Introduction
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| Illustration 1 | g01437528 |
General Information | |
The electric screed heating system heats the bottom surface of the screed for paving operations. The system includes heaters on the main screed, screed extenders, and optional screed extensions. The system also includes sensors and controls in order to set the screed temperature and the sensors and controls also maintain the screed temperature.
Note: The screed heating system is powered by a generator on the machine. See the generator section of the machine documentation for more information on the generator and generator controls.
25 kW Generator
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| Illustration 2 | g01437531 |
Left Side of Machine (1) Generator | |
25 kW generator (1) is located on the left side of the machine. The left side door provides access to the generator.
Machines that are equipped with 25 kW belt driven generator (1) or an optional 35 kW hydraulic drive generator provide power in order to operate the electric screed heaters and other equipment. The 25 kW belt driven generator is driven directly by the engine.
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| Illustration 3 | g01437532 |
25 kW Generator Set (2) Right screed extender and extension heating element (GFCI circuit breaker) (3) Right main screed heating element (GFCI circuit breaker) (4) Left main screed heating element (GFCI circuit breaker) (5) Left screed extender and extension heating element (GFCI circuit breaker) (6) Auxiliary power panel (main circuit breaker) | |
On machines that are equipped with the 25 kW belt driven generator, screed heater circuit breakers (2) through (6) are located on the generator set, under a hinged access panel. The position of the panel may vary from one generator to another generator.
This circuit breaker panel is equipped with five circuit breakers. Four of the breakers distribute power to the electric screed heating elements. The following list shows the assignments for the screed heat circuit breakers:
- Circuit breaker (2) (right screed extension and extender heating element)
- Circuit breaker (3) (right main screed heating element)
- Circuit breaker (4) (left main screed heating element)
- Circuit breaker (5) (left screed extension and extender heating element)
- Main circuit breaker (6) (auxiliary power panel)
Main circuit breaker (6) is not part of the screed heater circuit.
35 kW Generator
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| Illustration 4 | g01437536 |
Right Side of Machine (1) 35 kW Generator (2) Circuit breaker panel | |
The 35 kW hydraulic driven generator (1) is located on the right side of the machine in the pump compartment. The right side door provides access to the generator.
For those machines that are equipped with a 35 kW hydraulic driven generator, a variable displacement pump provides oil flow in order to operate a fixed displacement hydraulic motor that drives the generator.
The 35 kW hydraulic driven generator set distributes power to circuit breaker panel (2) with seven 25 amp GFI circuit breakers. Six of the circuit breakers distribute power to the screed heating elements. The seventh circuit breaker provides power to auxiliary functions on the machine. The breakers are located on the generator and under a hinged access panel. The position of the panel may vary from one generator to another generator.
Generator Control Switch
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| Illustration 5 | g01437539 |
Machine Instrument Panel (1) Generator control switch | |
Generator control switch (1) is located on the instrument panel of the machine.
The generator control switch is a two-position toggle switch. The top position of this switch is the ON position. The bottom position of this switch is the OFF position. The machine operator ECM receives a signal when the generator switch is in the ON position. In this case, the electronic control system prompts the screed heat controller to enable the main power switch on the heater control panel.
The generator control switch must be in the ON position in order to operate the electric screed heaters.
Heater Control Box
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| Illustration 6 | g01437543 |
Component Location (1) Main Power Switch (2) Main Power Indicator (3) Low temperature Indicator (4) Temperature Selector Switch (5) Medium temperature Indicator (6) High temperature Indicator (7) Error Indicator (8) Right Extender Temperature Indicator (9) Right Main Temperature Indicator (10) Right Extender Power Indicator (11) Right Main Power Indicator (12) Right Extender Manual Indicator (13) Right Extender Manual Switch (14) Right main manual indicator (15) Right main manual switch (16) Left main manual switch (17) Left main manual indicator (18) Left extender manual switch (19) Left extender manual indicator (20) Left main power indicator (21) Left extender power indicator (22) Left main temperature indicator (23) Left extender temperature indicator | |
The heater control box is located on the screed and to the right of the steps. The box is equipped with a lockable cover.
