You are just fine with that timer a 400 watt lite will pull 3.3 amps well under the rated amp draw of the timer. As long as you do not exceed the 15 amp rating of the timer you will not have a problem. All a timer is, is a switch on or off that all it does except that it is time controled. It will not change the voltage to the light it just turns it on and off. If you every wonder about what amp draw a light will draw just take the watts and divide by the voltage that is being supplied witch in most cases 99.9% of the time to be 120 volts you get the amp draw for example 400 watts divided by 120 is about 3.3 amps. hope this help Bizzy.
bizzy9 Reviewed by bizzy9 on . Question about timers Anything specific to use? I have a timer I bought to run my light, its a "heavy duty" timer, rated I think up to 1750watts, this for a 400 watt light. I plugged it in, but I wasnt sure if the ballast was charging up (which is doesnt really do) or if it was going to fry the hell out of it. Its made by Intermatic, it has a ground, Indoor use only, (growing indoor) It says 15 (A) 1750W "T" "H" "TV-5" "12 FLA (72 LRA) Motor, 125V A.C. 60Hz Hope someone can help... Rating: 5