AERCO Electronic Controls System (ECS) - Manual (Page 11)

Electronic Control System (ECS) and Type CXT-E Valve
1. GENERAL INFORMATION
VD2: 02/28/14 AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, New York 10913 • Phone: 800-526-0288 Page 11 of 82
AC-105 OMM-0003_0D
An Over-Temperature Switch is also included in the Control Box to constantly monitor the Water
Heater outlet temperature to ensure the Heater does not exceed the preset high temperature
limit. Typically, the over-temperature limit is set 20°F above the desired Heater setpoint
temperature. If an over-temperature condition occurs, this Switch sounds an audible alarm,
activates the Over-Temperature Solenoid and cuts off power to the Control Valve Actuator. This
closes the Control Valve and shuts off the heating fluid (steam or hot boiler water) to the Heater.
In addition, activation of the Over-Temperature Solenoid allows over-temperature water to be
dumped from the Heater shell.
The Control Box also contains a DC Power Supply and Voltage Regulator to provide the voltage
levels required by the ECS Control Box circuitry, flow sensor and safety devices. It also provides
24 VDC power to the Control Valve CXT-E Actuator.
The Control Box components are housed in a steel enclosure with a hinged front door. This
door contains a clear polycarbonate window which permits maintenance personnel to view the
controls and displays of the Temperature Controller, and other display devices mounted on a
recessed panel behind the door. All sensor and control signal connections are made via cable
connections at the bottom of the Control Box. External AC power (120 to 240 VAC, 50/60 Hz) is
supplied via a cutout on the right side of the Control Box.
1.2.2 Feed-Forward Flow Sensor
The Feed-Forward Flow Sensor is installed between the cold water inlet and the drain valve on
the Water Heater as shown in Figure 1-1. The Flow Sensor monitors a portion of the inlet flow to
the Heater and provides a feed-forward signal to the Temperature Controller which is
proportional to the change in flow through the Heater.
1.2.3 Outlet Temperature Sensors
The Control System includes a Dual Temperature Sensor which is installed in the hot water
outlet of the Water Heater. This sensor contains two identical Type J thermocouples. The first
thermocouple connects directly to the Temperature Controller in the Control Box to provide the
outlet water temperature. The second thermocouple connects to the Over-Temperature Switch
in the Control Box.
1.2.4 Heating Fluid Inlet/Outlet Temperature Sensors
When the Heater utilizes hot (boiler) water as the heating fluid, two additional Temperature
Sensors (Type J thermocouples) are provided with the Control System. One temperature
Sensor is installed at the heating fluid inlet and the other is installed at the heating fluid outlet.
These two Sensors are connected to two identical Temperature Display Indicators in the Control
Box to provide real-time indications of the inlet and outlet heating fluid temperatures. These
Temperature Indicators are physically identical to the Over-Temperature Switch, however they
are “Indicator-Only” devices and do not provide any switching functions.
1.2.5 Over-Temperature Solenoid Valve
As previously mentioned, the Over-Temperature Solenoid Valve operates in conjunction with
the Over-Temperature Switch in the Control Box. An over-temperature alarm is activated when
the preset high temperature limit is exceeded, thereby energizing and opening the Solenoid
Valve. This allows over-heated water and pressure build-up to be expelled from the Heater Shell
and relieve pressure build-up.