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Growroom Electricity and Wiring
- Thread starter Phillthy
- Start date
madpenguin
Member
Yea, you want the 4 prong receptacle and plug so you can isolate neutral and ground in your sub.... That's the only reason really.
rooted
Member
i'll be adding a seperate box with a relay/digital timer rather than use a 240 mechanical timer
when i wire in the relay, should i use the white to ground the relay box and discard the bare? or does the neutral come into play here somehow?
i couldn't get the proper ground bar today so i'll have to postpone til tomorrow......plenty more to be done around here though, back to work.........
mmmm velvet
when i wire in the relay, should i use the white to ground the relay box and discard the bare? or does the neutral come into play here somehow?
i couldn't get the proper ground bar today so i'll have to postpone til tomorrow......plenty more to be done around here though, back to work.........
mmmm velvet
madpenguin
Member
Well, then it sounds like you want to do something like this:
http://www.hydroponics.net/learn/grow-light-controller.asp
What I would try to do is put the relay inside your sub panel. Hopefully you have room for it.
If you need 120v power on 24/7 in the subpanel, then I would probably only hook one hot leg of the incoming 10/3 to the DP relay and then hook the other hot to one of the main lugs in your panel. That would give you every other breaker slot a 24/7 on. Then you jumper from the other side of the relay from the switched #10 hot over to the other lug on the MLO panel....
The down side is that your not killing both hots of your 240v loads at the same time. I'd have to think about that one for a bit and any repercussions it might have.
Having only one hot leg going to a 240v ballast shouldn't affect anything negatively.... It just won't turn on until the timer trips the relay which in turn would fire up the other half of your subpanel....
I just woke up. Let me digest my coffee some more, but doing something like that should work. For any 120v receptacles attached to the subpanel, make sure you stab a single pole breaker onto the hot buss that is fired up 24/7....
Don't use a screw for your grounding point like that tutorial shows. That's kinda chincey. Especially if your going to throw the relay in the subpanel, buy a grounding bar like you were already going to and terminate all grounds there. No neutral should land on that what-so-ever, else you'll get objectionable current on the frame of the panel along with providing a parallel path for returning current to travel back to the main on (the bare #10 grounding conductor).
Also, get a steel brush or one that attaches to a drill even and sand all the paint off the inside of the subpanel for where you attach your grounding bar. It's required by code believe it or not.
If your going to do it, then do it right. Besides, the satisfaction you'll get once your done will be well worth the effort involved.
http://www.hydroponics.net/learn/grow-light-controller.asp
What I would try to do is put the relay inside your sub panel. Hopefully you have room for it.
If you need 120v power on 24/7 in the subpanel, then I would probably only hook one hot leg of the incoming 10/3 to the DP relay and then hook the other hot to one of the main lugs in your panel. That would give you every other breaker slot a 24/7 on. Then you jumper from the other side of the relay from the switched #10 hot over to the other lug on the MLO panel....
The down side is that your not killing both hots of your 240v loads at the same time. I'd have to think about that one for a bit and any repercussions it might have.
Having only one hot leg going to a 240v ballast shouldn't affect anything negatively.... It just won't turn on until the timer trips the relay which in turn would fire up the other half of your subpanel....
I just woke up. Let me digest my coffee some more, but doing something like that should work. For any 120v receptacles attached to the subpanel, make sure you stab a single pole breaker onto the hot buss that is fired up 24/7....
Don't use a screw for your grounding point like that tutorial shows. That's kinda chincey. Especially if your going to throw the relay in the subpanel, buy a grounding bar like you were already going to and terminate all grounds there. No neutral should land on that what-so-ever, else you'll get objectionable current on the frame of the panel along with providing a parallel path for returning current to travel back to the main on (the bare #10 grounding conductor).
Also, get a steel brush or one that attaches to a drill even and sand all the paint off the inside of the subpanel for where you attach your grounding bar. It's required by code believe it or not.
If your going to do it, then do it right. Besides, the satisfaction you'll get once your done will be well worth the effort involved.
madpenguin
Member
Man, I really wish I had the spare money to go out and buy all this shit and make a tutorial of my own. Not only would it be fun, but I'd also need to return everything once I'm done because I'm piss broke right now.
