Q: After reading the article "Using Water Heaters for Radiant Heat" (11/98), I decided to replace my boiler with a 75-gallon propane water heater. In general, this is working great, except that about every three weeks the pressure-temperature relief valve, which is rated at 210°F, keeps tripping. I live in the cold climate of Michigan, and I need to keep the water heater temperature set on "High," which is about 180-190°F. When the relief valve trips, I notice that the water temperature is about 195°F. What’s going on?