The heater control panel is equipped with six tactile membrane switches and 17 status indicators. The switches provide input signals to the heater ECM, and the ECM operates the status indicators in order to alert the operator to current operating conditions. The heater ECM is mounted to the back to the display panel.
The function of each switch is as the following:
Main Power Switch
The main power switch (1) controls the burner system. The main power switch is only active when the generator is operating. A single depression of this switch when the screed heaters are OFF, causes the heater ECM to operate the screed heaters automatically. If this switch is depressed while the heaters are ON, the heater ECM discontinues operation of the screed heaters.
Temperature Selector Switch
The temperature selector switch (4) allows the operator to choose between three temperature setpoints. The status indicators above the temperature selector switch alert the operator to which of the setpoints is currently chosen.
Left Extender Manual Switch
The left extender manual switch (18) allows the operator to manually heat the left extender screed plate when the temperature sensor contains a fault. A single depression of the switch toggles the function between on and off. The ECM manually controls the heater based on time that corresponds to the temperature selector setting.
Left Main Manual Switch
The left main manual switch (16) allows the operator to manually heat the left main screed plate when the temperature sensor contains a fault. A single depression of the switch toggles the function between on and off. The ECM manually controls the heater based on time that corresponds to the temperature selector setting.
Right Main Manual Switch
The right main manual switch (15) allows the operator to manually heat the right main screed plate when the temperature sensor contains a fault. A single depression of the switch toggles the function between on and off. The ECM manually controls the heater based on time that corresponds to the temperature selector setting.
Right Extender Manual Switch
The right extender manual switch (13) allows the operator to manually heat the right extender screed plate when the temperature sensor contains a fault. A single depression of the switch toggles the function between on and off. The ECM manually controls the heater based on time that corresponds to the temperature selector setting.
The function of each status indicator is as the following:
Power Indicator
The heater ECM illuminates the power indicator (2) when the screed heating system is in operation.
Low Temperature Indicator
In the automatic heating mode, the heater ECM illuminates the low temperature indicator (3) when the system is in the low temperature mode. The system defaults to this mode upon start-up. When this indicator is illuminated, the temperature setpoint is 110 °C (230 °F).
Note: In the manual heating mode, the heater ECM activates the heating element for 30 minutes when the low temperature mode is chosen.
Medium Temperature Indicator
In the automatic heating mode, the heater ECM illuminates the Medium temperature indicator (5) when the system is in the medium temperature mode. When this indicator is illuminated, the temperature setpoint is 130 °C (270 °F).
Note: In the manual heating mode, the heater ECM activates the heating element for 45 minutes when the medium temperature mode is chosen.
High Temperature Indicator
In the automatic heating mode, the heater ECM illuminates the high temperature indicator (6) when the system is in the high temperature mode. When this indicator is illuminated, the temperature setpoint is 150 °C (300 °F).
Note: In the manual heating mode, the heater ECM activates the heating element for 60 minutes when the high temperature mode is chosen.
Error Indicator
The error indicator (7) alerts the operator when the heater ECM detects a fault in the system. The heater ECM creates a sequence of flashes on the error indicator. Each flash sequence represents a specific fault in the system.
Left Extender Temperature Indicator
The heater ECM illuminates the left extender temperature indicator (23) when the temperature of the screed plate on the left extender reaches the chosen setpoint. The heater will continue to be powered until the set point temperature has been exceeded by 11 °C (20 °F). At this point, power to the screed heater is discontinued. When the set point temperature indicator illuminates, the screed section is up to temperature and ready for paving. Heating will restart if the temperature of the screed plate falls to the set point. If the temperature of the screed plate falls to 3 °C (5 °F) below the set point, the temperature indicator will no longer be illuminated. If the heater ECM detects a fault in this circuit, the ECM generates a flashing error code with the indicator.
