Troubleshooting Common Chiller Problems and Solutions Guide

Find out about the most Common Problems when troubleshooting water chillers and Solutions Guide here. There are 3 main problems as follows.

1. Clogging problem

2. High-pressure system problem

3. Temperature system problem

 

 

 

A. Clogging Problem

• Failure due to oil clogging

The main reason for oil clogging:

The compressor cylinder body wears heavy or cylinder with too large clearance. With the compressor discharge gasoline into the condenser is discharged, and then with the refrigerant into the filter drier, because the oil viscosity is greater, through the filter desiccant blockage, too much oil into the filter inlet blockage, so that the refrigerant can not circulate normally.

In the water chiller system remaining too much refrigerant oil, so that the effect of cooling, and also can not be cooling, so the system must be cleared of refrigerant oil.

Oil clogging treatment:

filter oil clogging should be replaced with a new filter, while using high-pressure nitrogen gas to the condenser part of the accumulation of refrigerant oil, preferably in the passage of nitrogen gas, using an electric hair dryer to heat the condenser.

Hazards of the oil film:

• When the surface of the heat exchanger adheres to the oil film, the condensing temperature increases, and the evaporating temperature decreases, resulting in increased energy consumption.
• When the surface of the condenser adheres to a 0.1 mm thick oil film, the cooling capacity of the refrigeration compressor decreases by 16%, and the power consumption increases by 12.4%.
• And evaporator oil film reaches 0.1mm, the evaporating temperature will drop 2.5 ℃, power consumption will increase 11%.

 

How to Solve Oil film? 

The use of high efficient oil separator can greatly reduce the amount of oil entering the system pipes.

If an oil film is already present in the system, nitrogen flushing can be performed several times until no misty gas is

present.

 

• Error due to ice blockage

Ice blockage fault mainly occurs because the water chiller contains excessive moisture, with the continuous circulation of refrigerant, the moisture in the water chiller gradually concentrated in the throttle outlet, due to the lowest temperature at the throttle outlet, water into ice and gradually to a certain extent will be completely blocked capillary tube, the refrigerant can not be circulated.

 

Main sources of moisture:

• Residual moisture in the water chiller system components and connecting pipes due to insufficient drying.
• Refrigerant oil and refrigerants containing more than the permissible amount of moisture.
• The presence of moisture due to installation construction without vacuum or improper installation.
• Moisture in the insulating paper of the motor inside the compressor.

 

Manifestations of ice jams:

• Gradual weakening and interrupted airflow.
• The sound of airflow disappears when the blockage is severe, the refrigerant circuit is interrupted and the condenser gradually becomes cooler.
• Increase of exhaust gas pressure and operation noise of the machine due to clogging.
• No refrigerant flows in the evaporator, the frost area becomes smaller gradually and the cooling effect becomes worse.
• After stopping the machine for some time, the refrigerant begins to produce again (cold ice begins to melt).
• The ice blockage forms a moment to pass, a moment to block, block and pass, pass and block the cycle of repetition.

 

How to Solve when Ice Blockage?

Water chiller occurs ice blockage failure because there is excess moisture in the system, so the entire refrigeration system must be dried. Its treatment methods are as follows:

Evacuate, replace the filter dryer, for the moisture indicator in the refrigeration system will be qualified apparent liquid level turns green.

If the system has moisture in a large amount of water, we should use nitrogen segmentation to flush dirt, replace the filter, replace the refrigerant oil, replace the refrigerant, evacuate until the water indicator in the sight glass turns green.

 

• Error due to Dirty Clogging 

Dirty blockage in the water chiller because the refrigerant can not circulate, so the compressor continuous operation, the evaporator is not cold, the condenser is not hot, the compressor housing is not hot, listen to the evaporator no air flow sound. When there are more impurities in the system, the filter dryer is gradually blocked, and the choke mechanism filter is blocked.

 

Main causes of dirt clogging:

• Dust and metal French fries during construction and installation, detachment of the oxidation layer on the inner wall surface during welding of the pipeline.
• The parts are not cleaned on the inner and outer surfaces during processing, and dust enters the pipe if the pipeline is not properly sealed.
• Impurities in refrigerant oil and refrigerant, poor quality desiccant powder in filter dryer.
• The distance between the capillary tube and the filter in the filter dryer is too small, causing dirty blockages.

