Refconhvac, Indore (2026)

14/06/2019

Industrial refrigeration:
How does an industrial refrigeration system work?
Why it is important to use a backpressure valve ?
Case 1: Stopping of the refrigeration system
Case 2: Starting of the refrigeration system
Case 3. Safety devices in an industrial refrigeration system
Oil pressure sensor:
Electric heater for defrosting
Routine maintenance in an industrial refrigeration system:

Industrial refrigeration systems are heavily used in supermarkets, airports and provision stores for storing a variety of foods, vegetables, and frozen products using multiple ev***rators set at different temperatures.

Large refrigeration compressors usually consist of 2 to 4 cylinder units to handle large refrigeration plants.

Only some compressor cylinder units are provided with unloaders so that refrigeration capacity can get adjusted as the food stock starts becoming cold.

The commercial refrigeration system consists of thermostats, solenoid valve, a thermostatic expansion valve (TXV or TEV) or metering valve and back pressure valve with safety devices such as LP cut out, HP cut out, L**e oil cut out and compressor unit unloader.

Large industrial refrigeration plants have a commercial freezer and Meat room with the temperature maintained at -20°C or -24.8°F and -15°C or 5°F, hence temperature is sensed by thermostats.

Where’s Vegetable room thermostat set at +5°C or 41°F.

A thermostat has two functions one is to immediately stop the cooling of refrigerated room, and another one is to start the cooling operation of less cooled refrigerated room.

All is done by operating the solenoid valve to close and open the flow of refrigerant to the refrigerated room.

Solenoid valves are controlled by the thermostats attached at each refrigerated rooms.

Commercial Freezer room
Meat room
Vegetable room
How does an industrial refrigeration system work?
Generally, for commercial freezer room and meat room the thermostat differential temperature setting is set at around 5°C.

Which means, the solenoid valve opens and starts to increase cooling for the freezer room when its temperature drops to -15°C (ie 5°C drop in temperature).

The same goes for the meat room at -10°C.

Similarly, the solenoid valve opens for the vegetable room at (7°C).

The thermostatic expansion valve(TEV or TXV) adjusts the degree of superheat; so that ev***rator may not starve of refrigerant.

Why it is important to use a backpressure valve ?
A back pressure valve fitted at the ev***rator outlet for the vegetable room since vegetables are sensitive to excessive change in temperature, which could damage these perishable food items.

Therefore, a positive temperature is maintained in the vegetable room to keep the vegetables fresh and undamaged.

The back pressure regulator valve keeps the rate of ev***ration reduced to provide a gradual cooling.

It also creates back pressure on the ev***rator coil, to ensures that most of the liquid refrigerant is made available at lower temperature zones ie. freezer and meat room.

Back pressure valves are spring loaded and a non-return valve.

Case 1: Stopping of the refrigeration system
Now, let’s consider the meat room achieves its temperature of -15°C then the solenoid valve to this room closes which leads to a drop in suction pressure at the compressor.

Drop in suction pressure activates the unloader to unloads one of the compressor units and keeps the unit cut off by lifting its suction valve open.

Thereby reducing the compressor capacity and not allowing the compressor motor to stop on a low-pressure trip.

Working of commercial refrigeration in supermarkets,storing variety of food products,controlled byTEV or TXV,ev***rator etc ,safety devices and maintenance

14/06/2019

Essential properties required in a refrigerant are as follows:
1. High latent heat of v***rization
2. A High Suction gas density and a Low Compression ratio.
3. Non-corrosive, non-toxic and non-flammable
4. High critical temperature
5. Compatibility with the lubricating oil
6. High latent heat
7. Low boiling point
8. Low condensing pressure
9. High dielectric strength (for compressors with integral motors)
10. Should be cheap and readily available
11. Ease of leak detection
Refrigerant gas used in World War
– r12 refrigerant properties
– r22 refrigerant properties
How some refrigerants | HCFC’s and CFC’s got banned?
– r11 refrigerant (CCl3F) properties
What are Environmental friendly | Green Refrigerants?
a) r134a refrigerant properties
b) r134a and r407c refrigerant properties
c) r410a refrigerant properties
d) r404a refrigerant properties
e) r717 ammonia properties
f) r-401b Refrigerant properties
g) Carbon Dioxide refrigerant properties

1. High latent heat of v***rization

High latent heat of v***rization is desirable in a refrigerant because it results in high a refrigerating effect per unit weight of the refrigerant and low rate of circulation of the refrigerant.

More heat can be absorbed and ejected in each cycle of refrigeration.

2. A High Suction gas density and a Low Compression ratio.
High suction gas density at the compressor suction means low sized compressor and a lesser powered compressor motor because after the refrigerant passes through the ev***rator, the refrigerant gas expansion is not very high ie. Fluid to Gas expansion is low.