Between what I've said above and what that tutorial shows, you should be able to decipher how to do it... Just read and re-read everything here and on that link and it should all start to make sense.
Between what I've said above and what that tutorial shows, you should be able to decipher how to do it... Just read and re-read everything here and on that link and it should all start to make sense.
rooted
Member
now i'm slightly confused....what's the advantage to having one of the lugs tied in to the relay?....i want the relay to control only the (4) 240 outlets..... it seems to me that the relay should only be on the lamp side of the breaker (even though there are other breakers upstream)
???
i was going to run the two hots from the 30a breaker out to the relay, run the white from the ground bar in the sub to a ground bar in the relay box, and leave the bare out. that's why i was questioning where/if the neutral comes into play here. is there something wrong with this? seems logical to me
out of curiosity, if the 30a trips down here will it trip the 30a upstairs at the main also?
sorry for all the trouble bro, i know it's a pain in the ass....but i'm not willing to compromise safety or security.
???
i was going to run the two hots from the 30a breaker out to the relay, run the white from the ground bar in the sub to a ground bar in the relay box, and leave the bare out. that's why i was questioning where/if the neutral comes into play here. is there something wrong with this? seems logical to me
out of curiosity, if the 30a trips down here will it trip the 30a upstairs at the main also?
sorry for all the trouble bro, i know it's a pain in the ass....but i'm not willing to compromise safety or security.
madpenguin
Member
No, you tie the 120v neutral onto the relay just like the picture on that tutorial shows. Again, NEVER, NEVER terminate a neutral onto a dedicated grounding buss. That relay shouldn't close the contacts unless you have the hot on the top center screw and the neutral on the center bottom screw. The 4 outside screws are your line in and load out contacts.
Go read that tutorial I linked to and you will begin to understand how it's wired. Without terminating your 120v neutral to one of the center screws on the relay, the circuit will not complete and the contacts will not close on the relay to make the connection from your always hot 10/3 cable to the jumpers on the other side of the relay that will feed your two hot lugs in the panel.
I realize you want to run 240v lights, but are you going to run air pumps, sump pump and fans and shit off another circuit that is already in the room?
If all you want to use the subpanel for is for your 240v lights, then, sure, go ahead and hook both hots from the 10/3 to the outside right hand side of the relay, hook #10 jumpers to the outside left hand side of the relay that will feed the hot lugs in your sub panel, then you'll have 2 center contacts left on the relay. this is for your low voltage signal powered by a regular 120v cord. That is what gets terminated to the center screws. Plug your timer into the wall and then plug the other end of the 120v center contact cord into the timer.
When ever the timer kicks on, the relay contacts will close and your subpanel will be fired up. This is really the ideal way to run lights is by using a relay. Pluging individual HID lights into those cheap digital timers is a recipe for disaster.
This way, the only load the timer is seeing is like a watt. Maybe 20 watts. I don't know. It takes an insanely low amount of power to close those relay contacts. That way, your guaranteed to never fry a timer by plugging lights directly into it.
Go read that tutorial I linked to and you will begin to understand how it's wired. Without terminating your 120v neutral to one of the center screws on the relay, the circuit will not complete and the contacts will not close on the relay to make the connection from your always hot 10/3 cable to the jumpers on the other side of the relay that will feed your two hot lugs in the panel.
I realize you want to run 240v lights, but are you going to run air pumps, sump pump and fans and shit off another circuit that is already in the room?
If all you want to use the subpanel for is for your 240v lights, then, sure, go ahead and hook both hots from the 10/3 to the outside right hand side of the relay, hook #10 jumpers to the outside left hand side of the relay that will feed the hot lugs in your sub panel, then you'll have 2 center contacts left on the relay. this is for your low voltage signal powered by a regular 120v cord. That is what gets terminated to the center screws. Plug your timer into the wall and then plug the other end of the 120v center contact cord into the timer.
