Your electrical has to be installed in concrete walls before they are poured. Otherwise you will be bolting boxes and conduit to the surface and then explaining to the architect why the wall finish has to be changed. By carefully following the measurements provided on your approved blueprints and securing your electrical conduit and boxes in the concrete form, you will not have to worry about passing an inspections or pulling the wires later. Following the steps below will eliminate both of those worries.
Things You'll Need
- Electrical blueprints (specific to your building)
- Tape measure
- Electrical conduit
- Tie wire
- Side cutting pliers
- Nylon twine (if needed)
- Electrical boxes
- Duct tape (if needed)
Lay out and mark the path and locations of your electrical conduit runs and electrical boxes as specified on your blueprints. Use a tape measure to ensure accuracy. The electrical engineer assigned to the design team has already made sure that the placements of your elements are within the building code standards. Their work has then been reviewed and approved by the local agency in charge of making sure that all construction plans that receive a building permit comply with code. The more exactly you can duplicate the measurements on your drawings in a real life situation, the better able you will be to pass your final inspection.
Run your electrical conduit in the form. Make sure that you leave 12" of the conduit outside of the form so you can join it later to the rest of the buildings electrical supply. Tie the conduit directly to the rebar wall inside the concrete wall form using tie wire and a pair of side cutting pliers (these will also let you cut the wire without an additional tool). Do this every 4' along the conduit and try to tie it at the point the horizontal and vertical bars cross. This will give you a tie that will not be able to slide out of position under the force of the concrete pour.
Tie the end of your nylon twine to a long pieces of tie wire and push it through the conduit. Most conduit comes with twine already placed inside so you may not need to thread the conduit. If you do, work in short sections and splice the conduit sections together with duct tape as you thread each one. This twine is what you will use to pull the actual electrical wire through the conduit once the wall is poured.
Place your electrical boxes on the interior of the concrete wall form with the opening of the box flush to the face of the concrete form. Nail the boxes into position. An electrical box may be for an outlet, switch, junction or control panel (to name a few styles). Connect your conduit to the box and make sure that the nylon twine in the conduit is taped to the inside of the opening of the box so it does not fall back inside the conduit during the pour. Pay particular attention to the placement measurements detailed on your drawings as their are several different building codes that may affect your building. They may call for a specific measurement for the placement of electrical boxes. The drawings you are working on have been reviewed and approved by the local agencies responsible for making sure that everything complies to the necessary codes—do not deviate from the placements detailed.
Call for inspection. Once the building inspector has approved your installation the concrete pour may begin. When the concrete has cured and the forms are removed you may pull the electrical wires through the conduit and into your boxes and install the switches, outlets, junctions or other electrical items needed.