Squad 8, Wagon 4, Towers 1, 2, and Battalion Chief 5 (Wise) dispatched on Box 1-4 at 0223 hours to 14th & Swatara Streets for reported house fire. Additional info indicated 2 callers reporting a fully involved abandoned structure. Chief 5 requested the first alarm enroute bringing Wagon 3, Rescue 69, and Air 13 to the scene. Squad 8 went on the scene with a 3 story, wood frame, single, heavy fire 2nd and 3rd floor to the rear. An unattached exposure was starting to smoke from radiant heat as companies were stretching lines. Chief 5 arrived on scene, assumed command, reporting heavy fire all 3 floors throughout and companies will be going into a defensive posture. A 2.5" was stretched from the Squad and a 3 inch line was fed into Tower 1. The fire was darkened down in about 20 minutes with companies remaining on the scene for several hours performing overhaul.