Another garage question - electrical capacity?

[BerserkerCatSplat]

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^ thanks, that is really helpful if I decide to upgrade.

Happy to help! I actually misremembered - my conduit is also 3/4", not 1" like I thought. So if I can run 60A/240V through mine, so can you. If you wanted to save some $, you could do 8GA RW90 to get 40A/240V service for really cheap. Add a cheap subpanel and you'd be good to go.

Southwire has a handy conduit fill calculator you can use, your PVC is likely Sched40 and wire thicknesses are available for anything Southwire makes. Other manufacturers may have slightly different specs but it'll be within a few %.

I found that buying locally, TWN 6GA was actually noticeably cheaper than 8GA because wholesalers will cut 6GA for you to length, but will only sell 8GA in 300m spools. I ordered my TWN 6GA conductors from Electrical Wholesalers but had to go through Lowes for my TWN 8GA ground wire, which per-foot was more expensive than the 6GA. I think 8GA RW90 was the cheapest but you'll have to check on that.

[J-hop]

Damn that is tempting now. I have two neighbors that are electricians I’m sure would be happy to help me for a case of beer...

[J-hop]

@Crazyjoker77 (or others). When I picked up the lighting tonight I was looking at motion/occupancy light switches.

When I add up the lights on the circuit I get 4x35w=140w/120v =1.2amps. They only had the 2amp switch however that 2 amp switch said it was only rated for up to 150watt LED, what gives?

I was planning on going with the 5amp switch but I thought that was just weird.

Here is the switch in question

https://www.homedepot.ca/en/home/p.l...000720113.html

[Crazyjoker77]

It all has to do with power factor which is something pretty deep to get into. Incandescent bulbs are a pure load which means apparent power (va) and true power(w) are equal. When your dealing with anything that has transformers, capacitors, or synchronous motors, you will have a leading or lagging power factor and the true power will not equal the apparent power. You should be using the VA of the bulbs to figure out what it will actually be pulling. Those bulbs will actually pull more than the 1.2A you calculated but manufactures rate the bulbs in W because thats what people are use to seeing with traditional incandescent. Honestly most LED now a days have a very good power factor and are withing 90-95% of the true power but some of the cheaper ones can be pretty low so the switch manufactures put that in their to cover themselves. It usually is not an issue to be concerned with.

What mayl be a issue that you are going to run into is that I'm assuming it is just a toggle switch controlling the existing lights, which means you are more than likely not going to have a neutral to hook up the new switch to. Traditional switches don't need a neutral but some dimmers and motion sensor(pir) requires one. To make it to code you will have to run a neutral from the light fixture down to the light switch box which sucks if your garage is already finished. Some hacks will just use the ground wire in the box which WILL work but is very against code as the ground is not meant to carry current except in fault situations.

[J-hop]

Man thanks a ton this is really great @Crazyjoker77 . Did some reading and understand (at least somewhat) what you’re saying. Can’t seem to find what the apparent power for these fixtures is. I’ll plan for the minimum standard. Looks like in the US the minimum power factor is 0.7 for residential LEDs. Looks like that switch manufacturer is giving a bit of leeway on that as well with 0.62. This makes sense with their 5Amp switch that is using a factor of 0.6.

I’ll go with the 5amp switch as I originally planned just to be more than safe. I don’t want to be butting up against the max rating.

Thanks again the guys at homedepot didn’t have a clue when I was asking why the math didn’t add up. They acted like I was being an idiot haha which may be true but not on a relative scale in this case.

Your comment about the neutral totally makes sense now. My father in law installed a motion sensor switch in his kitchen. I always wondered why the fluorescent bulbs glowed ever so slightly when it was on the motion setting and no one was in the room. I’m guessing now that it’s one of those motion sensors that the manufacturer tried to get around the lack of a neutral by allowing a small current through to run the sensor, but it’s obviously just enough to power the light a bit as well.


So I could be wrong here but all of my wiring in the garage to the lights is 14-2. I think this means I should have a hot, ground and a neutral so I should be ok? If not since my garage isn’t dry walled and the rafters are not closed it would be super easy to run a new wire. Guessing I should technically permit and have that inspected if I do end up having to rerun wires? Not a big deal and a good learning experience

[Crazyjoker77]

Switches use the wires as hot, switch leg, and ground no need for a neutral on a regular toggle switch so contractors cut cost by not running it. You need 14/3 to have a switch function AND have a neutral. You will find the white wire is actually the hot(it may have a couple wraps of black tap around the ends) and the black is the switched hot that ties into all the fixtures.

Technically you should pull a permit but its such a small job there a good chance he would just sigh and face palm when he showed up. If everything is accessible now just replace the 14/2 with 14/3 from the fixture box its coming out of. Swap the current white wire for one of the colored ones and tie the white into the rest of the neutrals.

The neutral thing isnt really the reason why the fluorescent bulbs glowed it has more to do with the differences of switching methods. A traditional switch uses an actuall physcal opening to stop all the current where as in most electronic based switches use a solid state electronic switch of some sort (SCR,IGBT,Triac,) .All SS switches will have a tiny amount of leakage current going through them at all times. This little bit of leakage current is what causes the faint glow.

The switches without a neutral will rob you of a little bit of brightness on incandescent bulbs OR pull a little but more current(negligible) when used on lighting with a driver/ballast.

Honestly your trying to calculate it way to much. At this level your going to have more of a variation just because the voltage isn't going to be constant 120v throughout the day for various reasons. A little bit of power factor or power phantom losses isn't go to make any meaningful difference on a single 15A circuit.

[J-hop]

Thanks, Yea I know I’m going overboard. But the “I just did it and it works fine” mentality doesn’t sit right with me. I want to why and how haha

I guess I’ll have to look at a wiring diagram to understand why I need 14-3. 14-2 is a 3 conductor wire. The diagram I looked at showed it as hot, ground and neutral so guess I’m not able to visualize why I’d need a 4th wire between the switch and fixture?

[Crazyjoker77]

You related to mar by chance?

Here it is in the most basic form. Cable 2 needs 3 wires (stop counting the ground as a wire) 14/2 technically has 3 wires but its called 14/2 because it only has 2 current carrying wires.

white wire is depicted as yellow. Ground wires are not shows cause the have no impact and are always going to be included with the lumex.



Also neutral is the incorrect term. The white wire is actually called the identified grounded conductor.

[J-hop]

thanks, yea sorry I’m an absolute moron so it takes a while for stuff to sink in.

I just look at this like building cars. You can know less than nothing and get away with some shitty brainless off the shelf tune if you’re running a very mild setup. But as soon as you step up and try to build a serious engine the guys with that mentality start to pay heavily for their ignorance.