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Refrigeration Basics: Troubleshooting Fundamentals

         Don Gillis | Lead Technical Trainer

          Emerson’s Educational Services

Welcome to the second installment in our new series of blogs intended to help not just beginning service technicians, but anyone who wants to learn more about the basics of refrigeration. I will continue to share insights, best practices and other information from our Emerson training program as well as from our commercial and residential solutions experts. In addition, we’ve created companion videos about each topic that you can cross-reference while accessing other related information at Education.Emerson.com.

In this series, I’ll touch on topics ranging from how condensers, compressors and evaporators work, to superheating and subcooling, to the refrigeration cycle, vapor injection and basic refrigeration system troubleshooting.

In this blog, I explain several key topics related to troubleshooting common compressor issues:

  • The role of the condenser
  • Understanding superheat
  • Where to check superheat
  • Understanding subcooling
  • What discharge line temperature really tells us
  • Why compressor overheating is a problem
  • How low you can pump a compressor
  • The difference between floodback and a flooded start

How condensing removes heat from an environment

When we think of the role of a condenser, we’re essentially referring to the place where heat is rejected in a cooling system. What type of heat is rejected? Well, the motor generates heat, and so does the act of compression. The refrigeration system must also reject superheat as well as the load heat from the evaporator.

As part of the refrigeration cycle, the system also condenses the refrigerant. This process involves taking a vapor, removing the heat outside, and condensing it into a liquid by removing the heat and returning it to its condensing temperature.

You’ll notice on most condensers that the vapor enters at the top and leaves at the bottom, where the liquid is much heavier than the weight of the vapor.

What is superheat?    

Superheat is any heat added to a vapor above its boiling point. For example, water boils at 212 oF at atmospheric pressure. The second that last droplet of water evaporates, the temperature rises to 213 oF. That increase in temperature is 1 degree of superheat.

Superheat also is the temperature of the vapor leaving that evaporator on the suction side. A compressor needs superheat in order to function.

Where to check superheat

First, determine what superheat temperature is needed. A system designer more than likely will want to know the superheat leaving the evaporator. If you’re talking to a specialist at Emerson, they’re likely looking for the total superheat or the heat that’s entering the compressor.

Remember that superheat is a vapor, so you can check it on the low side — the evaporator side — of the system. Take a reading of the temperature from the suction line and subtract it from the saturated suction temperature inside the evaporator.

What is subcooling?

Subcooling refers to the heat that is removed from a liquid below its boiling point. For example, if we again use water with a boiling point of 212 oF at atmospheric pressure, its subcooled liquid temperature would be 211 oF.

Subcooling is determined by subtracting the condenser saturating temperature from the liquid line temperature — either leaving the condenser or entering the metering device.

What discharge line temperature really tells us

Discharge line temperature (DLT) is the temperature of superheated vapor leaving the compressor; it can tell us a lot about the conditions inside the compressor.

These temperatures are dependent on model, refrigerant type and application. Refer to Copeland for exact specifications

If the superheat temperature is also high, continue moving down the line to check the temperature leaving the evaporator. The high readings could be caused by a malfunctioning metering device, but more often than not, the DLT temperature is too high because of a high compression ratio.

Why compressor overheating is a problem

When compressor temperatures are higher than normal, it’s typically due to a high compression ratio. A high compression ratio indicates either a high head pressure and a very low suction pressure, or a combination of both.

So what are the typical causes of a high compression ratio? Often, it’s due to thinning of the oil inside the system, leading to more friction on moving parts inside the compressor. Friction adds heat, which can increase wear and tear on the parts and lead to premature compressor failure.

Compressors are designed with a thermal operating disc to provide internal protection. However, it’s crucial to monitor the compressor’s internal temperature; always check the discharge line temperature for an indication.

How low should you pump a compressor?

The answer depends on the model number of the compressor, the application and the refrigerant you’re using. Enter these details into the Copeland™ Online Product Information (OPI) website, where you can find the design specifications for the pump down number.

One more important note to remember with respect to pumping: Never pump a compressor down to zero or into a vacuum.

Know the difference between floodback and a flooded start

Floodback occurs when refrigerant leaves the evaporator and enters the running compressor as a liquid instead of a vapor — which can ultimately lead to system failure. Conditions contributing to floodback include air flow, ice buildup, overcharging refrigerant or misadjusted expansion valves.

Symptoms of floodback include overheating from a loss of lubrication and decreased system efficiency. Prevent floodback by modifying defrost cycles, checking refrigerant charging levels, adjusting or replacing expansion valves, and making sure that evaporator coils are cleaned and not damaged.

