Which model is it exactly of the HLG-240? if it's the A, the B or the AB model, then they can be dimmed.. A has an internal potentiometer, the B has cables to attach an external one, and the AB has both.. the one that doesn't have any other suffix cannot be dimmed.. So like the HLG-240-48A can be dimmed, the HLG-240-48AB as well.. the HLG-240-48 not..
When i searched google i came across a video of the SF2000, but that had the ELG-240-48A not the HLG model.. that to my understanding has the hole for the dimmer-controller on the bottom, not on the top of the housing..