The electrical ampacity ratings of wire are based on a number of things including the temperature rating of the insulation. If you are in an area where the NEC applies acceptable current ratings can be defined in the code (for specific usage). Transformers are an interesting discussion but I think I’d side with others and have to question the wisdom of 18ga wire in a secondary operating at greater than 15

The reality is comments from a transformer designer / engineer would shed more light on the issue. The other problem here is the fact that far too many online sellers have no idea what they are selling. The 18 ga could easily be the primary.
Quote Originally Posted by __Britt View Post
Disclaimer: I am not an electrical engineer; nor do I play one on TV.

Well, FWIW there is this:

https://www.powerstream.com/Wire_Size.htm

At 56v, 1000 watts is about 17.9... lets call it 18 amps.

18ga wire, according to that chart, should be good up to about 16 amps in free air; but only 2.3 amps in a bundle... this leads me to thinking that the wire in question is a bit on the light side for the task at hand. On the other hand; I often see transformers wound with lighter gauge wire than what is feeding them, so... ???