PAZ-32053-07, PAZ-4234. HEATING SYSTEM
Heating of the bus interior and the driver's workplace is carried out by a liquid heating system that uses heat from the engine cooling system and a liquid heater.
Interior heaters have two operating modes - full and partial. They are controlled using two-position keys located on the instrument panel.
For effective heating of the passenger compartment and blowing the windshields, it is necessary to maintain a sufficiently high temperature of the coolant in the engine cooling system and to circulate the liquid through the pipelines, which is achieved by the operation of the liquid heater and circulation pump, which must be constantly on.
The Webasto (Spheros) liquid heaters of Thermo E200 and Thermo E320 models are installed on the PAZ-32053-07 and PAZ-4234 buses, respectively.
Liquid heaters of the Thermo E200 and Thermo E-320 models are an autonomous heating system that works independently of the engine. The heater is designed to maintain the temperature of the liquid (antifreeze) within the limits sufficient for heating the passenger compartment, defrosting windshields, and preheating the engine.
When the liquid in the boiler is heated to 85 ° C, the pre-heater is automatically turned off. When the antifreeze is cooled to 72 ° C, the heater turns on.
The description of the heater is contained in its operating manual, which is included in the delivery set of the bus.
Switching on and starting the heater.
Attention! Before turning on the heater, make sure that there is a sufficient amount of liquid in the expansion tank and check the position of the valve cocks of the bus heating system. The valves must be in the open position before starting.
When the heater is turned on, the operation indicator lights up, the control unit starts the normal operation mode and checks the coolant temperature.
If the coolant temperature is below the upper temperature threshold, the pre-start phase begins. The combustion air blower and circulation pump are switched on. After about
12 seconds (pre-start time) high voltage ignition spark appears. Approximately one second thereafter, the solenoid valve in the fuel pump opens and the incoming fuel is injected through the high-pressure spray nozzle into the combustion chamber. In the combustion chamber, fuel is mixed with air. This air-fuel mixture is ignited by an ignition spark and burned in the combustion chamber. The flame is monitored by a flame sensor built into the control unit. Approximately 5 seconds after detecting a flame, the control unit switches off the ignition generator. Until this moment, the flame has stabilized and the heater is not yet in heating mode.
Heating operation. After the flame has stabilized, the heater operates in normal operation. If the upper switch-on threshold is exceeded, the heating operation ends and the purge phase begins. The solenoid valve closes, the flame is extinguished, but the combustion air blower and circulation pump continue to run. After about 120 seconds, the combustion air blower is switched off and the purge phase ends. The heater stops (work interruption). The operation indicator is on. The heater resumes operation in combustion mode when the lower switching threshold is exceeded. The same operations are performed as when turned on.
Temperature control. If the circulation rate of the coolant is insufficient or if there is poor air removal from the cooling circuit, the temperature may rise too quickly during heating operation. The control unit detects a temperature rise that is too fast and automatically sets the upper switching threshold to lower values. The faster the temperature rises,
the lower the switching threshold is set for the initiation of an outage. The restarting of the burner after an interruption in operation is also carried out at a lower switching threshold. This prevents the overheating protection from tripping due to residual heat. If the temperature rise (temperature gradient) is again within the permissible limits, the switching thresholds are set back to their normal values (lower switching threshold 72 ° C, upper switching threshold 85 ° C).
Shutdown. When the pre-heater is turned off, the combustion process ends. The operation indicator goes out and the purge phase begins. The solenoid valve closes, the flame is extinguished, and the combustion air blower and circulation pump continue to run. After about 120 seconds, the combustion air blower is switched off and the purge phase ends. If a problem occurs during the purge phase (eg flame detection), the purge phase may take less than 120 seconds. During the purging phase, the heater can be switched on again. After a purge phase of 30 seconds and a subsequent pre-start phase, the burner starts up again.
Operating and maintenance instructions
Attention! The maintenance and repair of the heater must be carried out by qualified specialists who have undergone company training at the manufacturer of the heater (Spheros and Webasto).
Before opening the pre-heater, it must be disconnected from the on-board network of the bus. The heater must always be disconnected from the vehicle electrical system before disconnecting the temperature sensor plug. Disconnecting in the reverse order will result in an AUTOMATIC LOCK OUT of the heater. Disconnect the temperature sensor plug before disconnecting the burner from the heat exchanger.
The temperature in the area of the heater must not exceed 85 ° C (maximum operating temperature). Excessive temperatures can cause heater malfunctions and irreversible damage to electronic equipment.
Electrical cables must not show any damage to the insulation (for example, as a result of pinching, heat, kinking, abrasion, etc.). The temperature sensor cable must not be subjected to mechanical stress (do not pull on the cable, do not carry the heater by it, etc.).
It is forbidden to use the heater without exhaust extraction in closed rooms (garages or workshops) even if the time has been set in advance due to the danger of poisoning and suffocation. This also applies to combustion operation during the setting of the exhaust CO2 value.
