Building automation systems include air conditioning control, which is the most common type of system. What precautions should be taken when installing air conditioning units?
Central control equipment installation and process
The central control equipment is primarily installed in the equipment monitoring room, and installation should be carried out after the civil engineering and decoration of the equipment monitoring room are completed. Installation requirements are as follows:
1. The equipment should be inspected before installation and must meet the following requirements:
A. The equipment is in good condition, with intact paint on both the inner and outer surfaces;
B. The outer dimensions of the equipment, the main board and wiring terminals inside the equipment, and their models and specifications meet the design requirements;
2. The dimensions of the base of equipment with a base should conform to the design. The allowable deviation for straightness is 1 mm per meter. When the total length of the base exceeds 5 m, the allowable deviation for straightness is 5 mm.
3. The installation of central control and network communication equipment shall comply with the following regulations:
A. It should be vertical, level, and secure;
B. The allowable deviation for verticality is 1.5 millimeters per meter;
C. The allowable deviation of the horizontal inclination is 1 mm per meter;
D. The allowable deviation in the top height of connected equipment is 2mm;
E. The allowable deviation of flatness at the joints of connected equipment is 1mm;
F. The gap between the joints of connected equipment shall not exceed 2mm;
G. When there are more than 5 connections between connected devices, the maximum permissible error for flatness is 5mm.
4. DDC Installation
The Data Center (DDC) should be installed close to the controlled equipment on-site. Generally, DDCs for building monitoring systems are installed in locations such as low-voltage electrical shafts, fresh air rooms, air conditioning rooms, chiller stations, and high and low voltage power distribution rooms. The DDC is connected to the system host via a network cable. The DDC is protected by a dedicated control box, which should be installed 800-1200mm above the ground in a well-ventilated, well-lit, and dry location away from direct sunlight. The temperature and humidity at the installation site should meet the DDC's operating requirements.
The equipment inside the control box should be arranged neatly, with high-voltage and low-voltage cables running separately, and the control box should have reliable grounding measures.
The control box should be reliably grounded, and the grounding resistance should meet all requirements. The building uses a combined grounding electrode, and the grounding resistance should be less than 1 ohm. The grounding wire should be a compliant cable.
The control box should also be grounded, and this ground should be separate from the signal ground inside the equipment box. It can be connected to the equipment's safety ground and meets the requirements of a safety ground.
02 Installation and Process of Main Input/Output Devices
1. Installation of temperature and humidity sensors
Temperature sensors are primarily used to measure the average temperature of indoor and outdoor environments, as well as air ducts and water pipes. Temperature sensors include indoor/outdoor and water pipe/air duct temperature sensors. They typically output a resistance signal and include platinum resistance temperature sensors, copper resistance temperature sensors, and semiconductor temperature sensors.
Humidity sensors are used to measure the relative humidity indoors, outdoors, and in pipes, and typically output current or voltage signals. Current signals are 4~20mA DC, and voltage signals are 0~10VDC or 0~5VDC.
2. Installation of temperature and humidity sensors
A. Installation location
1) Do not install in direct sunlight, away from areas with strong vibration or electromagnetic interference. The installation location should not damage the aesthetics and integrity of the building's appearance. Outdoor temperature and humidity sensors should have weatherproof devices.
2) It should be located as far away as possible from windows, doors, and air vents; if this cannot be avoided, the distance should be greater than 2 meters.
3) Sensors installed side-by-side should be at the same height from the ground;
B. Wiring Installation
The connection between the temperature sensor and the DDC should meet the equipment requirements, and errors caused by wiring should be minimized. For a 1K ohm platinum resistance temperature sensor, the total wiring current should be less than 1 ohm.
C. Installation of duct-type temperature and humidity sensor:
1) The sensor should be installed in a location where the wind speed is stable and the temperature and humidity of the air duct can be reflected;
2) The sensor should be installed after the duct insulation layer is completed, on a straight section of the duct or in a location that avoids dead corners and steam vents.
3) Duct-type temperature and humidity sensors should be installed in locations that facilitate debugging and maintenance;
4) After the duct temperature and humidity sensor is installed in the duct insulation layer.
D. Installation of water pipe temperature sensor:
1) Water pipe temperature sensors should be installed simultaneously with the prefabrication and installation of process piping;
2) The drilling and welding of water pipe temperature sensors must be carried out before the corrosion protection, lining, and purging pressure tests of the process pipelines;
3) The water pipe temperature sensor should be installed in a location where the water flow temperature changes are representative, and should not be selected near valves or other resistance components, or in dead ends or locations with significant vibration.
4) When the sensing section of a water pipe type temperature sensor is larger than half the pipe diameter, it can be installed at the top of the pipe. If the sensing section is smaller than half the pipe diameter, it should be installed on the side or bottom of the pipe.
03 Installation and Process of Pressure, Differential Pressure Sensors, and Differential Pressure Switches
1) The sensor should be installed in a location that facilitates debugging and maintenance;
2) The sensor should be installed behind the temperature and humidity sensor;
3) Duct-type pressure and differential pressure sensors should be installed after the duct insulation is completed;
4) Duct-type pressure sensors should be installed on straight sections of the duct;
5) The installation of water pipe type pressure and differential pressure sensors should be carried out simultaneously with the prefabrication and installation of process pipelines. The drilling and welding work must be carried out before the corrosion protection, lining, purging and pressure test of process pipelines.
04 Installation and Process of Flow Sensors
1. The installation of the flow sensor must ensure that the flow meter reading and the direction of water flow are consistent with the direction of water flow in the pipe;
2. The flow sensor must meet the straight pipe section requirements for installation;
3. The flow sensor should be installed in a location that facilitates maintenance and debugging;
4. The installation of pipeline flow sensors should be carried out simultaneously with the installation of process pipelines.
05 Installation and Process of Air Quality Sensors
The following issues should be noted when installing an air quality sensor:
1. The air quality sensor must be installed in a location that is easy to debug and maintain;
2. The air quality sensor should be installed after the duct insulation layer is completed;
3. The air quality sensor should be installed on a straight section of the duct.
4. Air quality sensors that detect gases with a lighter specific gravity should be installed in the upper part of the duct or room, while air quality sensors that detect gases with a heavier specific gravity should be installed in the lower part of the duct or room.
06 Valve Actuator Installation and Process
Installation of the damper actuator:
1. The direction of the opening and closing arrow on the damper controller should be consistent with the opening and closing direction of the damper;
2. The connection between the air valve controller and the air valve shaft should be secure;
3. The mechanical mechanism of the air valve should open flexibly without any looseness or jamming;
4. After the damper controller is installed, the opening and closing indicator position of the damper controller should be consistent with the actual state of the damper, and the damper controller should preferably face a position that is easy to observe.
5. The air valve controller is installed perpendicular to the air valve shaft, with a vertical angle of not less than 85°;
6. The damper controller should be simulated before installation;
7. The damper controller and output torque must be matched with the damper as required and meet the design requirements.
