Hello codys
CE marking applies to the finished product and is a declaration that the product complies with all relevant standards. This includes safety, low voltage directive, EMC etc. It is your responsibility to ensure that the product does comply to all requirements. There is no requirement that I am aware of for individual items to have individual complience requirements, but if you deem it necessary, then so beit.
Obviously, cords switches etc must comply with the appropriate standards, but that is a different issue from having individual CE marks.
In the case of UL and CSA, individual components must be approved before they can be included in the final product.
Be careful with any certification from China, there are some good and some bad certificates and it is very hard to differentiate. I heard of testing labs at a trade show that quoted a price for CE certification based on them doing the testing, and another price (double) for no testing!!
A company that I was doing some work with had a local plant and a p[lant in China. The Chinese wanted to mark their products with CE, UL and CSA on the grounds that the NZ product carrried these marks. They did not believe that they had to get their product tested and approved. The Chinese authority told them that the NZ operation just had to modify the certificates and add the Chinese operation and products.
Ultimately, it is your responsibility to ensure compliance, if you choose to accept a test certificate, you must be able to justify your decision.
Best regards,
Mark Empson