House appliance fires spark fuse holder standard change

September 19, 2016 // By EDN Europe
David Pike, Product Merchandiser – IP&E, RS Components
In the same way that a huge forest blaze can be caused by the smallest of sparks, household appliances have caught fire due to relatively small current overloads. But how is this possible when all household appliances have protection from current overloads, I hear you say? As it stands, current overload protection is not always adequate and below I’ll explain why.

All household appliances that comply with international safety rules use fuse holders or appliance inlets with integrated fuse holders. Designed to contain, protect and mount fuses, these come in various shapes and sizes and can be found in vertical or horizontal alignment, screw-in, snap-in, soldered, DIN-Rail mountable, drawer or clip form, and are rated for voltage, current and accepted power. Fuse holders are available both with and without integral protection against electric shock, the latter being for applications with additional means provided to protect against electric shock. For those with integrated protection, the fuse holder has an important safety role to play as the users’ first defence against direct contact with live parts.

There are three main standards related to fuse holders for electrical appliances for indoor use: the International Electrotechnical Commission standard IEC/EN 60127-6, the North American Underwriters Laboratories (UL) standard no. 4248-1 and the household appliance standard IEC/EN 60335-1. In response to growing concern about fuse holder design and use, IEC/EN 60127-6 has been revised to improve fire safety. According to fuse holder specialist SCHURTER, the original IEC standard (04/1994) focused specifically on contact protection and did not pay much attention to fire safety. Whilst defective parts, faulty electrical connections or electrical arcs when switching contacts can be blamed for many fuse holder-related incidents, significantly the new fuse holder standard sets higher glow-wire temperature requirements for the insulating material used.    

DD11 entry module with fuse drawers (source SCHURTER)

The changes to IEC/EN 60127-6 mostly impact fuse holder and appliance inlet manufacturers, who are now required to test glow-wire resistance and replace the materials used with more glow-wire resistant material to achieve increased temperature requirements. If the glow-wire material changes, these components will need to be re-tested (i.e. the material tests according to UL 4248.1 must be repeated). In addition, the components will now have to be endurance-tested both horizontally and vertically (they were previously only tested horizontally and in the intended installation position).

1) Specimen

2) Glow-wire

3) Flame

4) Tissue

5) Cotton

Different test methods according to IEC 60695 and UL 94-V (source: SCHURTER)

From October 2017, fuse holder manufacturers will only be allowed to market products that have been tested and authorised in accordance with the updated standard. Notably, the standard also affects IEC appliance inlets and power entry modules with and without EMC filters, if they have a fuse drawer. Approximately 80 of SCHURTER’s products are concerned and the company is committed to ensuring that updated versions that meet the new requirements will be in place by October 2017.

For domestic appliance manufacturers of products that contain fuse holders, IEC appliance inlets and power entry modules with or without EMC filters that have a fuse drawer, it will be necessary to ensure that end products meet the standard changes in place by October 2017. During the transition period, it is also important to recognise that fuse holder and appliance inlet components supplies will be subject to change. A knowledgeable supplier such as RS Components will be able to advise you on your fuse holder selection to help