AS3251C Asphalt Screed Caterpillar

Introduction

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. The sensors and controls set the screed temperature. Also, the sensors and controls maintain the screed temperature.

Note: The screed heating system is powered by a generator on the tractor. Since the generator is not part of the screed, there is only general information about the generator in this publication. See the generator section of the documentation for the Asphalt Paver for more information on the generator and generator controls. Refer to Specifications, Systems Operation/Testing and Adjusting, KENR5729, "Machine Systems".

Generator

Illustration 1	g01389137

Generator (1) is located on the left side of the tractor. The left side door provides access to the generator.

The Asphalt Pavers are equipped with a 25 kW generator set. The generator set provides power in order to operate the electric screed heaters and other equipment. Tractors may be equipped with a hydraulic driven generator or a belt driven generator. The belt driven generator is not shown.

For the Asphalt Pavers that are equipped with a hydraulic generator, a variable displacement pump provides oil flow in order to operate a fixed displacement hydraulic motor that drives the generator. For the Asphalt Pavers that are equipped with a belt driven generator, the generator is driven directly by the engine.

Generator Control Switch

Illustration 2	g01389142

Generator control switch (2) is located on the instrument panel of the tractor. The location of this switch may vary between Asphalt Pavers.

The generator control switch is a two-position toggle switch. The top position of this switch is the ON position. The bottom position is the OFF position. When the generator switch is in the ON position, power is sent from the tractor electrical system to 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.

Circuit Breaker Panel for the Screed Heater

Illustration 3	g01389152

Screed heater circuit breaker (3) through screed heater circuit breaker (6) are located on the generator set. This location is under a hinged access panel. The position of the panel may vary between generators.

This circuit breaker panel is equipped with five circuit breakers. Four of the breakers control power for the electric screed heating system. The following list shows the assignments for the screed heat circuit breakers:

• Circuit breaker (3) (right main screed heating element)

• Circuit breaker (4) (left main screed heating element)

• Circuit breaker (5) (right screed extension and extender heating element)

• Circuit breaker (6) (left screed extension and extender heating element)

• Circuit breaker (7) (auxiliary lights) (This breaker is not part of the screed heater circuit.)

Heater Control Box

Illustration 4	g01389158

The heater control box is located on the screed. The box is 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. Also, the switches and the ECM operate the status indicators in order to alert the operator to current operating conditions. The heater ECM (not shown) is mounted to the back to the display panel.

Function of the Switches

Main Power Switch

Main power switch (8) 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 automatically operate the screed heaters. If this switch is depressed while the heaters are ON, the heater ECM discontinues operation of the screed heaters.

Temperature Selector Switch

Temperature selector switch (11) allows the operator to choose between three temperature setpoints. The status indicators that are above the temperature selector switch alert the operator of the current chosen setpoints.

Left Extender Manual Switch

Left extender manual switch (25) 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 the ON position and the OFF position. The ECM manually controls the heater based on the time that corresponds to the temperature selector setting.

Left Main Manual Switch

Left main manual switch (23) 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 the ON position and the OFF position. The ECM manually controls the heater based on the time that corresponds to the temperature selector setting.

Right Main Manual Switch

Right main manual switch (22) 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 the ON position and the OFF position. The ECM manually controls the heater based on the time that corresponds to the temperature selector setting.

Right Extender Manual Switch

Right extender manual switch (20) 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 the ON position and the OFF position. The ECM manually controls the heater based on the time that corresponds to the temperature selector setting.

Function of Status Indicators

Power Indicator

The heater ECM illuminates power indicator (8) when the screed heating system is in operation.

Low Temperature Indicator

Note: In the manual heating mode, the heater ECM activates the heating element for 30 minutes when the low temperature mode is chosen.

In the automatic heating mode, the heater ECM illuminates low temperature indicator (10) 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 93 °C (200 °F).

Medium Temperature Indicator

Note: In the manual heating mode, the heater ECM activates the heating element for 45 minutes when the medium temperature mode is chosen.

In the automatic heating mode, the heater ECM illuminates medium temperature indicator (12) when the system is in the medium temperature mode. When this indicator is illuminated, the temperature setpoint is 116 °C (240 °F).

High Temperature Indicator

Note: In the manual heating mode, the heater ECM activates the heating element for 60 minutes when the high temperature mode is chosen.

In the automatic heating mode, the heater ECM illuminates high temperature indicator (13) when the system is in the high temperature mode. When this indicator is illuminated, the temperature setpoint is 132 °C (270 °F).

Error Indicator

Error indicator (14) 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 left extender temperature indicator (30) when the temperature of the screed plate on the left extender reaches the chosen setpoint. The heater will continue to be powered until the setpoint 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 the preset temperature and the screed is ready for paving. The heater will continue to heat for a further11 °C (20 °F). Then the power and the power indicator will discontinue. If the temperature of the screed plate falls by 5.5 °C (10 °F), the following will occur: the power will switch on, the power indicator will illuminate and the set point indicator stays illuminated.

If the screed plate temperature drops quickly by 11.6 °C (21 °F), the following will occur: the power light will illuminate, the set point indicator will discontinue and the heating will cycle again.

If the heater ECM detects a fault in this circuit, the ECM generates a flashing error code with the setpoint indicator.

Left Extender Power Indicator

The heater ECM illuminates left extender power indicator (28) 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 left main temperature indicator (29) when the temperature of the left main screed plate has reached the chosen setpoint. The heater will continue to be powered until the setpoint 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 the preset temperature and the screed is ready for paving. The heater will continue to heat for a further11 °C (20 °F). Then the power and the power indicator will discontinue. If the temperature of the screed plate falls by 5.5 °C (10 °F), the following will occur: the power will switch on, the power indicator will illuminate and the set point indicator stays illuminated.

