Originally Posted by iflytb20
And considering that the APU is always running at 100% RPM, I doubt if it has a MCT EGT limit.
APU is fuel-governed to maintain almost the exact RPM the entire time, since it acts as a constant-speed unit for the electric generator. This doesn't mean that it doesn't have a maximum continuous EGT limit (I wouldn't use the term MCT since the thrust output from APU is negligible) - EGT is not dependant only on RPM. On the APU, EGT is a good indication of the load on the APU - more load on the APU will require higher fuel flow scheduled by the fuel control unit - and if you increase fuel flow, the EGT will also increase.
I don't know specifically about the NG, but the Garret APU on Classic has a start EGT limit of 760°C and continuous limit of 710°C - so there is a maximum continous EGT limitation on some APUs.