So why are appliances allowed to not follow wire fill requirements.

[Zathius]

Honestly, I have never sat down and actually measured the junction box, but when you have a fan/light/night light/ heater combo, there is no way that isn't overfilled. Maybe I am wrong, if so, does anyone have the measurements of the j-box?

 

[LarryFine]

To answer your thread title, probably because it's utilization equipment, not branch circuit wiring.

 

[infinity]

No need to measure the junction box because the size isn't governed by the NEC.

 

[Dennis Alwon]

Honestly, I have never sat down and actually measured the junction box, but when you have a fan/light/night light/ heater combo, there is no way that isn't overfilled. Maybe I am wrong, if so, does anyone have the measurements of the j-box?

I am sure you are correct but as stated the NEC does not get involved in the manufacturing of the appliance. If the unit get a UL or a third party listing then it is good to go...

Sometimes I wish the box was a bit larger.