As my grow gets larger, more equipment is being added and it has me wondering how much more power my room can take. I recently moved everything to a new room inside a 4x8 tent. In the old room there were quite a few electrical outlets I could use, but in the new room there is only two spots to hook up two 400 watters, 400 and 100 cfm fan, fans to move air around in the tent, and some supplemental cfl lighting I am having to use right now. I plan to add a third 400w light, or switch to two 600's. Should I be thinking more seriously about calling an electrician, it's definitely not my thing. Any advise is greatly apreciated!
If you have multiple outlets on the same circuit, you must account for ALL loads in that circuit. Find the breaker for those outlets and all the loads on that circuit. The max circuit amps should be only 80% of the amp rating on the breaker. (IE a 25 amp breaker can safely carry 20 amps through the circuit) To find the amperage of your circuit, a VOM multimeter or an Ammeter would be your best bet. To mathematically calculate it, Watts = Amps X Volts 400 Watts divided by 120 Volts = 3.33 Amps However the amperage can increase on initial startup, this is called inrush current. The increased inrush current could pop your breaker(or worse) with multiple lights starting at the same time. So to be safe rather then sorry, buy a cheap Amp meter at home depot ($20) and check your amperage on both lights and your fan. If the breaker controls the entire room (overhead light, both 400W lights, and a fan) you are likely close to the limits of that circuit.