Final answer:
The typical temperature setting for a T and P relief valve on a domestic hot water tank is 210°F, which serves as a safety threshold just below the standard boiling point of water at atmospheric pressure (212°F at sea level).
Step-by-step explanation:
The temperature setting for a T and P (Temperature and Pressure) relief valve on a domestic hot water tank is typically set near the boiling point of water to protect against excessively high temperatures that can cause the tank to overheat or potentially rupture. Considering normal boiling point is 100°C (212°F) at sea level, and factoring in a safety margin, the standard setting for these valves is often at 210°F, which is slightly below the boiling temperature of water at atmospheric pressure. It's worth noting that these values can be affected by altitude, as seen in examples where the boiling point of water decreases at higher altitudes due to lower atmospheric pressure. Therefore, the correct answer to the question is C) 210°F.