BASIC INSTALLATION & OPERATION
Thermostat Operation: Standard residential water heaters use mechanical thermostats. With a mechanical thermostat, a dial setting of 120° F may shut the burner down at a tank temperature between 110° and 130° F. The heater will consistently shut off at this same temperature. For this same reason, water temperature may drop 15° F - 25° F, around the temperature probe, before the main burner is activated. Keep in mind that hot water in the upper part of the tank will probably be very near the “shut off” temperature of the control while incoming cold water drops the water temperature around the thermostat probe. Also short, repeating heating cycles caused by small hot water uses can cause temperatures at the point of use to exceed the thermostat setting by up to 30° F.
Gas Control Knob
OnPilotOff
Reset Button 
Gas Control Knob
OffPilotOn
130°F
140°F
150°F 
Robertshaw®
Gas Control Valve/
Thermostat
120°F Mark |
130°F |
140°F |
150°F |
Water |
Temperature |
Dial |
Gas Control Valve/
Thermostat
Note: Temperature marks noted above are approximate and may vary due to various factors.
Water Temperature |
| Time to Produce 2nd & 3rd |
|
| Degree Burns on Adult Skin |
160°F (71°C) |
| About 1/2 second |
|
|
|
150°F (66°C) |
| About |
140°F (60°C) |
| Less than 5 seconds |
130°F (54°C) |
| About 30 seconds |
120°F (49°C) |
| More than 5 minutes |
80°F (27°C) |
| - - - - - - - - - - - - - - - - |
| Figure 6 | |
12