I am in the process of rewiring an exterior neon sign. The neon sign consists of 6 separate neon tubes with a combined length of approximately 40 feet. The neon tubes are daisy chained together until the last one and the one next to it which are each hooked up to the transformer (two wires are connected to the transformer). The one of the two wires connecting the transformer to the neon sign previous melted. The type of wire was 14 gauge high temperature wire (copper in the center surrounded by a thick jacket, I believe it's rated for 90 degrees). The transformer is rated for 15,000 volts, 4.25 amps, 30 mA, 60 hz. I have a couple questions.

1) What would cause the wire to melt (bad transformer, too many neon tubes connected, too small of a wire)?
2) Is there a thicker wire available that would avoid this (like 12 gauge with a thicker jacket) and what temperature should it be rated for?
3) Is there a high temperature conduit available to run the wire through (it needs to be flexible). I checked Home Depot, and saw flexible conduit for use underground and/or liquid-proof but it did not say if it was rated for high temperatures.

Thank you.

Neon is a very specialized product. You should really have a sign company look at this.
Have you seen what 15,000+ volts can do?

The wiring must be rated 15,000 volts, and that is not available at Home Depot, only a sign contractor or supplier will have it. Penetrations must be done properly also.

Neon signs are not for DIY'ers.

Just to confirm so I have a clearer idea of the project when speaking with an installer:
1) The wiring must be rated for 15,000 volts. Is 14 gauge high temperature wire (copper in the center surrounded by a thick jacket) rated for this? I ask because it was used to daisy-chain the tubes together and I would like to know if it needs replaced. If it does need replaced could you please let me know what gauge and brand of wire (preferably with a link) would work?
2) Could you elaborate (or post a link) on what you mean by proper penetrations?
Thank you.

Ohio_Remodeler14 is the size of the wire. 15kV is the voltage rating rating. Neither is exclusive or related to the other.
A neon installer/tech will know if #14 is big enough. In fact, I bet he has everything he needs right on his truck or in his shop.

Penetrations are where the wire goes into the glass. This is a very specialized procedure.

The penetrations I was referring to is if the high voltage wire needs to pass through any structure. Most times this is avoided due to problems later.

Just because a wire is rated high temperature does not mean it is rated for high voltage.

As Stan said, any qualified neon sign installer will have the necessary parts available.

Thanks for you help Stanfortyman & tkrussell. I just saw a 15,000 volt jacob's ladder video on YouTube. I will definitely get an installer to handle this one.