ITAN20130029U1 - HYDRAULIC DEVICE FOR ELECTRONIC MANAGEMENT FOR HEAT PUMPS. - Google Patents

Description

DESCRIPTION

“ELECTRONICALLY MANAGED HYDRAULIC DEVICE FOR HEAT PUMPS”.

TEXT OF THE DESCRIPTION

This utility model patent application relates to an electronically managed hydraulic device for heat pumps to make them compatible with air conditioning systems that use water as a carrier fluid to achieve heat exchange with the air to be conditioned.

Such a type of device is described in the European patent EP 1 441 183 in the name of the same applicant. However, this device has drawbacks due to the presence of a thermostatic valve, an accumulation tank and limited electronic management.

The object of the present invention is to eliminate the drawbacks of the known art by providing an electronically controlled hydraulic device for heat pumps that is efficient, effective, versatile and functional.

These purposes are achieved in accordance with the invention, with the characteristics listed in the attached independent claim 1.

Advantageous embodiments appear from the dependent claims.

In the device according to the invention, the following main improvements have been made with respect to EP 1 441 183:

1. Replacement of the thermostatic valve with a LEV electronic valve with point-by-step control of the cooling capacity.

2. Modification of the electromechanical electrical panel by Γ installation of a programmable logic controller (PLC) with a specific program for the management, regulation and control of the device according to the invention allowing Γ elimination of various relays, selectors and control lights. In this way the device is managed by means of a remote panel, rather than by means of special switches installed on the machine.

3. Modulating heating and cooling capacity according to the capacity required by the rooms to be air-conditioned. This was possible through the creation of a specific program inside the PLC which, on the basis of some input parameters (such as external temperature, water return temperature, etc.), sends a signal to the external heat pump machine ( GHP), which in turn varies the number of engine revolutions and the number of compressors to deliver the required capacity.

4. Modbus RTU management systems connectivity, Webserver with dedicated Scada for management

5. Centralized management in the case of multiple installations with seasonal average efficiency optimization program (SPF).

The advantages over EP 1 441 183 are the following: i. use of the electronic valve LEV with the possibility of keeping the superheating of the refrigerant gas constant during cooling operation (with a feedback control of temperature and pressure) thus improving efficiency at partial loads.

ii. Improved Γ system efficiency, passing from an ON / OFF system to a modulating system capable of varying the deliverable capacity according to the required one, obtaining the following advantages:

- reduction of management costs

- reduction of primary energy and therefore of polluting emissions

- improvement of the comfort of the internal rooms (absence of thermal excursions)

- possibility of controlling the delivery temperature at a fixed point

elimination of the storage tank absolutely necessary in the case of an ON / OFF system to store Γ excess energy during operation at partial loads.

Further features of the invention will become clearer from the detailed description that follows, referring to a purely exemplary and therefore non-limiting embodiment, illustrated in the attached drawings, in which:

Fig. 1 is a hydraulic diagram, illustrating the device according to the invention;

Fig. 2 is an electrical diagram illustrating the connections to the power supply of the device according to the invention;

Fig. 3 - 5 are electrical diagrams of the PLCs of the device according to the invention;

Fig. 6 is an electrical diagram illustrating a printed circuit board (PCB) that manages the electronics of the device according to the invention;

Fig. 7 is an electrical diagram of a parametric controller of an expansion valve of the device according to the invention;

Fig. 8 is a graph illustrating the power of the heat pump as a function of the temperature;

Fig. 9 is a graph illustrating the water temperature as a function of the external temperature; And

Fig. 10 is a graph illustrating the power of the heat pump as a function of temperature.

With the aid of the figures, the electronically managed hydraulic device for heat pumps according to the invention is described, indicated as a whole with the reference number (100).

With reference to Fig. 1, the device (100) is arranged between a pre-existing hydraulic system and a heat pump (GHP).