Left Extender Power Indicator
The heater ECM illuminates the left extender power indicator (21) when power is available to the left extender heater. If the heater ECM detects a fault in this circuit, the ECM generates a flashing error code with the indicator.
Left Main Temperature Indicator
The heater ECM illuminates the left main temperature indicator (22) when the temperature of the left main screed plate has reached the chosen setpoint. The heater will continue to be powered until the set point temperature has been exceeded by 11 °C (20 °F). At this point, power to the screed heater is discontinued. When the set point temperature indicator illuminates, the screed section is up to temperature and ready for paving. Heating will restart if the temperature of the screed plate falls to the set point. If the temperature of the screed plate falls to 3 °C (5 °F) below the set point, the temperature indicator will no longer be illuminated. If the heater ECM detects a fault in this circuit, the ECM generates a flashing error code with the indicator.
Left Main Power Indicator
The heater ECM illuminates the left main power indicator (20) when power is available to the left main heater. If the heater ECM detects a fault in this circuit, the ECM generates a flashing error code with the indicator.
Right Main Temperature Indicator
The heater ECM illuminates the right main temperature indicator (9) when the temperature of the right main screed plate has reached the chosen setpoint. The heater will continue to be powered until the set point temperature has been exceeded by 11 °C (20 °F). At this point, power to the screed heater is discontinued. When the set point temperature indicator illuminates, the screed section is up to temperature and ready for paving. Heating will restart if the temperature of the screed plate falls to the set point. If the temperature of the screed plate falls to 3 °C (5 °F) below the set point, the temperature indicator will no longer be illuminated. If the heater ECM detects a fault in this circuit, the ECM generates a flashing error code with the indicator.
Right Main Power Indicator
The heater ECM illuminates the right main power indicator (11) when power is available to the right main heater. If the heater ECM detects a fault in this circuit, the ECM generates a flashing error code with the indicator.
Right Extender Temperature Indicator
The heater ECM illuminates the right extender temperature indicator (8) when the temperature of the screed plate on the right extender has reached the chosen setpoint. The heater will continue to be powered until the set point temperature has been exceeded by 11 °C (20 °F). At this point, power to the screed heater is discontinued. When the set point temperature indicator illuminates, the screed section is up to temperature and ready for paving. Heating will restart if the temperature of the screed plate falls to the set point. If the temperature of the screed plate falls to 3 °C (5 °F) below the set point, the temperature indicator will no longer be illuminated. If the heater ECM detects a fault in this circuit, the ECM generates a flashing error code with the indicator.
Right Extender Power Indicator
The heater ECM illuminates the right extender power indicator (10) when power is available to the right extender heater. If the heater ECM detects a fault in this circuit, the ECM generates a flashing error code with the indicator.
Left Extender Manual Indicator
The heater ECM illuminates the left extender manual indicator (19) when the left extender is in the manual heating mode.
Left Main Manual Indicator
The heater ECM illuminates the left main manual indicator (17) when the left main screed plate is in the manual heating mode.
Right Main Manual Indicator
The heater ECM illuminates the right main manual indicator (14) when the right main screed plate is in the manual heating mode.
Right Extender Manual Indicator
The heater ECM illuminates this indicator (12) when the right extender is in the manual heating mode.
Error Codes (Screed Heater)
Note: All of the status indicators except for the error indicator are green. The error indicator is amber.
| Flash Bit Sequence | Device At Fault | Cause Of Fault |
|---|---|---|
| "_ _ _ ." | Left extension temperature sensor | Short or value out of range |
| ".. . _" | Right extension temperature sensor | Short or value out of range |
| "_ _. _" | Engine sensor | Value out of range |
| ".. _ _" | Can bus | Communication time out |
| "_ _. ." | Left extender temperature sensor | Short or value out of range |
| ".. _ ." | Left main temperature | Short or value out of range |
| "_. _ ." | Right main temperature sensor | Short or value out of range |
| ". _ _ ." | Right extender temperature sensor | Short or value out of range |
| "_. . ." | No power available | Generator switch off |
The heater ECM monitors the condition of components in the screed heating system. If a fault is detected in one of the monitored components, the ECM displays information about the fault in a four bit sequence of flashes on the fault indicator. The above chart illustrates the flash code sequence, the device which contains the fault, and the cause of the fault.
