14
AMPERAGE TABLE/OVERCURRENT PROTECTION
The tables above provides the total connected heating element
load in amperes for branch circuit conductor and overcurrent
protection sizing. Single-phase heaters are two wire circuits.
Three-phase heaters are three wire circuits. In addition to the
foregoing, a grounded conductor is required.
The rating of the overcurrent protection must be computed
on the basis of 125% of the total connected load amperage.
Where the standard ratings and settings do not correspond
with this computation, the next higher standard rating or setting
should be selected.
HEATER CIRCUITS - ELECTRONIC CONTROL MODELS
The water heater’s electrical components are pictured and
identified in
and
The model and rating plate
illustration on page 4 identifies heater circuit ratings. The
ELECTRONIC CONTROL model has two electrical circuits:
• The control circuit, which controls the electrical power to
heating elements, referring the following control circuit
Figure 5. CCB Control Circuit Diagram - Electronic
• 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
380V/400V/416V/575V. 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
120V/24V transformer. The control circuit operates on 120V
supplied by a larger 100VA 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
mode information, water temperature, Operating Set Point,
heating status and operating mode.
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 (Central
Control Board) will energize contactor coils starting with
the lower bank of heating elements (each diagonal row of
three heating elements is considered a “bank” - see
) then energize the middle bank (if so equipped) and top
bank (if so equipped). 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 the Electronic Control Models Operation section for
more detailed information on temperature settings mentioned
above.
120-VAC CONTROL CIRCUIT TRANSFORMER CONNECTIONS
Table 6.
Full Load Current for Various Configurations
kW
Input
Number Of
Elements
Element
wattage
Full Load Current In Amperes
Number Of Ther-
mostats
Number Of
Fuses
Single Phase
Three Phase
208V
240V
277V
480V
208V
240V
480V
12
3
4000
58
50
44
25
34
29
15
3
6
13.5
4500
65
57
49
29
38
33
17
15
5000
73
63
55
32
42
37
18
18
6000
- - -
75
65
38
- - -
44
22
18
6
3000
87
- - -
- - -
- - -
50
- - -
- - -
6
12
24
4000
116
100
87
50
67
58
29
27
4500
130
113
98
57
75
65
33
30
5000
145
125
109
63
84
73
37
36
6000
- - -
150
130
75
- - -
87
44
36
9
4000
173
- - -
- - -
- - -
100
- - -
- - -
9
18
40.5
4500
195
169
147
85
113
98
49
45
5000
217
188
163
94
125
109
55
54
6000
- - -
225
195
113
150
130
65
Printed on 2/8/2018 9:05 AM CT
