EP0257576A2 - Method and apparatus for avoiding failures caused by contacts-welding in heating and cooling systems - Google Patents

Abstract

The invention relates to a bidirectional heat exchange system with a changeover valve (20) and a compressor (24) and a compressor monitoring device (45, 80) for determining faults caused by contact welding faults. The system is monitored to determine if the compressor continues to operate despite signals from the control system that would cause the compressor to shut down. If such a condition occurs, a safety operating mode is initialized, which causes the compressor to be loaded and to be prevented from self-destruction. This is preferably done by continuously switching the state of the switch valve.

Description

The invention is in the field of security technology and relates to a method and a device according to the preambles of claims 1 and 8.

In all systems that use a compressor to compress a coolant, a control device is provided for switching the compressor on and off at certain times. In its simplest versions, this control device can essentially only contain one thermostat and one relay or, in more sophisticated systems, multiple relays or, more recently, programmable microcomputers. Regardless of the complexity of the system, however, electromagnetic or electronic relays or semiconductor switches are used to switch the power supply from the power supply to the compressor on and off.

It is known that errors or defects due to contact welding can occur with electromagnetic relays. This phenomenon occurs when a current spike occurs when opening the relay contacts. Enough heat can be generated to melt the contacts and to close them together when closed the one to weld. It is obvious that the relay then loses its control function via the process and the compressor continues to run due to this contact welding, regardless of a corresponding necessity. Usually, the compressor is not loaded after the contacts have been welded, so that it continues to run until it is destroyed, unless safety devices are provided. This type of error is also referred to as "contact welding" if it is an electronic control system with semiconductors and there are no contacts in the actual sense. Similar errors occur in such electronic relays as in mechanical relays, in that a current path with a very small resistance forms within the electronic relay and an uncontrolled current flows to the compressor.

The destruction of the compressor caused under these circumstances can be devastating. Both the pressure and the temperatures in the compressor are often quite high. Failure of the system can result in an explosion that significantly endangers both people and nearby facilities. For this reason it is common to provide safety devices such as a ball valve in such systems. The latter can be installed in the housing of the compressor and thus forms an escape line for the liquid. As a result, a reduction in the possible high pressure difference can be achieved when contact welding occurs. This measure leads to protection against dangerous explosions, but cannot protect the compressor itself from damage, since it continues to run and is normally destroyed as a result.

Another variant of such a safety device uses an interruption switch which interrupts all current paths of the compressor motor as soon as very high pressures, temperatures or currents occur. While this type of device is effective, it is very expensive, increasing the overall cost of the system in which it is used.

It is an object of the invention to provide a method which protects the compressor in a heating or cooling system when contact welding faults occur and checks the system state in such a way that the occurrence of a contact welding can be determined before the system devices are damaged and in such cases the system is subsequently controlled so that the compressor is saved from a fatal defect.

It is a further object of the invention to provide a device which allows the method to be carried out, has low manufacturing costs and ensures a high degree of safety.

The invention relates to a method for monitoring a heating and cooling system with a compressor and a changeover valve, certain system parameters being monitored during normal operation of the system in order to be able to determine the conditions for switching off the compressor. The compressor is monitored to determine whether it has not yet switched off when these conditions occur, which suggests a contact welding error and initiates a safety operating mode if such a contact welding error is present. This safety operating mode includes a periodic switching of the state of the switching valve, whereby the system between a heating and Cooling mode is switched so that the compressor is permanently loaded until a manual correction is made.

• Fig. 1 zeigt ein schematisches Blockdiagramm eines Heiz- und Kühlsystems, in welchem das erfindungsgemässe Ver­fahren angewendet wird
• Fig. 1A zeigt ein funktionales Blockdiagramm des Systems
• Fig. 2. 3, 4 zeigen jeweils einen Teil eines Flussdiagramms, das insgesamt die Verfahrensschritte eines Beispiels des Verfahrens gemäss der vorliegenden Erfindung illu­striert

The method according to the invention and an exemplary embodiment of an apparatus for carrying out the method are described in more detail with reference to the following figures.