This property of refrigerant provided a low compression ratio for the compressor, the higher mass flow rate of the refrigerant leading to a low rate of circulation within the system.

3. Non-corrosive, non-toxic and non-flammable
Refrigerant must not be poisonous or lethal to air-conditioning, human health, and foodstuff. When coming in contact with metal parts like piping and compressor must not cause any sort of electrochemical corrosion.

Must be compatible with non-metallic parts such as nitrile rubber tubes, O-rings (used for sealing purpose).

As the refrigerant gets compressed under high pressure and temperature inside the compressor, it must not cause any explosion or catch fire within the system and continue its non-flammable properties.

Presence of moisture in the system may cause the formation of highly corrosive compounds (usual acids) which may react with compressor lubricating oil and with other materials in the system including metals.

Moisture may cause failure of compressor valves in case of hermetic compressor often causes breakdown of the motor winding insulation resulting in short-circuiting or grounding of the motor.

Presence of moisture in lubricating oil may deteriorate properties of lubricating oil and formation of metallic or other sludge which may lead to clogging or chocking of valves, filter, and other oil passages.

Moisture can enter into the system while charging of refrigerant, while repair ie. evacuation or vacuuming of the system where moisture can enter through leaky joints, moisture can exist as a free water although, a completely moisture free refrigerating system is not possible.

When moisture is present in the form of water it may lead to icing within the ev***rator coil and choking of the thermostatic expansion valve.

Avoid moisture formation by connecting a filter drier which absorbs moisture from the refrigerant.

4. High critical temperature
It is the temperature above which the vapour refrigerant remains in the vapour state and cannot be liquefied back into its liquid state even after passing through the condenser or any cooling medium at any given pressure.

This happens only when the refrigerant temperature reaches beyond its critical temperature, ie. when a refrigerant has a low critical temperature.

So, it’s better to select a refrigerant having a high critical temperature, to be able to condense these refrigerant gases into liquid form and subsequently heat transfer at the condenser can be carried out at a significantly higher temperature.

5. Compatibility with the lubricating oil
The refrigerant used must be compatible and miscible (means refrigerant can be easily separated) with the compressor oil as there are greater chances of intermixing inside the compressor, wherein such condition following problems can occur:

Acid or sludge formation.
Acidic corrosion decreases alkalinity in oil.
The decrease in viscosity leading to insufficient lubrication.
Oil carbonization with the rise in temperature.
Compressor damage due to the loss of the lubricating oil properties and load carrying property.

Detail description of refrigerant,r22,r12,r134a,r410a, R407C, R404A, R717 Ammonia,R-401B, Carbon Dioxide,properties and applications.

14/06/2019

Refrigeration System Problems and Solutions:
1. Room temperature warm
2. Compressor suction pressure high
3. Compressor suction pressure low
Highly reviewed products in Amazon
4. Compressor discharge pressure high
Causes for discharge high pressure:
5. Abnormal noise heard during operation
6. Compressor low oil pressure
The following would cause low l**e oil pressure:
Chocked oil filter
Oil separator blockage preventing oil return to the compressor
Carryover of oil into the refrigeration system.
Bearing wear within the compressor.
7. Excess compressor overload
Possible cause includes:
8. Refrigerant low on charge and overcharge indications and remedies
Undercharge symptoms:
Solution:
Overcharge symptoms:
Symptoms are:
Solution:
9. Moisture in the refrigeration system, problems, and remedy
Remedy:
10. Short cycling of refrigeration compressor
Reasons for above:
What is compressor anti-recycling?
11. Frosting at the suction of the compressor
Reasons:
12. What happens if air enters into the refrigeration system and how to remove it?
Indication for air ingress
Reason:
Remedy:

1. Room temperature warm

Lack of refrigerant present in the system.
Blocked filter at the drier or expansion valve.
Ev***rator inlet solenoid closed.
Condenser fan motor issue, less heat transfer available for a given mass of refrigerant.
Defrosting element still operational.
Compressor capacity control faulty leading to less coolant effect across the thermostatic expansion valve.

2. Compressor suction pressure high

Fractured compressor valves, causing the compressor capacity to fall.
Ev***rator load too high, caused by room items recently changed entry door left open.
Excess refrigerant charge. This fault is combined with a low compressor superheat and indicates liquid in the suction line. The solenoid valve should be closed quickly to prevent liquid damage to the compressor.
Expansion valve stuck in a fully open position, caused by dirt in the expansion valve.

3. Compressor suction pressure low

Blocked filter or closed valve in the system. In this mode, the compressor is extracting more from the ev***rator than the expansion valve is supplying leading to low suction pressure and possibly compressor to short cycle.