The device (100) includes a first hydraulic circuit (P) of water connected to the hydraulic system and a second hydraulic circuit (C) of refrigerant fluid connected to the heat pump. Advantageously, the refrigerant fluid used in the circuit (C) is freon.

The water hydraulic circuit (P) includes a suction duct (PI) to draw water from the hydraulic breadcrumbs and a return duct (P2) which brings the water back to the hydraulic system. A circulation pump (10) is arranged in the suction duct (PI) to allow the suction of water from the hydraulic system.

The water hydraulic circuit (P) and the refrigerant fluid hydraulic circuit pass through a heat exchanger (6). Advantageously, the heat exchanger (6) is a plate exchanger, in particular with brazed plates.

When the heat pump works with a cooling cycle (illustrated in Fig. 1), the heat exchanger (6) works in counter-current, i.e. the flow of water circulating in the circuit (P) is in counter-current with respect to the flow of refrigerant fluid. circulating in the circuit (C).

The refrigerant circuit (C) includes a delivery duct (Cl) in which the refrigerant fluid (liquid) flows, directed from the heat pump to the exchanger (6) and a return duct (C2) in which the refrigerant fluid flows ( gas) directed from the exchanger (6) to the heat pump. An expansion valve (3) is installed in the delivery duct (Cl) which allows the expansion of the liquid refrigerant fluid, transforming it into a gaseous fluid.

A by-pass duct (C3) is arranged in parallel with the expansion valve (3) to be able to bypass it. In fact, when the heat pump works with a heating cycle, the refrigerant fluid follows a reverse path to that shown in Fig. 1 and the expansion valve (3) is bypassed.

A non-return valve (2) is installed in the bypass duct (C3) which allows circulation in one direction only, i.e. from the exchanger (6) to the heat pump and not in the opposite direction.

The expansion valve (3) is an electronic LEV with a stepping motor. For this purpose, the device (100) comprises a parametric controller (1) adapted to control the expansion valve (3). A temperature probe (20) and a pressure probe (21) are arranged in the return pipe (C2) of the refrigerant fluid. Advantageously, the temperature probe (20) is of the NTC type and the pressure probe (21) works in 4-20mA current. The parametric controller (1) is connected to the temperature probe (20) and to the pressure probe (21) and controls the expansion valve (3) in compliance with the temperature and pressure values detected by the probes (20, 21).

Optionally the device (100) includes:

a water intake temperature probe (PT1) placed in the water intake pipe (PI) at the inlet to the exchanger (6)

a water delivery temperature probe (PT2) placed in the water return pipe (P2) at the outlet from the exchanger (6);

a differential pressure switch (7) placed between the two water pipes (PI) and (PI), to detect the difference in water pressure between the suction pipe and the return pipe;

an air purge valve (8) disposed in the water intake duct (PI); And

a flow switch (9) arranged in the water return conduit (P2).

With reference to Fig. 2, an electrical panel of the device (100) is illustrated. The first part of the electrical panel is in high voltage. A thermal protection of the pump (POS) is obtained by means of a magnetothermic switch (MSP) in series with a relay (KP) and a transformer (TR) which transforms the high voltage of 230 Volto into low voltage 12 - 0 - -12 Volt .

There is a relay (R) which is energized when the heat pump (GHP) is in alarm. The contact of this relay (R) is illustrated later. The use of the relay (R) is necessary given the instability of the clean contact present in the GHP.

With reference to Fig. 3, the PLC of the device (100) is powered at 24 Volt (1-0). To close a digital input it is sufficient to bring the voltage to 24 Volts, since 0 (0 volts) is already common to all the common IDLCs inside the PLC.

The main contacts of the PLC are:

REM If enabled, this contact allows you to control the switching on and off of the device (100).

REMI This contact, if enabled, allows you to control the operating mode of the device (100) (open - summer).

IDL3 Notifies the PLC if the parametric controller (1) of the expansion valve (3) is in alarm. The alarm is obviously communicated to the customer.

