Electrical Metal Tubing (EMT) - Conduits
Trade sizes and max. distance between conduit supports.
Electrical Metallic Tubing (EMT) - Thinwall Conduit
Electrical Metallic Tubing (EMT) is unthreaded with circular cross section dimensions:
| Conduit Trade Size | Outside Diameter | Inside Diameter | Max Distance Between Supports Rigid Metal (PVC) | ||||
|---|---|---|---|---|---|---|---|
| (in) | (mm) | (in) | (mm) | (in) | (mm) | (ft) | (m) |
| 1/2 | 16 | 0.706 | 17.9 | 0.622 | 15.8 | 10 | 3 |
| 3/4 | 21 | 0.922 | 23.4 | 0.824 | 20.9 | 10 | 3 |
| 1 | 27 | 1.163 | 29.5 | 1.05 | 26.6 | 12 | 3 |
| 1 1/4 | 35 | 1.510 | 38.4 | 1.38 | 35.1 | 14 | 5 |
| 1 1/2 | 41 | 1.740 | 44.2 | 1.61 | 40.9 | 14 | 5 |
| 2 | 53 | 2.197 | 55.8 | 2.07 | 52.5 | 16 | 5 |
| 2 1/2 | 63 | 2.875 | 73.0 | 2.73 | 69.3 | 16 | 6 |
| 3 | 78 | 3.500 | 88.9 | 3.36 | 85.2 | 20 | 6 |
| 3 1/2 | 91 | 4.000 | 101.6 | 3.83 | 97.4 | 20 | 7 |
| 4 | 103 | 4.500 | 114.3 | 4.33 | 110 | 20 | 7 |
- 1 inch = 25.4 mm
- 1 ft (foot) = 0.3048 m
The outside tube is galvanized for corrosion protection and the inside has corrosion-resistant coating.
According to National Electric Code (US NEC or NFPA 70) Article 344 for Rigid Metal Conduit and Article 358 Electrical Metallic Tubing.
- a conduit must be supported at intervals no longer than 3 m (10 ft) and fastened not more than 0.9 m (3 ft) from a box, fitting, etc.
- the distance between supports for straight runs of conduit shall be permitted in accordance to the table above provided the conduit is made up with threaded couplings and such supports prevent transmission of stresses to termination where conduit is deflected between supports