Do not operate the heater near combustible materials (leaves, dry grass, paper, cardboard, etc.).
When operating without coolant (overheating!), The heater casing can reach the ignition temperature of the diesel fuel! Dripping or vaporizing fuel must neither collect nor ignite on hot parts or electrical devices.
The openings of the air intake and exhaust pipes must be checked regularly and cleaned if necessary.
At petrol stations and at filling stations, the heater must be turned off due to the risk of explosion.
In places where flammable vapors or dust may form (for example, near fuel, coal and wood dust, grain storage, etc.), the heater should be turned off due to the risk of explosion.
The coolant in the heating circuit must contain at least 20% antifreeze.
When carrying out electric welding in the bus, to protect the heater control unit, the main electrical cable (plus) must be disconnected from the battery and grounded to the body.
In the event of deviations from normal operation, the pre-heater is automatically blocked.
There are two types of heater blocking - emergency blocking in case of malfunctions and blocking.
Interlocks are designed to protect the heater from damage primarily due to impermissible thermal loads. Thermal loads can arise for the following reasons: a) too low circulation rate of the coolant; b) insufficient amount of coolant (dry overheating); c) failure of the circulation pump.
When the pre-heater is blocked, depending on the time of occurrence, the purge phase can last up to 120 seconds. The reason for blocking can be determined by flashing indicator pulses.
Buses LiAZ, PAZ and LAZ have a heating system for heated bodies. The heat from the engine cooling system is used for heating. The air blown by the fan passes through the radiator, heats up here and enters the air duct located along the entire body. From the air duct through the slots in it, air enters evenly throughout the entire cabin.
The amount of air entering the passenger compartment through the air duct is regulated by a knob that controls the position of the duct flap. In summer, when there is no need to heat the passenger compartment, the handle must be set to the extreme forward position. In this case, the flaps will close, and the lower flap will open a hole in the bottom of the casing and air will escape into the engine compartment. When the flaps are fully open, all warm air will flow into the passenger compartment. If the flaps are in an intermediate position, the air flow into the passenger compartment will decrease. The bus heating system ensures the exchange of air in the passenger compartment every minute.
The ventilation of the LiAZ and LAZ buses is carried out through the opening vents of the side windows, through the air intake from under the visor, through the opening hatches in the bus roof. Opening and closing of hatches is carried out by lever-type lifting mechanisms.
The heating of the driver's cab is regulated by a flap. For windows, warm air is supplied from the heating system through hoses.
On buses LAZ-695M and LAZ-695N, the air channel ends at the front wall of the body, where two fans are installed in a special casing that capture air and create pressure in the glass blowing nozzles. Fans and nozzles are connected by hoses. To regulate the supply of warm air depending on the ambient temperature, there are two dampers: bottom and side. If these dampers are closed, then warm air through the lower window with a damper is discharged to the outside.
When operating the bus in the cold season (at temperatures below -10 ° C), in order to avoid overcooling of the engine, the fan shutters are covered and warm air is directed along a small circulation circle. The air from the passenger compartment enters the radiator, heats up and returns to the passenger compartment through the channel through the open valves.
Ventilation of the bus body is carried out through ventilation hatches, side windows, air intake from under the visor of the heating system.
A similar heating system on PAZ buses. The heating system of the body of the Ikarus-260 bus, in addition to the engine radiator, has two additional devices: a heater for the windshield and driver's cab and a heating device for the passenger compartment.
Warm water from the engine passes through pipelines to the radiator of the interior heater and the heater of the windshield and driver's cab. The air blown by the fan, passing through the radiator, heats up and then flows through the heater tube into the passenger compartment and into the driver's cab to heat the windows. The fan switches have two fixed positions for heating control.
The calorifier heating system of the Ikarus-260 bus is similar in structure to the system of domestic buses.
On some variants of the Ikarus-260 buses, a heating and ventilation device of the Sirocco type is installed. This device is autonomous and runs on liquid fuel.
Attention : It is not allowed to fill the cooling and heating system of NEFAZ buses with coolants of different brands and manufacturers, as well as liquids that do not correspond to the chemotological card ( ), to determine the corrosion of system elements.
At each TO-1 and TO-2, check the density of the liquid and check the coolant samples from the heating system for compliance with the TU requirements (for alkalinity and hydrogen index) with a mark in the service book. If not, replace the coolant.
If these requirements are not met, claims for failure due to corrosion of heating system elements by the bus manufacturer will not be considered.
Note ... Copies of passports describing the design and maintenance of heaters models A1-205.241.251 and A2-21.243.252.314, intended for heating the driver's seat and passenger compartment, are given in .
