Teach you a trick: how to maintain the hardware operation of building automation system

A building automation system is a system that replaces manual operations with smart operations. In operation, the screen may be unstable and the data may show abrupt changes.

Hardware maintenance mainly includes maintenance of control boxes, sensors, and actuators. A building automation system is a system that replaces manual operations with smart operations. During the operation, the screen may be unstable and the data may show abrupt changes. The building automation system uses a company's open Andover system (reference), the stability of the system itself has reached the industrial standard, far higher than the field instrumentation, wiring, transmitters and so on. Therefore, the problem arises mainly because the field instruments or transmitters are disturbed or the power distribution, process, and other aspects of the failure occurred. This section mainly describes the maintenance of field devices.

Teach you a trick: how to maintain the hardware operation of building automation system

First, DDC control cabinet devices and wiring

The DDC controller is the hub between the field device and the upper management machine. It plays a decisive role. The maintenance of the field device must be started from the control cabinet. The first step is to understand the distribution of the control cabinet and the devices controlled by each controller. See the BAS as-built drawing for details of its distribution and control equipment. Understanding the DDC control cabinet components and wiring is critical to maintenance:

Terminal Block: Used to connect the wiring of field devices and controllers. Terminal wiring is for wiring to the field device and wiring to the controller. This is the starting point for detecting the signal of the field device. If it is found that the signal on the host computer screen is not normal, it can be detected that the signal is normal here. The DI point can be turned on and off through the field device. Here, the signal detected is whether the signal is a short circuit and an open circuit. If the corresponding short circuit or off is corresponding to the open circuit, the signal is normal; the DO point can send the switch signal through the upper position. Check whether the signal sent out is a short circuit or open circuit. If the corresponding short circuit is off or off, the signal is normal. The AI ​​point can detect whether the signal coming from the field is 0-10V DC voltage or the resistance is about 1K ohms (only The temperature signal is the resistance value). If it is in this range, it is normal; the AO point can issue an instruction through the upper screen to detect whether there is a 0-10V DC voltage.

Air switch: Controls the power of on-site sensors, actuators, and controllers.

Relay: Assist the DO point to complete the start-stop control, with strong isolation. When the DO module issues an open command, it energizes the relay wire and controls the start and stop of field devices through the contacts. With the upper control point DO output, the corresponding relay should suck and emit a "click" sound. If there is no response, first check whether the DO output voltage, if the output is normal, you should check whether the relay is damaged.

Power supply: power supply for controllers, relays, on-site sensors, and actuators. See the BAS as-built drawing for specific power supply methods.

The on-site actuators of this system are mainly damper actuators and water valve actuators. The water valve actuator uses a 24V (220V air conditioner) AC power supply and the control signal is a 10V DC power supply. Under normal circumstances, when the control signal changes from 0V to 10V, the valve opening should also change from 0% to 100%. If the actuator does not operate when the system is running, you should first check whether there is 24V AC power. If not, check the corresponding position in the cabinet, whether the module sends a command or if the fuse is blown. If there is no such problem, check if the line is normal. If the actuator moves but the direction of action is reversed, the forward and reverse rotation of the actuator should be adjusted so that it rotates in the other direction. If the direction of action of the actuator still does not change at this time, check whether there is a control signal sent out. To the cabinet with a multimeter to actually measure, if the actual can not be measured, the channel may be damaged. If the module is normal, there may be a problem with the line, check the line. The damper actuator uses 24V AC power and the control signal is 10V DC. Inspection method with the valve actuator.

Two or four types of detection methods

The AI ​​points involved in the AI ​​system include temperature, humidity, carbon dioxide, carbon monoxide, and fresh air flow.

