Bradford White MII Series Service Manual page 25

Contactor Operation Testing (continued)
This procedure assumes control circuit is operating correctly.
Providing the water temperature in tank is within the operating
range of the thermostat, checking contactor operation can be
as simple as rotating the thermostat dial and listening to the
contactor(s) to see if they respond to a call for heat.
1. Turn Power "ON" and rotate thermostat dial to the maximum
setting, with water temperature in tank below the
thermostat setting, the contactor(s) will close. With the
contacts closed, check for line voltage across operating coil
terminals (see illustration 14).
A) Line voltage IS present, okay, go to step 2.
B) Line voltage NOT present, verify control circuit
operation.
2. Check for rated voltage across lower terminals of
contactor(s) (see illustration 15).
A) Rated voltage IS present, okay,
go to step 3.
B) Rated voltage NOT present, replace
contactor.
3. Rotate thermostat dial to the minimum setting.
With water temperature in tank above thermostat
setting, the contactor(s) will open. With the contacts
open, voltage should not be present at lower terminals
of contactor(s).
4. Check for line voltage across operating coil
terminals (see illustration 14).
A) Line voltage IS present, verify control circuit
operation.
B) Line voltage NOT present, okay go to step 5.
5. Check for rated voltage across lower terminals
of contactor(s) (see illustration 15).
A) Rated voltage IS present, replace contactor.
B) Rated voltage NOT present, contactor is okay.
SERVICE PROCEDURE MCE-X
High voltage exposure. To avoid hazard to
life or property, use extreme caution when
making voltage checks .
Check voltage across
lower terminals of contactor(s)
Page 25
Contactor Testing
DANGER
Illustration 14
L1 L2 L3
T1 T2 T3
Illustration 15
25