Because many of the equipment a successful grow requires runs @ periods longer than 6 hours, we must factor that into the wiring and equipment that powers the grow, because if we dont, in the least, you will have nothing but problems with breakers and gfci's constantly tripping, and in the worst, will have equipment damage, fires, injury, and even worse things... well now, your probably asking, how does this continuous duty thing work?
well the way it works is for
any equipment that is to be energized for a period greater than 6 hours shall be rated @ 120% of the maximum ampacity... 6 hours or greater of operation is considered a continuous duty cycle, this is done to protect the thermal element inside the breaker/fuse. not only can it cause premature tripping or nuisance tripping, but it can also fuse/weld the breaker shut and cause a failure to trip in a short circuit condition., if you run it @ its maximum rated load with a continuous duty cycle, especially over extended periods of time. the danger is not on the first run, but maybe on the 5th.... by rating your breakers @ 80%, you prevent that. also the wiring itself, has a slight resistance, which can cause it to heat up over extended periods of operation, and this is yet another reason that continuous duty rating must be applied to grow room equipment.
here is a basic demonstration on how a continuous duty calculation is applied to rating an electrical circuit/device:
with a 100 amp breaker, just because the numbers are simple to demonstrate-
100 amp breaker = 100% load = 100 amp
80% load = 80 amps.
80 amps x 120% = 100 amps
you can see you the 120% works now. by rating your breakers @ 80%, your rating your equipment for 120% ampacity, as required by code
multiplying the max amperage by .8 on a breaker, gives you the exact number of amps you can safely run. to find the watts, you can use the equations on the power wheel to convert the amps to watts. the equation works either way. i always use amps myself just because thats just easier for me, ive been doing it long enough i tend to have all the wattage's memorized anyway...
so to size a breaker for a grow op- multiply the max wattage of all connected equipment by 120%. then convert the wattage into amperage by dividing by the voltage.
here is an example: (im just inventing the wattage's, bear with me if there not dead on), for a basic setup, running on 240vac:
3 600 hid lights. max input power = 660w per ballast.
2 fans 45w each
2 pumps, 75w each
timer/contactor 20w
660 x 3
45x 2
75 x 2
+ 20
_________
2240w
x 120%
_________
2688w
2688w/240v= 11.2 amps @ 240v. you always round up to the nearest size so for our examples sake it would be a 15 amp breaker.
to find what you can run on an existing breaker-
multiply the amperage by the voltage by 80%
20 amp breaker, @ 120v... how many lamps can i run on it??
20 x 120 x 80% = 1920w of lighting goodness for your baby girls.
1920w x 120% = 19.2 (always round up, remember?? so its 20 amps.)
and that's how it works, continuous duty rating for any power equation.
common continuous duty grow operation wattages based on voltage, with breaker and wire sizes. all wire sizes are based on thwn-2/thhn Cu conductors with a max run of 300'
breaker size----volts------ max wattage allowed ----smallest wire size allowed
* 15 amp breaker @ 120v = 1440w(12 amps actual) max = #14 awg Cu wire, min
* 20 amp breaker @ 120v = 1920w(16 amps actual) max = #12 awg Cu wire, min
* 30 amp breaker @ 120v = 2880w(24 amps actual) max = #10 awg Cu wire, min
* 40 amp breaker @ 120v = 3840w(32 amps actual) max = #8 awg Cu wire, min
* 60 amp breaker @ 120v = 5760w(48 amps actual) max = #6 awg Cu wire, min
* 100 amp breaker @ 120v = 9600w(80 amps actual) max = #3 awg Cu wire, min
* 15 amp breaker @ 240v = 2880w(12 amps actual) max = #14 awg Cu wire, min
* 20 amp breaker @ 240v = 3840w(16 amps actual) max = #12 awg Cu wire, min
* 30 amp breaker @ 240v = 5760w(24 amps actual) max = #10 awg Cu wire, min
* 40 amp breaker @ 240v = 7680w(32 amps actual) max = #8 awg Cu wire, min
* 60 amp breaker @ 240v = 11520w(48 amps actual) max = #6 awg Cu wire, min
* 100 amp breaker @ 240v= 19200w(80 amps actual) max = #3 awg Cu wire, min