Note: The dot in the flash bit sequence column of the above chart represents a short flash. The dash represents a long flash.
| Flash Sequence | Cause Of Fault |
|---|---|
| Individual section power and temperature set point are both off | Temperature input signal out of range |
| Individual temperature set point indicator flashing once per second. | Temperature is not increasing at the expected rate. |
| Individual set point and section power indicators flashing alternately | Unknown error, output off |
| All indicators flashing alternately once per second | System fault, all outputs off |
The heater ECM will display additional fault information on the temperature set point indicators and the section power indicators. The above chart describes the flash code sequence and the cause of the fault.
Note: The dot in the flash bit sequence column of the Fault Indicator chart represents a short flash. The dash represents a long flash.
Heater Relays
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| Illustration 7 | g01437553 |
Relay Box Mounted on the Screed Behind the Touch Pad Controller (1) Left extension heater relay (2) Left extender heater relay (3) Left main heater relay (4) Right main heater relay (5) Right extender heater relay (6) Right extension heater relay | |
The heater relays are located in a box on the top of the screed, under the right deck plate. Left extension relay (1) and right extension relay (6) supply power to the heaters in the optional screed extensions.
Note: Screeds that are equipped with the optional extensions require an ID plug that must be installed in the harness. The plug tells the ECM that it has extensions with heat installed on the screed.
The coils of the heater relays are controlled by the heater ECM. When the ECM determines that a heating element should be operating, the ECM sends an output signal to the coil of the corresponding relay. When the relay is energized, power from the generator is sent to the heating element.
Heater Elements and Temperature Sensors
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| Illustration 8 | g01437555 |
Screed Plate (1) Heater elements (2) Temperature sensor | |
The screed is composed of six sections. The two halves of the main screed, the two screed extenders, and the optional extensions. Each section of the screed has two heater elements (1) and temperature sensor (2) mounted to the screed plate.
The temperature sensors are resistance type devices. The resistance through the sensor changes with changes in temperature. The heater ECM measures the resistance through the sensors. The heater ECM converts the reading to a temperature value.
System Operation
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| Illustration 9 | g01443554 |
Heater Electrical System (1) Machine to screed harness (2) Resistors (3) Relay box (4) To left screed extensions (5) To right screed extensions (6) Left extender screed plate (7) To left extension ground terminals (8) Screed ECM (9) "LX" relay (10) Left main screed plate (11) Touch pad (12) "LE" relay (13) "LM" relay (14) "RM" relay (15) "RE" relay (16) To main screed and extenders (17) Right main screed plate (18) "RX" relay (19) Diagnostic connector (20) Controller ESH (21) Generator to screed harness (22) Right extender screed plate (23) To right extensions ground terminals | |
The heater ECM receives power at terminal "1". The heater ECM is grounded at terminal "2". Power must be available at terminal "1" for the heater ECM to operate.
The heater ECM gathers analog input signals from the following input devices:
- Right extender temperature sensor
- Right main temperature sensor
- Left main temperature sensor
- Left extender temperature sensor
The heater ECM receives digital input signals from the following input devices:
- CAN bus communications (from machine)
- Left extender input
- Right extender input
The electric heating system is equipped with an automatic power management system. The heater ECM monitors the engine load (electronically controlled engine).
Engine high idle and engine load factor are controlled through the engine ECM. Load and rpm are communicated to the heater ECM through the CAN communications link.