When ever the timer kicks on, the relay contacts will close and your subpanel will be fired up. This is really the ideal way to run lights is by using a relay. Pluging individual HID lights into those cheap digital timers is a recipe for disaster.
This way, the only load the timer is seeing is like a watt. Maybe 20 watts. I don't know. It takes an insanely low amount of power to close those relay contacts. That way, your guaranteed to never fry a timer by plugging lights directly into it.
madpenguin
Member
Wait.... Your white neutral from the 10/3 romex needs to terminate directly to the floating neutral buss in the subpanel. Your getting me confused now. Your only switching the hots via the relay. Using 10/3 romex will give you 120v and 240v in your panel. If all you wanted to use the subpanel for is to power strictly 240v loads, then you wasted your money on 10/3. Should have just got 10/2 romex. In that case, you also wouldn't need a 4 prong receptacle and plug.
It shouldn't trip the main 30A breaker. Your putting a 30A double pole breaker in the subpanel? Your going to need to use 30A rated receptacles coming off the sub then....
I think you need to clarify just what it is you want to do from start to finish in minute detail.....
rooted
Member
i completely understand how a relay works, like i said i've built flip flops before, and i now realize it's a stupid question, seems like my inquiries are more confusing than the actual project at hand lol
i will take back the 30a breaker and trade for a 20a
i do need 120 circuits so the 4 prong stays
i will take back the 30a breaker and trade for a 20a
i do need 120 circuits so the 4 prong stays
madpenguin
Member
O.k.. You confused me with the neutral question. Wasn't sure which neutral you were talking about. The low draw SJO/timer/relay neutral or the #10 feeder neutral. Either way, NO neutral gets terminated to the grounding bar. Only green and bare grounding conductors go there.
Yes, putting your relay after the breaker in the sub would be the best option. Don't know why I was fixated on using the relay to fire up your sub.
I forget what your light load was intended to be now... Was that 4 - 1kw lights? Your going to be pushing it on that 30A dryer run.
So, if you are using 4 - 1000w lights, then I would use 2 individual 15A double pole breakers in the sub. 2 lights on each (that would also mean 2 relays).
If you don't want 2 relays, then stick with a double pole 30A in the sub, use #10 to the relays and then #10 from the relays to 30A rated receptacles. Don't let anyone here tell you that's overkill (30A receptacles to power one 5A 240v ballast). If you use a 30A OCPD, then you MUST, MUST use wire rated for 30A and receptacles rated for 30A REGARDLESS of the load served. That's why I'm suggesting 2 - 15A double pole breakers with 2 lights on each. Even then, I would probably use #12 the whole way and definitely use 240v receptacles so you don't accidentally plug any 120v appliances into those.
And then you'll really only have the power left over for about 4A if you want to keep your feeder cool. That 4A can be used by a single pole 15A breaker for your 120v loads. I suppose you could go an amp or 2 higher but try not to exceed 26A on the 10/3 run to the dryer receptacle. I would also use #12 on the 15A single pole breaker. The cost difference between #14 and #12 is extremely minimal. Especially considering all your receptacles will be affixed to the sub in boxes, we are talking just a couple feet worth of THHN. Don't strip #12 romex, go out and buy a few feet of red, black, white and green individual THHN conductor.
Even tho romex contains 90 degree celcius rated wire, it has no identifying marking on the insulation, therefore, technically can't be used as individual conductor. I'm getting nitpicky with you but it's code. Adhere to it or not. Up to you.
But it sounds as if you have a good handle on things. Post some pics when your done so others may benefit.
Yes, putting your relay after the breaker in the sub would be the best option. Don't know why I was fixated on using the relay to fire up your sub.
I forget what your light load was intended to be now... Was that 4 - 1kw lights? Your going to be pushing it on that 30A dryer run.
So, if you are using 4 - 1000w lights, then I would use 2 individual 15A double pole breakers in the sub. 2 lights on each (that would also mean 2 relays).
