Does the vehicle engine have to be running for the fridge to work?

No, all our fridge vans have "electric standby". We supply them with a cable that can be plugged into 13A domestic mains electricity. This is ideal when the van needs to be parked while loaded, overnight or during a catering event.

By contrast, the refrigeration on heavy trucks is usually powered by a separate engine (like a built-in generator) which draws from the main diesel tank. In a static position, a full tank may last 4 or more days before a refill is required. Alternatively, they can be run on electric but require a 32A 3-phase industrial supply.