SERVICE PROCEDURE MCE-IV
High Limit (ECO) Testing
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1. This procedure assumes line voltage and
fuses are in working order.
2. This procedure illustrates testing o f just one
surface thermostat. Repeat this procedure for all
surface thermostats on the unit.
3. Turn power “OFF” to water heater .
4. Remove lower control box cover and remove insulation
from insideof controlbox.
5. Remove plastic cover from thermostat(s).
6. Turn power “ON” to water heater.
7. Check voltage across terminals L1 & L4 for all thermostats
(see illustration 6).
A) Rated Voltage IS present, ECO is okay.
B) Rated voltage NOT present, proceed to step 8.
8. Turn power “OFF” to water heater and firmly press ECO reset button on thermostat(s).
Turn power “ON” to water heater a nd recheck voltage across terminals L1 & L4 of thermostat(s).
A) Rated voltage IS present, the ECO has previously opened indicating the water in the tan k, at
some point did overheat, Check the following:
1. Thermostat must be in full contact with tank.
2. Be sure heating element(s) is not shorted to ground (see page 15).
3. Proper thermostat operation (see page 21).
B) Rated voltage NOT present, water in tank may be over heated.
1. If water is overheated, turn “OFF” power to water heater and flow water through tank to cool belo w
set point of upper thermostat. Reset ECO and recheck voltage.
2. If water is cool, Replace thermostat(s).
High Limit Control (ECO) Testing for
Surface Thermostat models (not including 600V)
ECO reset
button
Illustration 6
DANGER
High voltage exposure. To avoid hazard to
life or property use extreme caution when
making voltage checks .
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