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8 Key Points for HVAC On-Site Construction Experience I. Equipment Installation 1. The installation location of the air conditioning unit should facilitate maintenance without affecting its operational functionality; special attention should be paid to heat dissipation. When there are multiple units in the machine room, the direction of all connections and the operation surfaces must be consistent； 2. The frames of end devices shall be uniformly made of channel steel. The specifications of the channel steel are determined based on the weight of the equipment, but they must not be smaller than No. 10 channel steel ； 3. The installation location of the fan coil unit should be 150 mm away from the wall and 200 mm away from the window; if there are pipes behind it, it should be 300 mm away from the wall (after accounting for the size of the return air box). When there is sufficient space on the ceiling, the coils can be installed horizontally alongside the air ducts; if the ceiling height is insufficient, the coils should be installed as close to the floor as possible (ensuring adequate drainage height is provided) ； 4. The serial numbers of the air conditioning units and fan coil units must be copied correctly; the accompanying documentation must be kept in good condition ； 5. The equipment must not be damaged during handling and installation, especially the paint on the main unit’s casing, the fins, the condensate trays of the fan coil units, the housing components, and the impellers ； 6. The wiring box of the fan coil unit, the condensate pipe connection, and the water inlet and outlet connections must all be in the same direction to facilitate future maintenance ； When the fan coil is connected to the return air duct, an inspection hole must be created at the bottom of the return air duct to facilitate the removal of the motor during maintenance ； 7. The equipment must be installed in the correct position, level and properly aligned ； 8. The screw rods of the coiled tube and lifting supports must be at least 8 mm in diameter ； 9. An electric two-way valve or a proportional-integral valve must be installed on the outlet pipe of all end devices ； 10. Soft-connected shock absorption devices must be installed at all equipment inlets and outlets ； 11. Shock-absorbing rubber sheets or shock absorbers must be pre-installed on the equipment base ； 12. A galvanized flat steel strip must be welded to the equipment base in order to connect it to the building’s lightning protection ground wire. In the machine room, all main servers, water pumps, and power distribution cabinets must also be connected to the lightning protection ground wire using galvanized flat steel strips (as required by electrical construction standards). II. Air system 1. The construction of the return air box must meet the requirements; the sealing strips should be properly installed to ensure good insulation ； Do not damage the insulation material during installation ； 2. When riveting the return air box to the fan coil, the return air box must be aligned properly; it must not be distorted or have its corners bent ； 3. There should be no missed welds or holes in the flange welding; the diagonal error of the flange must be less than 3 mm, and the flatness error must be less than 2 mm. The distance between the flange screw holes and rivet holes should be 120 mm. Before painting the flange, welding slag must be removed, followed by a second coat of red lead paint ； 4. The duct ends are sealed using socket joints, while the nozzles (0.05 meters in length) are riveted; sealant must be applied at each joint. When riveting the flanges, the bend in the duct must be at least 6 mm deep, and all four sides must be even ； 5. A baffle must be installed for downward air supply through ducts, and the air nozzles should have rounded edges ； 6. The installation of the air ducts in the living room is done in a manner consistent with that of the two fan-coil units. The air ducts are connected to the fan-coil units using waterproof flexible canvas strips, with a length of 200 mm; connection is achieved through single-flange pressing ； 7. Installation of the ductwork in the master bedroom (air supply from the side and return air at the bottom); the center points of the air supply and return outlets should be on the same horizontal axis ； In the case of side supply and side return, the supply and return air inlets should be on the same plane ； 8. For fan coil units installed with air supply directed downward on inclined roofs where the elevation exceeds 2800 mm, 45-degree (elbow) air ducts must be used at the air supply outlets ； 9. After the ductwork is fabricated, it must first be submitted for inspection before insulation installation can take place ； 10. When the larger side of the main duct exceeds 1000 mm, internal supports shall be installed at the center of the duct. When the main air duct passes through the wall outside the machine room, a duct sleeve must be installed, and a fire damper is also required. III. Water system: 1. The shrinkage rate when PP-R pipes are heat-fused must be less than 3%, and installation must comply with