Wire sizing for lights

[CJseven]

I’m going to be wiring my lights this weekend in my shop, I have 4 400 watt metal hylide high bays that I’m planning on hooking up 2 per circuit with 2 three way switches. Will 14-2 handle this?

 

[cybrdyke]

904 watts divided by 120 volts = 7.53 amps per circuit

 

[CJ7VFR]

904 watts divided by 120 volts = 7.53 amps per circuit

904 watts? How did you get that?

14 gauge wire, with a 15 amp breaker will work if you have two of the 400 watt lights on each circuit. That would be a total of 800 watts per circuit, or about 7 amps per circuit.

If you put all 4 lights on one circuit, then it would be 1600 watts, or about 14 watts on the circuit. In that case, then you would want to go up to 12 gauge wire with a 20 amp breaker to be safe.

Jim

 

[Norcal]

A 400 watt metal halide fixture is 4 amperes at 120V for each fixture.

 

[TRWham]

Regardless of wire gage, you are also going to need some 3 conductor cable to make 3 way switches work.

 

[wyliesdiesels]

I’m going to be wiring my lights this weekend in my shop, I have 4 400 watt metal hylide high bays that I’m planning on hooking up 2 per circuit with 2 three way switches. Will 14-2 handle this?

When calculating lighting circuits, you need to use the fixture amperage or wattage rating NOT the bulb rating.

 

[alfredeneuman]

A 400 W magnetic metal halide ballast, according to Advance, actually draws 462 watt.

 

[cybrdyke]

904 watts? How did you get that?

Jim

There's a ballast, and depending on what kind it is, it will draw anywhere from 45 to 65 watts.
CD

 

[Aquamoose]

Regardless, you should run 12g wiring. It cost a bit more but good in the long run. None of my wiring is 14g.


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[TRWham]

Regardless, you should run 12g wiring. It cost a bit more but good in the long run. None of my wiring is 14g.


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Why do you feel it is beneficial to oversize wires in lighting circuits?

 

[LS6 Tommy]

A 400 watt metal halide fixture is 4 amperes at 120V for each fixture.

400W is the output rating of the fixture, not the current consumption. Total consumed current is higher. You have to look at the manufacturer's specs for the ballast and add the current usage to the bulb usage.

Tommy

 

[alfredeneuman]

400W is the output rating of the fixture, not the current consumption. Total consumed current is higher. You have to look at the manufacturer's specs for the ballast and add the current usage to the bulb usage.
Tommy

...and 4A @ 120V = 480W, so NorCal's figure is essentially correct.

 

[Falcon67]

Why do you feel it is beneficial to oversize wires in lighting circuits?

It's just easier to buy/stock/pull one size wire. Everything in my shop is 12 and I keep a roll of 12 around for changes. I would admit to use a bit of 14 in the house as it was easier to snake around brick and tie off for some LED driveway lights that could run on 20 gauge LOL.

 

[Bopbop]

My shop is being wired this week. The electrician who does commercial/ industrial work said that the smallest he would run was 12 guage. He does not put 14 on the trucks

 

[Falcon67]

The more we go LED the more overkill the wall wiring gets LOL. I just put up 12 stands of "C9" LED red on the house and shop. Plugged into a 20A GFCI wired with 12. Total string draw is 27w. The landscape light draw total is 22w.

 

[SarcasticDwarf]

The more we go LED the more overkill the wall wiring gets LOL. I just put up 12 stands of "C9" LED red on the house and shop. Plugged into a 20A GFCI wired with 12. Total string draw is 27w. The landscape light draw total is 22w.

Agreed at least when it comes to lighting circuits. It is the outlet circuits that see more and more devices.

 

[pepi]

Regardless of wire gage, you are also going to need some 3 conductor cable to make 3 way switches work.

Are you sure, think it's 4 conductor, never mind I was including the ground as a conductor ..



Pep

 

[Bert_]

I like #14 for lighting circuits. It's easier to work with and making connections is faster. Sometimes you have to run more circuits vs. a #12 but lighting is a fixed load and easy to plan for.

 

[tfi racing]

Do yourself a favour. Throw those power hog POS metal halides in the trash were they belong, I wouldn't install them even if someone paid me.

 

[Jim greengo]

I like #14 for lighting circuits. It's easier to work with and making connections is faster. Sometimes you have to run more circuits vs. a #12 but lighting is a fixed load and easy to plan for.

 

[CJseven]

Thanks for the info, I guess I should have looked on the lights first before asking about the amps.



Good catch on the 14-3 , I knew to use that, just had so much other 12-2 had that in my head.

 

[ForceFed70]

Do yourself a favour. Throw those power hog POS metal halides in the trash were they belong, I wouldn't install them even if someone paid me.

I'm curious. How have you come to this conclusion? Considering that metal halide is actually a reasonably efficient lighting system, I find your statements a little suspect.

 

[seanc_mt]

Everything and I mean every light in my shop/house is LED. Still ran 12/2 for the lights. Overkill? Probably but you only get one chance.

 

[Dick in Wisconsin]

Do yourself a favour. Throw those power hog POS metal halides in the trash were they belong, I wouldn't install them even if someone paid me.

I thought the same thing.

I'm curious. How have you come to this conclusion? Considering that metal halide is actually a reasonably efficient lighting system, I find your statements a little suspect.

Amp/Watt draw. I suspect that you can get the same amount of light from LEDs that will draw a lot less power.

 

[Kevin54]

Everything and I mean every light in my shop/house is LED. Still ran 12/2 for the lights. Overkill? Probably but you only get one chance.

