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I have an 1800sf home with a 200amp service. I want to convert family room into an indoor vegetable growing room. The lighting (which will be on as much as 18hours/ day) will need 3.8amps each and for 6 lights total 22.8amps. There will be other items using an additional 2-5amps from time to time.

I would like to run a 30amp line to that room off of the breaker panel (the family room is only 12 feet from the box).

Can I install a 30amp breaker and run 10AWG wire to the room through conduit and get 120V for this lighting?

Thank you for your time!

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Since you've got conduit, and since most lights are not designed to be directly on 30A circuits (normally in the US designed for 15A or 20A circuits), run two 15A or 20A circuits through that conduit instead. It will take more spaces in your panel - if that is a problem, upload a picture of the panel for help.

Note that 2 x 15A is perfect for the lighting. Each 15A circuit should have no more than 12A of continuous use. In order to have additional stuff on the same circuits, you would need to bump up to 20A circuits - that would give you 5A total, 4A continuous additional on each circuit. But if the lights are hard-wired and the other items are plug-in then you really should have a 3rd circuit for the receptacles, as you should not put receptacles on a circuit that has hard-wired loads > 50% capacity.

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    That makes sense. Sometimes we miss the obvious answer. Thank you, 2 15s should be perfect! Jan 21 at 22:13
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    @EdBeal And when OP discovers that their home equity has vanished because they turned their living room into a steaming mould factory they might wish they had forgotten the whole idea right now and spent their money more wisely. Dumping thousands of dollars into a homewrecker project seems an absurd price to pay for a bushel of cucumbers.
    – J...
    Jan 22 at 13:58
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    "most lights are not designed to be directly on 30A circuits". Can you please explain what that means? I'm and old fart who's been wiring my own homes for more that three decades. Why would it be a problem to put a light on a "thicker" circuit than necessary? Amperage is just "available" current. It doesn't force the current down an appliance's throat. If this is a problem, why is it that you can plug your iPhone USB-based charger into a 15A or 20A circuit? Wouldn't that be way too much for such small appliances? I'm not trying to cause trouble here. I truly don't get it.
    – CryptoFool
    Jan 23 at 8:05
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    @Steve Most lights expect to be on 15/20A circuits so they have terminals that accept 14AWG and 12AWG wire. If you try to attach larger gauges the screws won't hold the wires. The terminals are not rated or listed to accept larger gauge wires or to carry 30A of current (in case of a fault) so it is not legal to fit them to circuits that require such larger gauges. Making a smaller gauge pigtail to make the connection is not legal either.
    – J...
    Jan 23 at 14:34
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    Ah. Ok. It's about the actual wiring, and the ability to connect the built-in lights to the circuit. I get it. Thanks!
    – CryptoFool
    Jan 23 at 16:49
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Your grow lamps plugs are probably NEMA 5-15 or 5-20 if not hard-wired. NEMA 5-15 or 5-20 are rated for a 15 or 20 amp circuit, but not a 30 amp circuit. If not hard wired, or not NEMA 15 or 20, you'll need to run 2 circuits....absolute minimum is 12 gauge on 20 amp breakers. That will give you 1,920 watts per circuit. The theoretical limit is 2,400 watts (120v x 20 amps), but your grow lights would be considered a "continuous load" and the circuits need to be de-rated 20% getting you to 1,920 watts per circuit. From what others have said here, oddly enough, if hard wired they don't need GFCI protection, but if plug-in, they do! Go figure.

A few other practical considerations: 1) 10 ga is hard to work with, even if stranded, it would be very very difficult to connect to an outlet, if even possible. 2) even a 30 amp circuit, would barely get you to the 2,736 watts you need when properly derated, and that doesn't include the other "occasional" use items. (30 amps x 120= 3,600 watts x 80% = 2,880 watts). A MWBC might be practical here, but they are falling out of favor given GFCI and AFCI requirements. I don't use them any more.

Like another comment said, you might need AC in that room. Or at least serious ventilation. You'll be dumping a lot of heat into that room. If you decide on A/C, that would probably also need it's own circuit. Go big on the conduit, it's cheap so if you have to add stuff later, you'll have the infrastructure to do it.

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With devices that are not listed to run on 30 amps the best option would be to go ahead and run the #10 and set up a small sub panel. With the sub panel you could run the circuits for the devices you want to use.