If you don't want 2 relays, then stick with a double pole 30A in the sub, use #10 to the relays and then #10 from the relays to 30A rated receptacles. Don't let anyone here tell you that's overkill (30A receptacles to power one 5A 240v ballast). If you use a 30A OCPD, then you MUST, MUST use wire rated for 30A and receptacles rated for 30A REGARDLESS of the load served. That's why I'm suggesting 2 - 15A double pole breakers with 2 lights on each. Even then, I would probably use #12 the whole way and definitely use 240v receptacles so you don't accidentally plug any 120v appliances into those.
And then you'll really only have the power left over for about 4A if you want to keep your feeder cool. That 4A can be used by a single pole 15A breaker for your 120v loads. I suppose you could go an amp or 2 higher but try not to exceed 26A on the 10/3 run to the dryer receptacle. I would also use #12 on the 15A single pole breaker. The cost difference between #14 and #12 is extremely minimal. Especially considering all your receptacles will be affixed to the sub in boxes, we are talking just a couple feet worth of THHN. Don't strip #12 romex, go out and buy a few feet of red, black, white and green individual THHN conductor.
Even tho romex contains 90 degree celcius rated wire, it has no identifying marking on the insulation, therefore, technically can't be used as individual conductor. I'm getting nitpicky with you but it's code. Adhere to it or not. Up to you.
But it sounds as if you have a good handle on things. Post some pics when your done so others may benefit.
rooted
Member
well, two relays is out of the question due to budget restrictions. i'm way over budget on this room somehow (i already had most of the equipment!)
yes i do need to power 4k, but as far as the leftover 4a for the 120v, the only thing that's going on that circuit is a 6" vortex and a couple small pumps.
i couldn't find any regular 30a outlets, just dryer receptacles, so again, out of the question due to budget
i'm going out on a limb here and wiring it up. seeing that i've run flip flops for years at my old house with 1k's plugged to #14 fed 20a 120v receptacles, and the fact that all my ballast power cords are #14 anyways, i'm going to say that it's going to get the job done safely as-is.
with that said, i don't want you to feel like i'm outright ignoring good advice. you're going by code and i can't argue with that; but given my budget and time frame i feel like i'm making the right decision. that's why i do all this researching and brain picking, so i can make a well thought out decision that suits my situation
this thread/you penguin are priceless. to have a resource like you and all the other good folks here at ic, in times of need like this, almost brings a tear to my already glassy eye
and i'll take pics for sure
yes i do need to power 4k, but as far as the leftover 4a for the 120v, the only thing that's going on that circuit is a 6" vortex and a couple small pumps.
i couldn't find any regular 30a outlets, just dryer receptacles, so again, out of the question due to budget
i'm going out on a limb here and wiring it up. seeing that i've run flip flops for years at my old house with 1k's plugged to #14 fed 20a 120v receptacles, and the fact that all my ballast power cords are #14 anyways, i'm going to say that it's going to get the job done safely as-is.
with that said, i don't want you to feel like i'm outright ignoring good advice. you're going by code and i can't argue with that; but given my budget and time frame i feel like i'm making the right decision. that's why i do all this researching and brain picking, so i can make a well thought out decision that suits my situation
this thread/you penguin are priceless. to have a resource like you and all the other good folks here at ic, in times of need like this, almost brings a tear to my already glassy eye
and i'll take pics for sure
madpenguin
Member
Stick with the DP 30A on #10 wire then. Atleast to the relay. That much should be common sense. If you want to run 4 individual sets of #14 from the load side of the relay to 4 20A pass through receptacles then that's up to you.
That's good. Try to stay as close to 24A as possible.
You should be able to find 6-30R receptacles at Lowes. If for some reason you can't, then your local electric supply house will. And they are not that expensive, but again.... Do what you will. I hope your money saving tactics don't come back to bite you. I used to walk by someones house every day who had their pitbull tied up in the front yard. Tried to get me every time but couldn't reach the sidewalk. One day that fucker was off his chain and harassed my ass all the way down the street. If I didn't know the proper way to deal with aggressive/loose dogs, I would have been toast.
The moral of the story.... Just because it hasn't happened yet doesn't mean it's never going to... Again, up to you.
