【 Weak current College 】 HVAC problems and solutions

Design of HVAC project design, controlled the norms, rules, standards, find HVAC design staff in implementing the existing norms, regulations, standards, systems design, equipment selection, network layout, there is a lot of problems. Now will see problems and their causes and solutions of the following. 1. implement HVAC design specification, standard problems 1.1 indoor and outdoor air in the computing argument does not meet the specifications of the design code provides that the calculation of indoor air in winter, bathroom, toilet parameter should not be lower than 12 ° c, the bathroom should not be less than 25 degrees centigrade. However, some public buildings of toilet, lavatory room (equipped with exterior Windows, facades), residential building of the bathroom (in winter there is a bath of hot water supply, should be treated as bathroom) is not set heat sink, it is difficult to reach room temperature not lower than 12 ° c and 25 ° c. There is also a kitchen of the apartment building is located the heatsink, I think, kitchen and interior temperature also should be not less than 12 degrees centigrade requirements set heat sink. The design code provisions, some of the major cities of outdoor weather parameter should be the norm in Appendix II. According to the Appendix b, Beijing area outdoor design temperature in winter heating except yanqing, Miyun, should be-9 ° c. While project is located in the Beijing suburbs, has access to-12 ° c, is obviously not appropriate. 1.2 heating load calculation leaky and wrong the design code provisions, winter heating system heat load should include heated indoor door slot into the cold air of the heat consumption. But some of the projects in the calculation of the heating load calculation that partly not heat loss, heat load and from larger; the design specifications "on the envelope's heat loss calculation done orientation correction rate, 0 ~ 10% in the North, East and West-5%,-15% to 30%, while the project was to become North orientation correction rate of 20%, 15% of the East, West, South-5%, contrary to the specification requirements. 1.3 bathroom radiator type selection is wrong with the design specifications ", the relative humidity larger room use cast iron radiators. However, many works of the toilet using steel radiator, nor the strengthening of protection measures, it is inappropriate. I have seen some of the Office building of the toilet using steel closed radiator, but I couldn't use a few years, the radiator series Tablet is corrupted, the remaining two tubes are also serious corrosion. Practice has proved that such places the best use of cast iron radiators or aluminum radiator. 1.4 staircase radiators, pipes are not individually configure the design code provisions, stairs or other frozen dangerous places, its radiator should be separate legislation, heating pipes, and shall not be equipped with control valve. However, some projects will staircase radiator and radiator adjacent room heating rooms sharing a standpipe, dual side connection, connect the stairs on one side and the other side of the radiator connections adjacent room room radiator and radiator pipes on the valve. In this way, because it is difficult to guarantee enclosed stairs, once the heating failure may affect adjacent room heating effect, even crack the heatsink. 1.5 heating pipe laying slope does not conform to the specifications of the design specifications, installation of heating pipes should have certain slope, for hot water pipe slope use 0.003, shall not be less than 0.002. However, some engineering heating for return pipe slope only 0.001 ~ 0.001 5. Of course, if there were constraints, hot water pipes can even lay no gradient, but should ensure that the water flow in pipes must not be less than the 0.25 m/s. 1.6 kitchen operations room ventilation problems the diet building design code (JGJ 64-89) on kitchen operations room ventilation was clearly defined: (1) calculation of the exhaust volume of 65% by exhaust hood flows into the outdoors, but the overall ventilation discharge room 35%; (2) exhaust hood mouth suction speed generally should not be less than 0.5 m/s, exhaust tube speed should not be less than 10 m/s; (3) should be heated up air flow between the exhaust volume of 70%, room vacuum value should not be greater than 5 Pa. However, there are works of kitchen exhaust hood is not set, only the walls located several pieces of the exhaust fan; while setting the exhaust hood, but cover mouth suction speed far less than 0.5 m/s, with optional blower air volume is low. Most of the works does not set the overall ventilation device, also does not take into account wind installations, difficult to maintain indoor health environmental requirements and negative pressure values. 1.7 expansion tank and thermal (cold) water system does not meet the specifications of the boiler room design standard "(GB 50041-92) provides high expansion tanks and hot-water system pipe should not be fitted with valves. The pipe is a pipe expansion pipe and circulation. This article on chilled water system is applicable. But some of the chilled water system expansion of high-expansion tank fittings to freezing room set on water and install a valve, which is not allowed. Once the mistake that will endanger the system security. 