OPERATION & SERVICE
SURFACE MOUNT THERMOSTATS
The Surface Mount Control Model water heaters covered in this manual have “separate” thermostat/ECO (energy cut out) combination controls mounted to the surface of the storage tank directly above the heating elements they control. IE: a water heater equipped with 9 heating elements will have 9 thermostat/ECO controls. These controls contain two bimetal thermal switches that react to heat sensed from the surface of the water heater’s storage tank.
Thermostat: The thermostat portion of these controls is an automatic SPST (single pole single throw) switch - see the Internal Wiring illustration below. As the tank (water) temperature rises and falls each individual thermostat will
ECO: The ECO portion of these controls is a manual reset DPDT (double pole double throw) switch - see the Internal Wiring illustration below. The ECO is a high temperature limit switch designed to protect against excessively high water temperatures that can be caused by defective thermostats and grounded heating elements. The ECO temperature setting is non adjustable and fixed at 200°F/93°C. If the ECO activates (contacts open) in response to abnormally high temperatures the contacts will not close automatically, the ECO must be manually reset by pressing the red button on the top of the control. The tank temperature must cool to approximately 120°F/49°C before the ECO can be reset. When activated (contacts open) the ECO will interrupt all power supplied to the thermostat portion of the control and the heating element.
THERMOSTAT/ECO FRONT VIEW | THERMOSTAT/ECO INTERNAL WIRING |
ECO DPDT
Contacts 
L1
Thermostat SPST |
|
Contacts | T2 |
| |
Heating Element |
|
Power Supply to
L1 and L3 Terminals
| ECO DPDT |
L3 | Contacts |
L4 |
|
Servicing should only be performed by a Qualified Service Agent
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