Why NOT to use #12 wire for lighting circuits

[sberry]

You are over qualified so doesn't pertain, but here I believe a 16 used as a powe strip needs breaker.
You also understand the load calculator needed when adding power tools to the lights, many others are not aware. Heaters may be different, use the feed thru, not daisy chain.

 

[westom]

"In a resistive load, the current is in phase with the voltage – the current rises immediately to it's steady-state value, without first rising to a higher value. Resistive loads can therefore be said to have little inrush current."

An example of research by locating soundbites - and not leaning the other relevant parameters.

That quote only discusses a fundamental theory based in limited context - while ignoring other parameters that are relevant. Once we include other relevant parameters, then the quote is incorrect. It should read "In a linear (non-varying) resistive load ..."

Not knowing that demonstrates missing knowledge - by not first learning the science and only reading isolated and subjective soundbites. For example "duty cycle" was only relevant when numbers (time) are included. National standard for 20 amp circuit was once 14 AWG. Even 16 AWG wire is safe for circuits with 20 amp breakers. Some 100 watt incandescent bulbs may first consume over 50 amps - and still not trip a 15 amp circuit breaker. Legal is to sell appliances that are unsafe (ie a 2000 or 3000 watt drier only powered from a 15 amp receptacle).

A resistive load, called incandescent bulbs (ie 6 amps), will actually consume somewhere above 50 amps when first powered on. Want a better number? Measure its resistance with a digital meter. Don't take my word for it. Confirm those numbers rather than reciting a vague and 'above corrected' quote.

 

[westom]

Those are NEMA approved then also... so the 15A-rated connection is passing more current than its rated for. Where do they draw the line? Why are #16 awg cords and power bars allowed to use a 5-15p? Why can I plug my 15A power tool into the end of my LED christmas lights?

Wires are significantly oversized. Then voltage losses are sufficiently minimal. 14 AWG wire was once the standard for 20 amp circuits. It was increased to 12 - not to eliminate overloads - to reduce voltage drops on those long branch circuits in a structure.

As noted, seven 100 watt light bulbs can demand over 50 amps when first powered on. And no 15 amp circuit breaker (or fuse) should trip as a result. Actual parameters are much more complex. So we make it simple. We give electricians a ballpark number (ie 15 amps) so that the right wire, receptacle, and circuit breaker can be selected for what is clearly a much more complex electrical event.

Lightning can be 20,000 amps. How thick must that wire be to safely conduct 20,000 amps to earth? An 18 AWG wire (lamp cord wire which we rate at 10 amps) should safely conduct that microseconds current of up to 50,000 amps. We simply do not discuss these complexities. We simply say it is a 10 amp wire - make it simple.

 

[alfredeneuman]

Don't take my word for it.

Do you have any data to back up your point of view?

 

[AntonLargiader]

He's talking about inrush current, which is brief but real for incandescent lamps.

https://www.google.com/search?&q=incandescent+lamp+inrush+current

 

[sberry]

I would like to see a couple of you guys play nice here, some I don't give a **** about but I wouldn't mind westom sticking around a little. This could be a resource we are slightly lacking here due to the fact he make some of it seem simple so I can get some general understanding,,, not that I could ever calculate much of it but its something about the nature of the current I try to work on,,, where we get some cases it is "obvious" that the understanding of the current "reactions" in the fuggin wire for lack of better wording.
Not that I know one number from another but in a few brief posts has enlightened me as to some concept how and where we sposed to deliver a strike, what makes the equipment work a little, enough to make it some kind of reaction to install it correctly.
I wanted him to chime in about some nonsense I wrote in another thread about gfci and no equipment ground,,, as to one of the viable reasons to put the little sticker on is 2 wire gfci isn't to have surge added to it. Some time ago it would have took me a while to consider that.

 

[sberry]

Wires are significantly oversized. Then voltage losses are sufficiently minimal. 14 AWG wire was once the standard for 20 amp circuits. It was increased to 12 - not to eliminate overloads - to reduce voltage drops on those long branch circuits in a structure.

