We're having record low sub-zero weather and need to get the batteries changed in our thermostat ASAP. The furnace wasn't working right this a.m.
Most electric hot water heaters have two thermostats, one near the top of the tank and one near the bottom, and are covered by removable metal cover plates. The thermostats are pressed firmly against the bare metal wall of the hot water heaters tank.
The top thermostat usually has a high limit switch that will trip if the water gets too hot. When it trips it shuts off the electricity to both the upper and lower heating elements.
To reset the high limit switch there is usually a red button that you must press. When the upper limit switch trips it is often an indication that something else has gone wrong with the heater.
When the top of the tank is hot the upper thermostat removes power from the upper heating element and transfers the power to the lower thermostat and heating element. If the lower thermostat is defective, then the lower portion of the tank will not be heated and the supply will be greatly reduced.
Check for power at the upper thermostat terminals where the power is sent to the lower thermostat and heating element. If there is no power then the upper thermostat should be replaced. If there is power then check for power at the lower heating element. If there is no power at the lower heating element then replace the lower thermostat.
If there is power to the lower heating element then it should be getting hot. If it is not, replace it. Another possibility is a broken dip tube. Check for a broken dip tube and replace if necessary.
Hope this helps out
Occasionally, the high temperature limit shut off device may trigger and shut the
system down. This occurs when water temperature exceeds 190Ā° F and shuts off
power to the heating element. The shut off device may also trigger from a power
outage or electrical storm.
To reach the thermostat:
1. Pry off the round cover plate (V Fig. 3/1) from its right hand edge (W Fig. 3/1) with
a small flat-head screwdriver.
2. Remove the Phillips screw revealed beneath the round cover plate.
3. The cover (C Fig. 3/1) can now be removed by pulling out its left-hand edge. When
reassembling, work in the opposite way being careful to insert the tongue of the
cover into the slot.
4. Firmly press reset button (B Fig. 4). Reconnect power.
5. IMPORTANT: Check the operation of the thermostat, turn temperature dial from
high to low, if the red light does not go off on low setting, turn off power supply and
call a service person to replace the thermostat.
6. If the system works, place dial setting to desired setting. Note: a lower setting is
more economical and reduces the risk of scalding. Replace cover plate.
CAUTION: Call a technician if the high limit needs to be reset frequently.
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