Answer: A, B, C.
Answer analysis: The content that needs to be checked before electrical installation includes the number of electrical components, whether the specifications of electrical components are the same as the drawings, and whether the accessories are complete.
Before electrical installation, the following checks are required:
Check the number of electrical components: It is necessary to ensure that the number of electrical components required is complete, whether there are omissions or missing components.
Check whether the specifications of electrical components are the same as the drawings: It is necessary to check whether the specifications of electrical components are consistent with the design drawings, including voltage level, current capacity, control mode, etc., to ensure that they meet the engineering requirements.
So, depending on the title, the answer is ABC.