Commercial Refrigerator Troubleshooting

Is this a commercial refrigerator troubleshooting call for a unit that's totally "dead"?



If it's plugged into a wall outlet, you'll need to check the outlet for power, and it's always a good idea to verify that the ground and neutral are wired correctly.

If it's wired to a disconnect, you'll need to check for power in the disconnect, and once again, it's always a good idea to verify that the ground and neutral are wired correctly.

If there's no power in the outlet or disconnect, you're going to have to find out why, and correct it.

If there is power in the outlet or disconnect, check the plug, or the connections in the disconnect; then check the wiring and connections into the unit to see if there's a broken wire or loose connection.

A non-contact voltage detector is a quick way to find broken wires and open connections, on commercial refrigerator troubleshooting calls, or on any HVACR service call.

If there is an on/off switch on the unit, check it to see if it's working.

Be sure you have a good neutral.

You might read a good voltage from your hot line to ground, but if your neutral line is bad, your unit won't run.

Is this a commercial refrigerator troubleshooting call for a unit that's freezing up?

Make sure the evaporator fan is running, and that it's rotating correctly.

You may have to melt the ice off the evaporator first.

Make sure the coil is clean, and that the drain line is clear.

If only the first section of evaporator piping is freezing up, you very likely have a low charge, or possibly a restricted drier, liquid line, or metering device.

Check your pressures, temperatures, superheat, and subcooling.

Our System Evaluation Manual has a cycle diagram and guidelines for evaluating pressures and temperatures for air conditioning and refrigeration systems.

Is this a commercial refrigerator troubleshooting call for a unit that might have a compressor problem?

Before you attatch your gauges, is the compressor doing anything at all?

Is it pulling any amperage?

Is the compressor hot?

If it's making a sound like "mmmmmm-TINK.....mmmmmmmm-TINK", it's trying to start, but tripping off on its overload.

Disconnect the wiring from the compressor terminals and check the resistances of the windings.

If there's an open winding, you'll have to replace the compressor.

If the compressor is very hot, the internal overload may be open.

It will take time for this to cool down and close, so don't condem the compressor yet.

You can either wait until it's cool, or cool it down with ice.

Once the overload closes, if the windings test OK, replace the start components and try to run the unit.

If the compressor runs, the unit should cool ok if there are no other problems.

If the compressor makes the "mmmm-TINK" noise again, it's locked up, and must be replaced.

If the compressor is running, with very low amp draw, very high suction pressure and very low discharge pressure, it has failed, and must be replaced.

Try to determine why it failed.

Is the condenser fan running?

Is the condenser coil clean?

Is hot air blowing into the condenser coil from another appliance?

If you're on a commercial refrigerator troubleshooting call and the compressor is running with low amp draw, low suction pressure and low discharge pressure, you may have a low charge, or a restricted liquid line, drier, or metering device.

Check the superheat and subcooling, and make the necessary repairs.

Is this a commercial refrigerator troubleshooting call for a unit that's cooling but not maintaining the correct refrigerator temperature?

Verify that the operating pressures, temperatures, superheat, and subcooling are in the normal range.

Make sure the gaskets are in good condition, are correct for the door, and are sealing good.

If the temperature control is turned to its coldest setting, and it turns off the compressor at too warm a temperature, it has failed.

Replace it.

On every commercial refrigerator troubleshooting call, check the fans; make sure they're running, turning in the right direction, and that the blades and motors are the right size.

Check the coils, and make sure they're clean.

Make sure no controls or safeties are by-passed.

Make sure the panels, grills, and enclosures around the fans and coils are installed and providing good air flow.

Verify that the supply voltage, operating pressures, temperatures, superheat, and subcooling are in the normal range.



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How Does A Water Cooler Work?

How Does A Water Cooler Work?

In our universe, heat can travel in only one direction: from a higher temperature to a lower temperature. Therefore, it seems that water coolers, along with refrigerators and air-conditioners, by freezing fluids (air and water), defy one of the most fundamental laws of nature!

Of course, this is untrue. In fact, it’s impossible, yet these machines are ubiquitous today – indispensable, in fact, to some. What magic is then obscured behind those curved walls of metal and plastic that enables the machine to achieve such a transformation?


