Why Is Your Chiller Not Cooling? Reasons & Solutions

When you are planning to change or upgrade your industrial cooling system, you have to know why your current chiller is not cooling efficiently. Delaying the troubleshooting process may lead to an increase in operational costs and unexpected system disruptions. This article helps you understand the reasons and solutions.

Chiller Components are Dirty or Blocked

Condenser Coils are Dirty

If condenser coils are dirty, they will act as a heat insulation layer and prevent your chiller from releasing heat. Dust, debris, and grease on the fins of the coil can highly hinder the heat transfer of the refrigerant. To compensate for poor heat rejection, the compressor has to operate longer with a higher temperature, largely increasing wear and the failure risk.

Solutions

There are two cleaning methods:

• You can use a soft brush to remove the dust in the direction of the fins (to avoid bending) and then compressed air to blow out fine particles.
• Cut the power first and then use a biodegradable and non-corrosive coil cleaner to dissolve the stains. Then rinse them thoroughly with clean water.

The Heat Exchanger is Dirty (Fouling)

The heat exchanger is where the actual “cooling” happens. If the heat exchanger is dirty, it will directly make the chiller lose the ability to absorb heat.

Dirt buildup inside the heat exchanger is caused by internal water, which is also called “fouling.” Such fouling includes lots of types, including scaling (minerals like calcium and magnesium form a hard, white crust on the internal surfaces), sedimentation (mud, silt, or rust particles accumulate in low-flow areas), and biological growth. All of these can reduce heat transfer efficiency across the heat exchanger surface.

Signs

You can judge if there is fouling by observing the pressure difference between the water inlet and outlet. If the pressure difference is large, there may be an internal blockage. Another way is to check if the difference between the leaving water temperature and the refrigerant temperature exceeds the design specs of your chiller.

Solutions

• Use a separate container and water pump to circulate the chemical scale removal solution to the waterside. The solution can be Hydrochloric and citric acid-based cleaners (which are good for stainless steel equipment).
• To clean a shell-and-tube heat exchanger, you can use a rotary tube cleaner to clean the interior of the tubes.
• You can reverse the water flow direction to remove loose deposits from the heat exchanger.
• Good water treatment is of great help to keep a clean heat exchanger. This includes adopting appropriate water filtration and chemical treatment.

Filters are Blocked

For an industrial water chiller, there are three kinds of blocked filters, all of which can make the cooling harder.

Air Filters (Air-Cooled Chillers)

Air filter blockage occurs in air-cooled chillers, which refers to the dust and debris clogging the panels that protect the condenser coils. This impedes air circulation, leading to the system overheating and causing a longer cooling time.

Solutions

You need to remove the filter and clean it with low-pressure water or mild soap. If you find that the filter is damaged, then it needs to be replaced.

Water/Process Filters

If there is a significant drop in pressure between the water inlet and outlet, it may be because of a water filter blockage, which refers to the filters in the water circuit being clogged with sediment, rust, or biological mucus. This can obstruct water flow and lead to evaporator freezing.

Solutions

First, you need to clean the filter screen. The process is to isolate the chiller, drain the water, and then unscrew the filter screen cover to clean the mesh filter.

Then, you need to replace the fine filter element. For high-purity chiller systems using sediment filters, the fine filter elements must be replaced regularly.

Refrigerant Filter Drier

The internal filter traps moisture and acidic substances within the refrigerant circulation system. If it is blocked, the evaporator cannot receive a sufficient supply of refrigerant.

Solutions

If the internal filter is blocked, you need to recover the refrigerant, replace the dryer, and conduct a deep vacuum treatment of the system. This must be completed by a qualified technician.

Critical Chiller Components are Failed

The Compressor has Failed

The compressor is the “heart” of your chiller. If the compressor fails, the chiller will stop cooling completely.

There are many reasons that can break the chiller compressors. For example, excessive heat or voltage fluctuations may melt internal motor windings; If the evaporator becomes dirty or the expansion valve fails, liquid refrigerant will enter the compressor and damage the internal piston; Not enough oil flow back to the chiller compressor can cause the components to become stuck; Frequently turning on and off your chiller can impose a huge burden on the compressor motor and lead to a failure.

Solutions

To deal with a failed chiller compressor, you need to ask for help from a professional. The professional technician will check the compressor and decide whether it needs to be replaced. If there is a burnout, you must flush the refrigerant lines with a special cleaning solvent to remove acidic substances.

The Expansion Valve has Failed

The expansion valve regulates the amount of liquid refrigerant entering the evaporator. If the expansion valve fails, the chiller system will have evaporator starvation and cannot cool.