Refrigerant charge too low. There is not enough refrigerant within the system to allow the compressor to operate at the present capacity setting. Increased compressor run time.
The liquid refrigerant flow may be disturbed: Fully open the valves in the liquid refrigerant line if not fully open. Confirm line filters not chocked.

Thermostatic expansion valve clogged with ice or oil dust mixture: Dissemble expansion valve (TEV) and clean the ice with dry compressed air. Activate the desiccant of drier filter by the heater. Take off oil mixture dirt.

Less opening for the expansion valve or superheat very low: Adjust the expansion valve opening and ensure temperature sensor attached properly to the ev***rator outlet.
Ev***rator cooling capacity lowered by dust and frost: Check fan operation working normal. Remove dust by soft brush and carry out defrosting.

refrigeration problem,solution,causes due to air,moisture,short cycling,anti cycling,warm room,low charge,over charge refrigerant, overload,pressure high,low

14/06/2019

15 Major Components and Controls of Refrigeration System

How refrigeration compressors work
1.HERMETIC Refrigeration compressor or (fridge compressor)
2. Commercial Refrigeration Compressor
2a. Question: Why a coupling is needed in a commercial refrigeration compressor and motor?
2b. Question: What is the function of a Mechanical Seal in a refrigeration compressor?
3. Thermostatic expansion valve (TEV or TXV)| Metering valve?
4. Why an equalizing line required in thermostatic expansion valve (TEV) or metering valve?
5. FILTER-DRIER in a refrigeration system
6. Sight glass|Moisture indicator
7. Heat exchangers in a Refrigeration system
8. Solenoid Valve
9. Back Pressure Valve
10. Compressor Safety Devices:
10a. Refrigeration Compressor Unloader Safety device
10b. Compressor High Pressure cut out Safety Device
10c. Compressor Low Pressure cut out Safety Device
10d. Compressor Differential L**e oil pressure Safety Device
11. How to remove oil from Refrigeration System?
12. Why refrigeration compressor takes suction from its crankcase?
13. Thermostats
14. Pressure Relief Safety Device
There are three types of relief devices
15. Refrigeration system: Hot gas Bypass valve

Hermetic compressor mostly used in household refrigerators, both motor and compressor is enclosed in a steel housing also known as a hermetic container where no gas or liquid can enter or escape from the welding seals welded around the container.

The hermetic compressor has a direct drive with no coupling and no mechanical seal.

The hermetic compressor has a low-pressure housing, which means that the interior of the compressor housing is subjected only to suction pressure whereas discharge can cause stress hazard inside the compressor.

The refrigerant and compressor oil inside the compressor housing is totally in contact with the motor rotor and stator windings. So, to avoid any short circuit within the motor winding the refrigerant used must have high dielectric strength and must be fully compatible with the insulation material.

The electric motor is directly connected to the compressor with a single shaft avoiding the use of any coupling or mechanical seal and leaving no chance of refrigerant leaking into the atmosphere.

The crankshaft is designed to circulate lubricating oil from the pump to all bearing surfaces.

A typical household hermetic compressor may be used continuously for more than 20 years, but often at the end of its service period, it is moved to secondary duty like it can be used as a refrigerant evacuation pump after some modification, traded and resold, or discarded.

Since the motor, as well as the compressor, is not accessible for repair or maintenance, a failure of the inbuilt motor winding like short circuit can cause decomposition of the refrigerant and serious contamination to the crankcase lubricating oil.

Therefore to avoid such damage, internal and external motor protection devices shuts off the motor power supply in case of any fault.

description of HVAC refrigeration components,coupling and mechanical seal,hermetic compressors,equalizing line,sight glass,moisture indicator,solenoid valve

14/06/2019

Basic refrigeration cycle:

How refrigeration compressors work
1.HERMETIC Refrigeration compressor or (fridge compressor)
2. Commercial Refrigeration Compressor
2a. Question: Why a coupling is needed in a commercial refrigeration compressor and motor?
2b. Question: What is the function of a Mechanical Seal in a refrigeration compressor?
3. Thermostatic expansion valve (TEV or TXV)| Metering valve?
4. Why an equalizing line required in thermostatic expansion valve (TEV) or metering valve?
5. FILTER-DRIER in a refrigeration system
6. Sight glass|Moisture indicator
7. Heat exchangers in a Refrigeration system
8. Solenoid Valve
9. Back Pressure Valve
10. Compressor Safety Devices:
10a. Refrigeration Compressor Unloader Safety device
10b. Compressor High Pressure cut out Safety Device
10c. Compressor Low Pressure cut out Safety Device
10d. Compressor Differential L**e oil pressure Safety Device
11. How to remove oil from Refrigeration System?
12. Why refrigeration compressor takes suction from its crankcase?
13. Thermostats
14. Pressure Relief Safety Device
There are three types of relief devices
15. Refrigeration system: Hot gas Bypass valve

Refrigeration basic schematic diagram separated into :

1. Compressor.
2. Condenser.
3. The thermostatic expansion valve (TXV or TEV) or Metering 4.Device.
5.Ev***rator.
6.Piping

The compressor in a Refrigeration system is to compress the low-pressure dry gas refrigerant from the ev***rator and raise its pressure and temperature to that of the condenser, to produce flow around the system.