I'm a big fan of overkill as I'm sure you can tell, especially when it comes to my home. I spent thousands on my attic build out and it's a small 10x10x7 room. It paid for it's self by the second harvest..... Money really shouldn't be a factor in our biz.... Of course you may just be growing for personal... But somehow 4kw tells me your not... ;-)
Either way, stay safe.
rooted
Member
ok, will check lowes tonight before they close since it's so close 
i know you're just trying to make this as safe as possible given the circumstances, so if i can't find them at blowes i'll wire everything but the 240 sockets and pick them up tomorrow.
got the receptacle in the wall today and tested fine....didn't do anything else because i can't find my damn strippers....another $20 down the drain
be back later with results
PS if i find the 30a receptacles i'll spring for the #10 solid too
i know you're just trying to make this as safe as possible given the circumstances, so if i can't find them at blowes i'll wire everything but the 240 sockets and pick them up tomorrow.
got the receptacle in the wall today and tested fine....didn't do anything else because i can't find my damn strippers....another $20 down the drain
be back later with results
PS if i find the 30a receptacles i'll spring for the #10 solid too
mr-natural78
Member
OK. I have a question and I don't understand some of this stuff. I want to run dedicated circuits for two grow spaces. A flower room containing two 1K lights and a veg room containing just one 1K. Both spaces are right next to each other in a basement and only about 15 ft. from the breaker panel. I'd like to stay with 120v because I have those cords for my ballasts. From the reading I've done I think I need to put in a 30A breaker for the flower room and use 10g wire. I also know I need 30a receptacles. Since the 30A receptacles are different than the basic 3 prong plug on my ballasts couldn't I chop the plug off and wire a 30a plug on the end? Also...I'm confused about what wire to use. Is 10/2 what I need? What is the difference between 10/2 and 10/3? If I understand this correctly, I would use 10/2 for 120v and 10/3 for 240v? Is that correct? For my veg room with only one 1K light I think I should use a 20a breaker and 12g wire. Am I on the right path here? Do you think it would be better to run a 240v circuit to my flower room and the two 1k's or would 120v with 30a be ok? I think the 240v cords for my SS-1 ballasts are only like 10 bucks. I don't have any experience with 240v though and I do have a small amount of experience with 120v and am much more comfortable dealing with that....but all I've ever done is changed some receptacles, replaced an old ceiling fan...stuff like that. I really need some help and want to get this done soon. I don't think my current set up is very safe.
madpenguin
Member
ok, will check lowes tonight before they close since it's so close
i know you're just trying to make this as safe as possible given the circumstances, so if i can't find them at blowes i'll wire everything but the 240 sockets and pick them up tomorrow.
got the receptacle in the wall today and tested fine....didn't do anything else because i can't find my damn strippers....another $20 down the drain
be back later with results
PS if i find the 30a receptacles i'll spring for the #10 solid too
Hah, hah.... And I just got back on here to "harp" some more about the importance of using the right gauge wire and receptacles for the breaker that controls the circuit....
I'm going to anyway, even tho you've decided to atleast make an effort to look for the right materials.
Here is a case in point. It's so minor that most everyone wouldn't think twice about it, but it IS a big deal.
Was punching in some kitchen coutertop GFCI receptacles in a home that was pending sale. One of those Home Inspector "TODO" lists before the house is sold. While inside a double gang box that has a receptacle and a light switch for the recessed cans above the sink, I noticed someone had added the lights at a later time and used #14 to tie onto the existing #12 countertop receptacle run....
The house was wired in the early 80's so the #12 was white. An easy mistake for people to make. They see white wire and just assume it's #14. Anyway.... It was either rewire the switch leg goinng up to the cans with #12 or derate the breaker down to 15A... I chose the later.
YOU CAN NOT USE LESSER GAUGE WIRE ON A CIRCUIT THAT ITS NOT RATED FOR. THAT ALSO INCLUDES THE AMPERE RATING OF THE RECEPTACLES
The entire circuit from breaker to receptacle has to be rated for the same amperage. No exceptions!!! Please don't take that cavalier attitude that "it'll be ok" because one of these days, it aint' gonna' be ok and you'll be in your front yard with a stick and some marshmellows singing koom-by-ah my lord.
