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About NEOZED fuse
Until they were replaced by circuit breakers, there were fuses in each house. In the industrial sector, the NEOZED system is still widely used today. We explain the design and operation of the corresponding fuses and what was to be observed when handling them.
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What was a NEOZED fuse?
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NEOZED fuse: Design and operation
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Some common operating classes
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The NH fuse switch disconnector
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Our practical tip: When changing fuses, pay attention to protective clothing
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What was to be observed when handling NEOZED fuses?
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FAQ – Frequently Asked Questions about NEOZED backups
What was a NEOZED fuse?
The NEOZED design introduced in 1967 is the more compact successor to the DIAZED fuse. NEOZED fuses are only used in the electrical installation in the residential area as a protection of the power supply of permanently connected devices, for example of flow-through heaters, and were otherwise usually replaced by circuit breakers. In industry, on the other hand, they are often used as overvoltage protection for power tools and machines. NEOZED fuses also perform their service reliably in combination with a motor circuit breaker. A NEOZED fuse is a fuse. The complete fuse device consists of the fuse base and a contact protection above it. The melt or fuse insert, together with the matching adapter sleeve, is inserted in the base. Finally, the fuse insert is secured with the screw cap.

NEOZED fuses are available in three sizes: For size D01, the rated current is 2, 4, 6, 10 or 16 A. The diameter is 11 millimeters, while the length is 36 millimeters. The thread is E 14. The size D02 has an E-18 thread, a diameter of 15 millimeters and a length of 36 millimeters. The rated current can be 20, 25, 35, 50 and 63 A. D03 NEOZED fuses, on the other hand, use an M 30 x 2 thread. The dimensions are 22
Millimeters in diameter and 43 millimeters in length, while the rated current can be 80 or 100 A.
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Illustration of NEOZED circuit
U = voltage source
F = fuse
H1 & H2 = load
NEOZED fuse: Design and operation

Image: NEOZED version
1 = fuse socket
2 = touch protection
3 = adapter sleeve
4 = fuse insert
5 = screw cap
A NEOZED fuse consists of a fusible element designed for a specific nominal current, which is made of electrolytic copper or fine silver. The fuse element is usually surrounded by quartz sand or air. This coating ensures that the resulting arc is cooled when the fuse is triggered. In addition, the contacts (head and foot contact) are located on both sides of the fuse. All these components are held together by the body of the fuse. This consists of insulating material such as ceramic, plastic or composite material and ensures that the arc created inside cannot cause any damage.
And what was happening if the NEOZED fuse link was triggered due to an overvoltage? In this case, the fuse literally blows. The melt conductor is melted by the flowing current. More precisely, the melt conductor changes the aggregate state from solid to liquid to gaseous. In the gaseous state, an arc is finally formed, which interrupts the current flow at the same time. The tripping behavior of device fuses is divided into FF (super-fast), F (fast-blow), M (medium-blow), T (slow-blow) and TT (super-blow). This refers to the response time that a fuse needs to trigger. While an FF fuse already responds to short voltage peaks, fuses with increasing inertia have a greater tolerance in their tripping behavior.
Some common operating classes

NEOZED fuses are divided into different operating classes. Here are some of the most common classes: The standard type for general applications is called GG. The tripping behavior of this type is slow-blow, i.e. slow at low short-circuit currents and fast-blow at high currents. The type GR is intended for the protection of semiconductor components (super-quick-acting). The type GS (super-quick-acting) fuses are also used for semiconductor elements and for line protection. The GF type (quick-acting) is used for industrial plants, power plants or similar. For photovoltaic systems, however, the type gPV is used (super-fast).
The NH fuse switch disconnector

A fuse switch disconnector acts as both a switch disconnector and a disconnector. With such a component, it is possible that a circuit is also disconnected or switched on under load. The functionality is provided until the respective rated current is reached. Protection against overvoltage and short-circuits is provided by fuses. In contrast to a simple fuse, the fuse switch disconnector has the advantage that a voltage-free state can be guaranteed when changing the fuse. Without such a switch, there is a risk of a dangerous arc when a fuse is replaced on a circuit under load. Life-threatening injuries can be the immediate consequence.
Our practical tip: When changing fuses, pay attention to protective clothing
Always wear suitable protective equipment according to IEC 61482 / EN 61482 when replacing a fuse on a circuit under load. Arcing that may occur during the change can cause serious injury.
What was to be observed when handling NEOZED fuses?

In contrast to a miniature circuit breaker, a fuse must be replaced after it has tripped. Bridging, however, is not permitted and can be fatal. It should therefore be left out! Make sure that the new fuse also has the appropriate rated current and the appropriate characteristic curve. If this is not observed, sufficient protection of the connected devices is no longer guaranteed in the event of an overvoltage. Please also note that a fuse is always subject to an aging process. During its life cycle, the tripping behavior of the fuse changes due to current peaks caused when a device is switched on, as well as diffusion processes. An original sluggish fuse tends to become more agile over time.
FAQ – Frequently Asked Questions about NEOZED backups
What was the meaning of the names NEOZED and DIAZED?
The term NEOZED is an artificial word consisting of the words New (Neo), two-part (Z) and Edison (ED). It is therefore a new or new two-part fuse with Edison thread. Also DIAZED is an artificial word consisting of the parts diametrically (slide), two-part (Z) and Edison thread (ED). It is referred to as a diametrically graded two-part fuse with Edison thread.