I do commercial lighting and even with that it is rare to have more than 1000w lamps at 240v that’s only ~4.1 amps or ~8.3 amps at 120v. A sub panel will allow you to protect the system with appropriate sized circuit breakers. Almost all lighting is approved for 20 amp circuits but very few things are approved for a 30 amp circuits (dryers, water heaters, hvac compressors, welders).

So the answer is NO it would be a code violation to power your lighting from a 30 amp circuit, but upgrading to a small sub panel makes this code compliant and the wiring is not much different than your current plan.

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NEC 210.23(A) Says 15 and 20A branch circuits "shall be permitted to supply lighting unit(s)...", and (B) say 30A circuits shall be allowed for "heavy-duty lampholders in other than a dwelling unit(s).."

So you can't do a 30A branch in a family room of a home. Multiple circuits or a subpanel (even if for 2 15A circuits) are your options.

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You may destroy your house. Growing plants put out a lot of water. If you are in a cold climate, you may have issues with condensation and mould throughout the rest of the house. If you do this, you want to keep the humidity in that room. This is difficult. You may want to do research on how this is handled in the head house in a greenhouse operation. I think the usual answer is that the head house is not a very tight building.

You don't say why you want to do this inside, as opposed to outside.

I suggest that for this scale of operation you make a greenhouse addition to your house.

18 hr * 30A * 120v = 65 kWh/day. At 10 c/kwh thats $200/month.

A greenhouse allows you to reduce your lamp time to about 6 hours a day. Depending on what you raise, and your climate you may need to heat your greenhouse at night in winter.

This may have issues with local zoning. (File a plan as a 'sun room') If you are handy, you can buy a tube bender and make your own bows from chainlink fencing post or top rail material. (1 3/8 vs 1 1/4) available in 30 foot lengths. Various places sell the anchor plates to secure to your soffet. Even this may put too much water vapour into parts of your house. I would make that part of the soffet and eaves air tight.

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    A greenhouse is visible to the outside. That is at odds with the implied nature of the question regarding particular plants. If this is for ordinary vegetables then a greenhouse is ideal, provided you have the land available. Jan 22 at 17:02
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    @manassehkatz-Moving2Codidact We are not here to speculate on or to help anyone engaging in illegal activities. This is the most sensible option from a legitimate homeowners perspective if we're to assume that the people we are helping here are interested in improving and maintaining the quality and value in their home.
    – J...
    Jan 22 at 20:06
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Unless your grow area is utterly gigantic, you don't need a 30 amp line provided you use LED grow lights. They are dramatically more energy-efficient than other options, putting out the same amount of light (but a fraction of the heat) with a fraction of the power draw when compared to traditional bulbs.

And when I say dramatically more efficient, I mean 'by an order of magnitude' when you compare them to off the shelf grow bulbs from a hardwares store - a tenth of the power draw for the same amount of light and way less heat to have to deal with. They outperform even modern HPS by about 2-3 times the efficiency. And they last longer. And when they do 'break', since it's an array of dozens or hundreds of LEDs, the light is still 99% useful because usually just one LED goes out.

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    The default hydroponics setup is a 1000W high pressure sodium lamp per 10 foot square, or about 10W/ft2. They are about the same efficiency as LED lighting. 30A at 110v = 3300 watts. About enough to do a 15 x 21 foot room. Jan 25 at 18:12
  • Sorry, said HPS but meant traditional bulbs. 'They are about the same efficiency as LED lighting' That's just not true. I get ~100k lux at 1 ft from a ~$65 LED array with ~110w input, and it puts out about as much heat as my computer. Granted, the light footprint is very different than a shielded HPS, but when you factor in heat production LEDs are at least twice as efficient as HPS. Jan 26 at 19:57
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I believe one workable option would be to run 14/3 from a pair of breakers just as would be done for a kitchen counter receptacle. There will be the equivalent of 15A @ 120V between each "hot" and neutral, effectively 30A @ 120V total capacity. You would obviously want to balance the load between each of the two 120V circuits.

This may be restating something obvious, but there will be 240V between each of the "hot" wires, so no, they can't be ganged - they must feed independent loads.

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  • I can't support MWBCs anymore, too many issues, too many false/nuisance trips. Jan 23 at 23:25

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