Taps are about the only thing I can think of off hand where it's ok but taps can be semi confusing to explain and it's not really relevant here anyway....
I'm especially suprised at the "electricians" on this board who advocate using 20A pass through receptacles on a 30A circuit with #14awg wire, "just because that ballast only draws 5 amps". Who cares? This is what we call plug-and-cord loads along with fixed receptacles. That means anyone at anytime can plug whatever they want into that receptacle, such as an AC unit or overly large dehumidifier. Guess what happens when that #14 wire, 20A receptacle and 30A breaker starts to see over 15A worth of current? Your circuit is only rated for it's weakest link. That includes little tiny pieces of pigtails that you may connect to the receptacle. Everything, from start to finish, has to be rated for 30A if your going to slap a 30A breaker on it. No exceptions.
Anyway... You guys kill me sometimes.... I'm literally popping xanax over here.... (but only partially because of you guys. I need it period...).
madpenguin
Member
Ugh.... You ran premise wiring to a portable subpanel?
Say it aint' so.
Now I really am pickin' on ya'.... 
Or was that a dedicated old-worked circuit from the main panel?
madpenguin
Member
First off, all good questions so I'm going to go into probably more detail than you want for the sake of others with the same questions.
Ah... Easy then. The joys of growing in a basement.
That would be correct. A 1kw lamp @120v will draw anywhere from 9-10A. If you have 2 of them, that'll be around 20A. Since the lights are on for more than 3 hours at a time, they are considered to be a "continuous load" and the branch circuit feeding them needs to be derated to 80% of it's total capacity or 125% of the actual load. The math works out the same either way you do it. 12A on a 15A breaker, 16A on a 20A breaker and 24A on a 30A breaker.
Ah.... But they're not different. Go check out page 5 of this sticky. At least I think it's page 5. I've listed all the NEMA receptacle configurations. You can plug a vacum cleaner or a toaster into a 30A receptacle. Just depends on what kind of 30A receptacle you get.
For 120v at 30A, you would need 10/2. The black wire is the hot at 120v. The white wire is the return neutral that takes current back to the panel, and the bare wire is the grounding conductor.
For 240v at 30A, you would need 10/2. The black wire is the hot at 120v, the white wire is another hot at 120v, and the bare wire is the grounding conductor. In order to have a voltage potential of 240v between the black and white wire, each wire has to originate from separate phases or legs in your panel. This is why you use a double pole breaker because it ensures that each wire will be fed from a different leg. On a 240v circuit where whatever/2 cable is used, you MUST re-identify the white wire at all accessible points with black or red electrical tape. This tells anyone who gets near it, that it is now a hot wire and no longer a neutral.
The only time you need to run 10/3 wire for a 30A circuit, is if you need both 120v and 240v at the same time. Take your kitchen stove for example. The heating elements use 240v power, so you need 2 hots. But you also have things like a clock, timer, inside lights and misc gadgets that run off of 120v. So, the red and black wires are 120v a piece with a voltage potential of 240v between them, the white wire is a neutral and the bare is a grounding conductor.
What ever runs at 120v, just uses either the red or the black wire for it's hot(only one), and then sends the current back down the white neutral back to the panel, which is how a 120v circuit works.
When you have a 240v load, you do not need a neutral. In the US, Japan and a few other places, we run at a frequency of 60 hertz. That means you get 60 cycles per second. A cycle is the midpoint of a sine wave, up to the peak, back to the midpoint, down to the trough and then back to the mid point. Anyway..... Current actually travels to and from the breaker on a 240v circuit by way of this mechanism, therefore, needs no neutral. A 240v circuit can be a little hard for some to understand because they are too used to 120v loads needing a neutral. The concept of the "black wire going to the load and the wire wire going back to the panel" just throws some for a loop when trying to understand a 240v circuit.
A 120v circuit is completed and works with 2 wires. A 240v circuit is completed and works with 2 wires. As long as the circuit is "complete", it'll work.
