I came up to a job installing a hot tub. The existing sub panel only has three wires making this a 120v sub panel. Can I convert this to a 4 wire by just adding a ground rod and connecting existing wires to the proper connection of two hots and a neutral in the main panel plus the ground wire to grounding bar in sub panel being fed only by the 7' ground rod?
Ground Box
- Thread starter EMolecule
- Start date
- Status
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
No the earth cannot be used in place of a EGC.
250.4(a)
(5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path.
250.4(a)
(5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Its more important that you know why not. Whats the ground fault current at 120 volts and 25 ohms resistance?
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
The 3 wire fed sub panel although is not correct is thousands of times safer method than your proposed method.
Read article 250 carefully as well as study some electrical theory and this will make sense.
Read article 250 carefully as well as study some electrical theory and this will make sense.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
even 3 ohms of resistance through the ground rod will allow 40 amps of current to flow if this hot tub is on a 50 amp circuit it will never trip an overcurrent device (fault on load side of GFCI yes) but that is not the issue here of using the earth as an equipment grounding conductor.
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