Sr. No.

Open Unit

Hermetic Sealed Unit

1.

Compressor and motor are connected with a V- belt

Compressor and motor have the same shaft and are placed in a welded dome.

2.

 Prime mover can be an AC/DC motor or an IC engine

Prime mover is a single phase induction AC motor.

3.

Speed of the compressor can be varied by using a stepped pulley.

Speed of the compressor is fixed.

4.

RPM of motor and compressor are different.

RPM of motor and compressor are same.

5.

A shaft seal is used for preventing the leakage around the shaft of the compressor.

No shaft seal is required.

6.

Compressor is mounted vertically and the motor is mounted horizontally.

Compressor and motor can be mounted in any orientation.

7.

Expansion valve is thermostatic/Low side float valve/high side float valve

Expansion valve used is the capillary tube.

8.

Uses suction and discharge service valves

Only  a charging tube is used.

9.

Charging of refrigerant is done from the high pressure side.

Charging of refrigerant is done from the low  pressure side.

10.

 It occupies more space.

It is a compact unit.

11.

It is costly.

It is cheap.

12.

It is noisy.

It is quiet.

13.

It is used for high cooling requirements in cold storage, ice plants and industries.

It is used for domestic units. These units are refrigerator, window air conditioner &  water cooler.

14.

Servicing is easy and less costly.

Servicing is difficult and costly.

15.

Chances of refrigerant leakage are more.

Chances of refrigerant leakage are remote.

16.

There is a receiver unit. Liquid refrigerant is stored in it. It supplies  more refrigerant during increased cooling requirements & vice versa.  Receiver is installed after the condenser

No receiver unit is  as large change in cooling requirements is not applicable.