You could get away with a 15A breaker and #14 romex but the larger the wire, the less resistance and voltage drop you will have. Seeing as how your 15 feet from the panel to receptacle, you don't really have to worry about that. When running new circuits for my grow room in the attic, I used 10/2 on a 20A breaker just because of the distance involved. That and the wire runs through a 130 degree F attic for part of the way. You are required to derate the load or increase the wire gauge depending upon ambient air temperature as you will find at the bottom of table 310.16 in the NEC, with 86 degrees being the starting point.
Anyway, a 120V 1kw ballast should draw right around 10A and your allowed up to 12A on a 15A circuit if it's a continuous load. See above for explanations on "continuous loads".
Either or. The deciding factor would be the main breaker rating in your main panel, or "the size of your service". A load calculation for the entire house would have to be determined in order to give you a definite answer. Give me the main breaker rating and a list of all your high draw appliances in the house and I could probably just tell you off the top of my head whether you should use 120v or 240v for your ballasts.
Just know that 240v draws half the amperage that it's equivalent 120v counterpart will. When you have a really small service (like a 60A main in an apartment or old duplex), you might want to think about running as much as you can off of 240v. Otherwise you run the risk of tripping your main disconnect.
I'm not sure what your current setup is, but post back after digesting the above and I'll be more than happy to help you run a safe setup. Some here would call my advice overkill, but me being a big fan of the NEC, call it a "required minimum safety".
Ah... Easy then. The joys of growing in a basement.
That would be correct. A 1kw lamp @120v will draw anywhere from 9-10A. If you have 2 of them, that'll be around 20A. Since the lights are on for more than 3 hours at a time, they are considered to be a "continuous load" and the branch circuit feeding them needs to be derated to 80% of it's total capacity or 125% of the actual load. The math works out the same either way you do it. 12A on a 15A breaker, 16A on a 20A breaker and 24A on a 30A breaker.
Ah.... But they're not different. Go check out page 5 of this sticky. At least I think it's page 5. I've listed all the NEMA receptacle configurations. You can plug a vacum cleaner or a toaster into a 30A receptacle. Just depends on what kind of 30A receptacle you get.
For 120v at 30A, you would need 10/2. The black wire is the hot at 120v. The white wire is the return neutral that takes current back to the panel, and the bare wire is the grounding conductor.
For 240v at 30A, you would need 10/2. The black wire is the hot at 120v, the white wire is another hot at 120v, and the bare wire is the grounding conductor. In order to have a voltage potential of 240v between the black and white wire, each wire has to originate from separate phases or legs in your panel. This is why you use a double pole breaker because it ensures that each wire will be fed from a different leg. On a 240v circuit where whatever/2 cable is used, you MUST re-identify the white wire at all accessible points with black or red electrical tape. This tells anyone who gets near it, that it is now a hot wire and no longer a neutral.
The only time you need to run 10/3 wire for a 30A circuit, is if you need both 120v and 240v at the same time. Take your kitchen stove for example. The heating elements use 240v power, so you need 2 hots. But you also have things like a clock, timer, inside lights and misc gadgets that run off of 120v. So, the red and black wires are 120v a piece with a voltage potential of 240v between them, the white wire is a neutral and the bare is a grounding conductor.
What ever runs at 120v, just uses either the red or the black wire for it's hot(only one), and then sends the current back down the white neutral back to the panel, which is how a 120v circuit works.
When you have a 240v load, you do not need a neutral. In the US, Japan and a few other places, we run at a frequency of 60 hertz. That means you get 60 cycles per second. A cycle is the midpoint of a sine wave, up to the peak, back to the midpoint, down to the trough and then back to the mid point. Anyway..... Current actually travels to and from the breaker on a 240v circuit by way of this mechanism, therefore, needs no neutral. A 240v circuit can be a little hard for some to understand because they are too used to 120v loads needing a neutral. The concept of the "black wire going to the load and the wire wire going back to the panel" just throws some for a loop when trying to understand a 240v circuit.
A 120v circuit is completed and works with 2 wires. A 240v circuit is completed and works with 2 wires. As long as the circuit is "complete", it'll work.
