Russ, maybe this will help. American Society of Sanitary Engineers standards…
Also, manufactures of tempering valves and water heater manufactures will provide you with temperature ranges.
ASSE 1017: Performance Requirements for Temperature Actuated Mixing Valves for Hot Water Distribution Systems
Publication Date: Oct 5, 2009
SDO: ASSE: American Society of Sanitary Engineering
DOD Adopted ANSI Approved Approved
Temperature Actuated Mixing Valves for Hot Water Distribution Systems (herein referred to as “device”) shall consist of a hot water inlet connection, a cold water inlet connection, a mixed water outlet connection, a thermal element and a means for adjusting the mixed water outlet temperature.
Dimensions of pipe threads, flanges and other connections shall conform to appropriate industry standards.
Maximum Working Pressure
The maximum working pressure of the device shall be at least 125.0 psi (861.9 kPa).
Inlet Water Temperature Range
The hot water inlet temperature range shall be 120.0°F - 180.0°F (48.9°C - 82.2°C) and the cold water inlet temperature range shall be 39.0°F - 80.0°F (3.9°C - 26.7°C).
Outlet Water Temperature Range
The device shall be capable of supplying the domestic hot water distribution system with a minimum adjustable range of 105.0°F- 120.0°F (40.6°C - 48.9°C), provided the hot water supply temperature is at least 20.0°F (11.1°C) greater than the outlet water temperature setting.