Reverse-engineering asynchronous serial protocol for EcoSmart Tankless Water Heater
The Data Protocol that you showed in the linked document looks like the modulation waveform common to some IR Remote Controls. It is possible that the wired setup that you describe may be devised so that the remote control link would also work if an IR receiver module were plugged into the remote header. (Communications would be one way though). 

Several common IR protocols are described in this document. 

I would venture to guess that the two longer times (7msec/4msec) are the start sync for the transmission. After the sync time the data looks to be encoded in bit cells that are 1440 usec wide encoded as Manchester modulation. One data level being 720usec high at the start of the cell and 720usec low in the second half of the cell. The opposite data level being represented by the data line low for the 720usec at the start of the cell and high in the second half of the bit cell.

This is definitely not an async format used by a typical UART protocol.