Sorry I missed this. DONT DO IT! You will burn the building down if you put to much load on that wire. 15amp breaker probably has 14 guage wire and the 20 would be 12. The wire cant take a 50 amp load and would start to heat and melt the insulation etc..... Been doing this since 1986. well I am a pencil pusher now but I did my time in the field. Years ago it was common to only have a couple circuits in your entire house but with the changing times and all the electronics and appliances now there is a much more intense code. If you live in an apt I would think they would have to have it to code and a call to the housing authority may clear that up for you. In MASS they have to keep it to the current code and if they dont the housing or whoever has jurisdiction will enforce it and cut the rent until it is done
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