The heater ECM analyzes the input signals. The heater ECM generates the appropriate output signal to the following output devices:
- Left extension relay
- Left extender relay
- Left main relay
- Right main relay
- Right extender relay
- Right extension relay
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| Illustration 10 | g01443559 |
Extension Heater Circuits (1) From heater relay box (2) Left terminal box (3) Left 750 mm extension heater circuit (4) To 250 mm extension or second 750 mm extension heater circuit (5) From left screed extender ground terminal (6) Left 250 mm extension heater circuit (7) From left screed extender ground terminal (8) From heater relay box (9) Right 250 mm extension heater circuit (10) From right screed extender ground terminal (11) Right terminal box (12) To 250 mm extension or second 750 mm extension heater circuit (13) Right 750 mm extension heater circuit (14) From right screed extender ground terminal | |
The AS4251C Asphalt Screed has two types of extensions available, a 750 mm extension and a 250 mm extension. Up to two extensions can be added to each side of a screed. The possible combinations are as follows:
- One 250 mm extension
- One 750 mm extension
- One 750 mm extension plus one 250 mm extension
- Two 750 mm extensions
The optional screed extensions include heater elements and a temperature sensor. The 750 mm extension has two heater elements. The 250 mm extension has one heater element. When more that one extension is attached to a screed, only the outboard temperature sensor is used.
When extensions are added to a screed, the end gates and outboard operator stations move out to the outboard ends of the extensions. An attachment cable is added to the end of the operator station cable so the cable can reach the new location of the operator station. That attachment cable includes wires in order to connect the extension temperature sensor to the heat controller. When extension temperature sensors are connected to the heat controller, remove the resistor network at connector "MH C27".
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| Illustration 11 | g01437563 |
Logic Flow Chart | |
Just after the screed heating system is initiated, the heater ECM performs an indicator check. The indicator check sequence is as the following:
- All indicators are simultaneously illuminated for one second.
- Each individual indicator is illuminated for one second, with a one second pause between each illumination.
- All green indicators except for the power indicator are simultaneously illuminated for one second.
- The power indicator is illuminated for one second.
- All indicators are simultaneously illuminated for one second, turned off for one second, and then illuminated for one more second.
After the indicator check is completed, the system operates.
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| Illustration 12 | g01437564 |
Logic Flow Chart | |
At start-up, the system defaults to the low temperature setpoint. The heater ECM monitors the temperature selector switch. Each time the temperature selector switch is depressed, the ECM advances to the next temperature setpoint in the cycle.
When the system is in the low temperature mode, the temperature setpoint is 93 °C (200 °F). When the system is in the medium temperature mode, the temperature setpoint is 116 °C (240 °F). When the system is in the high temperature mode, the temperature setpoint is 132 °C (270 °F).
Note: In the event of a temperature sensor failure, the heater can be operated in manual mode. In the manual heating mode, the heater ECM activates the heating element for set periods of time. This depends on the temperature mode which is chosen. Heating times for the manual mode are as the following:
- Low heat setting "30 minutes"
- Medium heat setting "45 minutes"
- High heat setting "60 minutes"
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| Illustration 13 | g01437957 |
The heater ECM will limit heater operation in order to prevent the heating system from using excessive engine power. The heater ECM looks for load factor information from the engine ECM. All heating elements are enabled when the load factor is less than 100 percent. All heating elements are disabled when the load factor is equal to 100 percent.
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| Illustration 14 | g01437566 |
Logic Flow Chart | |
The heater ECM determines if the optional screed extensions are installed. The ECM recognizes the extension because of the ID plug that must be installed with the extension. If the optional extensions are installed, the heater ECM alternates the output to the heating elements. The ECM alternates output to the heating elements for 1.5 minutes on the extender and 1 minute on the extension element. This sequence is continued until the temperature sensor on the extender reaches the set point temperature.
The heater ECM monitors the temperature of the screed. The ECM uses this information to control the screed heating elements and to control the indicators on the heater control panel.