There is a lot to study in this simple statement. We were debating why there were not more fires with the 30 on 14 just touches the tip of this. There is a lot of thought that the minimum standards are somehow inadequate which is not really true in regard to some wire size and maybe even more today with energy save, off peak, or less peak loads all the time.
Can light a whole house with a couple amps, instead of 40 welding we got 20, instead of 5 real hp we got 22A, we dont need bigger pipe to the toilet of shower but can now put 5 shitters on the same water and drain used to be for 1
How much does it really hurt your circ saw to drop from 122 to 115? The horror of the heat,,, like most guys here could work hard enough to put any real wear on one anyway and could the user ever notice.
I am highly experiences welder,, I can just tell the difference in a 140 wire feed adding 50 ft of 14 cord, a little bit,,,, wide open, never hurt the machine a bit. This is 23A. So do you really need 12 so for every chore10A battery charge, 8 grinder, same for a Sawzall and is each of these used 100 ft? I like one of the pex charts, they got one for 60 ft, 1 for 100. They know they aint all 100 with most being closer to 60, same for 120V and in my own case simply sub so my circuits didn't start off 120 ft when it mattered.
Got a couple lights,,, 75 ft long and intentionally used 14, 2 amp load. There seems to be some compulsion to assume every wire installed will be loaded 100% all the time cause it has a 15 breaker on it. Got some with 13 watts actual load.

 

[theoldwizard1]

WOW !! This thread has gone a long way from what I was trying to say ! In certain cases, where an existing chase must be used, using #12 NM-B for a LIGHTING circuit, just makes more work for the installer !

Also, being the old "skin flint" that I am, I can't see spending any extra for ANYTHING that is not needed !

 

[meathooker]

I just wire a house this week, all recepts on 20, all lights on 14, so much easier, some cheaper, so much better making terminations and having the fixtures on 14/15 cant hurt,,, lowers the potential fault current quite a bit.

We just did my new house. Doing all recepts on 12 and lights on 14 makes so much sense. Doing lights on recept circuits seems cheesy tome.

 

[westom]

We just did my new house. Doing all recepts on 12 and lights on 14 makes so much sense. Doing lights on recept circuits seems cheesy tome.

Putting lights on a separate circuit is done for many reasons. Since lights back then consumed so little power, then a 15 amp circuit was more than sufficient. Today's bulbs consume almost on tenth less power. So that already oversized 14 AWG circuit is even more oversized.

Then we wire smoke detectors on a second (dedicated) 14 AWG circuit. What a waste. Those things combined do not even draw one amp. But 14 AWG is the smallest size available.

We also put a refrigerator on its own circuit - for human safety reasons. But a refrigerator typically does not even need half of those 15 amps. But again, it is the smallest wire available.

Second, if something trips a breaker, then lights on a second circuit mean that room still has light. In this case, a human safety reason.

Some inspectors want that bathroom overhead light also on the GFCI. So when the bathroom GFCI trips, all bathroom lights go out. I never liked that (their) interpretation.

Third, one previously noted what I have always regarded as troublesome (but necessary). 14 AWG is much easier to wire than 12 AWG. It is not a code issue or a human safety issue. 14 AWG is just easier on the hands and good connections to receptacles are done faster.

Code only defines what is necessary for human safety. For example, it says nothing about appliances safety. Then we typically do things beyond code. For example, some position a receptacle ground prong on top. And some put all lights on a circuit separate from one that powers receptacles.

 

[westom]

How much does it really hurt your circ saw to drop from 122 to 115? The horror of the heat,,, like most guys here could work hard enough to put any real wear on one anyway and could the user ever notice.

Generally 120 volts is any voltage from 130 down to maybe 110. If voltage drops to 115, the motor will consume more current an get hotter. How much? It will vary with motors. But generally 115 will probably not increase that current by much.

A Kill-A-Watt (a powerful and inexpensive tool) might be used to better see those numbers. The motor at 120 volt under max loading might draw much more current than a motor on 115 with a more normal load. Making measurements would say more.

That same motor designed for 120 volt service may also work just fine in other nations where the standard is 110 (ie Japan).

A voltage below 110 or 100 generally is not good for long term use. AC utilities (to reduce power consumption) will lower voltage. So as to not harm motors, that reduction is never more than 5%. That is their standard for what is too low. And would be well above what actually is too low.

That Kill-A-Watt is a powerful tool (for about $20) that teaches layman much about AC electricity.

 

[theoldwizard1]

Then we wire smoke detectors on a second (dedicated) 14 AWG circuit. What a waste. Those things combined do not even draw one amp. But 14 AWG is the smallest size available.