A flooded start is different than floodback because it can occur when the compressor is not running — and has not been operated for some time. The difference in the temperature (DT) from the crankcase oil, and the vapor refrigerant in the evaporator causes it to migrate towards the compressor oil. There, it condenses into a liquid and is absorbed by the oil. Then, when the compressor is started, the refrigerant boils into a vapor, diluting the oil in the crankcase and reducing the lubrication of bearings, rods and other critical surfaces.

Symptoms include erratic wear or seizure damage to the rods or bearings and the crankshaft. Prevent a flooded start by installing a continuous pump down cycle on the compressor to remove from the low-pressure side. Pump downs would typically not be used in residential applications.  A crankcase heater can be installed or the compressor can be located where ambient temperatures are controlled.

 

Leveraging Predictive Maintenance in Commercial Refrigeration

JimMitchell_Blog_Image Jim Mitchell | Technical Manager of Customer Success

Emerson Commercial & Residential Solutions

Predictive maintenance is showing big promise in the HVACR market. I recently provided input for an article for ACHR The News that discusses how predictive maintenance technology is being used in the commercial and residential markets. You can read the full article, “Predictive Maintenance Brings New Potential to HVACR Service Market,” here.

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HVACR systems are becoming smarter and more connected using internet protocol (IP) networks and the industrial internet of things (IIoT). These allow the real-time monitoring of equipment, or predictive maintenance, which gathers data points from equipment to keep tabs on system performance in order to help reduce the likelihood of failure.

For HVACR contractors, this means identifying a problem before it causes a larger issue, so that maintenance can be done to prevent equipment negatively impacting food quality and safety or other operational imperatives. For instance, a refrigeration rack alarm may indicate an issue that can be addressed, preventing operational issues that could have a negative impact on multiple cases of perishable product or thousands of dollars in-store merchandise.

How it works

Drawing from a combination of equipment sensors and control system data, performance analytics can provide store operators and enterprise managers deeper insights for:

  • Real-time and historic operating conditions in their facilities and systems
  • Pressure, temperature and energy data to compare to established benchmarks for a single store, stores within a region or enterprise-wide
  • Enterprise-level and store-level dashboards and prioritized notifications

 

For an example of how this differs from a rack alarm scenario, let’s look at a display case analysis based on temperature sensor data. Performance analytics may detect an anomaly in case temperature deviations which, while still within safe ranges, could suggest the presence of a larger performance issue. Instead of being notified with an urgent alarm, operators can be alerted on their operational dashboards. This insight gives them an opportunity to investigate the issue at their discretion, and even potentially pre-empt a potentially larger issue. It’s important to keep in mind that timing is key.

This is also an example of how operational dashboards can help retailers to align maintenance and operational activities around performance. Today’s facility management dashboards typically break down the urgency levels of maintenance issues, as previously noted. By extending these dashboards also to include performance analytics, end users can gain a much deeper understanding of how their systems are performing and operators can take pre-emptive actions where they deem appropriate — not just respond only to systems where urgent problems are already present.

Equipped with this information, operators can receive advance notice of certain performance issues that may soon impact them — on which systems or pieces of equipment, and in which stores. Enterprise views quickly provide managers with visual snapshots of urgent and important issues across their store networks, while enabling investigation into specific assets in their respective facilities. Whether you’re a maintenance technician or an enterprise manager, operational dashboards help allow you to focus on those specific maintenance activities which may potentially impact performance in the near future.

A change in approach

Commercial refrigeration systems consist of many connected components — often originating from multiple vendors — designed to meet a wide variety of applications, ranging from coffin-style display cases to walk-in freezers. Industry macro trends further increase this complexity, including the adoption of new refrigerants and the migration from centralized to decentralized and stand-alone systems. Commercial contractors will need to do more than simply install connected sensors and devices; they will need to change their approach toward commercial refrigeration, including the ability to combine new technologies with deep experience within the context of widely varying system requirements.

Rather than focusing only on what is happening at any given moment in a location — whether that’s a low- or high-priority alarm — analytics can help operators gain deeper insights into issues that could have future operational impacts. Access to these insights helps operators transition to a condition-based, analytics-driven approach — one where they can take proactive steps, perform preventive maintenance, use resources more efficiently, and stop smaller issues from becoming larger problems — instead of a more reactive approach.

What to watch for

IIoT features new technologies that will likely result in operators being able to deploy interconnected devices more widely, potentially at a lower initial cost. These offerings may drive value for operators by causing significant energy savings, lower maintenance and service costs, and improved operator experiences.

At Emerson’s innovation centers and in customer field trials, we are working with our customers to tackle the challenges related to predictive maintenance head on. By modeling refrigeration applications, we have helped our partners take a more methodical, deliberate approach to predictive maintenance. Our goal is not simply to throw more IIoT at the problem, but to help provide true insights from the data while leveraging our deep intellectual capital and experience in the commercial refrigeration space. We believe this helps us deliver the transformative value that predictive maintenance represents. By doing so, we can be a part of simplifying the complex and uncover insights that are representative of the industry’s most common refrigeration scenarios.