• 1 shows a schematic block diagram of a heating and cooling system in which the method according to the invention is used
• Figure 1A shows a functional block diagram of the system
• 2. 3, 4 each show a part of a flowchart which overall illustrates the method steps of an example of the method according to the present invention

The person skilled in the art will readily recognize from the following description that the method according to the invention can be used in a wide variety of ways using a special control circuit for determining a contact welding fault and correspondingly controlling the compressor operation, which is described in more detail below. The most efficient and preferred embodiment is to integrate the method into the existing software control system of the heating or cooling device. The method is explained using an example of a previously known system. which is described in U.S. Patent No. 4,645,908 issued February 24, 1987 to Richard D. Jones and the entire contents of which are incorporated herein by reference.

In FIG. 1, which corresponds to FIG. 1 of the above-mentioned patent, an air coil 10 outside the system can be seen with a fan 11 which directs the outside air into and through the coil. This coil 10 is a conventional air-cooled heat exchanger as it is manufactured by various companies in the HVAC sector. In the system shown, this heat exchanger is arranged locally and thermodynamically in the usual way.

The arrangement which is to be heated and cooled by means of the system is indicated by a dash-dotted line 12 which schematically delimits this arrangement. One connection of the coil 10 is connected to a tube 13 which leads into this arrangement and into a module referred to below as the generator module 14, all elements of this module in the present system being in a single housing. The tube 13 is connected to a conventional thermostatic control valve 16. The control valve is followed by a filter drier 17, a collecting vessel 18 and the connection of the cooling side of a water-cooled heat exchanger HX-1 in the following order. The other connection of the cooling side of the heat exchanger HX-1 is via a line 19 with a conventional one. only shown schematically here, 4-way switch valve 20, which can have two states. This valve 20 is preferably a solenoid actuated and software controlled valve according to the above-mentioned patent.

The valve 20 is shown in the state of the cooling mode, in which the line 19 is connected via the valve to a line 21 which leads to a pressure accumulator 22, the other side of which leads to the suction side of a conventional compressor 24. The compressor is in the usual way with a crankcase heater 26 Mistake. The output of the compressor 24 is connected by means of a line 27 to the cooling side of a water-cooled heat exchanger HX-2, the other connection of which is connected to the changeover valve 20 via a line 29. In cooling mode, line 29 is connected to line 30, which leads back to the second connection of the outside air coil.

As can easily be seen from the schematic illustration of the valve 20, the line 29 is connected to the line 19 and the line 21 to the line 30 in the heating mode.

The water circuit which is connected to the water connection side of the heat exchanger HX-1 contains, in series, a pump P1, an interior coil 32 and a cooling or heating water storage tank S1, these elements being connected to one another by corresponding lines. The indoor coil 32 is provided with a fan or blower 34 which directs the air through the heat exchanger 32 and over its coils, thereby causing a sufficient heat exchange between the water and the air and conditioning the interior.

The water circuit side of the heat exchanger HX-2 contains a pump P2, which connects to this and leads the supplied water via the water circuit side of the heat exchanger HX-2 into the lowest area of an associated hot water storage tank S2. The other side of the water coil of the heat exchanger HX-2 is connected to an ordinary water line connection and a line 36 which leads to the bottom of the tank S2. At the upper end of the container S2 there is a hot water overflow 37, which is connected to the hot water supply line 39 via a mixing valve 38. It should be noted that the Lei device 36 is also connected to the starter valve, so that the required mixture between hot and tap water is carried out by means of the valve and hot water is available at the desired temperature at the outlet.

The tanks S1 and S2 also have, as shown schematically in FIG. 1, resistance heating elements 40, 42, so that, under appropriate conditions, additional energy can be supplied to the system in order to heat the water in one or both tanks. The heating element 40 preferably has two heating elements connected in parallel.

It can be seen that the heat exchanger HX-2 is arranged at the outlet or the pressure side of the compressor 24, so that it can be supplied at any time with the cooling medium brought to a higher temperature in order to close the water in the tank S2 during the heating or cooling mode heat or, if desired, heat or cool when the system is out of operation. The containers S1 and S2 are preferably 120 gallons of hot water tanks, the container S1 being provided with two 4.5 kW heating elements and the container S2 being provided with a 4.5 kW heating element.