Usually, a failed expansion valve is caused by a blockage. If the evaporator lacks refrigerant, the compressor cannot provide cooling. In contrast, if excessive refrigerant enters the evaporator, the liquid that cannot evaporate will flow back to the compressor and cause damage. Something like wax, moisture, or debris can clog the openings inside the valve too.

Solutions

• A loose bulb will give the valve the wrong instructions, so you can first check the bulb to ensure it’s working well.
• Frozen moisture can lead to valve shut-off. To solve this, you can use a warm cloth to heat the valve body.
• If the internal diaphragm or sensing bubble malfunctions, you need to replace the valve.

Sensors are Failed

If sensors fail, your chiller controller will give incorrect instructions. Your chiller may operate continuously because the sensor indicates that the target temperature has not been reached. This will lead to a poor cooling effect and energy waste.

Usually, sensors can be damaged by moisture or continuous vibration. In water-cooled chiller systems, mineral scales can insulate sensors and make them react slowly.

Solutions

• You can put the temperature probe into ice to check if it demonstrates 0°C (32°F). If not, you should recalibrate it.
• You can check the state of the wiring connections of the controller. If there are problems like loose screws, worn wires, or green corrosion, you can strip and reattach a wire.
• You can replace the sensor probe.

Breakers are Tripped / Fuses are Blown

Breakers tripping and fuses blowing always happen when your chiller needs protection from excessive heat or electrical faults.

Mechanical overload, short circuit, voltage spikes, and loose connections can all lead to breakers tripping.

Solutions

To solve this problem, you must be very familiar with electrical panels, or you need to ask technicians.

• First, you should check if there is an overload and a stuck fan or pump. Then, you can check if there is discoloration, melting, or burning at the main connection terminals of the circuit breaker and the chiller and tighten all loose screws.
• You can reset the circuit breaker by completely turning it off and on (If it trips again immediately, do not force the operation).
• The fuse has to be replaced with one of the same type and specification.
• If breakers only trip during peak hours, you can install a voltage stabilizer to control the power supply voltage.

There are Refrigerant Leaks

Suppose the refrigerant leaks, the ability of the evaporators to absorb heat will decrease. The evaporator pressure will drop, causing the outer wall of the evaporator pipes to freeze. This further hinders heat exchange.

Solutions

• For minor leaks caused by loose joints or aging gaskets, you can tighten the nuts or replace the sealing rings.
• Cracks on metal pipes or evaporators should be silver soldered or brazed.
• If the evaporator, condenser, or compressor is severely damaged, it’s best to replace them.

Chiller Water Flow is Insufficient

Insufficient water flow will lead to insufficient heat exchange, and the refrigerant in the evaporator cannot fully vaporize, which can cause low suction pressure for the compressor.

Besides, insufficient water can lead to the shutdown of anti-freezing protection and frequent start-stop of the compressor, disrupting cooling.

Solutions

• The scale in the pipes will restrict the flow, so you can check and clean the Y-type filters.
• If the air takes up the space of the water, it significantly reduces the actual circulation volume. For this, you can open the automatic exhaust valves at the top and end of the system or manually release the air.
• Sometimes, the bypass valve opening too wide can lead to insufficient water flow. You can properly adjust the valves.
• If insufficient water flow appears in a new chiller, it may be that the pipe diameter is too small or there are too many elbows. If necessary, you can install booster pumps or adjust the balance valves.

Chiller Wiring is Loose

Loose wiring connections can generate contact resistance, dropping local voltage, and the compressor and water pump motors cannot reach the rated speed. This largely reduces the cooling capacity.

Loose wiring of sensors, controllers, or flow switches can lead to signal loss or error reporting, which will lead to a sudden shutdown. And loose wiring in different connections can cause inconsistent component operation, which lowers the cooling effect.

Solutions

• Check all the screws on the contactors, air switches, frequency converters, and the terminal block, and fix them.
• If you find that the ends of the wires are blackened, the insulation is hardened, or the plastic parts of the terminal blocks have melted, you must cut off the burned sections, re-press the terminals, and replace the damaged contactors.
• You can use an infrared thermal imager to scan and discover the location before a fault occurs.
• Mechanical vibration is usually the main reason for loose wiring. So, you can check the shock absorption and sealing of the electrical control box and use a more shock-resistant cage clamp.

