VFD on submersible pump in a body of water

[kwired]

The constant velocity pump is also known as a constant pressure pump and is using a pressure xducer for feedback. The pump motor that was installed is a single phase and the controller will be for a 3 wire single phase motor which is configured for residential pump control. The motor and drive are seperate devices on this system.

My mistake on this installation was assuming that the ground fault detection on the drive was sufficient to meet rule 26-956 but in discussions with Pentair there is no defined specification at which the ground fault detection occurs - could be 1A or more. Of course this is not acceptable.

At this point I will most likely install system with a GF breaker feeding the standard start/run winding relay and motor. There is a large market for this VFD application if there was a safe and accepted solution.

Is likely safe enough, problem is NEC throws in a requirement kind of out of the blue for GFCI protection for things that haven't yet been evaluated for use on GFCI's, based on just one real world incident and a bunch of speculation about many other similar situations. These items weren't normally required to have GFCI protection in the past and therefore not required to pass same leakage levels for listing requirements.

 

[chris_3000]

Has anyone found a workable solution to installing a ground fault breaker on a constant velocity VFD drive for a submersible pump installed in a lake? I need to satisfy the CEC rules and the OEM pump manufacturers have said their pumps will not work with a GF breaker. I have a cable of 240' from the drive to the pump. Cable installation has passed inspection but I am struggling to find a solution that will actually meet the code and not trip the breaker. I have seen anecdotal discussion of a combination of certain drives and breakers that will work. My concern with trying this solution is that it will only work for a short period and then start tripping - at which point the homeowner will replace the GF breaker with regular 2 pole breaker.

I normally use a ground fault relay with zero sequence CT on the output of the VFD. The relay should be suitable for AC/DC conversion devices such as VFD to avoid the nuisance trip. Little Fuse and Bender have such relays. https://www.benderinc.com/products/ground-fault-monitoring-for-grounded-systems/linetraxx-rcma420/. Normal GFCI breakers cannot handle the harmonics from VFD.