【 Weak current College 】 on VAV systems running vulnerable to problems

1 VAV system basic technology
Air conditioning system through to the need to adjust the room temperature and humidity of the room and conveying air after a certain deal, to maintain indoor temperature and humidity required. But to maintain indoor temperature and humidity is essentially the same, you can use:
(1) air fixed, change the air temperature, air system, called up;
(2) the air temperature does not change, the change in the air, called VAV system.
The so-called VAV system (VariableAirVolumeSystem, VAV system), along with indoor hot, wet load changing, changing accordingly, in order to achieve the air remains laboratory environment temperature stability of a full air conditioning system.
As for air system into the indoor air is fixed, for load change larger was transferred space, will generate energy from waste.
The VAV system you can change the size of the air volume to meet the needs of indoor load changes, so that the whole system of total air volume reduction. Therefore, VAV system is an energy efficient air conditioning system.
A complete VAV system components include: you can adjust the fan speed of the air conditioning unit, several sets of VAV and necessary automatic control system.
VAV system has the following characteristics:
(1) the total reduction of the overall system load, achieve savings in reducing equipment specifications, and running costs of the early investment.
(2) VAV system can run according to actual needs, thus reducing the power consumption of fan, running costs can be further reduced.
(3) VAV terminal equipment can achieve each separate zone automatic temperature control, reflects the relative independence of the system.
(4) VAV system on indoor relative humidity control quality, constant air flow system less, but also to meet users ' requirements.
(5) because of VAV system increased fan speed control, VAV terminal equipment and so on, the system will increase the cost.

2 I Museum VAV system on the impact of fire alarm system
The second of our library is used in air conditioning systems: winter by heating hot water boilers, summer cooling by water chillers delivered two control system. Because the building is airtight, using the variable air system, the indoor air of change is relatively large, and the fire alarm using smoke detectors, vulnerable to the influence of air flow disturbances. In the absence of open VAV system for detection of various fire detector is very smooth, as long as the opening of VAV system, detect smoke detector is very difficult, affects the automatic fire alarm system with alarm function, which in turn affects the interaction time.

3 other uses of the problems encountered in the
(1) the amount of fresh air into the winter, indoor personnel feel oppressed.
(2) and force the use of exhaust, blower, long-running, it is necessary to increase the feeding, fan speed, increase the sent time, fan operation, which is equivalent to using the definite air flow system, increase energy consumption, increased electric fan and electric equipment of wear; full power of fan operation and increased environmental noise pollution.

4 discussions on existing problems
(1) for indoor workers feel oppressed, objective analysis is:
Winter air mode is to send hot air. When the environment is relatively closed and a large indoor personnel, indoor environment, the increase of heat sources; includes indoor personnel, lighting, various types of office equipment (such as computers, printers, copiers, scanners, etc.), allowing the gradual accumulation of indoor heat, temperature rises along with it. The VAV system with temperature, reducing the new amount of wind, so the cycle of the result is the oxygen content of air, so is the staff feel oppressed hypoxia. In order to avoid indoor personnel physical discomfort, you need to feed a lot of fresh air. At this point, you must enforce rushed, exhaust fan, exhaust gas opacity, fed into the fresh air, to meet people's needs, it also brings new problems.
(2) in force sent fresh air, VAV air conditioner fan speed increases, the indoor air flow speed, flow disturbance increases, resulting in a outlet near some distance from the fire alarm detectors can not be timely and accurately capture the fire alarm information, to the part of the fire alarm detectors provides alarm not timely. We know that the fire alarm detectors in accordance with the regulations, require uniform installed on each independent space below the relative Center ceiling (General press 1/80m2). In General, here is the most easy to reach and smoke-a place to stay. Indoor air flow should be relatively stable, that may arise from the fire smoke smooth reaches the ceiling fire detector location to ensure the fire detector promptly and accurately reported out fire insurance information.
(3) automatic fire alarm system, there are two kinds of detectors, smoke detector, temperature alarm detector, smoke detector for the vast majority of fire alarm monitoring is timely and sensitive; however, the subject of VAV system near the end of the probe equipment generates airflow, the detection sensitivity to reduce, delay fire alarm time. While the temperature alarm detectors on the implementation of coordinated control of large-scale equipment facilities only with auxiliary judgment function, in order to ensure the linkage between devices (such as fire shutter, gas fire extinguishing systems, sprinkler systems, fire dampers, and so on) the accuracy and reliability, avoid unnecessary losses, fire reported out is lagging behind. Fire can not be timely alerts, for building fire safety is harmful. Analysis that produces this contradictory reasons are: first, the air conditioning system designers and fire protection system design between communication and coordination is not enough, make the device layout is not reasonable; second, interior architecture, space is limited, the resulting device installation.

5 solutions
(1) first, the end of a delivery room, vents should keep away from fire detector settlements, the detector probe regional air relatively stable, so that may produce fumes rise properly, guarantee fire detector and smoke of timely contact, ensure that the fire detectorTimely alarm is designed to be taken into account.
(2) VAV system design in the end, it is necessary to consider a reasonable delivery, return air path, maximize efficiency, but also to consider the effect of air not to fire detectors in the normal sense.
(3) to further increase the density of the fire detectors, used to offset or reduce as VAV system, smoke control system, OA equipment uptime problems caused airflow disturbance on the impact of fire detector.

6 conclusions
In VAV system design, air duct, the layout of the terminal equipment should take full account of automatic fire alarm and detection system layout elements, this is the contradiction of opposites.
Sent to the room's air quantity, in addition to being able to make the room a relatively satisfactory air circulation, it should also be able to dilute the room of carbon dioxide and a variety of odors, making room for air to maintain a certain degree of freshness. Therefore, you must have enough fresh air echausting to compensation. Such as: timing window ventilation; improve the VAV system terminal equipment maximizing volume; increase channel exhaust volume, etc.
According to the indoor roof panel layout, combined with the airflow perturbation of the actual situation, reasonable increase in the number of fire detectors, to determine the appropriate installation location, ensure that the smoke detector able to monitor the risks, protect the fire smoke alarm and fire linkage system to work properly. The VAV system advantages into full play, improve system efficiency, reach the purpose of saving power.