If you manufacture electrical components or equipment, you will eventually have to submit them to UL Certification Service. Be prepared: these organizations are testing and certification companies and will not provide design assistance. When you are ready to market your component or electrical product, the need for CSA or UL certification will be one of the major hurdles to cross. This means you need to be ready. You can't afford test failures, or a long engineering letter telling you which clauses of the standard your product does not comply with.