Electrical code in U.S. for wiring...

Thread Starter

Externet

Joined Nov 29, 2005
1,411
Hi. A bunch of questions for electrical code knowledgeable members. Am not an electrician.

What wire are you supposed to use for a less than one Ampere current in household installations for 120VAC ?
For a single 9W LED lamp, from box to box? Pisses me that they call it speaker, control, alarm, doorbell, thermostat, hookup:rolleyes: wire...
Way too many electricians will say "use Romex 14' What about Romex 18, Romex 20 ...? cannot find such; is there an equivalent in the market ? What is it ? What about running several single conductor wires, instead of the three-in-one Romex that anyone has fixed in the brain ?

Is this acceptable ?
----> https://systoncable.com/products/hvac-thermostat-cables/7646-20-awg-6c-solid-thermostat-cable-cl2rcmr/
 

SamR

Joined Mar 19, 2019
1,179
My little pocket NEC guide stops at 18AWG for 14A depending on insulation. Not a residential guy so not sure what Romex insulation is except it's not UFW underground feeder wire I don't think which stops even higher. Romex is a trade name and I'm sure has several NEC classes of insulation...

edit: no any other wire uses a step down transformer to 12/18/24...
 

SamR

Joined Mar 19, 2019
1,179
I can only scratch my head at 14A since I have never heard of a fuse or breaker that size but that is what the table says. Maybe on a 10A fuse? Typical 120VAC breakers are 15, 20, 30, etc. Most modern panels use 20A 12AWG minimum and if it's not a single dedicated receptacle they can be rated for 15A even though it's a 20A circuit. Contractor's like 15A 14AWG to save a bit on construction cost. I caught an electrician using 12/3 wire for 2 circuits, Hot, Hot, NEU, no GND and he tried to tell me the Code says it's OK.
 

Thread Starter

Externet

Joined Nov 29, 2005
1,411
Wire size isn't determined by the size of the load current. It is determined by the size of the over current protection device.
Wait ! that is interesting... So if a 10 Ampere breaker (or fuse) in the breaker panel, feeds a subpanel with a dozen 1 Ampere AG3 fuses in it for each of the less than 1 Ampere dozen lighting circuits, it is allowed to run AWG 20 to each lighting circuit ?
 

SamR

Joined Mar 19, 2019
1,179
The wire size and its amp rating according to the NEC table depend on its insulation class which depends on its use. HI temp, buried, wet, plenum, etc. That amp rating cannot be exceeded by the protection device. Single conductors require conduit, cable does not for 120/240VAC. Anything less than 18AWG is not in table 310-16. That table is for 0-2000VAC. See link for table. Hookup wire, etc. is for use with a step down transformer. EG single pair twisted bell wire and such. And apparently, 14AWG is rated for 20A.

http://www.safecoelectric.com/images/resources_pdf/NEC2008 Table 310.16.pdf
 
You really have to do something else. You need to look at Class II wiring and power supplies. Class II will not require conduit. 120 VAC is not class II. The Class II power supplies are inherently power llimited.

For LEDs and lighting, I'd probably be looking at DALI systems.

I had to hook up a bunch of horns, strobes, etc. as part of a safety system that interfaced with the fire alarm.

The fire alarm provided a contact for me to use and i provided fire alarm contacts from gas monitors and hydrogen alarms at level 1 and level 2. Level 2 set off the building alarm. level 1, I handled.
The UL listed battery backed up power supply allowed me to control multiple class II circuits. Each strobe could be on a class II circuit, so no conduit.

My supplies were 24 VDC. Wiring was with Red outer insulation PTFE insulated Fire Alarm Cable usually about 16 or 18 AWG, firestopped and plenum rated as required. There were a number of firewalls that had to be penetrated, but did not stick all of the wires through a PVC pipe and seal them.
 

MaxHeadRoom

Joined Jul 18, 2013
19,063
What wire are you supposed to use for a less than one Ampere current in household installations for 120VAC ?
For a single 9W LED lamp, from box to box?
If going box to box from an existing circuit then you will need 14/2 and GND.
Here in Canada most of the service supply sites have a local wiring code aimed at DIY installations, usually a temporary license is needed.
The local web site usually offers advice or a Tel No or link for contact purposes.
Most likely the only way to go down in gauge is if it is a dedicated circuit and has the appropriate fusing etc applied.
Max.
 

Thread Starter

Externet

Joined Nov 29, 2005
1,411
Thanks, kiss.
Am really not wanting to consider dali. Plain 9W 120VAC LED bulbs use less than 0.1 Amperes.



Which a hair thin AWG 36:eek: wire can carry ten times. But what is the 'normal' action ? Waste copper and $ using 14AWG ! In theory, CAT1 - CAT2 :rolleyes: wiring could suffice.
upload_2019-10-10_10-31-37.png

Non-metal jacketed multiconductor (as Romex) does not requiere conduit. Non-metal jacketed multiconductor as "thermostat" AWG20 wire does not requiere conduit, and is rated 600V. But smells like would not comply with code using it for 0.1 Ampere current on 1 Ampere fused circuits.

upload_2019-10-10_10-52-41.png

Something is not right with demanding rules for modern low current consumption lighting...
 

Jon Hoover

Joined Oct 10, 2019
9
Here's my understanding of the question. He wants to run 120 volt LED light bulbs in a lighting fixture and wants to know why he needs 12 AWG or 14 AWG wire feeding the fixture if the LED(s) only draw < 1 amp. Here's the best answer I can come up with. Residential wire size is not specified according to the load. The load may change depending on what is plugged in or turned on. It is sized according to the size of the breaker/fuse that is feeding it. Remember that the protection device (breaker/fuse) is there to prevent the wire from melting in case of a short. So, if you have a 20 amp breaker feeding this circuit, you would want to use 12 AWG wire. 15 amp breaker = 14 AWG wire, etc. Make sure and verify this with the NEC or your local electrical inspector. When it comes to the type of wire, certain states or cities in the US regulate what type of wire must be used in residential wiring. Some areas let you use Romex, some areas require all wiring to be in conduit. You also need to be aware of the voltage rating of the insulation. If your bell wire insulation is only good for 100 volts and you are using it for 120 volts, then you could end up with a dangerous situation. I hope this helps answer your question. Remember, it's not the load but the size of the protection device that dictates the wire size.
 

Lo_volt

Joined Apr 3, 2014
80
If it's permanently installed, especially inside your walls, use 14 AWG Romex. Looks like you're wiring normal Edison sockets. This means there's a chance someone will screw in a normal incandescent bulb. Also, when you sell your house it won't be flagged by an inspector. As mentioned above, the wire is sized to the breaker.

I understand your concern about overkill using 15 amp capable wire on a circuit that uses 1/100 the current. Maybe we'll see changes to NEC code as LED's become more prevalent but, for now that's what we have.

Lastly, look at the bright side, there's precious little I^2R power loss in oversize wire.
 

DickCappels

Joined Aug 21, 2008
5,897
It looks as though if you want to meet code (and you should, even if it doesn't always make sense to your way of thinking) you will have to actually meet code.
 

Yaakov

Joined Jan 27, 2019
1,547
It's pretty simple, according to article 410.6 of the NEC:

"All luminaires and lampholders shall be listed."

Full stop, no qualifications.

Here's the 2008 version in PDF:(Sorry, the document has a copyright statement that says, in really tiny print,
"Copyright National Fire Protection Association
Provided by IHS under license with NFPA Licensee=Aramco HQ/9980755100
No reproduction or networking permitted without license from IHS" The link to the document has been removed. You can post an excerpt showing what you found.)
 
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