Refrigeration

Jul

Niwot Market refrigeration monitoring converted to Virtjoule Juice Cellular CT’s

Posted by randy at 9:27 am

Summary

Several months ago, Virtjoule converted the vibration sensors on four compressors at Niwot Market over to the Virtjoule Juice Cellular CT. Because there were two large Copeland compressors on each rack, there was a lot of vibration from one compressor being picked up on sensors for other compressors, what we call “cross-talk”.

Our goal for Virtjoule Juice Cellular CT was to isolate the runtime of each compressor by itself, making it easier to visually and programmatically analyze what was going on.

Remote mounting board for Cellular CT's

Key Points

CT’s are very good at isolating runtime behavior of components in more complex or integrated system of machines.

CT’s can be run a very long distance from the source to the Virtjoule sensor, 100′ or more.

Virtjoule Juice Cellular CT’s are like having someone standing with a clamp meter on a machine 24/7.

Need To Know It’s Running

The primary thing Bert Steele, owner of Niwot Market, needs to know is whether the compressors are running or not. Oil temperature problems, refrigerant changeover, refrigerant leaks, and plain old worn out compressors have caused numerous problems over the time. All of those problems have caused shutdowns on these critical compressors. Sometimes it was a single compressor. Sometimes the whole rack. Virtjoule’s monitoring service and its ability to tell him his compressors are running has been critical to running a tight margin grocery business.

The compressor racks at Niwot Market have been one of the toughest environments for the Virtjoule vibration input sensors. There are four compressors total, two each on a rack. Because these are heavy compressors, when one operates it will vibrate the entire rack. We were still able to distinguish one compressor from another via vibration, but analysis was more difficult and not as clear to the customer as we would have liked.

Niwot Market Low Temperature Rack

CT Installation

It’s easy to install CT’s. Simply pull the top off the CT, wrap the body of the CT around the alternating current wire you’re interested in, and put the top back on.

Magnelab 70 amp CT on one of three phases

The CT Run

In this installation, the compressors are in a basement room, underneath a corrugated metal and concrete floor, and situated near the center of the building. Needless to say, cellular coverage from this location was not good. We were able to find a location in a stairwell that gave us good cellular reception, but was still out of the way, yet accessible.

Conclusion

Virtjoule Juice Cellular CT’s can easily isolate and monitor electrical components such as large electric motors, compressors, fans and blowers, chlorine generators, sump pumps, air conditioners, walk-in and reach-in refrigerations, and many more types of critical electric machinery.

With amperage information, you can not only make power estimates, you can use Virtjoule’s 10 second data to determine if the machine is running, how often it’s cycling on and off, how long those cycle times are, and produce critical alerts via text, email, or callout.

[Randy Cox - CEO and co-founder of Virtjoule - He is the software designer and analytics engineer for Virtjoule Sense sensors. He studied Chemical Engineering and Petroleum Refining at the Colorado School of Mines. You may contact Randy at: randy at virtjoule dot com] – See more at: http://blog.virtjoule.com

Aug

Walk-in Refrigerator Door Left Open

Posted by randy at 10:27 am

Summary

Refrigeration faults aren’t always blamed on the condenser or evaporator. Sometimes there is a perfectly good explanation and a cheap fix. This article shows the effect on cycle times when a walk-in refrigerator door was accidentally left open overnight after a produce delivery.

Key Concepts

Virtjoule detects extended cycle times that can be due to problems with the walk-in cooler box itself.

When door seal gaskets wear out and doors need an adjustment, the unit will have to work harder to make up for heat leaking into the cooler.

The first chart shows the normal cycle pattern for this Heatcraft HyperCore. Cycle times are between 8 and 15 minutes long and the unit cycled 33 times.

Normal walk-in cycling pattern

The next day, in the early morning hours, the unit began a very long 3 hr and 40 minute cycle followed by a 33 minute cycle, a 47 minute cycle, and two 52 minute cycles. By that time the morning crew figured out the cause of the problem and got the door closed.