The control software of this system controls the compressor, pumps and fans so that the storage tank is brought to the desired temperature outside of the peak power consumption times, ie the liquid contained therein is heated or cooled depending on the position of a switch on the control console 44 this allows the system to use the memory to heat or cool the environment during peak periods, minimizing the compressor on time during these peak periods. The software can, for example be contained in a device controller 45, which are connected to the various elements of the system, including the control console 44 and a plurality of temperature sensors, which are shown in FIG. 1 by circled capital letters. These sensors are of great importance for the various control mechanisms made possible by the system. For this purpose, in particular the sensor C for measuring the outlet temperature of the compressor 24 (t_dis); the sensor B for measuring the temperature of the liquid distributor of the outside air spiral 10 (t_liq), which represents the evaporating temperature during the heating mode and the outflow temperature of the liquid during the cooling mode; and the sensor G, which measures the temperature of the ambient air (t_amb) at the input of the heat exchanger 10.

The other time functions and parameters used in the system are of course also available in the control unit described here.

FIG. 1A shows a functional block diagram of the device of the system according to FIG. 1, the functional blocks which form the device controller 45 and the sensors being shown in somewhat more detail and illustrating the relationship between the software parts contained therein. The microprocessor subsystem 50 is bidirectionally connected to the data bus 52 and has outputs to an address bus 54 and a microprocessor control bus 56. The subsystem 50 also contains interrupt inputs via the line 58. A program memory 60, for example a disk drive with a Disk drive controller is provided so that the program for controlling the system can be stored on a hard disk or floppy disk or the program is stored in a corresponding chip, for example a ROM. The program memory receives data, addresses, microprocessor control and input-output control input signals and provides data and interrupt output signals. An I / O address, decode and monitor unit 64 also receives address, data and microprocessor control input signals and provides data and I / O control signals.

The system signal inputs are connected to sensors that indicate the energy supplied to the space conditioned by the system, as well as to temperature sensors A, B, C, D, F, G, and H that measure the temperature at different locations in the system. These sensors are described in somewhat more detail in connection with Figures 1 and 5 of U.S. Patent 4,645,908. The energy is measured by means of current sensors 88 and 89 and voltage measuring transformers 103 and 104, which are coupled to the main supply lines, for example from the main supply switchboard 66, which are connected to the supply and the main measuring instrument 68, which measures the energy supplied to the arrangement for billing purposes , connected is. A signal 69 from this measuring instrument indicates when the measured values are high during an "on peak" interval.

These various signals from the temperature and electrical sensors are provided to signal conditioning circuitry 70 which converts the signals into a desired, analog form (except for the main meter signal, which is digital) and adjusts them to an appropriate amplitude. The outputs of the signal conditioning circuit 70 are fed to an analog multiplexer circuit 72, the signal outputs of which lead to an analog / digital converter circuit 74.

A universal control logic unit 76 is also with the I / O control lines, address lines, the data bus and the micropro Processor control bus connected to perform various monitoring functions. This unit receives and delivers peripheral, local control signals (LPC) from or to a discrete, digital input unit 78 and a control output unit 80.

The control output unit 80 provides supply control values for various measuring devices and valves, including the outside air fan 11, the four-way switch valve 20, the compressor 24, the indoor fan 34, the heating elements 40 and 42, and the pumps P1 and P2 . They control both the digital interface and the optical isolation (e.g. optocoupler), the relay coil drive and the power control relay.

Of particular interest for the present invention are the control output unit 80 and the program memory 60, which interact with the microprocessor subsystem 50 and the universal control logic unit 76. The control output unit 80 contains the electronic - or other relays which control the KomPressor and therefore contain the "contacts", be they semiconductors or others, which must be monitored by the program. Likewise, sensors B, C and G are monitored as mentioned above.

The microprocessor subsystem, which contains the microprocessor and the microcontroller, ROM, RAM, system clock and the time circuit, the interrupt controller, the system control circuit, and the address data and control buffers carry out the current process, with the program in the program storage unit 60 is stored.

FIGS. 2 to 4 show a simplified flowchart of a program for executing the method, which determines whether a safety mode should be initialized, thereby indicating the existence of a contact welding error. In the system described, switching to safety mode means that normal operating conditions are disregarded and the system is controlled in such a way that the conditions causing this safety mode can be taken into account. The procedure is explained in more detail using a program written in the C programming language and the printout of which is given in Appendix I.

The individual program steps are represented within the program with the same symbols as are used in FIGS. 2 to 4. Those symbols that are not included in the program are shown in the column on the far left.

