What are the effects of using all of the 80% of the power supported by 15A circuit breaker (220 volts, #14AWG wire)?
In the US under the NEC (I believe Canada is similar) you can run 80% load on a circuit 24/7. You can run 100% load intermittently, or by accident, or even occasionally if it's not expected, even for three hours or more.
The key is the actual definition of &quot;Continuous Load&quot;, not an arm-chair definition, or what an old timer always told you.

Continuous Load.-
A load where the maximum current is expected to continue for 3 hours or more.