Extended cycle times when door is open

Virtjoule caught this problem through the use of cycle duration rules and recognizing several extended duration cycles. No crisis call was made to this client because of the early morning time and the fact that the unit was still cycling.

When we see a unit extend cycle times like this, but still cycle off and on, we can safely assume the unit is still meeting demand. It’s obviously taking a lot longer to meet the demand and the unit should be looked at.

The fix in this case was cheap and obvious…close the door. Other situations could be more insidious. Walk-in refrigerator doors are used a lot. Door seals wear out. Hinges sag. Latches break. When door seals start to fail or the door doesn’t fit as well, it can be hard to know.

When you’re monitoring the cycle count and cycle durations, you can see the unit begin to work harder and harder to make up for the cooling loss.

Apr

6 Phases of a Refrigerant Leak

Posted by randy at 11:25 am

Summary

Of all the faults that Virtjoule can detect, refrigerant leaks generally give the most warning. In most cases there is plenty of time to fix the problem before it becomes critical and before you have to spend money on expensive overtime or disrupt your business.

That being said, this article has a unique perspective in that it covers a refrigerant leak that progressed from normal to total failure before being addressed.

Key Concepts

- Refrigerant leaks cause very common behavior changes in a condenser or package unit that can be detected by Virtjoule

- Most refrigerant leaks occur slowly enough that they don’t have to turn into crises

- It’s simple to measure and show that a fix has worked

- Temperature is a lagging indicator of a problem. By the time temperature control is lost, the failure has already occurred. Runtime and cycle monitoring can give warnings of impending failure days in advance.

The Setup

I will run through a set of six charts, one per day, that illustrate various phases of runtime behavior that we saw when a walk-in split system was on its way to total failure.

Not surprisingly, refrigerant leaks can occur at various rates. Some occur over months while others, once developed, can progress over the course of a few days. We have the luxury of monitoring a unit whose leak progressed at a very specific rate, day by day, over the course of six days, each day exhibiting a new and interesting behavior.

From experience, we see split systems are much more prone to leaks. This is primarily because there is more custom-installed refrigerant line and longer runs with more field soldered joints. These installations often have to work around difficult building designs, turning several corners along the way. In many cases a split system may be installed well after the building was built. Computer room air conditioners (CRAC units) are one example. Another is restaurants where a new walk-in refrigerator is added to a space that lacked one before.

Package units can also develop refrigerant leaks, but our experience shows us this scenario is rarer. Because refrigeration circuits are built at the factory, they can be subjected to higher quality standards. Because the compressors, condenser, and evaporator are all in the same unit, there are fewer things to go wrong and fewer people coming together to make the thing work. It can more easily be pressure tested before being shipped.

Phase I – Normal Operation

Normal Refrigeration Cycling

One of the nice things about 24/7 monitoring is that you can easily determine what is normal. This is a normal looking cycling pattern for a walk-in condenser unit. Very regular cycles in lower load times of the day. Cycle times stretch out a little and intensity increases when the unit is under the most load: from opening at around 9 am through to about 6 pm.

Phase II – Unexplained shutdown for 1.5 hrs

Intermittent Refrigeration Cycling

On Day 2, we called a fault at around 2 pm because there was a non-operation alert indicating that the unit had not come on for about an hour and a half, something that was very unusual for this machine. You can also see that cycle times before the shutdown were much longer than the day before.

The unit started up again on its own. The next cycle was understandably longer as the unit worked to catch up with the demand caused by no runtime for 1.5 hrs. Notice that all of the cycles after that were longer than the day before, even when the unit didn’t have as much load.

Phase III – Erratic cycling

Erratic refrigeration cycling

The slightly elongated cycles continued throughout the next morning. At 6 am there was another unexplained shutdown which triggered a non-operation alert. From then on, cycles became much longer with longer shutdowns than normal in between.

By now, even an untrained observer of these graphs could tell you that Day 3 of runtime looks a lot different than Day 1.