1.8 fire ventilation and air-conditioning system valve settings do not meet the specifications set forth in the regulations ", duct should not pass through the firewall or deformation seams, as must pass through the Fire Department set through the firewall; through the deformational slots, you should set the fire damper on both sides. However, some tall buildings, wind pipes through the firewall is not set fire dampers, air ducts only through the deformational slots in the side of a fire safety valve, and the other side it is not set. In addition, some engineering fire damper position is set incorrectly. According to the requirements of fire safety valve should close the firewall settings, and connect the fire damper of through-wall air pipe thickness mm, δ = 1.6 firewalls on both sides from 2 m wide air pipe should be non-combustible materials and thermal insulation. But some engineering ventilation and air-conditioning duct on the fire damper casual setting, away from the firewall, during which wind pipe is neither marked thickening, nor take any protection measures that exist. 1.9 smoke staircase in front of the room air flow of problematic the resistance of the law on high-rise building smoke stairs before pressurization provides air volume, and points to the specific air flow value. In the notes to that article to open door through the door of the wind speed is less than 0.7 m/s; provisions provided in the notes to the door opening number, 20 layer following is 2, 3-20 layers above. The doctrine of law also stipulates that the smoke before the Chamber of the stairwell pressurization outlet should have one on each floor. Under these provisions, the layers can be projected from in front of room air in air should be L/2 (20 stories) or L/3 (20 layers above, L-front room total pressure air). However, some project of smoke front staircase room supply outlet of the air flow is labeled L/n (where n is the number of building layer), it is clear that small. As a 12-story building, smoke stairs before the total pressure air for 16 000 m3/h, but each layer front room air flow but callout is 16 000/12 ≈ 1 300 (m3/h), it is clear that its air inlet with small. Correct dimensioning is 16 000/2 = 8 000 (m3/h), this configuration outlet size. 1.10 wrongly smoke partition exhaust volume calculation does not get to the exhaust fan of the doctrine of the exhaust fan was clearly defined: take a smoke exhaust system partition, you should press the smoke partition area per m2 not less than 60 m3/h, with two or more exhaust smoke partition should be maximum preventing smoke partition area per m2 not less than 120 m3/h. Please note that there is a choice of air exhaust fan and not smoke partition exhaust volume doubles (on each smoke partition exhaust volume still press the smoke partition area per m2 not less than 60 m3/h), but when the exhaust fan either horizontally or vertically with two or more smoke partition smoke, just press the two exhaust smoke partition at the same time to determine the exhaust fan of the air flow. However, some project exhaust fan horizontal shoulder area of size 2 ~ 3 exhaust smoke partitions, design errors, the exhaust fan of 2 ~ 3 smoke partition has a total area of not less than 60 m2 per m3/h, not by one of the biggest smoke partition area per m2 not less than 120 m3/h, causing the exhaust fan is small, it is difficult to meet fire protection requirements. There is also the exhaust fan (systems) in vertical orientation with two or more smoke partition (aisle) exhaust, design errors will each smoke partition (aisle) exhaust volume according to the respective area per m2 not less than 120 m3/h calculation, instead of by their respective area of not less than 60 m2 per m3/h, imperceptibly to vertical smoke partition (aisle) exhaust volume more than doubled, making each floor duct, Tuyere configured on the high side. 1.11 high-rise building exhaust system and exhaust port selection misconduct the resistance of the law, (HVAC) ducts pass through fire partitions partition should set fire damper. In my view, would not be appropriate for exhaust air pipe, such as through a firewall, you must pass through should wear the firewall is set when the gas temperature of more than 280 ° c will automatically close when the fire damper, and exhaust fan interlock. However, some project at design time on this negligence. If a basement an exhaust system with 3 bedrooms and 1 internal walkways (all rooms and corridors between doors are fireproof door) of smoke, fume duct with a smoke fire dampers, and all rooms and corridors of the exhaust vents are single louver, exhaust pipe passes through the firewall is not set up smoke fire dampers. This problem is caused by: each room fire door useless, once a room there is a fire, through the exhaust pipe affecting other rooms. The correct approach is: in a single layer blinds exhaust mouth (exhaust duct through firewall) additional smoke fire dampers (280 ° c auto-off) or will be changed to single-layer louver dedicated exhaust outlet (usually the normally closed, open automatically when the ignition, the exhaust gas back off 280 ° c).