 

Performance after dirty clogging：

• A cool or cold feeling in the evaporator when it is partially clogged, but no frost.
• The cool feeling when touching the outer surface of the filter dryer and choke, even when frost.
• The evaporator is not cold, the condenser is not hot, compressor housing is not hot.

 

How to solve when Dirty clogging?

Dirty clogging is generally in the filter drier, throttle mechanism mesh strainer, suction filter, etc. The filter of the choke mechanism and the suction filter can be removed and cleaned, and the filter dryer is generally replaced. After the completion of the replacement, the need for water chiller leak detection, vacuum.

 

 

 

B. High-Pressure Problem

Condensing pressure is what we usually call “high pressure”, condensing pressure system failure, there are generally three types of.

01. condensing pressure is too high.

02. condensing pressure is too low.

03. pressure fluctuations.

 

1. Condensing pressure is too high.

 

Why happen for High refrigerant pressure?

When the condensing pressure is too high, the possible causes are usually the following:

(a) Air or other incompressible gasses in the water chiller system.

(b) The condenser surface is too small.

(c) Too much charge in the refrigeration system (liquid recovery in the condenser).

(d) The condensing pressure control is set to too high a pressure.

(e) Fouling of the condenser surface.

The above reasons are common causes of faults in air-cooled and water-cooled chillers.

 

How to Solve High-Pressure Problem? 

(a) Clean the condenser by starting and running the system using the recovery system until the system reaches operating temperature. If necessary, remove again;

(b) Replace the larger condenser.

(c)Recover refrigerant until condensing pressure is normal. The sight glass must be kept full.

(d)Set the correct pressure.

(e)Clean condenser.

 

For air condensers (plate-fin heat exchangers), high-pressure alarms are usually also analyzed in the following areas.

1) The fan motor or blades are defective or too small.

2) The airflow to the condenser is restricted.

3)The ambient temperature is too high.

4)The airflow through the condenser is in the wrong direction.

5)Short circuit between the pressure on the airside of the condenser fan and the suction side.

 

How to Exclusion?

1) Replace the motor or the blade, or replace the motor and the blade at the same time.

2) Remove the air inlet obstruction or move the condenser.

3) Form a clean air inlet or move the condenser.

4) Change the direction of rotation of the fan motor. The air in the condensing unit must flow through the condenser and then into the compressor.

5) Install ducts that may be suitable for outside air.

 

For water-cooled condensers (plate-fin heat exchangers) with high-pressure alarms, the following aspects usually need to be analyzed as well.

1), The cooling water temperature is too high.

2), the water quantity is too small.

3), Precipitates in the waterline (dirt, etc.).

4), the cooling water pump is defective or no longer works.

 

How to Exclusion?

1) Ensure a lower water temperature.

2) Increase the amount of water, possibly with automatic water valves to increase the amount of water.

3) Clear the condenser water pipe, possibly with the role of deoxygenation to remove.

4) Investigate the cause and replace or repair the cooling water pump (if installed).

 

 

2. Low condensing pressure.

Why happen low condensing pressure?

a) The surface area of the condenser is too large.

b) Low load on the evaporator.

c) The inlet pressure is too low, as the evaporator in the liquid is not enough.

d) The suction or discharge valve of the compressor may be leaking.

e) The pressure setting of the condensing pressure control valve is too low;

f) The uninsulated vessel is too cold compared to the condenser (the vessel is used as a condenser).

g) The temperature of the cooling air is too low; (air cooling).

h) The air volume of the condenser is too large; (air cooling)

j) The amount of water is too large; (water-cooled)

k) The water temperature is too low; (water-cooled) (water cooling)

 

How to troubleshooting when Low condensing pressure happens？

Depending on the above faults, the following methods are used to fix one by one.

a) Adjust the condensing pressure or replace the condenser.

b) Adjust the condensing pressure.

c) Locate the fault in the line between the condenser and the thermal expansion valve (see “Low suction pressure”).

d) Replace the compressor valve plate.

e) Set correct pressure for the condensing pressure control valve.

f) Relocate the receiver or install a suitable insulated outer cover for the receiver.

g) Adjust the condensing pressure.

h) Replace the smaller fan or adjust the motor speed.

j) Reduce the cooling water flow.

k) Increase the cooling water temperature.

