They include open wires on metal cleats, wiring laid directly in plaster, andwiring in wooden molding. The oldest wiring system that may still be acceptable, and one still foundfairly often in houses built before 1930, is "knob and tube." This systemutilizes porcelain insulators (knobs) for running wires through unobstructedspaces, and porcelain tubes for running wires through building components suchas studs and joists.
Note whether knob and tube wiring splices are mechanicallytwisted, soldered, and taped, as required.
This assessment should be conducted onlyby a qualified electrician who is experienced in residential electrical work.
When universal design is a part of a rehabilitation, consult the Housing and Urban Development publication The building's service capacity is the lowest of the above threefigures.
How much it costs to upgrade will depend on the particular house and the location.
Most houses today have two 110 volt wires and one neutral wire running into the house from the local distribution system. If there are two 110 volt wires running to the house, then the house has 220 volt service and appliances, such as dryers and air conditioners.
Once the service ampacity has been determined, compare it to the estimatedampacity the building will require after rehabilitation.
If the estimatedampacity exceeds the existing ampacity, the building's electrical service willneed upgrading.
Foundfairly often in houses built before 1930, "knob and tube" wiringshould be carefully inspected to failed insulation and other safety issues.
Ifit has adequate capacity and is otherwise safe, it is still legal in manyplaces.