Ambient Temperature is Too High

Too-high ambient temperature reduces the temperature difference between the refrigerant and the air, so the heat exchange efficiency significantly drops. This increases condensing pressure and temperature. As the condensing pressure rises, the compression ratio of the compressor increases, which reduces the mass flow rate of the refrigerant delivered. Thus, the cooling capacity is largely lowered.

If the temperature exceeds the critical point designed for the chiller, the system will force a shutdown.

Solutions

• To reduce the impact of high ambient temperature, you can improve heat dissipation by cleaning the condenser fins and enhancing ventilation.
• You can also add some equipment, such as shading facilities, fine mist spraying systems, or cooling fan speed. And you can spray high thermal conductivity anti-corrosion coating on the fins of the condenser.
• In hot temperatures, you can appropriately raise the set temperature of the chilled water to reduce the pressure difference burden on the compressor.

The Heat Load of Your Chiller is Excessive

An excessive heat load can cause the chilled water temperature to fail to meet the standard even when the unit is operating at full load. Besides, the circulation system will be unbalanced due to the excessive heat load, making the chiller more likely to shut down.

Solutions

To solve the excessive heat load, you can first try to improve the chiller heat dissipation and conversion efficiency.

• You can clean the heat exchangers to ensure no scale or dust disturbs cooling.
• For water-cooled chillers, you can improve heat dissipation by fan optimization or cleaning the fillers to reduce the temperature of the cooling water entering the chiller, thus achieving more cooling capacity.
• You can add a temporary small-sized chiller unit to assist in heat dissipation or install an insulated water tank to assist in releasing cold during peak load periods.
• If your current chiller system actually cannot match the load, you have to change to a chiller with larger power.

Chiller Size is Not Proper

An undersized chiller can always lead to cooling problems. If the chiller size is small, the chilled water temperature can never drop to the target value. An oversized chiller can also cause issues such as short cycling and poor temperature control accuracy.

Solutions

• To solve undersized chillers, you can add a smaller chiller unit to bear the load, enhance pipeline insulation, improve the cooling environment, and adjust the production plan to stagger the operation times of high heat-generating equipment.
• For oversized chillers, you can install buffer tanks or VFDs or adjust the bypass valve for hot gas.

FAQ

How to Troubleshoot a Chiller That Is Not Cooling?

To troubleshoot chiller problems, you need to check many parts. First, you can check the power supply and control panel. Second, you can check the water circulation, including the pump, valve, water flow, and pressure difference. Third, you can check if the heat dissipation is good. Fourth, you can check the refrigeration cycle, including the refrigerant, compressor status, and heat load in operation.

If you have any difficulties, you can contact our teams to receive professional advice and help.

What are the Signs of a Failed Compressor?

If you find the following phenomena appear, it may be that your compressor is going wrong:

• The compressor emits a loud buzzing noise after the relay starts and then trips and disconnects the fuse.
• Excessive vibration and noise, such as friction or metal “clinking” sounds.
• The shell is very hot.
• Circuit breaker tripping.

When is the Problem of Not Cooling Is Not Repairable?

Some problems are unable to be repaired, so you have to replace the chiller system. Generally, such problems include catastrophic component failure (such as the motor winding of the compressor has burned out, large-scale perforation of the internal tubes in the heat exchanger, etc), severely corroded shell, extensive frost cracking, (technological or economic) obsolescence, and inappropriate chiller size.

How to Choose the Right Chiller to Avoid Cooling Problems?

To prevent cooling problems, you need to think twice when choosing the chiller. First, the calculation of chiller capacity must be accurate. The pump set is properly matched and has a sufficient head to overcome the resistance of the pipeline on site. The type and component quality are also very critical. And you may consider whether your industry needs the VFD or a modular design.

How Often Should a Chiller Be Serviced?

To avoid cooling problems, we recommend that you have a basic inspection every week, including recording pressure and temperature, observing the sight glass, and checking for abnormal vibrations or noises.

Every quarter, you can clean the filter and condenser and inspect electrical connectors.

Every year, before the summer peak period, we recommend that you have a thorough cleaning and inspection, which includes deep cleaning of heat exchangers and condensers, inspection and replacement of lubricant and filter, sensor calibration, and safety tests (high-pressure protection, anti-freezing protection, and flow switches).

Final Thoughts

From refrigerant issues to system design limitations, every detail can affect the overall chiller cooling efficiency. Therefore, choosing a reliable chiller with appropriate design and stable components is of great importance. As an experienced chiller manufacturer in China, Chillerone has helped multiple factories achieve their tailored chiller cooling solutions. Contact us, and get your customized one-stop cooling solution without cooling problems.