The method consists in monitoring certain parameters of the system during operation in order to be able to determine whether conditions occur which indicate the occurrence of a contact weld. For this purpose, three temperatures are measured, which serve to determine whether such a system condition exists. If the temperatures are as expected under normal operating conditions, no safety measure is taken. If, on the other hand, conditions are determined which should not occur, a safety mode for "saving the compressor" is initialized.

The conditions for switching between normal operation and safety mode are briefly outlined below. The individual modules, which are part of the control software for the system in FIG. 1, are arranged in such a way that their function NEN are essentially independent of each other. Each module fulfills its own task and generates a corresponding output after a certain time, ie periodically. Regardless of whether this output is required or is ignored, the module performs its function again in the following period. The output can consist of a calculation result that is used in other modules or a trigger signal for a specific action. This action can consist, for example, of activating a hardware element or triggering security mode.

It should be noted that the modules do not send an execution command themselves, but only report a corresponding request signal. It is quite possible that several modules want to activate a certain element of the device at the same time. In addition, it can e.g. it can happen that two modules send contradicting signals at the same time, which can have different reasons. For example, it is possible for one module to determine an internal temperature, which should actually result in the compressor being switched on so that it cools the room, but another module for determining that the room can be adequately cooled from the storage tank S1 using cold water and the compressor should not be switched on because a high electricity tariff applies at this time of day.

All these request signals are cleaned up using a special module called REDUCTION, which determines and filters out the one to be taken into account in the case of a plurality of signals. A switch-off signal usually has higher priority than a switch-on signal and request signals for activating the safety mode are taken into account first, since they indicate potential dangerous situations. Another one called SEQUENCER The module receives the filtered output signal of the REDUCTION module and sends the current signal, which switches the corresponding hardware elements on or off, according to a defined priority order. Since the present program ensures that the safety mode is switched on when the corresponding conditions occur, its output is recognized by the REDUCTION and SEQUENCER module and processed within the same or the following period in such a way that the safety mode is switched over.

The three temperatures to be measured already mentioned above, i.e. The initial temperature at the compressor (t_dis), the external ambient temperature (t_amb) and the temperature of the liquid coolant in the outside air coil (t_liq) are identified with capital letters, for example as TLIQ, TDIS, TAMB, if they are to cause changes in the system .

The calculation or measurement period is e.g. Four seconds and the various system temperatures are accordingly fed to these modules on a regular basis. In addition, various values such as the upper and lower values of t_liq of the last 16 periods and the average temperature TLIQ are calculated and / or saved. In addition, the occurrence of certain events or certain signals is recorded and logged, e.g. switching the compressor on and off or changing the status of the changeover valve.

The first step is to determine whether the time period since the start of the overall system is less than 8 seconds (A *). If this is the case, this indicates that the system is in the special state of the start phase. It can be done that no contact welds occur and that no safety precautions need to be taken (B).

As soon as the system is no longer in the start phase, it is checked whether a security measure has already been activated or taken (C *). In this case, it is obviously no longer necessary to continue the test routine and the program is ended.

It is then checked whether the system is in an initialization phase (D *). In this exemplary embodiment of the system, the software is aligned with regard to three different time phases. During normal operation, the cycles last approximately 4 seconds each. During the start-up, two different types of phases can be distinguished, which are also treated differently. The first, which lasts approximately 4 to 8 seconds, is called phase 1 and is followed by the so-called initialization phases. A sequence of such initialization phases follows this phase 1 for a period of approximately five minutes during which additional further system initialization procedures take place. If it is determined that the system is in an initialization phase (E1) and less than 12 seconds (E2) have passed since the restart, it is necessary to determine some initialization values for the execution of the program.

For this purpose, the output temperature of the compressor is set equal to the current output temperature and t_liq to the current liquid temperature (F). In addition, pumps P1 and P2 are switched on by means of request signals from the system and the switchover valve is deactivated, so that the valve is switched to heating or cooling mode. The switch valve mode will open Zero and the timeout flag set to zero. The time-out flag is used to check the time to ensure that the system has not overlooked or passed over any dangerous situation. An interval of 10 minutes after switching off the compressor is decisive. If the initial temperature is less than 110 ° F after this interval, it can be assumed that something has been overlooked. This will be determined at a later date.

