JACKPOT! Found unused 30-amp circuit for old dryer... what to do?

Hey RIU! I posted a thread a few weeks ago about increasing ampacity in my garden area, and I may have just come much closer to a solution.

I noticed a 50-amp rated 240v outlet (USA) in what used to be a laundry room, now a bedroom. I did some testing with the panel and it is the only outlet on an unused 30-amp circuit. It is also directly above my basement garden area.. I used a multimeter to confirm it is still getting 240v.



Now I’m delving into a world of 240v extension cords and transformers and single phase vs double phase and I’m pretty stumped.

I would like to run a maximum of 3 1k HID lights, 3 centrifugal exhaust fans, and a couple of room circulating fans on this circuit. Since it’s 30 amps at ~240v, I should have a max capacity of 7,200w, so practically around 6,000w. My question is, what equipment should I buy to make this happen?

I could get an extension cord that plugs into this outlet (I hope!), and a step-down transformer, and run all of my lights and fans with the their current 3-prong 110v cords. I see some of the transformers on Amazon say they are for single-phase 240v power and not USA double-phase ... does this mean I can’t use them?

I also see that all of my ballasts run on variable voltage and automatically detect what they’re getting from the wall. Would it be better to get 240v power cables for my ballasts? I would like to run my fans on the same circuit as the lights so there’s less chance my fans shut off and my lights come on and start a fire... but my fans only run on 110v.

I feel like there’s a fairly simple solution here but I’m a little over my head. If any electrically-minded gardeners here could point me in the right direction, I would greatly appreciate it!

No need for transformers. Here in the USA all the 220 volts are just two 110 volt lines on different phases. So the plug has one neutral and two 110 volt lines to make the 220 volts. To get 110 volts you would just need to tap into one of the 110's along with the neutral. Pretty simple but you might want to have a electrician wire it up for you for safety.

Ok, so just replace that outlet with a 110v outlet using the neutral and one of the 110v wires? Running the lights at 220 would cut my amperage in half, which is why I was thinking about trying to use a transformer or getting different plugs. I’m open to anything, but I want the simplest and most cost-effective solution that will give me the amps I need. Thanks for the reply

Just get a 30 amp 240v light relay and have the plug rewired to that, if you get one with a 120 plug you can use a splitter to run the fans and use the 240v plugs to run the 240v grow lights.

vtguitar88 said:

Ok, so just replace that outlet with a 110v outlet using the neutral and one of the 110v wires? Running the lights at 220 would cut my amperage in half, which is why I was thinking about trying to use a transformer or getting different plugs. I’m open to anything, but I want the simplest and most cost-effective solution that will give me the amps I need. Thanks for the reply

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Doesn't really matter if the amperage is cut in half you will still be using the same amount of wattage. 1 amp @ 220 volts is 220 watts if it is a dual voltage device it will use 2 amps @ 110 volts which equals 220 watts. Some things get a little better efficiency running 220 volts but it is not a lot. If you split the 220 into two 110's they would each be on a 15 amp circuit so the total 30 amps just like the 220 circuit is now. But really I would hire a pro , electricity is nothing to play around with especially since there is no cure for death in most cases.

JavaCo said:

Doesn't really matter if the amperage is cut in half you will still be using the same amount of wattage. 1 amp @ 220 volts is 220 watts if it is a dual voltage device it will use 2 amps @ 110 volts which equals 220 watts. Some things get a little better efficiency running 220 volts but it is not a lot. If you split the 220 into two 110's they would each be on a 15 amp circuit so the total 30 amps just like the 220 circuit is now. But really I would hire a pro , electricity is nothing to play around with especially since there is no cure for death in most cases.

