Yes, Omron D3D series. And I also have a similar looking switch on my HVAC air handler in the primary circuit made in 1995 for US (probably no CE). I am concerned not only with the issue of inadvertent activation but also the operational acceptability (min operations). Hence the questions about the applicable switch standards. But I don’t know if the argument presented where reactivation buy closing the switch by itself is not normally possible stands up. The challenge with concealing behind a small hole is keeping the equally small switch actuator protrusion from becoming a hazard itself. For example when used with a hinged guard that opens up to avoid a hand getting a good jab when the cover is closed. There are ways to do it with the right mounting arrangements and offsets.
thanks -Dave From: IBM Ken [mailto:[email protected]] Sent: Wednesday, June 11, 2014 1:05 AM To: Nyffenegger, Dave Cc: [email protected] Subject: Re: [PSES] Safety Interlock Switches I had a very similar situation. Are you using a C&K or Omron switch? I also remember seeing the switch and thinking it looks like the door light switch from an old refrigerator. I have a very similar-looking switch in my home oil furnace (which is from the 1980s) What we did was put the switch inside a little metal enclosure with a small hole on the top. The panel then had a small metal protrusion which reached inside the hole, this way the test finger could never actuate the switch. You could try to take your designer's argument to your NRTL, but I doubt they will accept it; I think the point is not that someone's finger slips onto the switch accidentally and activates it, but rather - a service person wants to see if the product he just worked on will start up and so pushes in the interlock to see if what he fixed/replaced worked. -Ken On Tue, Jun 10, 2014 at 11:39 PM, Nyffenegger, Dave <[email protected]<mailto:[email protected]>> wrote: Hi folks, I'm reviewing a design for some medium duty office/business equipment which handles mail and is subject to the Machinery and Low Voltage Directives i.e. EN 60950-1 and EN 60204-1. The design is using an interlock switch which I think is more suitable for turning the light on/off in a refrigerator. The switch is in the secondary low voltage circuit to operate the main contactor coils. It's only rated for 50K min operations (electrical) and is approved to UL 1054 and VDE EN 61058-1. The electrical specs are fine for the application. I'm not familiar with these standards so one question is if those standards in anyway qualify or disqualify (by using the switch in a way not intended) the switch for use as a safety interlock. I thought I read in one of the safety standards that interlock switches should be designed/rated to last the lifetime of the equipment (based on some estimate of number of operations in application). But I haven't been able to find that. Does that sound familiar to anyone? My estimate is that 50K operations is much lower than the number of operations over the lifetime of the equipment. A similar older switch is only rated by the manufacturer for 6K operations. EN 60950 2.8.7 basically requires a minimum of 10K operations the way I read it. Am I right in thinking the 6K switch would not be suitable for interlock usage regardless of other aspects? These switches have plungers that can be easily finger operated once the guards are opened. EN 60950-1 says that interlocks must be designed to prevent inadvertent reactivation and that the ability to operate the interlock with a test finger is considered likely to cause inadvertent reactivation of the hazard. The argument from the designer with this switch is that once the guard/interlock is open, reclosing the interlock by itself will not re-energize the protected circuit and therefore there is no inadvertent reactivation. This is because the control circuit requires operation of another start switch in order to energize. This assumes there is no concurrent failure of the control circuit while the interlock is being manually overridden, one person can't operate/reach the start switch and override the interlock at the same time, and no second person operating the start switch while someone is overriding the interlock. My question is if this argument actually holds with! out violating the EN 60950 requirement. thanks David P. Nyffenegger, PMP, SM-IEEE - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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