If it is determined that the system is in the start-up phase and two sets of conditions occur, a safety flag is set. A set of conditions that enable this flag assumes the system is in cooling mode (G1-G6). The program checks whether TDIS is greater than 140 ° F (all temperatures are given here in Fahrenheit); whether TDIS is at least as high as the measured start temperature t_dis minus 10 °; whether TLIQ is at least 20 ° lower than the ambient temperature and also at least as high as the start temperature t_dis minus 10 °; and whether the ambient temperature is above 50 °. If all of these conditions are met, a flag is set (I) as this indicates a serious danger to the compressor.

The system is in heating mode (H1-H6); is TDIS greater than 140 ° and greater than t_dis at start-up minus 10 °; and if TLIQ is at an ambient temperature of 50 ° or less, less than 15 ° below the ambient temperature and less than 5 ° below t_liq when starting up, the compressor is at risk and the safety flag is set (I, J *, K , L).

These sets of conditions during cooling and heating modes indicate conditions when the compressor and of the rest of the system should not occur, i.e. if the coils are undamaged and the exchange liquid can circulate, the system contains enough cooling liquid, etc. In both operating modes, the compressor temperature TDIS should quickly drop below 140 ° and the liquid temperature at the outside air coil should decrease start in cooling mode by at least 10 ° and in heating mode by at least 5 °. If this is not the case, the system must be considered at risk and the security mode must be set.

The program then checks the conditions in order to delete registers that still contain switch-on or switch-off data. If more than 4 minutes have passed since the start-up and TDIS is less than 130 ° (M1, M2, M3), the compressor is either not connected or there is not enough coolant in the system. In both cases, it is not necessary to set a safety flag, so that both the register for the switch-on signal and the register for the switch-off signal intended to avoid contact welding errors are set to zero (Qa, Qb).

If the system is in the normal operating phase, but not all previous states (P1, P2, P3) occurred, a crisis entry flag is set to TRUE and the safety mode is switched on depending on the position of the switch on the HOC 44 control panel protect the compressor in both heating and cooling modes (R, S *, T, U).

As can also be seen from FIG. 3, the program sets a request signal for switching on the pump P1 if the system is in the normal operating phase, has been switched on for more than 7 minutes and 4 seconds and if the compressor is switched on (V *, W). If less than 5 minutes have passed since the last request signal for a status change of the compressor or the changeover valve, the upper and lower liquid temperature are stored in the system according to the temperature TLIQ at this time (X *, Y *, Za, Zb). If the cooling mode is set on the HOC control console or if there is a request signal for switching off the cooling mode (AA1, AA2, BB1, BB2), the program delivers a request signal for switching on the changeover valve (CC). If the stored upper liquid temperature is below the current value of TLIQ, the upper temperature t_liq is set to this current value (DD *, EE).

If cooling mode is selected using the switch on the control console, the changeover valve is set to cooling accordingly (FF *, GG).

If the compressor was switched on for a period of time that is a multiple of exactly 15 minutes, the upper temperature TLIQ is set to the calculated average temperature TLIQ (HH *, II). In other words, the former is reset every 15 minutes during the operation of the compressor. Conversely, since it is possible that the cooling switch is switched so that the changeover valve is in heating mode, it should be switched to defrost (JJ, KK). Otherwise the changeover valve must be switched off. Logic must be used here to ensure that any data bit that would require the switching valve to be switched off is deleted. The corresponding data word requiring switching off is therefore masked in order to remove this bit. If the lower temperature t_liq is greater than the current temperature TLIQ, the lower temperature t_liq is set to TLIQ (MM *, NN). When the heat pump ends a defrost cycle, the changeover valve is switched to recuperation mode (OO *, PP). Otherwise, the program branches to heating or "valve off" mode as standard and the changeover valve mode is set to "heating" (QQ). If more than 30 minutes have passed since the last change of the valve position and the compressor was switched on for a time period that corresponds to an integer multiple of 15 minutes, the lower value of t_liq is set to the average value TLIQ (RR1, RR2, SS ).

To go to the next program section, the compressor must be switched off, i.e. it must have received a switch-off signal generated by the SEQUENCER (i.e. the FALSE output value of V *).

The routine checks when the compressor has been switched off. If the time period since switching off is less than two time periods, the time barrier flag is deleted (false) and the temperature t_dis is estimated at the current value of TDIS, or assumed at this value (TT *, UU).

