Regulatory: IEC60950 safety classification: need advice

[jandersson]

fire enclosure plastic

Hi,

I'm involved in a protocol converter project. This device has a number of ethernet (100baseTX) ports, and an external power supply. The PCB is mounted in a plastic case with wall mounting "keyholes".

Our regulatory partner claims that the wall mounting keyholes makes the product "stationary equipment" and that the plastics must be made of 5VB fire class material to make the plastic case a "fire enclosure".

I could (almost) understand this if the device was a "primary circuit" but the external power supply classifies this device as "Class III" and "SELV circuit", according to IEC60950 chapter 1.2.4 and 1.2.8, "Classes of equipment" and "Circuits and circuit characteristics".

Are really all DSL modems, hubs, printer servers and similar equipment made out of 5VB plastics? Most of them have this kind of wall mounting keyholes.

Section 4.7.1 of 60950 states two different methods (1&2) to ensure fire safety. I understand the methods as this:
1. Use components, material and wiring which is fire resistant (I will need a fire enclosure), or
2. Test all fault cases on relevant components. (I will not need a fire enclosure).

If I go by method 2 my guess is that I can keep the current enclosure but I will have to specify a number of test cases to the test house.

The power consumption is above 15W so I cannot use the Limited Power Source (LPS) way to get this device approved.

Any help on this subject would be really appreciated. Please share your experience, I really need to understand this to get this project closed.

 

[jandersson]

iec60950

I could really use some help on this.

Will a fuse close to the power input limit the number of components to be tested to
those before the fuse?

Thanks in advance.

 

[eziggurat]

limited power source (lps) iec60950

Hi,

I am currently looking at the IEC 60950. If your system uses external DC supply, it will be class as a limited current circuit. Also if your circuit uses a lot of current like my application, 20A overall but shared among several circuits, I will use a fuse network in fire enclosure suggested by an external expert advice. I will be meeting him in the near future to discuss my application a bit more further to see what else I need to meet the standard.

Added after 2 minutes:

of course overspec your cables and wires for your product possibly twice the current rating and voltage rating to meet electrical and also materials for flammability. I believe PTFE wires meet the flammability.

 

[rogerynt]

Some points and hopefully helps

1.) Plastic normally made of ABS

2.) PCB : 94V0 ROHS

3.) No metal parts e.g. charging pins, jacks etc. can be touched by human body. ( This is a MUST, part of LVD test otherwise the requirement is very tough)

4.) wall mount keyholes : electronic parts, pcb etc must not expose to outside world. The wall mount should be an addition part that click onto your plastic box. Therefore bigs holes only appear on wall mount but not the box itself.

5.) External power supply, do you mean using adaptor ? If yes, the adaptor MUST with CE or UL certificate.