We discussed this before. If the transformer is part of the building wiring you need to ground the secondary, with few exceptions. If it is a cord and plug connected appliance you don't. (that was where I went wronmg the last time it was discussed) It is very common that a lab work bench supply is flaoting but this is a cord and plug cionnected appliance, not building wiring. We had the same situation with our compressor at the shop. The whole assembly was behind a 5-15 plug.