Second, in HVAC engineering design problems 2.1 heating entry setting too many settings when heating, both entrances to consider the reasonableness of indoor heating system, and to consider the reasonableness of the outdoor pipelines linking, not only figure indoor system design is convenient, easy, regardless of the outdoor pipe network system. However, some engineering heating too many entrances.　　 In the case of a 7 storey building, indoor heating system is divided into 10 loops (1 ~ 2-4, 3-7-6), heating entrances are also up to 10, with an outside line convergence points, there are several directions, not only to get an outside line construction caused trouble, but also to future inconvenience indoor system regulation. 2.2 heating system design is not reasonable heating system design unreasonable: ① the heating system consists of: 1 Master Li (stem)-introduction, a few loops, a ring no valves, to the system operation, maintenance and management. ② the heating pipe layout is reasonable, and not easy to coordinate construction professional, or heating riser directly in the window, use, and affects both unsightly; or heating in horizontal pipe laying in channels, affecting both on the ground, he is not in a position to place the goods. ③ the supply and return water dry pipe set high point leakage, once the exhaust gas, it is difficult to eliminate, the impact of system use. ④ the heating system for the same program, a 300 m long loop fare, resulting in supply and return water dry pipe slope is very difficult to meet the specifications provided for not less than 0.002 requirements.　　 ⑤ the heating system for two-sided connections, both sides heat load and the number of the heatsink, and two vastly the radiator pipes for water, but to have the same diameter, two hydraulic imbalance, it is difficult to be allocated according to the design flow. 2.3 exhaust system design unreasonable if a dark basement toilet (WC) and few living room and equipment rooms located a ventilation system, horizontal duct length 60 m, the section only 200 mm× 200 mm, wind resistance is large; selection of roof fan exhaust, but the fan installed in the walls, were not coordinated.　　 There are also located in the basement of the works of several private rooms (both darkroom), all rooms have a ceiling fan exhaust through dozens of m-long horizontal wind pipe from the outside, there is only wind pipe cross-section 150 mm 150 mm×, resistance, poor ventilation effect. 2.4 air-conditioning system choice unreasonable if a project has a commanding Hall, conference rooms, computer rooms, etc., this nature House, ideal for air conditioning system should be a low-speed air duct system, and designed it with fan-coil system and is not set, the fresh air supply system was clearly unreasonable. As a project owner requirements section of the room interior design parameters for: winter tn = 18 ~ 22 ° c, φ = 55% ± 5%, summer tn = 25 to 26 ° c, φ = 60% ± 5%; another part of the roomTn = 22 ± 2 ° c, φ = 40% ~ 60%, clean level is less than 10 000, the fresh air 40 ~ 60 m3/(h *). The nature of these two types of rooms, all designed with fan-coil system and fresh air supply system is not set.　　 Such a system cannot satisfy the request of the party. 2.5 toilet with air blower plate Tube, open air toilet has to meet the temperature requirements, and to eliminate odour, guarantee hygienic requirements.　　 However, some of the works of the toilet without exhaust and no fresh air supply, simple horizontal dark dress fan coil for cooling, heating, the cycle itself caused odor, which is not appropriate. 2.6 balance valve settings and aperture selection problems chilled water system should set balance valve, should generally be set on the return pipe. But some engineering air supply unit chilled water supply and return pipe has set the aperture and the diameter of the same valve. The author believes that water supply pipe on valve does not have to be set, only set on the return pipe.　　 Balancing valve diameter should be determined through the check calculation. Third, HVAC design drawings problems 3.1 design description incomplete the design depth of regulations on HVAC design descriptions should include content clearly. Design description should have indoor and outdoor design parameters; heat and cold sources, htm, refrigerant parameters; heat load and heat consumption indicator, the system total resistance; radiator models; air-conditioning cooling load, thermal load; system forms and control method; noise, vibration isolation, fire prevention, corrosion resistance, insulation, air duct, pipe material selection, installation requirements, system pressure test requirements.　　 However, some design Notes content is incomplete. 3.2 floor plan is not enough, some depth should be drawn content omission "provisions on the design depth on HVAC plan to indicate the detailed provisions. However, a considerable number of engineering design drawing is not fully in accordance with the regulations, the main problems are: heating floor plan, some not tagging level dry pipe diameter and position size; there is no number of standpipe; some have labeled risers, but will stand pipe leak pictures; the two-story to the front and draw the floor plan, radiator also conducted a callout, hierarchy but does not indicate the appropriate levels; there's only the first layer of the painting, without heating plane painting two layers to the top-level heating plane. Ventilation and air conditioning plan, some did not indicate the number and positioning of equipment; there's no dimension describes the chilled water piping diameter and position size.　　 