Hi Chris,
I have not be involved in this argument I’ll call it for over a decade. The common argument for class B given to me decades ago when I worked for a telecom company that sold business/commercial hardware systems was that if a company was located in a High St. shop that had an apartment above it, the business and residential area would both be on the same mains feeder and could be within 3 meters of each other. While that argument could have conceivably been applied for our low end products it was rejected by the company’s management for its mid- to high-end products. We supplied appropriate warnings from CISPR 22/24. We also tested immunity to the higher industrial limits, so the class A emissions and the immunity requirements were in line with each other. We also sold components, boards that plugged into PC-based and other types of commercial servers (remember VME and ATCA?). For those we had internal requirements to meet class B so that the end customer could have a better chance to meet class A with their complete system. We did not sell them as class B though, they were class A with lots of margin. For both systems and components we had internal margins that had to be met, quite large for class A, not quite so large for class B. We never ran afoul of regulators in Europe with our systems rated as class A. We did have one customer who was using our boards in a system they were selling in Italy that had problems with local authorities, but we were able to provide them with a persuasive argument to stay with class A. I think even today class A is quite common for clearly non-consumer applications, though you may find regulators and test labs that advise otherwise. Good luck! Dan From: Chris Wordley [mailto:[email protected]] Sent: Wednesday, March 17, 2021 11:19 AM To: [email protected] Subject: [PSES] EMC emission Class A versus Class B All I’d be interested to hear views on the use of Class A EMC emission limits for equipment that is intended for use in non-domestic (commercial, light industrial) properties; I’m only concerned with the EU situation here. More than one well known manufacturer of test equipment (e.g. oscilloscopes) declares it as EN 61326-1 Class A, with instructions that the item is only intended for use in non-residential areas. Such equipment is often used in workshops, laboratories and service centres, which along with residential properties are listed in EN 61326-1 as examples of a "basic electromagnetic environment", defined as “locations characterized by being supplied directly at low voltage from the public mains network”. EN 61326-1 defines Class A equipment as "equipment suitable for use in all establishments other than domestic and those directly connected to a low voltage power supply network which supplies buildings used for domestic purposes" Is it OK to employ Class A limits for professional test or laboratory equipment even when it will likely be connected to a public mains supply? I realise that EN 55032 only requires Class B for equipment that is intended primarily for use in a residential environment (and for broadcast receivers) and stipulates Class A elsewhere, but most other standards tend to group commercial and light industrial together with residential, and permit Class A only in (heavy) industrial environments. So in what scenarios can Class A limits, in conjunction with a “not for use in residential environment” instruction, be legitimately used for products intended for use in non-residential properties that are typically fed from the public mains supply? Best Regards Chris - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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