I just installed such a fan yesterday.
The motor was rated at about 1.5 amps, plus a 60 watt bulb. So, we're looking at 2 amps total. Three such fans would be about 6 amps.
From an engineering standpoint ONLY, #18 wire ought to be able to handle about 7 amps. Therefore, I'm not surprised that this unit ran fine, or that there are no signs of overheating.
Of course, there are still the issues of insulation rating, mechanical protection, and short-circuit protection. The breaker is still let 20 amps go through the 7 amp wire- which would allow the wires to imitate toaster filaments.
Need to be fixed? Absolutely. End of the world? I don't think so.