 

3. Condensing Pressure oscillation.

Why happen Condensing Pressure oscillation? 

a) There is a difference in starting/stopping the pressure regulator because the condenser fan is too large. Because the refrigerant recovered in the condenser can form vapor in the liquid line after the condenser fan has been started for a while.

b) Vibration of the thermal expansion valve.

c) Fault in the condensing pressure control valve KVR/KVD (flow orifice is too large).

d) Result of vibration of suction pressure.

e) Selection of check valve in wrong size or installation of check valve in the wrong position in condenser line.

 

 How to solve this troubleshooting?

 

Depending on the above faults, please proceed as follows to correct them one by one.

a) Set a lower differential or use the valve setting (KVD+KVR) or fan motor speed setting.

b) Set a higher superheat for the thermal expansion valve or substitute a smaller flow connection.

c) Replace the valve with a smaller one.

d) See “Suction pressure oscillation”.

e) Check the size. Install a check valve under the condenser near the receiver inlet.

 

 

 

C. Temperature System Problem

1: The exhaust gas temperature is too high.

On the exhaust gas temperature theoretical calculation formula.

T2 = T1 (P2 ÷ P1) ^ [(k-1) ÷ k]

Including:

T2: Exhaust gas temperature;

T1: Intake temperature;

P2: exhaust pressure;

P1: Intake pressure

K: Adiabatic index of the gas (K=1.4 for air).

This formula reflects the importance of the suction temperature (T1) and the importance of the pressure ratio (P2 ÷ P1).

These two data are directly related to the temperature and the quality of the air compressor used.

In fact, the higher the intake temperature, the higher the compression ratio and the exponentially higher the exhaust temperature!

The following can be derived from the above equation.

Factors affecting abnormal exhaust temperature: Adiabatic index, compression ratio, intake temperature.

The compressor discharge temperature can be read from the thermometer given to you by whoever is in the discharge line. It is related to the adiabatic index of the refrigerant, the compression ratio (condensing pressure/evaporating pressure), and the suction temperature.

The higher the suction temperature and the higher the compression ratio, the higher the discharge temperature and vice versa.

If the suction pressure remains the same, when the discharge pressure increases, the discharge temperature increases; if the discharge pressure remains the same, when the suction pressure decreases, the discharge temperature should also increase.

Both situations are caused by increasing the compression ratio. Excessive condensing and exhaust temperature is unfavorable to compressor operation and should be avoided. A high exhaust gas temperature will cause the lubricant to thin and carbonize, worsening the lubrication conditions for the compressor.

The discharge temperature is proportional to the compression ratio (condensing pressure/evaporating pressure) and the suction temperature. When the superheat temperature of the suction gas is high and the compression ratio is large, the discharge temperature is also high. When the suction pressure and suction temperature are constant, the compression temperature also increases as the compression pressure increases.

 

Here are the reasons for the increase in exhaust temperature:

(1) higher suction temperature, the refrigerant vapor due to the compression of the exhaust gas temperature will be higher.
(2) the condensing temperature increases, the condensing pressure is also high, causing the exhaust gas temperature to increase
(3) the exhaust valve piece is broken, high-pressure steam is repeatedly compressed and the temperature rises, the cylinder and cylinder head is hot, the exhaust pipe is that the thermometer reading also rises.

 

Here are the most common factors:

Low intercooler efficiency or too much scale in the intercooler will affect the heat exchange, then the intake temperature of the rear stage will inevitably be high, and the exhaust temperature will also rise.

Leaky air valves and leaky piston rings. This not only affects the exhaust temperature but also the pressure change between stages; as long as the compression ratio is above normal, the exhaust temperature will rise. In water-cooled engines, lack of water or insufficient water will cause the exhaust gas temperature to rise. The condensing pressure is not normal and the exhaust gas pressure is reduced.

 

Here is another article to inform you of the 3 main causes of compressor failure.

 

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