. If I can get the same series rating with a breaker-breaker combo, then I don't use fuses.
Breakers have come a long way in some areas they used to lack in, such as current limiting capabilities. There is no competition with regard to communications and failure analysis, as a fuse can't do it without a separate meter. Even with the separate meter, you might not know which part of the trip characteristic activated when using a fuse.
The only time I uses fuses instead of a breaker is when I need them for series rating of equipment. If I can get the same series rating with a breaker-breaker combo, then I don't use fuses.
Breakers have come a long way in some areas they used to lack in, such as current limiting capabilities. There is no competition with regard to communications and failure analysis, as a fuse can't do it without a separate meter. Even with the separate meter, you might not know which part of the trip characteristic activated when using a fuse.
brian john
Senior Member
- Location
- Kilmarnock, Va
- Occupation
- Retired after 52 years in the trade.
Re: Fuses vs Circuit Breakers
I prefer fuses, as for having spares. Well shame on you if you don't have a spare in a SPARE FUSE CABINET (commercial). But just in case you don't have them I do stock all standard fuses 1-4000 amp.
I bought out a company that was going out of business got 1000's of fuses they had for spares, cost $850.00. We Have done quite well selling these over the years, at 2:00 AM Sunday morningt the price goes up dramatically. The first or second time we sold a fuse we got our return on the investment.
Even if that was not the case I still prefer fuses.
I prefer fuses, as for having spares. Well shame on you if you don't have a spare in a SPARE FUSE CABINET (commercial). But just in case you don't have them I do stock all standard fuses 1-4000 amp.
I bought out a company that was going out of business got 1000's of fuses they had for spares, cost $850.00. We Have done quite well selling these over the years, at 2:00 AM Sunday morningt the price goes up dramatically. The first or second time we sold a fuse we got our return on the investment.
Even if that was not the case I still prefer fuses.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Fuses vs Circuit Breakers
I use a Hoffman 12x12x6 NEMA 1 enclosure for spare fuses.
One big advantage of fuses is higher ampcity and faster time for fault clearing. The 2005 NEC will probably require labeling equipment with arc fault energy in calories, with current limiting fuses:
The available fault current is lower.
The short circuit current is lower
The calories are lower
Less PPE is required
I use a Hoffman 12x12x6 NEMA 1 enclosure for spare fuses.
One big advantage of fuses is higher ampcity and faster time for fault clearing. The 2005 NEC will probably require labeling equipment with arc fault energy in calories, with current limiting fuses:
The available fault current is lower.
The short circuit current is lower
The calories are lower
Less PPE is required
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: Fuses vs Circuit Breakers
IMO from safety only the fuse would win.
IMO from safety only the fuse would win.
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
Re: Fuses vs Circuit Breakers
I believe that below 32k of incident energy, you will find some current limiting circuit breakers to perform better than fuses, reducing PPE as compared to an equivalent circuit with fuses.
An interesting article below compares non-fused circuit breakers to fused circuit breakers for this particular manufacturer, but the idea is similar.
http://ecatalog.squared.com/pubs/Circuit%20Protection/Insulated%20Case%20Circuit%20Breakers/Masterpact%20NT%20UL489%20Circuit%20Breaker/NT%20Accessories/0613DB0202R603.pdf
Ampacity between fuses and breakers are similar, time for fault clearing depending on the available fault current and associated incident energy is similar, the available fault current is not necessarily lower for one vs the other across the board, the short circuit current is not necessarily lower for one vs the other, the calories are are not necessarily lower for one vs the other, and PPE requirements are not necessarily lower one vs the other.
I still think it's easier to re energize a circuit after circuit trip when a survey is completed, when you don't have to find a replacement fuse.
[ December 31, 2003, 08:36 PM: Message edited by: ron ]
I believe that below 32k of incident energy, you will find some current limiting circuit breakers to perform better than fuses, reducing PPE as compared to an equivalent circuit with fuses.
An interesting article below compares non-fused circuit breakers to fused circuit breakers for this particular manufacturer, but the idea is similar.
http://ecatalog.squared.com/pubs/Circuit%20Protection/Insulated%20Case%20Circuit%20Breakers/Masterpact%20NT%20UL489%20Circuit%20Breaker/NT%20Accessories/0613DB0202R603.pdf
Ampacity between fuses and breakers are similar, time for fault clearing depending on the available fault current and associated incident energy is similar, the available fault current is not necessarily lower for one vs the other across the board, the short circuit current is not necessarily lower for one vs the other, the calories are are not necessarily lower for one vs the other, and PPE requirements are not necessarily lower one vs the other.
I still think it's easier to re energize a circuit after circuit trip when a survey is completed, when you don't have to find a replacement fuse.
[ December 31, 2003, 08:36 PM: Message edited by: ron ]
Re: Fuses vs Circuit Breakers
And there is also the 3 phase applications. Blow a fuse a one phase of a 3 phase system and what damage can be caused when a system is single phased?
Blow a pole on a 1ph 3w 120/240v system and the live side can back feed through a a 240v load, such as a baseboard heater as an example, and energize the thought to be dead line.
When a two or three pole beaker trips all poles and/or phases open.
And there is also the 3 phase applications. Blow a fuse a one phase of a 3 phase system and what damage can be caused when a system is single phased?
