Switch Fuse
- Thread starter Oxia
- Start date
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that looks like an isolator to me 
that looks like an isolator to me
its the only picture I could fine, the question is about the switch fuse versions like a 20A one or 32A one.
mem kxtn is a switchfuse used for fusing down to a smaller cable supply
mem Axtn is an isolator used to isolate motors etc for maintenance
mem Axtn is an isolator used to isolate motors etc for maintenance
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why are fuses used compared to breakers?
Less susceptible to nuisance activation. Arguable more reliable.
Because fuses can withstand load fluctuations, like start load surges and short term overload better than mcbs can.
Mccb's are used for the same purpose but usually have adjustable settings to delay the tripping slightly.
In my experience Mcb's used for sub mains tend to trip too easy when a fault develops on one of the DB's local circuits fed from said MCB
Mccb's are used for the same purpose but usually have adjustable settings to delay the tripping slightly.
In my experience Mcb's used for sub mains tend to trip too easy when a fault develops on one of the DB's local circuits fed from said MCB
Those fused isolator are generally used in industrial and commercial environments, there's nothing stopping one being used in domestic. They have a hole for a proper padlock for locking out for isolation, they also have a visible air gap when the forks are opened inside.
Fuses are more reliable than circuit breakers as a circuit breaker is a mechanical device. It is fairly easy to design systems with fuses an provide discrimination as their energy let through's are a fair chunk lower than circuit breakers, a fuse will disconnect quicker where the fault current is higher whereas a circuit breaker still takes time to open.
Then there is the cost of a fuse over a circuit breaker, a 100A fuse as found in a switch fuse is around £5, a circuit breaker is many times this price.
Fuses are more reliable than circuit breakers as a circuit breaker is a mechanical device. It is fairly easy to design systems with fuses an provide discrimination as their energy let through's are a fair chunk lower than circuit breakers, a fuse will disconnect quicker where the fault current is higher whereas a circuit breaker still takes time to open.
Then there is the cost of a fuse over a circuit breaker, a 100A fuse as found in a switch fuse is around £5, a circuit breaker is many times this price.
K
kai
They are also used where the Short-Circuit Fault Current is too high for a breaker to safely handle.
High SC Fault Currents are likely to be present in commercial and industrial environments, less likely in a typical 100amp single phase household supply.
High SC Fault Currents are likely to be present in commercial and industrial environments, less likely in a typical 100amp single phase household supply.
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