Originally Posted by OTRA15
The AS OEM 30 amp cord with our FC20 is #10 AWG and only about 20' long, so you will need a much heftier cord/wire for your 75' run. Like a #6 or larger [lower AWG number]. Please consult with a licensed electrician or wait for an expert to post here. Your current setup carries with it the risk of damaging your electrical appliances incl. the AC, plus a risk of fire or bodily injury.
I am not a licensed electrician but I probably qualify as an expert (electrical engineer) so I will endeavor to answer your question.
If I remember correctly the National Electric Code specifies #12 AWG wire for 20 A circuits and #10 AWG for 30 A circuits. Buried in there is a footnote "for runs up to 100 feet", since the code is concerned not only with heating of the wire but also delivery of satisfactory voltage at the outlet.
30 Amp cords are generally #10 AWG wire and assuming the wire is in good shape (i.e. not too many broken strands) your 75 feet of cord should not be a problem.
If the connectors between cords are getting hot, there's the problem. Give them a good look and replace either or both connectors as needed. Problems might include loose connection or broken strands at the joint between the wire and the connectors.
All of these "20 Amp vs 30 Amp" threads depend on a whole bunch of variables which nobody ever specifies. Offhand I can think of several,
1. Voltage that the power company is delivering to the service entrance.
2. Distance from the service entrance to the 20 or 30 A outlet in question. (Assuming it's wired with the correct size wire.)
3. If a 20 A outlet, whether it's a 35 cent economy grade outlet (typically rated 15 Amps, even if supplied with 12 AWG wire) or a good quality 20 A outlet.
4. Whether the wire is attached to the outlet with screw terminals or by the popular strip-and-insert-in-the-little-hole clips, which have a bad reputation among electricians.
All of which might explain why Joe can run his air conditioner off a 20 A outlet and you can't