If there is a request signal, another element (P1, P2) should be switched off to prevent a fault caused by contact welding, the time since the last change of the compressor status is less than 10 minutes (VV1a) and the water temperature of the inside Coil THX1W is below 25.5 ° or above 115.5 ° (VV1b), the switch-off request signal for the contact welding safety mode is linked to the space fan mask or (VV2a, VV2b). The system then checks the temperatures of all four possible modes, ie heating, cooling, defrosting and recuperation modes. If the changeover valve is in heating mode (WW *), the compressor output temperature is higher than the temperature t_dis at the time of switching off minus 10 ° and if TLIQ is more than 5 ° below the lower temperature t_liq, the contact welding safety mode is switched on and the crisis entry flag is set to TRUE (XX1, XX2, YY). If the output temperature has dropped by 10 ° or more and if the liquid temperature is higher than the lower temperature t_liq, the safety mode is not switched on (ZZ1, ZZ2, AAA).

As FIG. 4 shows, the contact welding safety mode is switched on and the crisis entry flag is set to TRUE if the changeover valve is in cooling mode (BBB *), the compressor outlet temperature is above the temperature t_dis at the time of switching off minus 10 ° and if TLIQ is at least 5 ° lies above the higher temperature t_liq (CC1, CC2, DDO). If the output temperature has dropped by 10 ° or more and if the liquid temperature is below the upper temperature t_liq, no safety mode is set (EE1, EE2, FFF).

If the changeover valve is in defrost mode (GGG *), the compressor outlet temperature is 2 ° or more above the temperature t_dis when switched off, the liquid temperature is 10 ° or more above the stored value of the upper temperature t_liq and if t_liq is greater than Is 45 °, the safety mode is switched on (HHH1-3, III). If the output temperature is at least 20 ° below the switch-off temperature, no safety mode is set (YYY *, KKK).

If the changeover valve is finally in "recuperation after defrosting" (LLL *), TDIS is above the switch-off temperature minus 10 °, TLIQ is more than 15 ° below the stored lower temperature and has been more than 5 minutes since the compressor status changed the security mode is set (MMM1-3, NNN). However, if the initial temperature is more than 20 ° below the switch-off temperature, the safety mode is not set (OOO *, PPP).

The previous sections dealt with the conditions for the compressor shutdown commands. If more than 10 minutes have passed since the compressor was switched off and if there is a request command to switch on the contact welding safety mode and TDIS is not above 100 °, the safety mode is not switched on and the time limit flag is set to TRUE (QQQ1, 3 , RRR). However, if there is no request command to switch on the safety mode, the time limit flag is set to TRUE and the output temperature is above 110 °, this indicates that something has been overlooked and a safety mode is set (SSS1-3).

The "formal" way in which the safety mode is switched on when the time limit flag is set to TRUE, whether in heating, cooling, defrosting or recuperation mode, is determined by the last part of the program.

When the safety mode is switched on - in any mode, the compressor and the changeover valve are brought into an operating mode in which the valve position is switched over at regular intervals. This is a normal, time-dependent switching function, which ensures that the compressor remains permanently loaded and therefore no extreme temperatures and pressure conditions can occur, which could lead to self-destruction of the compressor. In the present example of a system, the changeover valve is continuously switched over until the system is switched off manually.

The program for the "compressor rescue" routine follows on from the "contact welding protection" routine. Because of the brevity and simplicity of this routine, no flowchart is provided. The main purpose of this "compressor rescue" routine is to recognize the crisis entry flag and control the system so that the compressor remains permanently loaded. In the present system, a load is maintained by alternately heating and cooling the space schematically delimited by line 12. This could also be done by alternately heating and cooling the storage tank S1 or, in another system, also by means of other loads. It will have been found that the printed program is designed for the conditioning of the memory and has been written with this in mind. The corresponding terms have been modified to refer to airspace.

The crisis entry flag and the security flag are checked in the SEQUENCER module described above. If the flag is set, this routine is implemented. If the flag is set to "1", the system is placed in a "room conditioning" mode, i.e. either heated or cooled. First of all, this routine checks the state of the system. The heating mode is assumed as standard; the "contact welding safety" routine then checks whether there is defrosting or heating. The reason for this is that you first want to bring the system into the opposite state to the state immediately preceding it. If the system was in defrost mode, the coil must continue to be defrosted by energizing the coil. If the system was in heating mode, the storage tank and airspace were probably hot, so cooling should begin.