There is also the design of public buildings, the kitchen part of heating, ventilation, air conditioning, and other content for kitchen equipment manufacturers to do, it is not appropriate. 3.3 system map depth not enough the design depth of regulations on HVAC system diagram rendering explicit requirements. But some of the engineering design for failing to comply with the prescribed execution. The main problems are: heating system diagram, there is no number of risers, but to the axis, instead of building; a pipe, note the grade, slope, but did not indicate the beginning or end of pipeline end elevation; pipeline changes (turn) elevation leakage note; some even not art heating system diagram or riser diagram.　　 HVAC design, some works were not art air-conditioning chilled water system diagram and system diagrams (if the floor plan fully explain clearly, can not draw a system diagram, but for some of the more complex design of ventilation and air conditioning, rely on the floor plan is difficult to express clearly). 3.4 boiler room design simplistic the design depth of regulations on boiler house construction drawing design for detailed provisions. 　　 However, some of the boiler room design, drew a plan only, no profiles and system diagrams, and many should be accountable for the content is not answerable from the design depth requires very different. 3.5 account book content is not full or even all blank the design depth of regulations on HVAC design account book shall include the detail of the content. However, a significant part of the engineering design no HVAC design account book. Some heating air-conditioning design notwithstanding the account book, but the content is incomplete. The design of heating, heat loss calculation, only without the hydraulic balance calculations and calculation; the radiator of high-rise buildings of central air-conditioning and smoke control design, only the summer cooling load calculation without air-conditioning system and water system hydraulic calculation, no refrigeration and air conditioning equipment selection calculation, calculation of smoke-free.　　 There's air conditioning design, regardless of room size, direction, level, location (intermediate or end) are the same indicators to estimate the summer air conditioning air-conditioning cooling load and thermal load in winter, and to configure the air-conditioning equipment, this is inappropriate. 3.6 HVAC equipment is not numbered list indicated that the picture is not clear to the complicated drawing standards law, the heating, ventilation and air conditioning equipment, components, parts, preferably numbered list indicated that their models, performance should fill in the table is complete, clear, only specify their drawings.　　 However, some HVAC design did not press this regulations, but a variety of devices, part of the name, model, or are written on the surface, surface text complexity, costs, and note write incomplete, unclear. 3.7 floor plans, elevations, system diagrams are not consistent in HVAC design, flat, profiles and system diagrams corresponding parts of the equipment, size, and so should be fully consistent, to construction and installation, use and management. But the design of heating, radiator, floor plan and the system diagram is not consistent; supply and return water dry pipe diameter, floor plan and the system diagram is not consistent; pipe connections, floor plan and system diagrams are not consistent.　　 There is air conditioning and ventilation design, duct sizing, layout and system diagrams; equipment, parts, location plan and profile dimensions are not consistent; the device number, quantity, drawings are not consistent with the device table; air-conditioning design choice of air-conditioning and refrigeration equipment models, floor plans, systems and equipment table note write, let the people do. 3.8 design drawings and calculation of books are not consistent in HVAC design, all equipment, pipes, part of select are determined by calculation, in a sense, design drawings, is the embodiment of computing books, design drawings and calculation should be identical. But the design of heating, radiator, lap dry pipe diameter, design drawings and calculation of books is not consistent, or even considerably, account book, drawing on, account book in small, drawing on the zoomed in, account book, drawing on the narrows. To complete the calculationThe drawings found unreasonable allows adjustments, but should be adjusted calculation of books or adjust the description, the drawings and calculation of the final book.　　 IV. the problem cause and solution to current design standard 4.1, regulations, standards of learning, implementation, thus strengthening the existing design rules, regulations, standards of learning, improve the implementation of the design specification. 4.2 design process lack technical and economical comparison of multiple scenarios, randomness.　　 Should be the same as in architectural design, a number of programmes, make reasonable design. 4.3 drawing review is not strict, or even mere formalities. Should insist triple (since the audit, audit, examination) system to ensure that the design (including drawings, account book) quality and eliminate errors.