I recently undertook installing a Navien tankless in my home. Its a cr240a. The box itself seems to work. I have checked the gas pressure (11-13 column inches) and the water pressure, on a well, (40-60psi). It works well enough with one shower on although its warmer and cooler with the cycling of the well pump. I also notice that when more than one person takes a shower at a time, the hot water pressure drops significantly, especially in the upstairs bathroom. I think there may be 2 different problems and wondering the best solution. One is the variable water pressure. I wonder if a stop cycle valve is the the way to go. The other problem is the cold water pressure overcoming the hot water when more than one appliance is on. Is a tempering shower valve the best solution for this or is there someother fix? I bought the larger unit believing it would power 2 showers at one time, but apparently there is more complexity to this concept. Thanks, Jim