The next program instruction containing a condition sets the device contacts. If the system is put in cooling mode all elements, including pumps P1 and P2, the outside fan, the changeover valve and the inside fan, are switched to cooling. It should be noted that the compressor does not have to be activated since it is either already switched on, which is the reason for executing this routine, or there is an error otherwise. In both cases, it is not desirable for the compressor to be activated. The program section initiated by "else" corresponds to the heating mode.

Certain cooling and heating limits are set for this routine. The following part of the routine checks whether these limits have been exceeded in one direction or the other. If the temperature TRETA of the return air is equal to or lower than the value set on the HOC control panel minus 5 °, or if it is below 65 °, the heating mode is switched over and the device contacts are switched accordingly. In a similar way, starting from the heating mode, the air is only heated to 78 ° or up to 5 ° above the control console value HOC, the lower of these values being decisive.

In the last part of the program, a digital output word is formed by building up "high byte" and "low byte" segments. Each word is 16 bits long and is captured as part of the digital system output. The crisis entry flag is then set to 2. Note that after a complete system reset, the system will no longer return to the "Contact Welding Safety Mode" routine once it has run through the "Compressor Rescue" routine. The "compressor rescue" routine then starts on the second program instruction containing a condition ((if cmp_cond_of_sto_in_crisis_mode = COND_STO_CRISIS_MODE_COOLING)) and then continues, whereby the air temperature is checked again and the operating mode is switched over if the corresponding limit is exceeded.

In addition to the preferred exemplary embodiment of the invention described above, a wide variety of variants and systems can of course be carried out without exceeding the scope of the invention as claimed in the patent claims. In particular, in addition to this preferred embodiment, in which the method is carried out via a software program, it is possible to provide an essentially hardware-based implementation of the regulation or control described with the aid of the program.

Claims (11)

1. A method for monitoring and controlling a heating and cooling system with a compressor and at least one heat exchanger with coolant circulating between them, characterized in that the following method steps are carried out: a) monitoring at least one specific parameter of the system during operation to determine conditions under which the compressor should be switched off and b) determining whether the compressor has not stopped under the corresponding conditions, in which case a fault caused by a contact welding fault is displayed, and c) Initialization of a safety operating mode in response to the detection of such a contact welding fault, this safety operating mode causing the compressor to remain so loaded that the compressor is prevented from self-destruction until a corrective measure is taken. 2. The method according to claim 1, characterized in that at least one of the parameters contains the outlet temperature at the compressor. 3. The method according to claim 1 or 2, characterized in that at least one of the parameters contains the coolant temperature of a heat exchanger of the system. 4. The method according to any one of the preceding claims, characterized in that in the safety operating mode, a changeover valve provided in the system is continuously switched between different states, so that the compressor remains permanently loaded. 5. The method according to any one of the preceding claims, characterized in that the compressor is loaded by switching the system from heating to cooling mode at certain intervals. 6. The method according to any one of the preceding claims, characterized in that to determine whether the compressor has not yet switched off, the constant energy exchange of the coolant is measured. 7. The method according to any one of the preceding claims, characterized in that to determine whether the compressor has not yet switched off, the energy dissipated and / or supplied to the coolant is measured. 8. Device for monitoring and controlling a heating and cooling system with a compressor and at least one heat exchanger with coolant circulating between them, characterized in that a) the device contains sensors for monitoring at least one specific parameter of the system during operation in order to determine conditions under which the system compressor should be switched off, b) a computing module is provided which determines whether the compressor has not switched off under these specific conditions, in which case a contact welding error is displayed, and c) that load elements and control means are present, the former being controlled by these control means and the computing module or an additional computing module under a safety operating mode, which is initialized when a contact welding error occurs, in such a way that the compressor remains loaded so that a Self-destruction of the compressor is prevented until corrective measures are taken. 9. The device according to claim 8, characterized in that sensors contain a temperature sensor for measuring the outlet temperature of the compressor. 10. Device according to one of claims 8 or 9, characterized in that the sensors contain a temperature sensor for measuring the temperature of the coolant in a heat exchanger of the system. 11. The device according to any one of claims 8 to 10, characterized in that the control means are designed as a changeover valve, this control valve being continuously switched between different states during the safety operating mode, so that the compressor remains permanently loaded.

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