SERVICE PROCEDURE MCE-IX
Thermostat Testing
Immersion Thermostat Operation Testing
Thermostat Control Conti nuity Testing.
1. This procedure assumes line voltage, ECO and contactor(s) are in working order.
2. STOP, DANGER! Turn power “OFF” to water heater.
3. Remove lower control box cover a nd insulation.
4. Locate thermostat control (see general controls layout on page 4) and remo vewi re leads to control screw terminals.
5. Water temperature in tank must be within operating range of thermostat f ort his test. If above or below, it will be
necessary to drain tank and remove thermostat immersion bulb from tank to warm or cool the bu lb to be
within operating range of thermostat.
6. Set multi-meter to the “Ohms” setting.
7. Rotate thermostat dial to highest setting.
8. Check across screw terminals of control
(see illustration13).
A) Continuity IS present, okay,
Go to step 9.
B) Continuity NOT present,
replace thermostat.
9. Rotate thermostat dial to lowest setting.
10. Check across screw terminals of control
(see illustration 13).
A) ContinuityNOT present, thermostat is okay,
B) Continuity IS present, replace thermostat.
Providing the water temperature in tank is within the operating range of the
thermostat, checking thermostat operation can be as simple as rotating the
thermostat dial and listening to the contactor(s) to see if they respond t oa call
for heat.
Use caution and turn Power “ON” and rotate the thermostat dial to call for heat.
With water temperature below the th ermostat setting, the contactor(s) close.
With the contacts closed, use caution and check for rated voltage across lo wer
terminals of contactor(s) (see illustration 12), If rated volt age is present, the
thermostat is calling for heat.
Rotate thermostat dial to the minimum setting. With water temperatu re above
the thermostat setting the contactor(s) will open. With the contact s open,
voltage should not be present at lower terminals of contactor(s).
Follow the procedure below If preliminary testing above does not verify
thermostat operation.
Thermostat Specification:
Calibration: 184°F/176°F
Max Differential: 6°F
Operating Range 80 to 180°F
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DANGER
High voltage exposure. To avoid hazard to
life or property use extreme caution when
making voltage checks .
T1T2T3
L1 L2 L3
Check voltage across
lower terminals of c ontactor(s)
NOTE: Disconnect
Wire Leads to Control
Screw Terminals
Thermostat
Dial
Thermostat Immersion Bulb
Illustration 12
Illustration 13
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