FL-Com Fl-No This contact comes from the flow switch (9). If at least one compressor is running and the contact is open, the system goes into alarm and the alarm must be reset manually. If the pump is not working and the contact is closed, the system goes into alarm and signals a possible tamper.

PD-Com PD-NO This contact comes from the differential pressure switch (7). If the contact is open and the pump is running, the system goes into alarm and communicates it to the user.

GHP consent It communicates to the PLC when at least one compressor is connected (the signal comes from the AISIN electronic card borrowed from a normal direct expansion indoor unit).

Defrost control It communicates when the heat pump is carrying out defrost operations.

GHP alarm (currently not in use).

R is the relay contact that communicates the GHP alarm to the PLC

POS communicates to the PLC when the thermal protection of the pump activates. The system communicates an alarm.

With reference to Fig. 4, all PLC outputs are clean contacts, including:

Hot / cold selection The PLC communicates to the heat pump whether it is to operate in summer or winter mode (open = summer).

KP is the relay that controls the operation of the pump.

N05 is an output that can exclude Γ power supply to the AISIN electronic board (when the system is in alarm Γ power is cut off to avoid possible unwanted restarts).

15-16 is a contact that reaches the AISIN electronic board. The T1T2 contact of the card controls the ignition of the heat pump.

Alarm This contact closes when the heat pump or the device (100) are in alarm.

GND-DI1 Contact that controls the parametric controller (1) of the valve (3). When the contact closes, the repetition starts according to the PID rule that will be explained later.

At the bottom of Fig. 4 there are eight electric resistors for managing the capacity. (4 steps for winter operation and 4 steps for summer).

With reference to Fig. 5, the following PLC contacts are illustrated:

PT3 is an optional current probe for pump management. The pump is stopped when the temperature inside any tank exceeds a set point.

CAP is a 4-20 mA analog input for external capacity control

Dynamic Setpoint is a 4-20 mA analog input for external control of the setpoint temperature.

PT2 and PT1 are the water inlet and outlet temperature probes.

RS485 is a 485 serial port to access the PLC via ModBus

R / C is optional and are communication (CAN) and power cables for a user keyboard.

With reference to Fig. 6, a printed circuit board (PCB) of the electrical panel of the device (100) is shown, which comprises the following contacts:

F1F2 communication cable between heat pump and internal AISIN card (proprietary protocol)

XI 3 A air intake probe simulated by the 8 electrical resistances shown above

XI 2 A liquid pipe probe (refrigerant) XI 3 A vapor pipe probe (refrigerant) XI A power supply PCB AISIN

XI 6A compressor ON alarm (not in use) defrost. These signals go directly to the PLC, already described above.

With reference to Fig. 7, the parametric controller (1) expansion valve (3) is shown. The pressure sensor (21), the temperature sensor (20) and the expansion valve (3) are connected to the controller (1). The controller (1) has the following contacts:

DII Signal from the PLC. Controls when the driver starts to regulate (Compressor ON Summer mode) NO A is an open contact when the regulator is in alarm. The alarm is then communicated by the PLC to the user.

The power management of the heat pump is carried out by the programmable controller (PLC).

The power does not vary linearly depending on the building's demand. In fact, with reference to Fig. 8 there are 4 power steps from 25% to 100%.

Depending on the inlet water temperature detected by the probe (PT1) and the derivative of the temperature, the PLC decides the power step. To communicate the desired power step, a particular fictitious air intake temperature is simulated through 8 digital outputs of the PLC (from NO 13 to NO20). There are 8 electric heaters since 4 temperature values are used for summer operation, while 4 values for winter.

The graph in Fig. 8 illustrates the power trend in a winter cycle. The parameters to be set are the Set Point temperature and a Band within which the delivered power varies.

The LEV valve (3) allows to keep the superheating of the refrigerant gas constant during cooling operation (with a retro-activated temperature and pressure control).

The superheat control during summer operation is carried out by the parametric regulator (1). The control logic is PID.

