I have two Envirotech ESI-2000 electric tankless water heaters (28KW), one of which has recently started to malfunction after 4 years. Specifically, the overtemperature cutout breaker keeps tripping, not allowing the heating element relays to be activated (energized). The cutout can be reset, but it trips a few days later. I cannot locate a wiring diagram or service manual anywhere. An internet search yields nothing. I have checked the obvious things. Power inputs are all active, no clogged filters, and I replaced the flow sensor (since I happen to have 2 extras). I am aware that Envirotech Systems Worldwide, Inc. has ceased to exist due to contractural lawsuits and has been bought out (or reformed) by Skye International, Inc. Unfortunately, the latter does not wish to support this product. I am surprised that an internet search has revealed zero results. I know the company is out of business, but it is as if all references to almost any information about this unit have been erased from the planet. I can get a schematic for a thirty year old television, immigration records from 1918; why can't I find any service information on the Envirotech ESI-2000?