Temperature detection: When a certain temperature deviates from normal conditions such as -46°C or 121°C, this temperature is in a fault state. The sensor uses a 10KT thermistor. The normal resistance value is less than 500Ω. When a fault occurs, the resistance at the corresponding DDC control terminal is measured to determine whether the resistance is within the normal range. If it is negative, it indicates the field short circuit; if infinity, it indicates that the site is open circuit and the line between the terminal and the sensor is checked. , you can return to normal.

Humidity detection: When there is a large deviation between a certain humidity and other humidity values, or about 88% in the long term, it means that the humidity is in a fault state. The feedback signal of the humidity sensor is 0-10 VDC voltage. By measuring the voltage at the corresponding terminal, it can be judged whether the line or humidity sensor is normal, and it can be restored to normal for maintenance.

AO point: The AO point of this system mainly includes valve position control. Water valve control output commands are 0-10V voltage. When the valve position opening and the display of the upper man-machine interface are larger, the voltage can be measured on the terminal to see if the voltage is 5V when the upper interface is set to 50%, and whether the terminal voltage of the actuator is consistent along the straight line. If the terminal voltage does not match the actuator terminal voltage, check the wiring and replace it.

DI point: The system's DI point mainly includes various states, hand/auto, and fault points. The DI point is a passive contact. When the controlled device is in a closed state, if the status point cannot be returned under normal conditions, a multimeter should be used to measure whether the corresponding terminal of the secondary circuit control cabinet is closed. If the terminal is not closed, it is two. Secondary loop control cabinet problems, adjusted by related parties.

DO point: The DO point of this system is mainly the control of the equipment. Sending a control command causes the corresponding relay to pull in and close the controlled end line. Use the upper position to issue a control command. If there is a relay, if there is none, check the line of the controlled device.

Third, maintenance examples

1. How to check if the network controller is offline: When the operator station computer displays a network controller offline, check the following method:

1) Check whether the connection between the central control room and the network controller is normal.

2) Check if the network controller power is normal.

Check if the network controller E's OFF light flashes red, and the communication flashes alternately.

4) If the above three items are all normal, there may be a problem with the device itself. Please contact XX.

2. How to check DDC offline

When the operator station computer displays a DDC offline, it can be checked as follows:

1) Check if the connection between the network controller and DDC is normal.

2) Check whether the DDC is supplying power normally, whether the fuse is burned (the controller's power fuse and the controller's fuse, and the DDC's fuse must be opened to see the panel).

3) If the above two items are normal, there may be a problem with the device itself. Please contact XX.

3. How to check if the temperature sensor is normal

The temperature sensor used in this project is a BD-10KT series sensor provided by Perstorp (reference) and is RTD-resistive. The correspondence between the resistance value and the temperature returned can be found in the attached product specification. When the spot temperature on the operating station computer is found to be abnormal, it can be checked as follows:

A. Find the corresponding terminal in the field control box, remove the return signal line and measure its resistance value, check whether the corresponding temperature value is correct; if correct, see item (B). If not, see (C) item.

B. Check the wiring of the control box to check if there are any problems with the wiring. If no problem is found, the controller may have problems. Please contact us.

C. Check the location of the temperature sensor on the site. Check if the temperature probe return resistance is correct. If there are still problems, the sensor has a problem and needs to be replaced. If the returned resistance is correct, it is the temperature sensor to the control box. There is a problem with the wiring, please find the relevant staff to solve.

4. How to check if the CO2 concentration sensor is normal

The CO2 concentration sensor used in this project is the LTM8733 product, which is 0-10V voltage type. The corresponding value of the returned voltage and CO2 concentration is 0-2000 PPM. When an on-site CO2 concentration is found to be abnormal on the operator station computer, it can be checked as follows:

A. Find the corresponding terminal in the field control box, remove the return signal line and measure the voltage value, check the corresponding CO2 concentration value is correct; if correct, see (B), if not, see (C )item.

B. Check the wiring of the control box for any problems. If no problem is found, the controller may have problems. Please contact XX.

