Tech Square

Posted by 6bq5 (A) on June 21, 2011 at 09:53:27

In Reply to: RE: what's the difference between 'hot' and 'neutral' in 240v AC power? posted by Tom Schuman on June 19, 2011 at 18:52:26

AC Mains power is delivered via one hot and one neutral wire. the power is available when a load (such as a motor)is connected across the potential - or both wires are connected to the load. Most AC (Alternating Current) appliances and not overly sensitive to the phase of the mains; however in some instances the reversing of the phase (hot for neutral) can cause or potentially cause a problem - mostly when there is only a switch on the intended HOT leg. An AC volt meter can be used to identify the HOT leg: setting the voltage to the correct range (so as to not overload the meter) the voltage potential should be the same between the HOT leg and the neutral and the Hot leg and one of the mounting screws for the faceplate.
If this does not make sense to you there should be a device sold in a local hardware store that can 'diagnose' your phase, and there are single probe units that can distinguish Hot from Neutral. see attached links:

Failing all the above, Locate the breaker and turn off the power to the plug in question, then remove the face plate the HOT wire SHOULD bee either Black or Red in colour.
If you don't feel comfortable with this, call an electrician.

Happy Listening.

• Single Probe devices; plug in device (USA-120VAC)   (Open in New Window)