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Thermostat must sit flat against tank wall so temperature reading is accurate and water heater is protected from overheating
Some thermostats, the L2 and T1 screws are empty slot or rivet since wires do not connect to either L2 or T1.
Brands of thermostat vary slightly, screws are located differently, some numbers are slightly different, but basic concept is same from brand to brand. Water heater manuals available on-line. Label on side of tank shows watts and volts of appliance.
Each thermostat comes with instruction sheet.
When replacing thermostat, take digital photo of water heater and old thermostat to hardware store or plumbing store for quick identification.
Brands of thermostat vary slightly, screws are located differently, some numbers are slightly different, but basic concept is same from brand to brand. Water heater manuals available on-line. Label on side of tank shows watts and volts of appliance.
Each thermostat comes with instruction sheet.
When replacing thermostat, take digital photo of water heater and old thermostat to hardware store or plumbing store for quick identification.
Thermostat must sit flat against tank wall so temperature reading is accurate and water heater is protected from overheating
Diagram on left illustrates basic thermostat function. This thermostat is found on 240 Volt water heaters that have 2 elements. Check label on side of tank for voltage info. See diagram below.
Power from breaker box connects to L1 and L3 screws > some thermostats, the screws are marked simply 1 and 3.
Top half of thermostat is the ECO or energy cut off > The ECO is heat sensitive, so if temperature reaches dangerously high 150-180°F, then ECO trips and water heater no longer has power. This prevents water heater explosion.
Viewing the diagram, power from L1 and L3 pass through ECO red reset and go to L2 and L4 screws.
After power passes through ECO, it is available for heating water. To control heating, power arrives at the thermostat which begins at T1 screw.
Inside the thermostat a bi-metal switch. Two different metals are fused together. Each metal expands differently when heat is applied. Since the two metals are joined, the metal that expands most causes the bi-metal switch to bend. The bending action opens and closes the switch.
In the diagram, the bi-metal switch is connected to T1. When temperature inside tank is cool, the bi-metal switch rests against T2 so power travels from T1 to T2, and then on to the upper heating element. When temperature inside tank is hot, the bi-metal switch disengages from T2 and clicks over to T4. When this happens, T1 sends power to T4, so the upper heating element is turned off and power travels to lower element and thermostat through the T4 screw.
In a 240 Volt water heater, elements must receive power from 2 hot leads. The diagram shows the hot leads at L1 and L3 screws. In the description above, power from one hot lead was switched between T2 and T4. From there, power traveled to the elements but the circuit was not yet complete. To complete the 240 circuit, each element must connect back to the L4 screw. See complete circuit diagram below.
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Upper thermostat is made of two parts >> the top part is the ECO, the bottom part is the thermostat
