Make note of building feeders when doing your take-off and preparing an electrical estimate. Feeder wires are generally size # 4 and larger. Label the feeders “from” and “to”.
Example: From Panel M-1 to Panel L-1
Take off feeders in order (one after the other) from the single line diagram in a logical sequence. Make sure to highlight each feeder when you measure it and write the length on your take-off sheet.
List the feeder conduit type (GRC, EMT, PVC, etc.) And, list the conduit size, number of wires and size of wires, number of runs, supports, ells, condulets, adapters, special fittings etc. Make notes on the take-off sheet (margins or other blank space) of the type of conduit fittings and wire make up lengths.
On your take-off sheet, under each feeder heading, count and show core drills, fire seals, water seals, concrete cutting or patching, if needed.
Red Rhino Electrical and Structured Cabling Estimating Software has many training videos online so you can learn at your own pace
Always measure conduit at right angles - Take off all conduits at right angles to the plan. (All 90 deg turns) Do not measure on diagonals. By measuring at right angles, you will allow enough conduit and wire to go around obstacles or obstructions in the building that you do not know about when you are doing the take-off. Take-off any interior trenching and backfilling.
Take-off conduit risers - A conduit riser is the conduit that runs vertically out of the top or bottom of a panel. When you are estimating and rolling off or measuring conduit, it is essential to include the risers in your take-off.
Underground risers going into the bottom of a panelboard are usually around 5 feet (for 1st floor applications). To figure out what conduit riser length out of the top of a panel; figure the distance between the top of the panel and the roof or deck above it (deduct the distance that the hangers hang down).
Remember to calculate conduit riser lengths at each end of every conduit. Add the correct conduit riser length (plus wires) to your take-off sheet.
Add for wire make-up length - Wire make-up length is the distance that wire sticks out of the conduit so it can reach the termination point. It is necessary to add enough wire coming out of the end of the conduit to reach the termination point.
Say that the conduit lands on top of a 7' 6" switch board. You must include enough wire to reach the breaker, lug, or make up point, where the wires are to be made up. You must consider how much make-up length is needed at both ends.
Wire make-up for feeders is usually 7 feet for switchboards and 5 feet for panel boards (for both ends, it equals 12 ft.). Wire make-up should also be included when you are pulling thru pull boxes or junction boxes. It can be very expensive to leave out wire make-up lengths.
Add for conduit and wire waste - When electrical estimating, allow 10 to 25% additional MC cable in your take off for “trim off” or waste. The percentage that you add for waste will vary, but with experience you will be able to gauge the percentage that works for you. The amount of wasted conduit and wire on a job depends on your crews, or more accurately, the supervision of your crews.
Instructing your foremen to keep the amount of waste to a minimum will make a huge difference on the amount of waste that is created. You will want to track on your jobs and develop a history for conduit and wire waste. Do your jobs consistently run over cost for conduit and wire? Learn what that percent of waste is, and add it to your estimates.
Also, allow a minimum of 10% additional EMT, GRC and flex conduit to the take-off for “trim off” and waste. Again, you should adjust these percentages according to the history of jobs that you have done. If you do not add something, then you are losing money. No job is completed with zero conduit and wire waste.
Take-off branch circuits
1) Branch circuit is generally ½” through 1” conduit size and #14 through #6 wire size.
2) MC cable 14/2 through 6/3 is generally included in a branch circuit take off.
3) Site lighting and power is generally ½” through 1 ½” conduit size (usually PVC or PVC coated RGC) and wire size #14 through #4.
4) Communication branch is usually ¾”, 1” 1 ¼” 1 ½” EMT or flex.
List the common conduit size and number of wires on your take-off sheet. Also list the other conduit and wire sizes, as you see them, throughout the rest of the branch takeoff. Note the plan sheet number or area number on your take-off sheet. This will help track or review where you found and measured branch circuit. This will also make it easier to adjust for changes or addendums.
List the conduit size, number and size of wires, number of runs, supports, ells, condulets, adapters, special fittings, etc. Make notes on the take-off sheet (margins or other blank space) of the type of conduit fittings, and wire make up lengths. This information will be useful to you when you input and price your estimate.
Take-off all conduits at right angles to the plan (all 90 deg turns). Do not take-off on diagonals. On your take-off sheet, under each branch home run heading, count and show core drills, fire seals, water seals, concrete cutting or patching, if needed. Take off any interior trenching and backfilling.
Remember that electrical estimating works best when you do your feeder and branch circuit take-off systematically, highlighting each conduit as you go. Good electrical estimating software will include a conduit wizard for rapid input of conduit.