Complex sentence: These modern PTAC units replaced the radiators throughout the community when the central boiler heating system was abandoned and still can be seen from the exterior of the building as grates under the windows throughout the property.
Split into simpler sentences: These modern PTAC units replaced the radiators throughout the community when the central boiler heating system was abandoned. The PTAC electric units still can be seen from the exterior of the building as grates under the windows throughout the property.