Just installed a new Pentair Superflo VST and immediately noticed all LED lights in the main house flicker when the pump is on. I've read about this issue several places and understand it's due to harmonic distortion from cheap VFD circuit back-feeding into the supply. Some say it's to do with cheap quality LEDs but I wanted to check this claim for myself (since mine aren't cheap LEDs!) So I hooked up a scope to the main load center and when the pump is running at full rpm the below pic shows the added noise on the bottom half of the sinewave of the 60Hz / 230V supply. Scale on scope is 20V per division so roughly 40V peak-peak noise - which is quite frankly ridiculous, regardless of high much you spend on LEDs, they are going to flicker with 40V noise @ 300-400Hz!! I am wondering if anyone has come up with a solution to this? I am looking at line reactor filters (e.g. LR2-21P0-1PH-A) to connect just before the supply, or possibly just an isolation transformer (not sure how effective it will be). Anyone tried this or have any insights? Thanks.

(P.S. before anyone asks, yes the wiring is 100%, no neutral or earthing issues, correct gauge wiring, separate subpanel, etc. In fact to double test, I switched it over to the old 2hp "on/off" style pump and the lights don't even blip when the pump kicks in with over 35amps of in-rush current! So this is definitely a VFD issue. Edit by Jim R.

Installing a new liner tomorrow, home owner has 20 year old walls. I suggested new walls because it is unsafe.. am I wrong?