Who is the electrician here? Who deals with this kinda stuff everyday? His cabinet is metal, how is that going to start on fire? As long as he isn't stupid about how he does this there will be no fire hazard if the light is on and the exhaust is off.
finally.Good thing there's nothing flammable inside the growbox.
I'm done here, good luck with your quest for stealth.
finally.
You would think hes your son or something. Im sure hes well aware of the fact that the lamp gets hot.
WOW I think you got it back wards ( just suggesting ok ) black=power in red brown is switched coming out then feed the power to the rely this will move the contacts and open it or close it which ever you select but black should be power in to the sensor ( but I am not there to help sorry ) I hope you get it sorted out