[PDF] Electrical Plan Design - Jones & Bartlett Learning electrical systems for an existing building, then the electrical designer works to incorporate all the new electrical wiring into the existing system. The de-signer must evaluate the existing electrical system to ensure that existing electrical systems can accom-modate new additional electrical loads that will be imposed on them. Home Building Plan: Electrical Wiring - saybuild Spec Plan H: Electrical Wiring . what you need to do — Identify any special wiring needs by room: — home sound system who will can customize a building plan or revise an existing plan that meets your specs. use your spec sheet and floor plan to bid the construction project to contractors .