Blow a pole on a 1ph 3w 120/240v system and the live side can back feed through a a 240v load, such as a baseboard heater as an example, and energize the thought to be dead line.
When a two or three pole beaker trips all poles and/or phases open.
Re: Fuses vs Circuit Breakers
I investigated a house fire that was caused by the loss of one line fuse.
The owner turned on the dishwasher and left for work. The dishwasher motor caused one of the main fuses to blow. This shut down the dishwasher. When the lawn sprinkler started, the well 240 volt pump pressure switch closed.
This caused the dishwasher to start again only it was in series with the well pump. The dishwasher motor overheated due to the low voltage. The wall and floor was ignited.
A common trip breaker would have prevented this incident.
I investigated a house fire that was caused by the loss of one line fuse.
The owner turned on the dishwasher and left for work. The dishwasher motor caused one of the main fuses to blow. This shut down the dishwasher. When the lawn sprinkler started, the well 240 volt pump pressure switch closed.
This caused the dishwasher to start again only it was in series with the well pump. The dishwasher motor overheated due to the low voltage. The wall and floor was ignited.
A common trip breaker would have prevented this incident.
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: Fuses vs Circuit Breakers
Thats cute, almost funny except for the fire
Why didn't the DW burn its own fuse out?
Thats cute, almost funny except for the fire
Why didn't the DW burn its own fuse out?
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: Fuses vs Circuit Breakers
Its because of things like this that i dont like seeing #14 protected by a 30 amp breaker.Its rare but s--- happens.Never did understand dishwashers having open wiring,but UL thinks its safe.I always think in terms if for some reason that wire draws something other than the amperage it can handle that it will kick a breaker.They were lucky to still have a house.
Its because of things like this that i dont like seeing #14 protected by a 30 amp breaker.Its rare but s--- happens.Never did understand dishwashers having open wiring,but UL thinks its safe.I always think in terms if for some reason that wire draws something other than the amperage it can handle that it will kick a breaker.They were lucky to still have a house.
charlie
Senior Member
- Location
- Indianapolis
Re: Fuses vs Circuit Breakers
Only if it is a common trip circuit breaker. A common two or three pole beaker is actually two or three single pole beakers with a handle tie. The reason for the handle tie is for common switching. The common trip breakers cost a little more and are required to be used on most circuits.
jsinclair
Member
- Location
- Pennsylvania
Re: Fuses vs Circuit Breakers
I would have to agree with the breakers people. I have seen many motors and been called out in the wee hours of the morning many times due to a blown fuse on one phase. The most interesting fuse related problem I encountered was a 225HP motor on a shredding unit that had blown a fuse on phase. The motor single phased and created enough back EMF on the open circuit to make it appear as though it was energized at first glance. (The voltage was just lower.) Needless to say, it caused quite a few problems in the plant. It did however bring to light that a previous contractor didn't properly install the motor disconnects or thermal trips. Got a nice job out of that.
I would have to agree with the breakers people. I have seen many motors and been called out in the wee hours of the morning many times due to a blown fuse on one phase. The most interesting fuse related problem I encountered was a 225HP motor on a shredding unit that had blown a fuse on phase. The motor single phased and created enough back EMF on the open circuit to make it appear as though it was energized at first glance. (The voltage was just lower.) Needless to say, it caused quite a few problems in the plant. It did however bring to light that a previous contractor didn't properly install the motor disconnects or thermal trips. Got a nice job out of that.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Fuses vs Circuit Breakers
On the other hand I feel fuses, dual element time delay, offer the better motor protection, if:
1. The fuses are sized close to the FLA of the motor, say 125%.
2. IEC overloads are used.
Bussman recommends sizing fuses to back up the motor running overload protection. If a motor single phases, a propely sized fuse will open.
The IEC overloads have a differental trip mechanism that on a single phase becomes more sensative to current on the other two.
For an IEC contactor or starter, only fuses offer NEMA type 2 protection. IEC contactors and starters are "delicate" and have to have current limiting fuses ahead of them to protect on a short circuit.
So keep spare fuses, size correctly and you will prevent motor damage.
The maintenance techs at our local paper mills agree that fuses are best. Also Dow Chemical only uses fuses in there MCC's...
On the other hand I feel fuses, dual element time delay, offer the better motor protection, if:
1. The fuses are sized close to the FLA of the motor, say 125%.
2. IEC overloads are used.
Bussman recommends sizing fuses to back up the motor running overload protection. If a motor single phases, a propely sized fuse will open.
The IEC overloads have a differental trip mechanism that on a single phase becomes more sensative to current on the other two.
For an IEC contactor or starter, only fuses offer NEMA type 2 protection. IEC contactors and starters are "delicate" and have to have current limiting fuses ahead of them to protect on a short circuit.
So keep spare fuses, size correctly and you will prevent motor damage.
The maintenance techs at our local paper mills agree that fuses are best. Also Dow Chemical only uses fuses in there MCC's...
brian john
Senior Member
- Location
- Kilmarnock, Va
- Occupation
- Retired after 52 years in the trade.
Re: Fuses vs Circuit Breakers
Jim: I have seen the single phase back EMF on two different occasions......Strange.
As for single phasing any motor of a critical nature should have 3 phase UV relays.
Jim: I have seen the single phase back EMF on two different occasions......Strange.
As for single phasing any motor of a critical nature should have 3 phase UV relays.
- Status