the manufacturer’s technical specifications ； 2. Sleeves must be used when pipes pass through walls; PUC70 sleeves are to be used for De25 and De32 pipes ； De40, De50, and De63 use PUC110 sleeves ； De75 and De90 use PUC133 vectors ； 3. For pipe supports indoors, use L30 angle steel with aluminum powder paint applied as the topcoat ； Use L40 angle steel outdoors ； Large pipelines must use channel steel supports. (DN150 and above) 4. Before installing the pipe supports, it is necessary to mark lines first; the spacing between them should be less than 800 mm, and they must be evenly distributed in the same plane. The type of support used in one area should be consistent ； 5. The installation of pipes in the pipe shafts must be coordinated with the collaborating units to avoid mutual interference ； 6. The installation position of the pipe support should be more than 150 mm and less than 300 mm away from the PP-R pipe elbow ； Pipeline supports must be installed properly and should not be skewed ； 7. The center alignment of pipe supports must have identical pre-installed holes, and pipes must be installed horizontally and vertically ； 8. After the water pipes are installed, they must be flushed and pressure-tested first. The test pressure is 1 MPa; the pressure must be maintained for 10 minutes without any drop ； Then reduce the pressure to 0.6 Mpa and maintain it for 60 minutes; the pressure must not drop, and no leaks detected upon visual inspection constitute a pass. Insulation can only be applied after the inspection and verification are passed ； For high-level pipelines, a hydrostatic test at 1.5 times the working pressure is conducted. 9. An automatic exhaust valve must be installed at the highest point of the chilled water pipe, and it should be connected via a hose to the condensate tray of the nearest fan coil unit or to the condensate pipe ； A drain valve should be installed at the lowest point of the chilled water pipe ； 10. The heat fusion joining of PP-R pipes shall comply with the following requirements: ① The heat fuser selected shall be appropriate, the die shall be in good condition, and the operating temperature should be between 230–260 degrees. The hot melt apparatus can be operated only after it reaches the set operating temperature ； ②For cutting pipes, special pipe cutters, steel saws, or pipe cutting machines should be used. The edges of the cut surface must be cleaned of any burrs or roughness, and the cross-section of the pipe must be perpendicular to its axis ； ③Before welding, it is necessary to remove any dirt from the connection surfaces of the pipes and fittings, ensuring that they are clean, dry, and oil-free ； ④Control the heat melting depth during heat melting to reduce the shrinkage rate ； ⑤When welding elbows or tees, attention should be paid to their orientation; auxiliary markers can be used along the straight direction of the fittings and pipes to indicate their positions clearly ； ⑥During heating, the tube end should be inserted into the heating jacket without rotation to the specified depth; simultaneously, the fitting should be pushed onto the heating element without rotation to the same specified depth. The heating time must meet the required standards ； ⑦Once the heating time has been reached, immediately remove the pipe and fittings from both the heating sleeve and the heating head, and quickly insert them in a straight line without rotation to the specified depth, so as to form a uniform flange at the joint ； ⑧Within the specified processing time, the newly welded joint can still be slightly adjusted, but rotation is strictly prohibited ； ⑨During pipeline installation, it must not be axially twisted, and forced correction should be avoided ； ⑩During pipe installation, the open ends of pipes that are not to be terminated for the time being must be sealed tightly to prevent debris from falling into the pipes ； IV. Installation of condensate pipes 1. The diameter of the condensate pipes must meet the technical requirements, and their installation must be completed before the interior wall plastering and waterproofing work are carried out ； 2. When installing the condensation pipe, a line must first be marked (for inspection), then a groove is cut using a cutter; thereafter, chiseling is performed. The depth of burial in the wall should be 15 mm ； Chisel grooves along the joint seams of precast slabs; do not chisel horizontally ； If grooves are to be made in beams or shear walls, approval from the owner and supervisor must be obtained first ； 3. The installation of the condensate pipe must be avoided in the area near the bathroom entrance; the distance from it to doors, windows, etc. should be more than 200 mm ； 4. The spacing between the supports for the condensate pipe installation should be less than 800 mm ； The exposed parts must be insulated (except for pipe shafts) ； When installing the condensate pipe, the length of the flexible hose should be between 20 mm and 30 mm (the distance between the pipe ends) ； 5. After the condensate pipe installation is completed, a water flow and filling test must be carried out; once self-inspection shows it is satisfactory, the result shall be submitted