Yep ! You are not going to see Southwire or QO or any other manufacture push for 18AWG NM-B and 5A breakers !

We also put a refrigerator on its own circuit - for human safety reasons.

Explain that logic (or is it now code) ?

Some inspectors want that bathroom overhead light also on the GFCI. So when the bathroom GFCI trips, all bathroom lights go out. I never liked that (their) interpretation.

Concur !

Third, one previously noted what I have always regarded as troublesome (but necessary). 14 AWG is much easier to wire than 12 AWG. It is not a code issue or a human safety issue. 14 AWG is just easier on the hands and good connections to receptacles are done faster.

And that was also one of the things I was trying to say in my original post !

Code only defines what is necessary for human safety.

I am not sure I buy that ! We have electricity in millions of home in the US some for over 100 years. Thank goodness we got past "knob and tube", but I still have fuses and have not blown one in YEARS (probably over a decade). IMHO, tamper resistant outlets and arc fault breakers are code so that the equipment manufactures can charge more and make more profit !!

 

[theoldwizard1]

A voltage below 110 or 100 generally is not good for long term use.

A lot of medium duty ( > 1/2 HP) motors are now designed for a wide input voltage range (208VAC-240VAC) and 50Hz or 60Hz. (Japan is weird. IIRC 100VAC-110VAC but 50Hz. Brazil is weird also. Mostly 240/120VAC split phase @ 60Hz, but there are pockets of 220VAC @ 50Hz.)

 

[Jim greengo]

Yep ! You are not going to see Southwire or QO or any other manufacture push for 18AWG NM-B and 5A breakers !


Explain that logic (or is it now code) ?


Concur !


And that was also one of the things I was trying to say in my original post !


I am not sure I buy that ! We have electricity in millions of home in the US some for over 100 years. Thank goodness we got past "knob and tube", but I still have fuses and have not blown one in YEARS (probably over a decade). IMHO, tamper resistant outlets and arc fault breakers are code so that the equipment manufactures can charge more and make more profit !!

Theres nothing wrong with knob and tube wiring,its when hacks start butchering it that problems arise.

 

[AntonLargiader]

..A Kill-A-Watt (a powerful and inexpensive tool) might be used to better see those numbers.

I looked them up last week. A lot of reviews indicate that they melt when used near the 15A limit.

 

[sberry]

Originally Posted by westom
Code only defines what is necessary for human safety.

I think the language is more to the effect that its to protect persons and property and not neccesarily good design or max efficiency.
It doesn't mean its inadequate either and the majority of the worlds load is significantly less than fully loaded branch circuits in developed countries.
I got a thousand amps of breakers in the panels and a couple amps load at the minute with little bursts and some minor heat. Could actually run most of the time at 30A service if it was managed. 400A service thru a 15kva ******.

 

[Stuart in MN]

Wires are significantly oversized. Then voltage losses are sufficiently minimal. 14 AWG wire was once the standard for 20 amp circuits. It was increased to 12 - not to eliminate overloads - to reduce voltage drops on those long branch circuits in a structure.

That must have been a long time ago...I have a 1938 code book here on the shelf above my desk, and it says #14 for 15 amp circuits and #12 for 20 amp circuits.

 

[alfredeneuman]

That must have been a long time ago...I have a 1938 code book here on the shelf above my desk, and it says #14 for 15 amp circuits and #12 for 20 amp circuits.

The 1897 NEC lists #14 rubber covered wire as the ampacity at 12Amps and weatherproof wire at 16Amps

 

[u2slow]

Putting lights on a separate circuit is done for many reasons. Since lights back then consumed so little power, then a 15 amp circuit was more than sufficient. Today's bulbs consume almost on tenth less power. So that already oversized 14 AWG circuit is even more oversized.

Agreed. You can run a whole house-worth of LED lighting on one circuit now. 20A lighting circuits used to come in handy when I wired shops and warehouses with 400W MH highbays.

Then we wire smoke detectors on a second (dedicated) 14 AWG circuit. What a waste. Those things combined do not even draw one amp. But 14 AWG is the smallest size available.

Second, if something trips a breaker, then lights on a second circuit mean that room still has light. In this case, a human safety reason.

