I plan on rewinding my 175w NEMA ballast when it croaks. It has some chips on the enamel, is slovenly wound, and looks to have thin application. I will measure the gauge of the wire when the ballast gets woodshedded after it does die. I have a few questions.
What temperature rated wire should I buy?
What temperature varnish should I use, I only see the red class h varnish. Thanks.

Rewind it now, while you can still unwind it properly and count turns etc

Besides, measuring the wire thickness with calipers etc is as inexact as it gets.. Better measure its resistance and then calculate with the resistance and the length of the unwound wire. And check the same with the new wire you are going to use

If there is some big room in the window of the core, you might consider thicker wire... But it depend on your winding skills how well you can compact it there

Most ballasts over here are tw130 = 130C = 266F. Definitely try to get higher than that by atleast few tens C / ~100 F

Protect the wire from scratching on the inner edge of the core whne putting the new wire in

Ash, I did some digging and figured I shoyld use 200 Celsius wire. But, I still am unsure on the class f varnish. Should I use concentrated isopropyl or acetone to weaken the old varnish? I forgot to mention that the ballast has a thermally rated plastic bobbin which the coils are wrapped around. Also, thanks. I fortunately have a 100 watt HPS NEMA kit to use until I get the ballast to do ballast things properly.

Are you going to take apart the core or rewind it by pulling the wire through ?

Are you going to take apart the core or rewind it by pulling the wire through ?

since I don't have access to welding gear or an angle grinder to grind the weld apart, I think I'll feed the wire thru, but I will wrap the exposed parts of the core with electric tape so I won't scratch varnish off in the process.