You could get away with a 15A breaker and #14 romex but the larger the wire, the less resistance and voltage drop you will have. Seeing as how your 15 feet from the panel to receptacle, you don't really have to worry about that. When running new circuits for my grow room in the attic, I used 10/2 on a 20A breaker just because of the distance involved. That and the wire runs through a 130 degree F attic for part of the way. You are required to derate the load or increase the wire gauge depending upon ambient air temperature as you will find at the bottom of table 310.16 in the NEC, with 86 degrees being the starting point.
Anyway, a 120V 1kw ballast should draw right around 10A and your allowed up to 12A on a 15A circuit if it's a continuous load. See above for explanations on "continuous loads".
Either or. The deciding factor would be the main breaker rating in your main panel, or "the size of your service". A load calculation for the entire house would have to be determined in order to give you a definite answer. Give me the main breaker rating and a list of all your high draw appliances in the house and I could probably just tell you off the top of my head whether you should use 120v or 240v for your ballasts.
Just know that 240v draws half the amperage that it's equivalent 120v counterpart will. When you have a really small service (like a 60A main in an apartment or old duplex), you might want to think about running as much as you can off of 240v. Otherwise you run the risk of tripping your main disconnect.
I'm not sure what your current setup is, but post back after digesting the above and I'll be more than happy to help you run a safe setup. Some here would call my advice overkill, but me being a big fan of the NEC, call it a "required minimum safety".
mr-natural78
Member
ok. I'm starting to understand this a little better. I went back and looked at the chart of recepticles/plugs you posted. Maybe I'm not understanding the chart. I don't see anything listed for 30a 120v that is the same as the basic plug on my ballasts. I was browsing at home depot yesterday and didn't see any there either. They had 15a and 20a receptacles that a normal household plug would fit and then they had 30a for 120v and 240v but they were all a different configuration. With my set up now I am running one 1K and one 400w. I'm also running a couple of fans. This is on the 20a circuit that was already in the basement. I'm also using some cheap orange extention cords. The only other thing on that circuit are a few overhead lights with pull-chains. I plan to use that circuit for my fans and such and the two dedicated circuits just for lights. Anyway....I will check the main breaker and the high draw appliances that I have and post those shortly, but it is a single family home. Not an apartment or old duplex.
mr-natural78
Member
ok. The main breaker doesn't say anything on it. The inside of the panel door says the main is 200a. After looking at my panel more, I have more questions. Do all 240v circuits use double pole breakers? All the ones in mine are single pole. All are 20a except for two. Those two are 40a single pole. All of our appliances have regular plugs with ground as well. Even the dryer and stove. Nothing uses the 240a type receptacles that you see a lot of dryers and such. In this home we have the well pump and it is on one circuit. The furnace is on one circuit...the hot water heater may be on that circuit as well, but I'm not sure. We just have a basic kitchen with stove, frig, microwave. The basement has two other circuits. My grow is on the back circuit. The front circuit has a water softener plugged into it and a sump pump and basement watchdog battery back up sytem plugged into it. I can't really think of anything else. Everything else is just tv's and stuff like that. Oh, one other thing, in case it matters. In my first post I said my garden was in the basement about 15ft from the panel. It would probably take 25ft of wire to run it correctly to where I will mount a timer and receptacles. I want to be sure that doesn't change anything. I'm going to get a mechanical timer like what was posted here before. I saw them at the big box home stores. The ones that need to be hard wired. I don't think that short of a distance makes much differance really...but wanted to be sure. I don't think I need to take into account the distance of wire until I get up over 100ft. Like I said, just want to be sure.
mr-natural78
Member
oh wait...looked at the receptacles/plugs again. Are 5-30R what I need? Will a regular house hold plug with ground fit those? I think so. The little L shoped one through me off. But right next to it in the 20a column those have a T shape on one and I know regular plugs fit those. We have a bunch of those here. I think that is the one I need. I don't know how I missed that the first time I looked. Maybe I should read the whole thread again and some of this will sink in a little better.