The most easily recognizable compressor is a positive displacement type, which is the reciprocating or piston compressor.

Let’s take an example of a refrigerator when the refrigerant passes from the ev***rator, it changes its state from liquid to v***r by taking away the heat from the refrigerated space.

Now to convert back the refrigerant from v***r to liquid state, the compressor comes into action.

The compressor increases the refrigerant temperature and pressure so that the refrigerant gets converted into a liquid state by circulating hot surrounding air over the condenser coils.

In the absence of a compressor, the heat may start to flow from the condenser to the outside air.

Like in hotter regions the outside air temperatures can go up to 42°C – 48 °C with this hot outside air, the refrigerant gets cooled back from v***r to the liquid state.

This is possible due to the refrigerant property which is the “critical temperature of a refrigerant”.

Refrigeration cycle basics in an HVAC refrigeration system with explantion of heat and ton of refrigeration in btu. Metering valve(TEV), Ev***rator coil

14/06/2019

“Refrigerant charging”
1. Why do we need to evacuate an air conditioning system or a refrigeration system?
2. Liquid refrigerant charging
3. Refrigerant Gas charging
4. What is Copper Plating process in a refrigerating system?
Refrigerant Charging Methods:
Case 1: Refrigerant gas charging in ac | air conditioner
CASE 2: Air Conditioning system: Low refrigerant charge
Major HFC refrigerants:
5. Liquid refrigerant charging procedure for an air conditioner, window a.c (HVAC system)
6. Liquid charging on large commercial plants:

Why do we need to evacuate an air conditioning system or a refrigeration system?

All the refrigeration system are designed to run without moisture and non-condensable gases else it may not work as designed and is likely to fail prematurely.

Presence of moisture in the air conditioning system may lead to the formation of acidic sludge in the oil and may cause restrictions on various places like expansion valve and ev***rator coils thereby reducing the overall cooling effect.

In case of a hermetic compressor, it may cause deterioration of the insulation winding which may lead to short circuit and compressor motor burn out.

Non-condensable gases are just air which can enter during refrigerant charging, repair or maintenance. These gases take up space in the condenser and limit the amount of liquid refrigerant leading to reduced cooling efficiency.

Evacuation is carried out by using a vacuum pump and a recovery bottle, ones the system evacuates we need to wait for about 20-25 min to check the pressure gauge is holding the negative pressure (vacuum) as shown in the image.

This process may ensure that there are no leakages in the system as chances are air or moisture could enter via pipe cracks or leaky gasket or joints while performing evacuation procedure.

Refrigerant charging is the process of adding or replenishing refrigerant in a refrigeration, air conditioning, or HVAC (Heating, Ventilation, and Air Conditioning) system.

14/06/2019

Factors affecting an air conditioning system.
1. Relative humidity
2. Dew Point
3. Specific humidity
4. Dry bulb temperature
5. Wet bulb temperature
6. What is a Comfort zone in Air Conditioning System?
Five Major Dry Air Problems From Air conditioner | AC On our Body
Effect of Legionella bacteria in Air Conditioning Systems
8. Commercial ducted air conditioning systems
8a. Single Ducted Air conditioning System
8b. Dual Ducted Air conditioning System
9. Role of Psychrometric Charts in AC systems
9a. Warm climate
9b. Cold climate

The atmosphere contains a number of water particles in suspension from the ev***ration of water at sea, lakes, ponds, etc. which takes place at all temperature. The amount of water particles held in suspension varies but is limited by the capacity of the air itself.

At any given temperature the air can only hold a certain amount of water particles at which point it is said to be saturated, any reduction in temperature will then cause excess v***r to be condensed back into the water leading to Rain.

Air conditioning is vital to the comfort for those living in higher humid areas.

Effects of dry air:

1. Eyes become dry.
2. Skin dryness.
3. Itching and scratching of the skin.
4. Nose bleeding.
5. Legionella

This article covers the 9 factors you need to consider before installing an AHU, such as location, size, noise, efficiency,diseases and maintenance.

Refconhvac

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