Heating the interior of the bus produced from the engine cooling system. To the engine cooling system ( see Figure 216 - Schemes of operation of the heating and engine heating system on city buses (with three COs), on commuter buses (with four COs) and on intercity (with six COs) and Figure 217 - Installation diagram of a damper and an air separator in the heating system of a bus interior) includes: a liquid heater, pipelines, a pump, a damper, an air separator, a drain valve, air release valves, valves No. 1, No. 2 and No. 3, presented in the above diagrams. The arrows indicate the direction of fluid circulation in the system.
Figure 216 - Schemes of operation of the heating and engine heating system on city buses (with three COs), on suburban (with four COs) and on intercity (with six COs)
PZhD - heater; FO - frontal heater; СО - interior heaters; H - pump PZhD; Kp1 - Kr3 - system valves; M - electric motors; VO - air separator; D - damper; K - air release valves; KS - coolant drain valve; RB - expansion tank
Figure 217 - Installation diagram of a damper and an air separator in the heating system of the bus interior
1 - damper; 2 - air separator; 3 - crane Kr. 2 (red); 4 - crane Kr. 1 (blue); 5 - tap Kr. 3 (black); 6 - coolant drain valve (KS); I - to the interior heaters; II - outlet from the heater; III - fluid supply from the system; IV - air outlet from the system to the expansion tank of the engine; V - outlet to the water pump; VI - supply from the heater; VII - removal of the heated liquid into the engine
Heating system works like this:
- for accelerated heating of the engine without heating the passenger compartment - open valve No. 1 and close valves No. 2 and No. 3;
- when heating the passenger compartment from the engine and the heater, close tap No. 1 and open taps No. 2 and No. 3;
- when heating the passenger compartment from the engine, without turning on the heater, close tap No. 1 and open taps No. 2 and No. 3;
- when operating the bus in the summer - open tap No. 1 and close taps No. 2 and No. 3;
- prohibited operating mode of the system - open valve No. 2 and close taps No. 1 and No. 3.
The heating system that heats the driver's workplace consists of a passage valve, pipelines and a front heater mod. A2-21.243.252.314 (Passport A2-01N.000.000 PS).
An automobile heater consists of two main units: heating and fan.
The heating unit consists of a double aluminum radiator and a casing. Six outlet pipes 4 ( Figure 218 - Air intake control) with a diameter of 72 mm.
Figure 218 - Air intake control
1 - bus bumper; 2 - louver shutter; 3 - heating and fan blocks of the heater; 4 - outlet pipes; 5 - louver flap control lever
The fan assembly includes two radial fans, a cover and an air intake control mechanism. To remove air bubbles in the heating system, there are air release valves and a centrifugal air separator (in Figure 216 - Schemes of the heating system and engine heating on city buses (with three COs), on suburban buses (with four COs) and on intercity (with six COs) the arrow shows the direction of circulation of the working fluid).
The damper is designed to smooth out pressure surges of the working fluid in the heating system.
The design of the heater allows air intake from outside the bus or from the driver's cab by adjusting the louver 2 (see Figure 218 - Air intake control) located on the front heater radiator.
Lever 5 adjusts the position of the louver with a cable connection. When the lever 5 is pushed upwards, the louver flap rotates along the axis, by its movement it opens the flow of air outside the bus (recirculation mode).
The air heated in the frontal heater is directed through the air duct system into the air intake box (on the driver's instrument panel), and from it through the air vents to the windshield and into the niche, to the driver's feet and the front door leaf. In the reverse position of the damper, the heated air is drawn into the heating system from the driver's cab. The louver travel is 55 mm.
The heating system that heats the interior of the bus consists of pipes and three dual-mode heaters located inside the wheel arch podiums. Interior heaters are of a radiator type with forced air supply by electric fans through radiators. The same heater is installed in the cab under the driver's seat. The heaters are connected in parallel with each other and connected to the engine cooling system.
To remove air bubbles in the pipes of the heating system, there are air release valves behind the driver's partition behind the driver's partition.
The heating system of the bus interior provides for the installation of a centrifugal air separator 2 ( see Figure 217 - Installation diagram of the damper and air separator in the heating system of the passenger compartment of the bus) - to remove air from the system, and install damper 1 - to exclude hydraulic shocks in the system (to smooth out pressure surges of the working fluid in the system).
Attention ... To avoid water hammer, it is strictly forbidden to switch the heating system taps while the engine is running.
Ventilation the bus can be carried out in a natural and compulsory way. Natural ventilation of the bus is provided by air intakes located in the front part under the windshield, emergency ventilation hatches in the roof and through the vents in the side windows. Forced ventilation is provided by four overhead electric fans (optional) and a rotary electric fan installed in the driver's office.
The ventilation of the driver's workplace is carried out through the movable glass of the side window. The ventilation intensity can be increased by turning on the front heater fan in recirculation mode ( see above).
The ventilation of the passenger compartment is carried out through the vents in the side windows and emergency ventilation hatches in the roof of the bus.
