2KI-OM-0591 Rev 3
Introduction
Temperature Control ± 1°C (± 2°F)
1.3 Theory of Operation
1.3.1 Basic Control
The temperature control system of the WHE-3 has been designed to be simple and effective.
The unit heats water in the heater tank using five banks of heater elements. These heater
banks are controlled with five switches, mounted on the electrical enclosure. The banks of
heaters are configured to deliver a variety of heating capacities depending on the combination
of banks selected. When all five heater circuits are on, the total rated heater output is
approximately 180 kW. The appropriate heater circuits must be selected manually according
to the relative temperature rise required. A schedule is attached to the front of the control
panel door indicating the heater banks to be used for the required temperature rise.
Example: Temperature rise through the WHE and heater bank selection.
Td Required outlet water temperature, at diver 43ºC
T∆h Temperature drop (Hose from deck to diver) 11ºC
Ti WHE Inlet water temperature is 5ºC
To WHE desired outlet water temperature Td + T∆h
= 43 + 11ºC
= 54ºC
∆T Temperature rise through the WHE To - Ti
= 54 - 5ºC
= 49ºC (Use heater banks 1, 2, 3, 4
and 5)
The above example shows that if a bottom temperature of 43ºC is required with a
temperature drop through the hose to the diver of 11ºC and an inlet water temperature of 5ºC.
The temperature required at the outlet of the WHE would be 54ºC. The Temperature rise
through the unit would be 49ºC. The heater selection schedule shown in Table 3, indicates
that heater banks 1 through to 5 should be used as this would provide a temperature rise of
47 - 50ºC through the unit.
Once the correct configuration of heater banks has been selected, the temperature controller
regulates the temperature of the outlet by adjusting the flow rate of water passing through the
heater tank. This is achieved by controlling the electric actuator on the bypass valve. The
valve is connected in such a way that it will dump water overboard to increase the flow rate
through the heater tank. A higher flow rate through the heater reduces effective temperature
rise and maintains the desired set point temperature. The temperature controller monitors
temperature at the fluid outlet manifold using a PT100 temperature sensor and adjusts the
temperature control valve position to achieve the set point temperature.
Switching the temperature controller input from local to remote input allows fine control of the
outlet temperature by adjustment of the potentiometer on the remote control panel.
Manipulation of the potentiometer will change the set point of the temperature controller.
Refer to the temperature controller manual in Appendix B for instructions regarding switching
between local and remote temperature set-point adjustment.
Notes 1 The calculated required temperature rise may be indicated on the heater bank
selection table as a maximum for one configuration and a minimum on the
subsequent selection of heater banks. In this case practical application will dictate