to the supervisor for approval. V. Electrical Installation 1. The spacing between wire tube clamps should be less than 600 mm; they should be aligned horizontally and vertically, and the length of the bellows should not exceed 500 mm ； 2. The inlet pipe for the wiring box of the fan coil unit must be supplied from above through piping ； 3. Wire connections must be soldered (connections inside conduit are prohibited); they should be wrapped twice with insulating tape and waterproof tape ； 4. Electrical insulation must meet the requirements ； 5. The speed control wire of the fan coil unit must be connected correctly; it must not be confused with the neutral wire. VI. Insulation 1: When insulating water pipes, glue must be applied and tape must be wrapped at the junction between the insulation sleeve and the wooden ring ； 2. When insulating air ducts, the insulation adhesive should be applied evenly, with no air bubbles. The surface must be smooth and flat, free of any contaminants ； The joining of sheets must be done above the duct, and the joints must be glued ； 3. The insulation material must not have any signs of peeling, cracking, or damage; the insulation tape should be properly bonded and not come loose ； 4. When insulating water pipes, fill the areas where the pipe casing cannot pass through with a foaming agent ； 5. After the pipeline pressure testing is completed, the pipe shafts and the areas where water pipes pass through walls must be protected first, so as not to interfere with the plastering work in the civil engineering works ； 6. After the pipeline insulation is completed, a film should also be wrapped around it; it is preferable to wrap it around each pipeline individually, and the visual inspection should meet the required standards. VII. Provisions for coordination with civil engineering work 1. Cutting grooves or making holes in walls and floors must be carried out only after obtaining approval through inspection ； 2. For drawing lines, powder-based lines are used; stones are used as red pigments, and ink pots are no longer employed ； 3. Do not scribble on the walls, such as drafting or making any unnecessary marks ； 4. If the putty gets dirty from external sources, it should be removed promptly with sandpaper ； If other items are damaged due to external factors, they must be repaired or compensated for in a timely manner ； 5. Holes drilled in the wall should be square and of appropriate size; they must be chiseled carefully, and it is strictly prohibited to strike them directly with a hammer ； 6. Without approval, it is strictly prohibited to drill holes or make grooves in shear walls and beams ； 7. Pay attention to protecting the finished products of other units; do not soil walls or floors, and do not damage waterproofing, doors, windows, corners of walls, window corners, or other components ； 8. The construction site must be kept clean and orderly. Materials should be stacked neatly, and construction waste must be cleared away in a timely manner; it is prohibited to litter. It is also forbidden to throw garbage from upper floors downward ； 9. During construction, strengthen coordination with the civil engineering team to ensure proper handover of the site. VIII. Relevant Regulations 1. When using a electric hammer, it is necessary to install a limit device; the limit dimension should be 60 mm to prevent penetration of the roof ； 2. Construction safety: Safety helmets must be worn when entering the construction site ； Safety measures must be in place for work at heights ； Power tools (cutting machines, bench drills, etc.) should be checked regularly and used by designated personnel only ； 3. Urination and defecation are prohibited in the construction site; violators will be subject to severe penalties ； 4. Only one male employee is allowed to stay in the on-site warehouse ； 5. A person must be stationed at the on-site warehouse 24/7, and cooking over open fires is prohibited ； 6. The use of materials should be considered comprehensively to improve their utilization rate, prevent theft or damage to them, and keep material losses at a minimum (within the approved loss limits) ； 7. The installation of units of the same type must be consistent (based on the model unit), including the equipment, the layout and diameter of the supply and return water pipes, as well as the layout and diameter of the condensate pipes; the installation locations and methods must be essentially the same ； 8. Weekly meetings are held at 5 p.m. on Sunday each week to report on construction progress, address project issues, and assign construction tasks ； 9. The confirmed project milestones must be completed; otherwise, penalties will be imposed in accordance with the regulations ； 10. Strengthen management efforts, carry out construction in strict accordance with the technical instructions and relevant standards; quality supervision and safety inspections must be carried out simultaneously to prevent the occurrence of quality and safety incidents ； 11. All work on site must be carried out with the assurance of project quality and schedule as a prerequisite, to ensure that the construction tasks are completed on time and to a high standard.