C. Check the installation location of the CO2 concentration sensor on site. Check if the temperature return value of the temperature probe is correct. If there are still problems, the sensor has a problem and needs to be replaced; if the returned voltage value is correct, the CO2 concentration sensor is There is a problem with the wiring of the control box. Please find someone to solve it.

5. How to check the temperature and humidity sensor is normal

The temperature and humidity sensors used in this project are BD-10KT series products supplied by Perstorton (reference), in which the temperature is RTD resistance type. The correspondence between the resistance value and the temperature returned can be found in the attached product specification. When the temperature of the on-site temperature is found to be abnormal on the computer of the operation station, the above 3 ways can be checked. The humidity is 0-10V voltage type. The corresponding value of the returned voltage and humidity is 0-100%. When the humidity of the site is found to be abnormal on the computer of the operating station, the above four ways can be checked.

6. How to check whether the air-conditioning unit air valve is normal

The damper actuator used in this project uses a * (reference) product, which uses a 24VAC power supply to drive the regulator valve. The 0-10VDC return voltage signal indicates the valve opening. Wiring can be found in the attached product data sheet.

When the operator finds that the valve opening is greatly different from the control signal, it can be checked as follows:

A) Cut off the power of the corresponding control box at the site, then open the corresponding valve driver housing and manually turn the gear on the driver to check if the valve is blocked.

B) Check the external and internal wiring of the control box to see if there are any problems.

C) Check if the output voltage of the controller is normal. If it is not normal, there may be a problem with the controller. Please contact us.

D) If the above three items are all normal, there may be a problem with the drive. Please contact the manufacturer for replacement of another drive.

7. How to check the differential pressure switch is normal

The differential pressure switch is a switch signal and there are two signal lines connected to the differential pressure switch. When the signal on site is found to be inconsistent with the actual status, the following method can be checked:

A) Check the external and internal wiring of the control box to see if there is a problem.

B) Test one of the "+" tubes. If there is a change of state, it is normal.

C) If item B is abnormal, there may be a problem with the sensor. Contact the manufacturer for replacement of another new driver.

8. How to check the level switch is normal

The level switch is a switch signal and there are two signal lines connected to the level switch. When the signal on site is found to be inconsistent with the actual state, it can be checked as follows:

1) Check the external and internal wiring of the control box to see if there are any problems.

2) Check to see if the liquid level float is reversed.

Fourth, hardware maintenance rules

1. Periodically clean the system control cabinet. Long-term retention of dust may cause short circuit or open circuit within the system hardware device, causing equipment failure.

2. Maintain the air circulation in the control room and clean the floor; maintain the indoor temperature at 20~25°C.

3. Regardless of whether the equipment is powered on or not, non-authorized persons must not insert or pull out system components, and must not disturb the system communication cables and power cables. When the system is powered on, it is strictly prohibited to move the machine.

4. It is forbidden to do anything unrelated to the work on the computer host, prohibiting external computer floppy disks from entering the control system, and prohibiting playing games on the computer so as not to infect computer viruses.

5. After the system is working normally, you must not arbitrarily exit the graphic monitoring screen, and you must not shut down the system at will.

6. Regularly check the working status of each module of the controller and find that the problem should be dealt with promptly.

Fifth, software maintenance rules

The software maintenance mentioned here mainly refers to how to solve some problems of the system and make it run better.

1. Do not arbitrarily modify the software without fully mastering the software or without adequate control

2. It is forbidden to play games on the computer and run other irrelevant software

3. It is forbidden to modify the configuration of the system and application software when it is not very clear. Found that there are problems with the software and report to relevant departments in a timely manner.

4, regular backup data in order to avoid unnecessary losses

Sixth, emergency measures

1. When all kinds of problems occur, the first thing you need to do is switch all system loop control to manual, and then handle other problems.

2. If smoke or special odor (such as paste) is emitted from the control cabinet, if it comes from the controller, please quickly turn off the controller power supply, and then proceed to check and solve the problem.