^^^^this^^^^

For the money....Run 12g.

 

[Norcal]

If the metal halide fixtures are not going to be used a lot, it will be a long payback of the costs of LED lighting and they still provide good light and color.

 

[ForceFed70]

I thought the same thing.



Amp/Watt draw. I suspect that you can get the same amount of light from LEDs that will draw a lot less power.

Actually, cheap LED light fixtures would be in same efficiency range of typical metal halide. Metal halide is comparable with T8 in regard to efficiency. It's more efficient than CFL. But yes, it's less efficient than LED (except for cheap/poor quality LED fixtures).

Long story short, there is a more efficient form of lighting available in the form of LED but it's not accurate to call Metal halide inefficient or "power hog".

 

[Bert_]

That's something that annoys me to no end on here. Everybody is like "LED, LED, must get LED. It's so much better than ____".

But then they proceed to go buy and put up the cheapest, crappiest led fixtures they can find. Poor quality light, short lifespan and overall cheap build quality...But hey you got a led. Guys like Platonic Solid have way more patience than me and mange to guide quite a few people to decent lights.

I see nothing wrong with reusing some old fixtures if they fit the bill for your shop.

 

[Norcal]

That's something that annoys me to no end on here. Everybody is like "LED, LED, must get LED. It's so much better than ____".

But then they proceed to go buy and put up the cheapest, crappiest led fixtures they can find. Poor quality light, short lifespan and overall cheap build quality...But hey you got a led. Guys like Platonic Solid have way more patience than me and mange to guide quite a few people to decent lights.

I see nothing wrong with reusing some old fixtures if they fit the bill for your shop.

This I have to agree with, buy cheap get cheap. The OP's MH fixtures will provide good quality light.

 

[7635tools]

Everything and I mean every light in my shop/house is LED. Still ran 12/2 for the lights. Overkill? Probably but you only get one chance.

Not if it’s in conduit. Romex is garbage. Would never use that ****.


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[wyliesdiesels]

Not if it’s in conduit. Romex is garbage. Would never use that ****.


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Since NM-b (Romex is a brand of NM-b) has been around for a long time im curious why you consider it "garbage" and "****"...

 

[cybrdyke]

Do yourself a favour. Throw those power hog POS metal halides in the trash were they belong, I wouldn't install them even if someone paid me.

Abso-f'in-lutely.
There's so much misinformation here.
Maybe if the OP got them for free and is installing them himself and doesn't have the budget for anything else. Or maybe he's just a fan of vintage stuff. Or is into repurposing things. Then, maybe I can see it....

But other than that, they are very much POS power hogs...
ÇD

 

[DwightS]

Has anyone mentioned the slow warm up to full brightness and the long time restrike in case of a power blip? You will have lots of light, as long as you can wait 5-10 minutes for it. That used to be OK for gyms and warehouses that was opened up and left on for multi hours, but not a great solution for the off and on, spur of the moment visit.


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[cybrdyke]

That's something that annoys me to no end on here. Everybody is like "LED, LED, must get LED. It's so much better than ____".

But then they proceed to go buy and put up the cheapest, crappiest led fixtures they can find. Poor quality light, short lifespan and overall cheap build quality....

So very true.
How many times does someone ask "what's the best LED fixture"...and then someone inevitably answers... Costco or Sam's Club or Feit, etc...?
Drives me nuts.
It also drives me nuts when someone builds a $100,000 shop and then puts in crappy lights.
CD

 

[cybrdyke]

Has anyone mentioned the slow warm up to full brightness and the long time restrike in case of a power blip?

Yes, many times.
And also the steep lumen drop-off of Metal Halide, and the crappy fixture efficiency, and the extreme heat, and the annoying buzz, the short lamp life
and the weird color shifting, and on and on...
CD

 

[TRWham]

I like #14 for lighting circuits. It's easier to work with and making connections is faster. Sometimes you have to run more circuits vs. a #12 but lighting is a fixed load and easy to plan for.

Exactly. And it costs less. 12 costs about 50% more than 14 in quantity and provides no operating benefit on a typical lighting circuit. That's about the same percentage difference as 10 versus 12, so to be consistent, why not also use 10AWG for your 20 A circuits? While we're at it, let's run 3/4" water pipe where 1/2 is called for, and install our door casings with 16d nails, and so on.

I get using a few feet of oversize wire I have on hand versus running out to get more, but when planning a new project, it's just wasteful to oversize.

 

[CJseven]

Thanks again for all the info, after seeing I’m only using maybe 2/3 capacity of the 14 wire and I will be needing about 500 ft for other lighting that’s what I plan on using for these four lights, any replacements later on will be less amp draw so still no need for larger wire. Just a little info as for why I’m using them, I have them, I bought them new for my old shop, they have very little run time and provide a lot of light when I do use them. Four years ago led lights were still really expensive for GOOD lights so I kept these. So for now I’m installing these, which I am doing myself if paying someone then I may have went a different route now. When I have a failure I will be replacing with led which could be a few years down the road and by then the technology should be even better.

 

[seanc_mt]

Not if it’s in conduit. Romex is garbage. Would never use that ****.


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I've got about 3k feet of it in my shop. Seems to carry the electricity just fine.

 

[CJ7VFR]

There's a ballast, and depending on what kind it is, it will draw anywhere from 45 to 65 watts.
CD

That makes sense. Thanks for the info!

Jim

 

[dcg9381]

[ROMEX] I've got about 3k feet of it in my shop. Seems to carry the electricity just fine.

I agree, seems to flow electricity the same as other solid wires.
In or out of conduit.
I understand the single wire preference though.