For example, a typical refrigeration system or rack has alarms that identify current issues only, and slow leaks often can be difficult to discern from normal fluctuations. But with a machine-learning supervisory app, multiple models can account for variable operating envelopes with up to ~90% accuracy and identify leaks as many as 30 days before physical detection devices.

While it is difficult to predict five years in the future accurately, it is safe to assume that with the adoption of 5G technology and other advances in component miniaturization and cost reduction, solutions will continue to get smarter. With a flood of data occurring at both the enterprise level (reporting) and the device level (gathering data), we will need more intelligence in interpreting this information in order to help deliver better, more accurate results.

In the meantime, one thing that contractors can do is avoid the rush to recommend IIoT implementation that can result in applications which can create more “noise” — i.e., a barrage of events to monitor and triage — and trigger false errors or events that identify issues too early (or too late).

 

 

Information in this article was first published in ACHR The News, March 16, 2020.

Strengthening the Cold Chain With Connected Technologies

AmyChildress Amy Childress | Vice President of Marketing & Planning, Cargo Solutions

Emerson Commercial & Residential Solutions

Maintaining food quality and safety is a primary challenge facing retailers who rely on the global cold chain to fulfill the growing demand for fresh food offerings. New technologies are emerging to provide improved visibility and traceability of perishable items, help stakeholders communicate, and ensure adherence to food safety best practices and/or regulatory requirements. I recently contributed to an article by Progressive Grocer which speaks to the importance of leveraging these technologies to achieve those goals and maintain an unbroken cold chain.

With the Food and Drug Administration’s (FDA) recent announcement of its New Era of Food Safety initiative, the technology that provides traceability and other key services is becoming more important than ever. This rapidly advancing technological toolset includes internet of things (IoT) condition sensors, temperature-sensitive flexible barcodes and blockchain. Combined, these tools are helping growers, shippers and retailers help ensure the freshest and safest possible product for consumers.

As I stated in the article: “This is especially critical with the global demand for year-round access to perishable products. Achieving this feat can require fresh produce to be transported by land, sea and air, encompassing the point of harvest, processing, cold storage and distribution — all before it ever begins the last-mile delivery to a store or restaurant.” In fact, a perishable shipment may be subject to as many as 20 to 30 individual steps and multiple changes of ownership before it reaches its destination.

Gaining visibility with IoT monitoring and tracking infrastructures

To better manage the sheer complexity of this cold chain journey, stakeholders are leveraging connected IoT monitoring technologies and tracking infrastructures. Operators now have better potential visibility into each step of food’s journey — even the possibility for comprehensive cold chain traceability. These tools — such as Emerson’s GO Real-Time Trackers and GO Loggers combined with our cloud-based Oversight online software portal — are giving stakeholders at each point the abilities to monitor and track a variety of conditions necessary for preserving food quality, including: temperature, humidity, CO2 levels, lighting and much more.

As I pointed out in the article, one of the key values of this technology is the ability to receive email or text notifications in real time when an in-transit shipment falls out of the ideal temperature range: “This allows suppliers to correct the issue promptly with the carrier or even reroute the shipment to a nearby location and preserve that perishable cargo.” Retailers and growers can also track these in-transit shipments to monitor delivery timelines and ensure that carriers are following proper shipping routes. Retailers rely on these devices to help them validate produce quality on receipt and monitor all their suppliers to ensure they’re meeting the freshness standards that their customers demand.

With Emerson’s connected monitoring and tracking infrastructure, data from our GO Real-Time Trackers and GO Loggers is pushed to the cloud and presented in Oversight, giving our customers both visibility and analysis of critical cold chain information with which to make better supply chain decisions.

End-to-end cold chain certainty

Of course, Emerson also provides the critical refrigeration components, controls and compressors to help retailers ensure optimal refrigeration temperatures in their refrigerated cases, walk-in coolers and freezers. Our advanced facility and asset monitoring systems provide real-time access to the critical information that retailers need to track, triage and quickly respond to issues that could potentially impact food safety and quality. What’s more, our automated temperature monitoring and recording devices help operators eliminate the need for time-consuming manual documentation — giving them the abilities to access on-demand reporting as needed for food safety compliance purposes and provide historical cold chain data.

 

Why Refrigerant Leak Repair Still Matters

Jennifer_Butsch Jennifer Butsch | Regulatory Affairs Manager

Emerson Commercial & Residential Solutions

Proactive refrigerant management isn’t just good for the environment. It is also sound business practice. I was recently interviewed by ACHR’s The News magazine on the Environmental Protection Agency’s (EPA) partial rollback of Section 608 provisions for appliance leak repair and maintenance. You can read the full article here  and more on our perspective below.

