Lochinvar 100 Series Instruction Manual page 16

Installing the Water Heater
• The control circuit, which controls the electrical power to
heating elements, referring the following control circuit diagram
Figure 12 (page 44).
• The power circuit, which is operated by the control circuit
carries the electrical load of the heating elements. The
following describes the heater circuits and includes wiring
diagrams for Delta configuration, refer to the WYE Configuration
Insert for water heaters operating at 380 V / 400 V / 416 V / 575
V. All heater circuits are designed for 50/60 cycle alternating
current.
Control Circuit - Electronic Control Models
These models are equipped with an electronic control system. The
system includes a CCB (Central Control Board), an immersion
temperature probe with ECO for temperature sensing and limiting, a
UIM (User Interface Module) for user interface & information display
and element current sensors for monitoring the power circuits. Refer
to the control circuit label on the water heater for details. The CCB
is powered by a small 120 V / 24 V transformer. The control circuit
operates on 120 V supplied by a larger 100 VA transformer. Standard
equipment includes control circuit fusing using two, 3 amp, class G
fuses with 600 volt rating. Do not substitute fuses of a different rating.
Sequence of Operation
1. When the control is powered, the UIM should display model
information, water temperature, Operating Set Point, heating
status and operating mode.
16 • Commercial Electric Water Heaters
2. If the control determines that the actual water temperature inside
the tank is below the programmed Operating Setpoint minus the
(1st) differential, a call for heat is activated.
3. After all safety checks are verified, the CCB will energize contactor
coils starting with the lower bank of heating elements (each
diagonal row of three heating elements is considered a "bank")
then energize the middle bank (if so equipped) and top bank
(if so equipped). See Figure 1 (page 8). The middle and top
banks (if so equipped) are energized according to programmed
2nd and 3rd differential set points.
4. The control remains in the heating mode until the water
temperature reaches the programmed Operating Setpoint. At
this point the contactors will be de-energized in the reverse order.
5. The control system now enters the standby operating mode
while continuing to monitor the water temperature and the state
of other system devices. If the water temperature drops below
the programmed Operating Setpoint minus the (1st) differential,
the control will automatically return to step 2 and repeat the
heating cycle.
Note: See Set the Operating Set Point at the lowest setting which produces
an acceptable hot water supply. This will always give the most energy
efficient operation. (page 20) for more detailed information
on temperature settings mentioned above.