If the screed plate temperature drops quickly by 11.6 °C (21 °F), the following will occur: the power light will illuminate, the setpoint indicator will discontinue and the heating will cycle again.

If the heater ECM detects a fault in this circuit, the ECM generates a flashing error code with the setpoint indicator.

Left Main Power Indicator

The heater ECM illuminates left main power indicator (27) 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 right main temperature indicator (16) when the temperature of the right main screed plate has reached the chosen setpoint. The heater will continue to be powered until the setpoint temperature has been exceeded by 11 °C (20 °F). At this point, power to the screed heater is discontinued.

When the setpoint temperature indicator illuminates, the screed section is up to the preset temperature and the screed is ready for paving. The heater will continue to heat for a further11 °C (20 °F). Then the power and the power indicator will discontinue. If the temperature of the screed plate falls by 5.5 °C (10 °F), the following will occur: the power will switch on, the power indicator will illuminate and the setpoint indicator stays illuminated.

If the screed plate temperature drops quickly by 11.6 °C (21 °F), the following will occur: the power light will illuminate, the setpoint indicator will discontinue and the heating will cycle again.

If the heater ECM detects a fault in this circuit, the ECM generates a flashing error code with the setpoint indicator.

Right Main Power Indicator

The heater ECM illuminates right main power indicator (18) 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 right extender temperature indicator (15) 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 setpoint temperature has been exceeded by 11 °C (20 °F). At this point, power to the screed heater is discontinued.

When the setpoint temperature indicator illuminates, the screed section is up to the preset temperature and the screed is ready for paving. The heater will continue to heat for a further11 °C (20 °F). Then the power and the power indicator will discontinue. If the temperature of the screed plate falls by 5.5 °C (10 °F), the following will occur: the power will switch on, the power indicator will illuminate and the setpoint indicator stays illuminated.

If the screed plate temperature drops quickly by 11.6 °C (21 °F), the following will occur: the power light will illuminate, the setpoint indicator will discontinue and the heating will cycle again.

If the heater ECM detects a fault in this circuit, the ECM generates a flashing error code with the setpoint indicator.

Right Extender Power Indicator

The heater ECM illuminates right extender power indicator (17) 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 left extender manual indicator (26) when the left extender is in the manual heating mode.

Left Main Manual Indicator

The heater ECM illuminates left main manual indicator (24) when the left main screed plate is in the manual heating mode.

Right Main Manual Indicator

The heater ECM illuminates right main manual indicator (21) when the right main screed plate is in the manual heating mode.

Right Extender Manual Indicator

The heater ECM illuminates right extender manual indicator (19) indicator 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.

Illustration 5	g03074037
Error codes

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.

Illustration 6	g01389287

The heater ECM will display additional fault information on the temperature setpoint 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 Control Box

Illustration 7	g01389292

The following heater relays are located inside the heater control box: left main heater relay (33) , right main heater relay (32) , left extender heater relay (34) and right extender heater relay (31) . The heater control box cover must be removed in order to access the heater relays.

Note: Screeds equipped with the optional extensions will have two additional heater relays. An ID plug is also required and must be installed in the harness. The plug communicates to the ECM that the screed 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.

Each relay is equipped with green status indicators (35) , (36) , (37) , and (38) . The status indicator is illuminated when the coil of the corresponding heater relay is energized.

Temperature Sensors

Illustration 8	g01389296

The right and left sides of the main screed and each screed extender are equipped with temperature sensors (39) . Each section contains one temperature sensor. The temperature sensors are located at the rear edge of the screed plates.

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. Also, the heater ECM converts the reading to a temperature value.

Heating Elements

Illustration 9	g01389299

The right and left sides of the main screed, and both screed extenders are equipped with two heating elements (40) . The heating elements are mounted to the top of each screed plate with a heat transferring compound.

Control Circuit (Screed Heater)

Illustration 10	g01389661
(1) Screed ECM (2) Asphalt paver to screed harness (3) Left electrical screed plate extender (4) Left electrical screed plate extension (optional) (5) Touch pad (6) Left electrical main screed plate (7) Screed plate extension (may have one or two heaters depending on length) (8) Right electrical main screed plate (9) Asphalt Paver to screed harness (10) Controller (ESH) (11) Diagnostic connector (ESH) (12) Relay (LX) (13) Relay (LE) (14) Relay (LM) (15) Relay (RM) (16) Relay (RE) (17) Relay (RX) (18) AC ground (19) AC ground (20) Right electrical screed plate extender (21) Right electrical screed plate extension (optional)

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 Asphalt Paver)

• 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. Also, 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

Control Logic

Illustration 11	g01389685

Just after the screed heating system is initiated, the heater ECM performs an indicator check. The indicator check sequence is as follows:

• 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.

Illustration 12	g01389704

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 action depends on the temperature mode which is chosen.

Heating times for the manual mode are as follows:

• Low heat setting (30 minutes)

• Medium heat setting (45 minutes)

• High heat setting (60 minutes)

Illustration 13	g01389715

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.

Illustration 14	g01389721

The heater ECM determines if the optional screed extensions are installed. The ECM observes 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. Then, the ECM alternates output to the heating elements for 1 minute on the extension element. This sequence is continued until the temperature sensor on the extender reaches the setpoint temperature.

The heater ECM monitors the temperature of the screed. The ECM uses this information in order to control the screed heating elements. Also, the ECM uses this information to control the indicators on the heater control panel.