Going from 14-3 to 18-3 wire through a 120 volt switch

I want to install a switch on a 120 volt line for .6 Amp (AC) LED lights. Can the LED side of the switch be 18-3 AWG wire while the supply side is 14-3? The short wires on the four 18 watt lights are either 18-3 or 20-3.

 

If the voltage out is 120v then the wiring must remain at #14 gauge.
You would have a junction box connecting the 14-3 with the 18-3.

 

Since the overcurrent device/circuit breaker for 14 gauge wire is 15 amps you will be required to complete the circuit in 14 gauge wire. 18 gauge wire would not be protected by the existing 15 amp breaker.
There might be a way to install a new/additional fuse or circuit breaker, but I think you would spend more money than using 14 gauge wire.

 

Glad I asked...thanks
The wires that plug into the 4 LED lights are 18-3 so to have them supplied from a 15 Amp 120 volt breaker, through a 14-3 wire I would place the switch within the 14-3 run and locate the junction box after the switch? I need to run an extra foot twice to run two sets of two lights each. I was hoping to use 18-3 for the extra two feet as they will terminate at 18-3 very quickly anyway.
I guess the other way of asking this is how to connect a switch to a 14-3 wire to run power to 18-3 light power cord?

 

Unfortunately you are missing a vital part of this project. The manufactures instructions. I am going to say from looking at the picture you uploaded, that you are missing a transformer somewhere. LED lights that hook up to an 18 Gauge wire are going to be a lower voltage than what is traveling through your 14/3 from your breaker box. Which brings up another question. Why do you have a 14/3 coming from the breaker? Or is it 14/2 from the breaker and you have a couple of three way switches, so that is where the 14/3 comes from?

 

You're correct. I kept putting 14-3 rather than 14-2 with ground. It's the 18-3 than has the third wire to complete the ground. Just a mindless mistake.
I've attached a photo of the label which indicates it takes a wide range of AC voltage.

 

this is going to seem like double speak. Manufactures can and DO get assemblies passed by inspection agencies all of the time. Item, water heater, takes a 30 amp breaker, and #10 wire to feed. Inside the heater is #12 wire, at least all of the ones I have connected. I am referring to UL, CSA, or ETL for N. America. These three certs can be interchanged with no worries.

It would appear you purchased a product that has NOT undergone safety testing, no label shown. Believe me if they had paid the money and got passed they would have the label plastered everywhere. Last product I was involved with was a terminal box at 1200 amps, we paid $80K to UL 3 times and made changes to get it passed.
The box flap gives you a lot of information. The mfgs 18 wire is good for 6 sets. 6 x 18= 108 watts
108 watts/ 120v = 5.4 amps. A quick check online says 18 gauge wire is good for 10 amps.
To pass the NEC, cause that is the code your working by, not the code the mfgs use. You need to connect a fuse or circuit breaker at the end of your 14 gauge wire where 18 starts. Inline fuse holder rated at 120 v would be fine, fused at 5 amps. My safety recommendation.

There are a ton of products out there to by. A large volume have not passed any safety inspection. Use them in you home and IF there is a problem and the arson guys find this product to be at fault. Your insurance company is probably going to deny the claim.

 

The next time you connect one of these electric water heaters take a closer look at the internal #12 wire and you'll find a higher temperature rated insulation than is typically found on building wire, that #12 is rated for 30 amps.