What are the precautions in the design and construction of hotel central air conditioning project?

Xingding mechanical and electrical equipment engineering Co., Ltd. tells you the problems that should be paid attention to in design.

1, host selection

At present, the commonly used models are VRV system, modular machine, screw chiller, centrifugal chiller and lithium bromide absorption chiller. The selection principles are: energy saving, emission reduction, environmental protection, high efficiency, low operating cost and flexible operation according to load. Suggestion:

A) In areas with industrial steam supply, lithium bromide absorption refrigerator is the first choice;

B) Screw chillers and centrifugal chillers are preferred for large and medium-sized centralized buildings;

C) VRV system and modular machines are preferred for villas, resorts and other buildings.

2, air conditioning system piping design

A) Try to use the same procedure to close and change the system, and add a pressure balance valve between the inlet and outlet headers. According to the operation of several projects, there are several advantages:

1) facilitates the adjustment of the system in winter and summer, and solves the problems of low bottom temperature in winter and high top temperature in summer;

2) It is convenient for the system to exhaust;

3) Solve the problem of temperature difference between the end and the head of the system;

4) The required power of chilled water pump is low;

5) It is convenient to be matched with building automation system.

B) Choose multi-area cold and hot parallel piping system in complex commercial environment.

In Jiangsu province, considering the complexity and construction cost of the system, the dual control system is generally adopted, but it can not meet the requirements of high-star hotels when the temperature changes in spring and autumn. For example, restaurants, dance halls, KTV and gyms need refrigeration, while guest rooms and conference rooms need heating. In order to solve this problem, it is recommended to adopt the piping system shown in the following figure:

1) In summer and winter, all valves of the auxiliary water supply and return separator are closed, and the main water supply and return separator provides cold/warm sources;

2) In spring and autumn, close the valves on the main water separator leading to dance halls, gyms and restaurants, close the valves on the main water supply and return pipeline leading to the main water supply and return separator, open all valves attached to the water separator and open the valves on the main water supply and return pipeline. In this way, the main water separator supplies room heating, while the auxiliary water separator supplies air conditioning for restaurants, gyms and dance halls.

C) The inlet and outlet valves of the unit shall adopt butterfly valves. Butterfly valve has the characteristics of light weight, small floor space, clear switch sign and simple operation, and is an ideal choice for installation, operation, maintenance and safe operation.

3, reasonable arrangement of computer room

A) When arranging equipment in the computer room, it is necessary to consider the overhaul space of condenser and evaporator, and also provide a noise-proof duty room for operators, and the host operator in the duty room can observe the changes of the instrument. Especially for screw chillers, the noise of centrifugal chillers is as high as 89 ~ 95 dB, and it contains some low-frequency noise, which is harmful to human cardiovascular system.

B) The power distribution cabinet in the basement computer room should be waterproof, and the foundation of the power distribution cabinet in the computer room should be 150 ~ 200mm above the ground. Cables and control lines should be arranged by bridge, and cable trench wiring should be avoided as far as possible to prevent accidents caused by water entering the cable trench.

C) The underground machine room should have good ventilation facilities. According to the operation practice, if the refrigerant in the machine room leaks a lot or the safety valve in the machine room jumps, there will be hypoxia in the machine room, which will lead to suffocation of the operators. Therefore, it is recommended to install ventilation equipment in the computer room. In addition, the exhaust pipe of the safety valve on the water chiller is connected to the outside by pipeline.

D) When the central air-conditioning unit is located in the basement machine room, there are many basement equipments, such as water treatment equipment, domestic water pump, fire water pump, etc., and the host needs to be cleaned regularly. In case the water flow breaks down, the equipment will be flooded. Therefore, the collecting well with water level controller should be equipped with vertical sewage pump or submersible pump separately to control the water level in the basement, and it is best to have a backup.

E) For systems with multiple units running, safety valves shall be set on the inlet and outlet pipelines of the evaporator. Because many units are not started at the same time, they are started in turn, so the water temperature in the evaporator is generally (7 ~ 12)℃ when stopping, and the temperature in the machine room is sometimes as high as (30 ~ 36)℃ (especially in some machine rooms, in order to shorten the length of heating pipes, the central air conditioning unit and boiler are often arranged together in winter, and the temperature in the machine room will be higher), and the water inlet and outlet valves of the units must be closed.

4. Cooling tower

A) The cooling tower located on the roof shall be equipped with a fan maintenance control switch. The general switches are in the computer room, and the roof can't be controlled. If the maintenance personnel make mistakes during maintenance in the tower, starting the fan may cause casualties.

B) The cooling tower located on the roof leaks. When designing roof pipes, the design of support foundation must be considered. Because some engineering designs do not meet the requirements, the construction unit directly puts the support on the waterproof layer. When the equipment is running, the pressure and thrust of the support damage the waterproof layer, resulting in roof leakage.

C) It is recommended to choose a spray cooling tower with nozzles. Because the spray cooling tower of the water distributor is easily blocked locally and the water distributor rotates unevenly, the tray bearing is damaged for a short time and the maintenance is difficult. If the spray cooling tower is not equipped with a water distributor and a water storage device is added at the outlet of the water tower to reduce floating water, the transformation effect of several projects has been proved to be very good.

D) A vertical decontaminator shall be installed in the cooling water system. At present, the decontamination devices installed in the central air conditioning of water chillers all over the country are inverted Y-shaped and installed on the vertical pipe in front of the entrance of the air conditioning unit. This inverted Y-shaped dirt remover on the vertical pipe can only capture the construction garbage at the initial stage of equipment operation and prevent these garbage from entering the condenser. However, this inverted Y-type dirt remover can't catch fine scale and rust scale in daily operation, so it will cause impurities such as condenser scaling and mud accumulation. The correct way is to install a vertical decontamination device in front of the condenser water inlet (the same as the decontamination device in the hot water boiler system) to intercept all kinds of impurities in the cooling water system in the decontamination device.

5. Piping and insulation

A) condensate system design. Don't choose galvanized steel pipe, because there are too many tapes at the welding or pipe joint, which is easy to cause rust and blockage, leading to the impassability of shower pipe. Suggestion:

1) PVC pipes or plastic-lined galvanized pipes are selected;

2) increase the slope of the pipeline;

3) Set more drainage points;

4) Connect the water outlet of the drip tray with the condensed water pipeline with reinforced plastic pipes.

B) Design of air conditioning system bracket. When designing air-conditioning cooling pipes, the concrete methods of supports and hangers must be explained in the drawings. Some engineering designs are not explained, and the construction is not insulated, which leads to dew condensation and serious corrosion of supports and hangers, rust pollution on decorative surfaces, and it is difficult to deal with air conditioners after they are put into operation, which will leave hidden dangers of accidents.

C) insulation design of air conditioning system. In the design drawing of thermal insulation system, the thermal insulation practices of pipes, air ducts, equipment and valves must be explained, and the materials and construction methods of thermal insulation layer, steam insulation layer, protective layer, anticorrosion layer and waterproof layer must be explained in detail. (See Xingding Electromechanical Website for details)