Offsets in EMT, or electrical metallic tubing, usually are made in the field, using a hand bender. The most common reasons for an offset are to avoid an obstacle or to raise the EMT off the surface of the structure to match a knockout in a box or panel. Before marking the conduit for bends, you must make some calculations.
Things You'll Need
- Tape measure
- Hand EMT bender
Measure the height and determine the angle to be used on the offset. The most common angle for an offset is 30 degrees. Multiply the cosecant of the angle by the height of the offset. The cosecants of commonly used angles are: 10 degrees-5.76, 22.5 degrees-2.6, 30 degrees-2, 45 degrees-1.414, 60 degrees-1.15. For example, if the offset is 6 inches high with a 30-degree angle, multiply 6 inches by cosecant 2 for a total 12-inch length between bends.
Measure from the starting edge of the conduit to the obstacle that the offset is going over or around. Mark this spot on the conduit. Measure from the mark back toward the starting edge of the conduit. Determine the distance by multiplying the height of the offset by the cosecant, which in the example in Step 1 is 12 inches. Mark this spot on the conduit. The two marks on the conduit are the starting spots for the bends of the offset.
Place the conduit in the hook of the shoe, or head, of the bender with the end of the conduit that is to remain flat aimed away from the rocker on the shoe. Line the arrow on the shoe up with the first mark on the conduit. The lines on the side of the shoe indicate the degrees of angles. Pull the handle bending the conduit until the side of the conduit reaches the line indicating the desired angle.
Reverse the bender on the conduit to bend the conduit in the opposite direction. Line the arrow on the shoe up with the second mark. The rocker is on the opposite side of the line from the first bend. Bend the conduit to the desired angle.
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