The error is defined as the difference between real superheat and desired superheat. The superheat is calculated considering the steam duct temperature (C2) and the saturation temperature given by the pressure sensor (21). At the output, the steps of the step motor of the valve (3) for the correction are obtained.

Each PLC installed in the device management panel (100) has an integrated ModBus RTU gateway. By connecting to the COMI RS485 serial port, you have access to all the parameters previously described. Each parameter can be read and modified by any ModBus Master system. There is no specific software to access Modbus connectivity.

WEBSERVER connectivity is not typical of a hydronic module, to obtain it it is necessary to connect the device (100) to a ModBus system equipped with Web Server connectivity

The PLC program envisages establishing the setpoint temperature as a function of the external temperature measured by an active external probe. The chosen law is shown in figure 9. The input parameters are the three pairs (Tl-Ta) (T2-Tb) (T3-Tc).

Once the set point temperature is stable, the algorithm shown in figure 10 is performed.

The five power steps that are obtained are characterized by 100% (all AWS ON at 100%), 75% (all AWS ON at 75%), 50% (all AWS ON at 50%), 2/3 (2/3 of AWS ON at 50%), 1/3 (1/3 of AWS ON at 50%). The graph in Fig. 10 refers to the winter case.

Numerous variations and modifications of detail can be made to the present embodiment of the invention, within the reach of a person skilled in the art, however falling within the scope of the invention expressed by the attached claims.

Claims (4)

CLAIMS 1) Electronically managed hydraulic device (100) for heat pumps, intended to be placed between a hydraulic system and a heat pump, comprising: a water circuit (P) connected to the hydraulic system, a refrigerant gas circuit (C) connected to the heat pump, a heat exchanger (6) crossed by said water circuit (P) and said refrigerant fluid circuit (C), an expansion valve (3) arranged in a duct (Cl) of said refrigerant fluid circuit to allow 'expansion of said refrigerant fluid from the heat pump towards the heat exchanger (6), when the heat pump operates in a cooling cycle, characterized by the fact that said expansion valve (3) is an electronic valve LEV with stepping motor, e said device (100) further comprises: a temperature sensor (20) and a pressure sensor (21) arranged in said refrigerant fluid circuit (C) for detecting the pressure and temperature of the refrigerant fluid, a parametric controller (1) connected to said expansion valve (3) and to said temperature and pressure sensors (20, 21), to control the valve stepper motor, in accordance with the temperature and pressure detected by said sensors, a PLC to control the operation of said device (100). 2) Device (100) according to claim 1, characterized in that said temperature and pressure sensors (20) are arranged in a steam or gas duct (C2) of the refrigerant fluid circuit in which the gas flows from the heat exchanger (6) to the heat pump. 3) Device (100) according to claim 2, characterized in that said parametric controller (1) performs a retro-operated temperature control in which Γ error is defined as the difference between real superheat and desired superheat, in which superheat is calculated considering the temperature of the steam duct (C2) detected by the temperature sensor (20) and the saturation temperature given by the pressure sensor (21) and at the output from the feedback, the steps of the valve stepper motor are obtained (3) . 4) Device (100) according to any one of the preceding claims, characterized in that it further comprises: a recirculation pump (10) arranged in a duct (PI) of the water circuit, a water intake temperature probe (PT1) placed in the water intake pipe (PI) at the inlet in the exchanger (6) a water delivery temperature probe (PT2) placed in the water return pipe (P2) at the outlet from the exchanger (6); 5) Device (100) according to any one of the preceding claims, characterized in that it further comprises a differential pressure switch (7) arranged between the two water ducts (PI) and (P2), to detect the difference in water pressure between the suction and return pipes. 6) Device (100) according to any one of the preceding claims, characterized in that it further comprises: - a by-pass duct (C3) is arranged in parallel to the expansion valve (3) to be able to bypass it, during the heating cycle of the heat pump, - a non-return valve (2) installed in the bypass (C3), which allows circulation in one direction only, ie from the exchanger (6) towards the heat pump and not in the opposite direction.