Water cooler working principle

The working principle of a cooler, or for that matter, a refrigerator or air-conditioner, is quite simple: introduce the object whose temperature you wish to decrease to an even colder object, so that when the heat from the hot object is transferred to the colder object, the former is rendered cold. Similarly, water is made colder by acquainting it with an even colder fluid. It surrenders its heat to this colder fluid, thus becoming colder itself. Heat is still traveling in the only direction it can, meaning that no fundamental laws of physics are violated.
However, bear in mind that we desire cold water at room temperature or an even lower temperature, which means that this magic liquid must boil — thereby extracting water’s heat — at room temperature. What’s more, it must also freeze at a meager temperature, since it must be refrozen to be reheated. Otherwise, one would be required to refill the machine with more magic fluid each time all of it is heated, thus rendering it unusable for further use.



The magic fluid that boils and freezes at a very low temperature is called a refrigerant. Consider, for instance, one of the most commonly employed refrigerants, which is called R22. While water boils at 100 degrees Celsius, R22 boils at an astounding -40.8 degrees Celsius! However, refrigerants are not amazing because they boil from a liquid into a vapor or condense from a vapor into a liquid at a low temperature, but rather because they do so very rapidly and seamlessly. How and why is irrelevant to our present discussion. Now, let’s wrap our heads around how the components of a water cooler exploit this property to cool water.

The water is introduced to the cooler by filling a container called the cooler reservoir. The reservoir is effectively a mini-fridge and is therefore often called the bank fridge. The reservoir is surrounded by coils in which the refrigerant flows.

The cooler has four major components: the compressor, the condenser, the expansion valve and the evaporator.

First, the low-pressure and low-temperature refrigerant gas is pumped into the compressor. The compressor, as the name suggests, compresses the gas, thereby raising its pressure. What the compressor does, by pushing the piston over the gas, is reduce the volume that the same number of molecules previously occupied. This causes them to collide more frantically with each other. These collisions elevate the pressure and temperature of the gas. This is exactly why a bike pump becomes hotter when we pump it vigorously.

The high-pressure, high-temperature gas is then passed onto the condenser. As the name suggests, it condenses the gas, meaning that it decreases its temperature. This is achieved by making it flow in long, circuitous coils. The area of the tubes is optimized to achieve maximum condensation. An additional loss of heat is achieved by blowing on the pipes with a fan. The condenser causes the gas to lose its heat in the same way that blowing on your hot coffee makes it more tolerable. The extracted heat is vented out into the surroundings, which is why the back of your fridge is always so warm.

The gas is now converted into a liquid of moderate pressure and temperature. The temperature of this refrigerant is further decreased by squeezing it through an expansion valve. An expansion valve is very similar to the nozzle of a spray can. The liquid inside the can is pressurized, but when one pushes the nozzle, the liquid spurts out into a region of low pressure. When the compressed liquid enters such a region, it immediately expands. This expansion, representing a decline in pressure, simultaneously causes a drop in temperature. You have probably experienced how cold the liquid is that leaks from the nozzle incidentally. Therefore, our refrigerant, after exiting the valve, becomes a cold, low/moderate-pressure liquid.

Now, the final component, the component that produces our cold, thirst-quenching water. This last component is called the evaporator. The evaporator in an air-conditioner is a system that comprises a fan to suck in the air of the region intended to be cooled. The temperature of this air is significantly higher than the boiling point of the refrigerant. The cold refrigerant enters the evaporator in pipes, which are exposed to the “warm” air the evaporator sucked in. Heat flows in only one direction. The heat of the air is transferred to the refrigerant, thus making it hotter. The air, now divested of heat, is recirculated into the region through a vent. Voila! Cold air!

The image below neatly summarizes the entire process of cooling.

 However, a water cooler doesn’t necessarily employ a separate, dedicated mechanical unit to evaporate the cold refrigerant. The coils that surround the reservoir often form the condenser itself. The “warm” water surrounded by cold coils transfers its heat to them, and what pours out of the faucet is cold and rejuvenating water. The refrigerant in the pipes, now heated, is pumped into the compressor and the cycle repeats.

 Akash Peshin  9 Months Ago
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