If you can possibly use a certified module, do it - certifying a unit from scratch can run to hundreds of thousands, and that's per certification. And if you do use a pre-certified unit, then make sure you follow all the design and implementation guidelines and can show it otherwise the cert can be rendered invalid
If you can possibly use a certified module, do it - certifying a unit from scratch can run to hundreds of thousands, and that's per certification. And if you do use a pre-certified unit, then make sure you follow all the design and implementation guidelines and can show it otherwise the cert can be rendered invalid