Types Of Air-conditioning Controls

Air-conditioning Controls :

The field of application of air-conditioning control device depends upon the size of the area under consideration, the number and size of the units involved, etc. Depending upon particular requirements the following three types of control are used for air conditioning :

1. Manual
2. Automatic
3. Semi-automatic.

1. Manually Controlled System :

The manual control can be an ordinary knife switch which must be operated by hand when the actuating mechanism is started or stopped. This method requires personal attention and regulation at frequent intervals,especially when the load varies. Even if the plant is in operation only at certain times of the day, inside and outside conditions may vary so greatly that constant changes in adjustment are necessary. In this type of control constant attention is required by the operator to maintain the predetermined conditions, and the cost of operation is usually found to be excessive. If a manual control is provided, the user may permit the unit to operate until the room is too cold, or else he may forget to start the machine until after the room has reached an uncomfortable warm temperature. In either case, the will not be satisfied, and therefore it is usually wise to install an automatic control.

2. Automatic System :

To meet the varying load almost constantly completely automatic system may be employed. The various instruments used in this type of control are : Time clocks, thermostats, humidity controllers, and automatic dampers. Automatically operated controls provide all the features that are considered most desirable for temperature and humidity regulation as well as economy of operation. In this system operator or owner is relieved of all responsibility for maintaining the predetermined conditions.

3. Semi-automatic Control System :

This system makes use of a close-differential thermostat and in most cases it is entirely satisfactory. Time clocks are also very desirable on installations where definite shut-down periods are required. The fresh air intake from outdoors should be equipped with adjustable louvers, so that maximum amount of air can be regulated for both summer cooling and winter heating. On any unit below 25 TR capacity it is desirable to keep the control system as simple and free from service liabilities as possible.

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