shop lights and amps, i need help

[tjg911]

i have some questions about amp draw with shop lights. i really know nothing about electricity so perhaps my comments below are unfounded? please explain this like you are talking to a child!

my present setup has a 6 year old fridge that the owner's manual states requires 15 amps and it is on a 20 amp breaker. in 2004 i added my grow light stand to that breaker. since it just has 4 shop lights with 8 T8 32 watt tubes i figured that breaker could handle it. so that 20 amp breaker has the fridge drawing a max of 15 amps and the shop lights that use 256 watts. i've done this for 2 years without any problems.

i now want to add more shop lights and i was going to use the same breaker. there is a definite LACK of outlets in my basement! this is where i am getting concerned. 6 more shop lights would add another 12 tubes using another 384 watts. the shop light total would then be 640 watts. the fridge is 15 amps. the breaker is 20 amps. per a google search i found this formula to convert watts to amps ====> AMPS = WATTS / VOLTS. so 640 watts / 120 volts = 5.33 amps and that with the fridge totals a shade more than 20 amps.

while the fridge may normally draw say 8 amps (?) there maybe times it draws say 12 (?) so to be safe the manufacturer suggests a 15 amp breaker (?). i'm guessing i don't know that but i am guessing they have a safety factor in that 15 amp requirement that i don't know. so will my additional 6 shop lights be too close to the limit on that 20 amp breaker or is my amp formula incorrect? i suppose i could use just 4 more shop lights for just an additional 256 watts. then the formula says the 8 shop lights use just 4.25 amps. but with the fridge that is still close to the 20 amp limit.

i think i discussed this with john (jtcm05) on sunday but i don't remember. someone in work suggested doing this. the overhead lights in the basement are on a different breaker and i'm assuming it is also 20 amp tho i will check. so if it is 20 amps all that is presently on that breaker is the 4 basement ceiling lights (100 watts each but i usually only have 2 of them on), the 2 garage ceiling lights at 100 watts each which are seldom on, the 2 garage door openers (not sure what they draw), the motion detector spot lights i think they are not more than 200 watts each which are rarely on and an outside GFI outlet i seldom use. if all those lights were on at once (8.3 amps) + all 10 shop lights were on (5.3 amps) i would draw 13.6 amps leaving room for the 2 garage openers to use about 6.4 amps before the 20 amp total is hit. so my coworker said to replace the base that 1 of the ceiling light uses with a base that has an outlet you can plug into. that would allow me to plug in the power strip with the shop lights. i may have to buy a new power strip that'll handle 10 plugs and the amps that draws, my current strip has just 6 plugs. to hook another power strip to that power strip may run more current thru it than it is designed for. a variation on this option is to change 2 ceiling light bases to have the plug. i then could plug each power strip into a different base. that would put 4 shop lights on 1 ceiling base and 6 shop lights on the other ceiling base - it is still all on the same breaker which will handle the draw. so the replacement of 2 ceiling lights' bases putting each set of grow light stands on a different outlet all on that breaker with minimum use seems like the best method.

am i rambling or does all this make sense? suggestions and comments about all these concepts would be appreciated.

thanks,

tom

[bonekittyslug]

Tom,

I am no expert, but it seems to me your basic reasoning is reasonably sound. Good work! However, please let me throw in a bit more.

Alternating current (AC) comes out of your wall socket. The formula AMPS = WATTS / VOLTS is actually only valid for Direct Current (DC) such as a car battery.

A more proper term for AC WATTS would be VOLT-AMPS.

Confused? Relax, point is WATTS and VOLT-AMPS are not the same between AC and DC.

On some of the flourescent lights I've seen say to multiply the tube watts (32 for 1 tube) by 1.25 to get VOLT-AMPS. So 1 tube would actually not be 32 WATTS, but actually 40 VOLT-AMPS.

Your first set-up would be closer to 320 VOLT-AMPS, not 256 WATTS. Second set-up would be closer to 480 VOLT-AMPS, not 384 WATTS.

Combined that would be about 800 VOLT-AMPS or approximately 6.66 AMPS.

Combined this may work on either breaker you mentioned. May be a bit much for being on with fridge. The other circuit depends on how many lights and garage openers are on at the same time.

Things are usually safer if you figure worst case.

If I were doing it I believe I would leave first set-up as is, since it's been working. And, put second set-up on breaker with garage openers. Sounds safer to me, by splitting up the load.

Did this make any sence, man my head hurts when I have to think!

[tjg911]

thanks mark. beleieve it or not i do understand what you said. i thought those calcs i found via google were for ac i never considered dc! see if someone told me to put in a new breaker in the panel that's where i claim dummy status! i don't understand electricity but can rewire a lamp or those bases, that's just common sense. so i wanted to avoid a lot of technical stuff just in case.

i think putting all 10 sets on the #1 breaker, the one with just minor things that seldom are on at the same time, makes the most sense. i also found out home depot sells an adaptor that has an electrical plug and a light bulb socket that screws in the existing spot the current bulb is in. a guy here in work has bought them and is using them so it is available. that's take 5 seconds to install,. i'll get 2 and put each power strip into a separate plug but all on #1 breaker.

thanks for your reply.

tom

[clay199]

If it were me, and all that stood between my seedlings success or failure was a beer fridge? I have and did throw the useless electrical appliance out.

[geol]

Tough choices!

[tjg911]

Originally Posted by clay199

If it were me, and all that stood between my seedlings success or failure was a beer fridge? I have and did throw the useless electrical appliance out.

clay it is not a beer fridge, i store potatoes, onions, rutabagas, carrots and winter radishes it in. i need that fridge it is not incidental, the extra seedlings are superflous but nice to have.

john, i don't want to pay an electrican to install another breaker and run wires and install outlets. they charge $75 to come then $45 per hour. i know this cuz last winter i had one come over. i'd never do this myself cuz i don't like messing with electricity. i left work early due to the storm yesterday and spent all afternoon rearranging the basement! what a job but after 5 hours i have a good sized space freed up so i now have the room to put the extra light stand down in the basement. those inserts into the ceiling light sockets will work. i just wish i'd had boxes put on each wall during construction.

tom