From an article on VS pump motors and GFCI issues :
Why do variable speed pumps require a different type of GFCI than other pumps that have single-speed induction motors?
All variable speed motors have switching power supplies which induce line harmonics. Effectively, line harmonics are a distortion of the electrical waveform provided by the utility company. Line harmonics can be generated by any electrical appliance that uses a variable speed motor, such as dishwashers, washing machines, etc. IntelliFloŽ is not unique in this regard; any appliance that uses a variable speed drive/motor may induce some line harmonics. A variable-frequency drive is a system for controlling the rotational speed of an alternating current (AC) electric motor by controlling the frequency of the electrical power supplied to the motor. By controlling the speed of a motor attached to a swimming pool pump, users can save energy by allowing the exact volume of water moved to match the requirements of the pool system. Significant efficiency gains can be realized by using variable speed pumps, resulting in large decreases in power consumption. However, the nature of variable speed appliances means that it is impossible to avoid the presence of line harmonics caused by their variable frequency drives.
I notice GFCI compatible variable speed devices specifically advertised. Unless his GFCI is at the breaker box or the head of the circuit, he could just swap the outlet(?).
Last edited by glenn bradley; 10-03-2013 at 04:51 PM.
Any sufficiently advanced technology is indistinguishable from magic.
- Arthur C. Clarke