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Yes wattage is the same but wires are rated for amps, why breakers say amps not watts. 3000 watts at 110v would be close to full 30 amps, 3000watts at 240 is around 15 amps (much safer). Buy a 240v light controller with built in timer and 110v accesory outlet. Example https://www.amazon.com/gp/aw/d/B072FH757Y/ref=mp_s_a_1_1?ie=UTF8&qid=1520175233&sr=8-1-spons&pi=AC_SX236_SY340_FMwebp_QL65&keywords=240+volt+light+controller+with+timer&psc=1

stoned-monkey said:

Yes wattage is the same but wires are rated for amps, why breakers say amps not watts. 3000 watts at 110v would be close to full 30 amps, 3000watts at 240 is around 15 amps (much safer). Buy a 240v light controller with built in timer and 110v accesory outlet. Example https://www.amazon.com/gp/aw/d/B072FH757Y/ref=mp_s_a_1_1?ie=UTF8&qid=1520175233&sr=8-1-spons&pi=AC_SX236_SY340_FMwebp_QL65&keywords=240+volt+light+controller+with+timer&psc=1

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Thank you, that’s a good suggestion. So would you just disconnect that old, ungrounded range/dryer outlet upstairs, and wire this controller up to the now-vacant 30-amp circuit? How would I connect the controller to the panel? If it’s as easy as getting the right wire, turning off the main breaker on the panel, and following a guide to wire it to the breaker, I could probably handle that myself.
Trying to avoid hiring an electrician because I only know one who is confirmed 420-friendly and he’s too busy so I can never get him over here. That’s why I thought I might find an adapter for the NEMA 10-50p outlet upstairs and run an extension cord from there, but that’s such an old outlet that it’s hard to find adapters for it, and it’s not even grounded so that would be pretty sketchy anyway

Since it’s 2-phase 240v power on that 30-amp circuit, could I just:
1) disconnect the unused line/outlet from the panel
2) run two 15-amp 120v lines from that one breaker?

Seems like I’m definitely going to need an electrician but that’s not as easy as it sounds

As @JavaCo so eloquently put it, "there is no cure for death in most cases" so the most important consideration should be safety... I would recommend hiring an electrician but there are books that can teach you how to wire to code safely... One circuit won't be that hard... Just don't take any shortcuts! Best of luck!

vtguitar88 said:

Thank you, that’s a good suggestion. So would you just disconnect that old, ungrounded range/dryer outlet upstairs, and wire this controller up to the now-vacant 30-amp circuit? How would I connect the controller to the panel? If it’s as easy as getting the right wire, turning off the main breaker on the panel, and following a guide to wire it to the breaker, I could probably handle that myself.
Trying to avoid hiring an electrician because I only know one who is confirmed 420-friendly and he’s too busy so I can never get him over here. That’s why I thought I might find an adapter for the NEMA 10-50p outlet upstairs and run an extension cord from there, but that’s such an old outlet that it’s hard to find adapters for it, and it’s not even grounded so that would be pretty sketchy anyway

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The existing wiring can easily be connected to the light relay.

somedude584 said:

The existing wiring can easily be connected to the light relay.

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Ok, so just pull from the old outlet and connect that end to the light relay. That does sound easy enough. Should I be concerned that it’s old wiring with no ground? Or just wire up the two hots and the neutral to the light relay and ground it another way? Really appreciate the help man!

i have done almost the exact same thing, idk about running 6k watts as you will only have 2 15a 110v circuits which dont supply that kinda power running a light relay will allow you to do what you want tho but 2 15a circuits will probably cost you around 30 dollars for a subpanel and breakers

and double phase just means your using 2 110v leads if that makes any sense you surly dont have 3 phase in your home so really your not changing much people will say your overloading the neutral wire but ive discussed this with an electrician and you will be fine doing this would be the same as using 2 separate circuits that are on the same bus in your main panel

I have 4 or 5 220v circuits like that in my shop. I used regular 14/2 house wire to run the black and white wires on their own 15amp breakers from one of those 220 lines and put it in a box with two regular and separate 110v duplex plugs so I have a couple extra sets of plugs in my grow room. Been using it like that for about 15 years with no problems. They share the neutral. Up to a 1000W light on one pair of the plugs and the others only get used to power fans or air pumps. The heater for the grow room is on a separate, pre-existing circuit.