Some inspectors want that bathroom overhead light also on the GFCI. So when the bathroom GFCI trips, all bathroom lights go out. I never liked that (their) interpretation.

In Canada the smoke detector may NOT be on its own circuit. I think the intent is sound. Interesting you bring up an 'inspector's interpretation'... quite sure I got criticized heavily on GJ for suggesting an inspector's opinion, because everything in Code is distinctly black or white...

Rule 32-110 provides installation requirements for permanently connected smoke alarms and carbon monoxide alarms in dwelling units that are required by the National Building Code of Canada (see Appendix G). The rule requires that smoke and carbon monoxide alarms be supplied from a circuit, such as a lighting only or mixed lighting and receptacle circuit, that will provide an indication if shut off. The circuit shall also have no disconnect or a GFCI or AFCI device between the alarms and the branch circuit overcurrent device.

We have electricity in millions of home in the US some for over 100 years. Thank goodness we got past "knob and tube", but I still have fuses and have not blown one in YEARS (probably over a decade). IMHO, tamper resistant outlets and arc fault breakers are code so that the equipment manufactures can charge more and make more profit !!

Agreed! The focus is about profits, under the guise of 'safety' for new installations. Apparently there's no major safety concerns with what was installed in the last 40-50 years otherwise the rules would be retroactive. Currently, its only when house insurance rejects you that there's any incentive to improve things.

 

[AntonLargiader]

Agreed! The focus is about profits, under the guise of 'safety' for new installations. Apparently there's no major safety concerns with what was installed in the last 40-50 years otherwise the rules would be retroactive. Currently, its only when house insurance rejects you that there's any incentive to improve things.

Oh puh-leez. Here in the US we have practically zero tolerance for retroactive improvements to pretty much any privately owned non-commercial property (real estate, automobiles, whatever). Implementing forced upgrades to millions of houses is simply a non-starter. Conflating that with "there must be no actual safety aspect" is ridiculous.

 

[Roundhouse]

I use 12 for lights , it’s not worth having to keep up with two different rolls of wire and which one goes where and what’s going to be on the circuit ,

Just do em all with the same one

A one inch chase ?
You mean conduit ?

And it’s always fun to watch a novice attempt to wire a three way switch

And as previously posted
ALL the “reality” shows are totally totally fake .
The home improvement ones are fake , the hot rod builder ones are fake
They are all fake

The only one that was not fake and was very entertaining was “my obnoxious fiancé “
That was hilarious

 

[sberry]

Nothing wrong with 12, just not needed most of the time. They make 50A single pole breakers I believe, 30 are often used for lights and that's why there is often an additional fuse in some fixtures,, for hooking them to circuits above 20A.

 

[u2slow]

Oh puh-leez. Here in the US we have practically zero tolerance for retroactive improvements to pretty much any privately owned non-commercial property (real estate, automobiles, whatever). Implementing forced upgrades to millions of houses is simply a non-starter. Conflating that with "there must be no actual safety aspect" is ridiculous.

Exactly.

 

[nsula_country]

I'm in the US. Wired our ENTIRE house. I placed 6 smoke alarms on a single 20A circuit. Passed inspection. They have batteries too, if low they chirp and piss off wife. Then I replace 6 batteries.

Every bathroom (4) has fart fans and can lights over the showers. Separate 20A GFCI BREAKER for bath lights and 20A GFCI BREAKER for bath receptacles.

Dedicated 20A circuit for septic air pump. Dedicated 20A circuit to alarm panel. Dedicated 20A circuit for network closet. Dedicated 20A circuit for 6 motion lights on 3 way switch at 2 doors. Dedicated 20A for dishwasher (non GFCI). Dedicated 20A for fridge (non GFCI). Dedicated 20A for 2 island receptacles (non GFCI).

Overkill, maybe. But in the grand scheme of a $300k house build, 12 vs 14 wire would not have affected the budget $500.

Also ran 8GA to 3.5T and 2.5T condensing units... Had it on hand when pulled the wire to range top and double oven. Could have used 10GA and 12GA.

CT

 

[nsula_country]

I do a lot of control wiring. Which most is 24VDC now. Mostly use 16GA and 18GA for control cabinet wiring. Field device cables may be as small as 24GA. Most Input and Output circuits are fused at 1-2A.

Older AC cabinets were 14GA and 16AG control wiring, 5-10A fuses.

CT