pete_c said:@vc1234
I had ordered the 16VAC 30 VA transformer from Amazon and it did not have a ring to box connector rather it was just a set screw which I did not like so returned it.
With low load current/idle losses generating heat predominantly happen in the core itself (eddy currents mainly). Perhaps the 24/40 transformer is heating more than the 16/10 simply because its core is bigger and the designers cut corners and did not try to lower core losses more than necessary to stay within specs re. heat. Not entirely sure, it's been more than 40 years since I studied this stuff.
Optimistically, the temperature may remain more or less constant assuming the core losses still predominate for the entire rated load range !