Why Refrigerant Leak Repair Still Matters

In February, the EPA eliminated leak repair and maintenance requirements on appliances containing 50 or more pounds of substitute refrigerants, such as hydrofluorocarbons (HFCs). As a result, equipment owners are no longer required to:

  • Repair appliances that leak above a certain level
  • Conduct verification tests on repairs
  • Periodically inspect for leaks
  • Report chronically leaking appliances to the EPA
  • Retrofit or retire appliances that are not repaired
  • Maintain related records

But just because these leak repair provisions are no longer required doesn’t mean food retailers should ignore these best practices. There is a price to pay for refrigerant leakage that extends far beyond environmental damage. Detecting, repairing and even proactively reducing refrigerant leaks will help operators avoid a variety of associated costs.

The high cost of refrigerant leaks

The rollback of legal penalties for refrigerant leaks does not change the math on the operational costs. An average food retail store leaks an estimated 25 percent of its refrigerant supply each year, which can quickly add up to thousands of dollars in lost refrigerant. In addition, retailers must consider the maintenance and equipment costs. Persistently low levels of refrigerant can cause:

  • Excess compressor wear and tear
  • Reduced compressor and system capacities
  • Premature system failures
  • Double-digit efficiency losses

Left unchecked, even minor leaks can eventually lead to equipment failure. When this occurs, emergency repair costs are often only the tip of the iceberg. Operators may also be looking at revenue loss from food waste, business disruptions and reputational damage.

Proactive refrigeration management

So what can operators do to prevent leaks, even in the absence of federal requirements?

In the near term, they can — and should — implement rigorous leak detection and repair programs. Refrigerant leaks can occur anywhere in a system. Thus, an effective refrigerant leak detection program will combine monitoring, detection and notification.

Multiple technologies are available to support these efforts, including active and passive devices for monitoring and detection. Internet of things (IoT) capabilities allow for remote monitoring, enabling operators to focus on more pressing tasks. And with the integration of data analytics platforms, operators can uncover trends, identify persistent problem areas, and make informed choices about equipment upgrades and replacement options.

Over the longer term, operators can adopt refrigeration architectures that reduce the potential for refrigerant leakage in the first place. Legacy, centralized direct-expansion rack systems are high leak-rate offenders. That shouldn’t be a surprise; with thousands of feet of pipe, hundreds of joints and large refrigerant charges, there are many opportunities for leaks to occur.

In contrast, distributed micro-booster, indoor distributed and outdoor condensing unit (OCU) architectures experience lower leak rates by design. As an added benefit, they offer more options for lower-GWP alternative refrigerant use. This is a crucial advantage for operators who want to position their business for future regulations.

Sustainable best practices

The EPA’s Section 608 leak repair provisions were good for the environment. They are also part of a larger body of best practices for optimizing HVACR equipment. As states take the lead in adopting standards for leak detection and control, operators may find the rollback of these regulations to be short-lived.

Emerson is proud to take a lead in developing sustainable and cost-effective refrigeration systems and supporting technologies. Operators and original equipment manufacturers count on us to deliver strategies and solutions that anticipate emerging trends and regulations. From pioneering refrigeration architectures to refrigerant leak detection tools, we are committed to providing operators with the capabilities to meet their sustainability and operational goals today and into the future.

 

 

 

Emerson’s Transportation Solutions Business Compliant With DCSA’s New IoT Recommended Standards

Brian_Robertson Brian Robertson | Vice President, Sales & Support

Emerson Transportation Solutions

Worldwide connectivity helps keep the global food chain intact. According to The Economist, four-fifths of the planet’s 8 billion mouths are fed in part by imports. Fleets in the air, on the sea and on the road connect tens of millions of farms to hundreds of millions of shops and kitchens.

Transportation Solutions

Emerson’s Transportation Solutions business has a proven reputation for tracking this freight, regardless of where it is within its journey. The world’s leading shipping companies, truck lines and refrigerated container manufacturers count on these refrigeration products and monitoring solutions. Building upon the smart communications it provides, Emerson’s Transportation Solutions business now supports Digital Container Shipping Association’s (“DCSA”) new internet of things (“IoT”) connectivity standards for shipping containers. DCSA is a nonprofit group founded by major ocean carriers to digitize and standardize the container shipping industry.

These recommendations focus on ensuring interoperability within the industry on the standardized methods for communications of IoT devices on container to IoT gateways at sea and on land. These universally adaptable standards align internal radio communication protocols for IoT gateways, addressing the network connectivity requirements for reefer containers, dry containers, and the RFID registration of these containers.

With these recommendations in place, carriers and supply chain participants will be one step closer to providing customers with an uninterrupted flow of relevant information regarding the whereabouts of containers and the status of their contents at any point along their journey.

For more information, visit https://dcsa.org/.

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