To the OP, I first suggest looking up your local electrical code and investigating the appropriate regulations and specifications.
Here in Canada, the minimum size of wire that may be permanently installed, run through walls, etc. for
MAINS is 14 ga (AWG). This corresponds to the minimum conductor ampacity required for the minimum sized circuit, 15A (120v, 60 Hz, of course.) You are never allowed to use smaller wire, under any circumstances for
MAINS installations. Low voltage, fine. You can use things like 18ga bell wire to wire your 24v doorbell, etc. There are separate regulations and requirements for these low-voltage circuits. In most parts of the world, these classes generally change at around 48 Vac or 60 Vdc, but it can vary by jurisdiction.
An extension cord or appliance cord that is used to temporarily connect an item to a mains plug, never run through a wall or permanently installed, can be smaller and it is up to the manufacturer of the appliance or the user of the extension cord, etc. to ensure that the cable used is appropriately sized,
however, there are still rules! Here in Canada, an extension cord or device cable on an appliance may
never be less than 18ga, even if the load is only a few watts. This allows enough ampacity to allow a breaker to blow if there is a short in the appliance before the wire bursts into flames.
Interestingly, the only exception to the 18ga rule is for Christmas lights. "
Tinsel Cord" as our code calls it, is allowed to be as small as 20ga, but modern regulations require a 3A fuse in the plug itself (typically a one-time, non-replaceable imbedded fuse) to help protect the tiny cord. Other than this, we typically don't have fuses in the device plug like they do in Britain.
My main point is that you probably are never allowed to use 24ga wire of any insulation type to run mains. Under
any circumstances! It is a good idea for a reason and is minimum code for a reason. There is plenty of math behind these decisions and I suggest to the OP that he begin by doing the math as to how well a 24ga conductor will handle a fault condition at 220 volts and go from there.
The reasons why you "
don't do that" should begin to be self evident.