When I plug-in a conventional heating pad or a hair dryer into any bedroom duplex, the lights dim; and/or trips the circuit breaker. The home is of new construction-- placed in service 31 Dec 2013. My question is: Can I safely replace the existing 15 AMP Breaker with that of a 20 AMP? . . . the service cable is of 14 Gauge Copper Conductor.
The only safe way to increase the circuit's capacity is by replacing the wire with one of adequate gauge. For 20 amps, 12 AWG copper is adequate for up to about 100 feet.
If you simply replace the breaker, the wire can overheat and ignite the building from inside the walls.
To resolve the dimming issue, check that the outlet is in good condition and that the wires are securely fastened and not showing any signs of overheating: blackening or loss of the copper shininess. Also, check the end of the wire inside the service panel, both neutral and "hot" (black) wire. If those are okay, set the appliances to a lower wattage setting or replace them with lower wattage models.
It's like this... Wireing is sort of like tubes you use to run water. Breakers are like an on off valve that also controls how much water(electricity) can to into the tube(wire). If you force too much water in a tube, it breaks and water gets everywhere. If you force to much electricity in a wire it breaks(melts) and gets fire everywhere. Fire is a lot more of a pain to clean.