Phase IV – Failure begins

Walk-in refrigerator going into failure

Notice that the morning cycles continued at much longer intervals indicating that the unit is still working hard to keep up. Around 10:30 am, both the intensity jumped as well as the cycle times started to lengthen each and every cycle. By the middle of the afternoon the unit was running non-stop.

Once a unit is running in a non-stop state like this, the only thing we can tell the customer is that the unit is almost certainly not meeting the cooling demand required. How long it will be from here before there is a noticeable temperature rise in the cooler depends on a lot of things: what time of day constant runtime began, how often the walk-in is accessed thereby placing more load on the cooler, whether the walk-in is a freezer or refrigerator, how much product is in the cooler, how big the cooler is, and what the air temperature is outside the cooler.

We get very nervous on behalf of the customer at this point. The clock is ticking and something should be done — soon.

Phase V – Total Failure

Full failure of walk-in refrigerator

We confirmed for the client the next morning that the unit ran non-stop all night. We had no reason to believe the situation was going to get better as we’ve seen this degradation pattern a number of times before. The client confirmed that temperature was rising in the cooler. They had to crowd all of the product into another unit until the leak could be found and fixed.

The HVAC technician worked on it that afternoon, but had not confirmed the leak yet. The unit was not restarted.

Phase VI – The Fix

Refrigerant leak fixed. Catch up and then normal cycling begins

By the next day, the leak was located and fixed. The unit was restarted. A condenser unit will always run a long time until the cooler reaches the right cold temperature. This is normal. By about 6 pm the unit fell back into its normal cycle rhythm and has been running this healthy pattern ever since.

Conclusion

Because normal cycling behavior was well established for this unit, abnormal cycling behavior was very apparent, both to the eye and to our fault detection algorithms.

Unless a refrigerant line is physically damaged, most refrigerant leaks occur over much longer periods of time. The rate of the refrigerant leak will determine how long the customer has between fixes, if the leak is not found.

Condenser units often have plenty of capacity which is part of why they cycle as much as they do. A refrigerant leak can go for a quite a while until the condenser unit runs out of capacity to meet heat rejection demand. The pre-failure phases mentioned above can often be seen over the course of a few days or even a few weeks, giving the client ample time to address the problem before it turns into a crisis.

Temperature monitoring is a lagging indicator of a failure. By the time temperature control is lost, the failure is already mature and you’ve lost valuable time to get it repaired. Runtime and cycle monitoring the condenser unit can detect system wide degradation and failure sometimes giving days of warning. In this case there were indications of a major problem three days before the failure.

[Randy Cox - CEO and co-founder of Virtjoule - He is the software designer and analytics engineering for Virtjoule Sense sensors. He studied Chemical Engineering and Petroleum Refining at the Colorado School of Mines. You may contact Randy at: randy at virtjoule dot com]

Dec

How many cycles are too many?

Posted by randy at 8:16 pm

Summary

The official answer is 165,000 cycles per year is too much. That’s true and facetious at the same time, but just when we thought we’ve seen most of the reasons for short cycling, we now have one more to add to the list. In this article you’ll see how a temperature control short cut done to make up for the lack of a defrost cycle clock led to a setup that caused this Heatcraft HyperCore walk-in condenser unit to cycle about 9,900 times more per month than it should have.

Key Concepts:
- Short cycling can be caused by a number of problems, control design being one of them.
– Fixing detrimental operational behaviors can add years of life to a machine and save maintenance problems in the meantime.

At this point it would be very hard for us or the customer to know when this bad control setup happened since no monitoring had been done with the condenser unit and the walk-in cooler itself had not lost control of the temperature. It’s quite likely they may have inherited this condenser and evaporator unit set up when they leased the space. But let’s back up.

When we started monitoring this unit back in August we knew right away that it was short cycling. This is the first full day of monitoring and it was cycling over 400 per day.

Heatcraft HyperCore short cycling caused by control workaround

Notice how dark the chart gets. When you see more dark than light area in the chart you not only have a lot of run time, you also have a lot of cycles as the graph is showing. It’s quite easy to visualize this fault without the benefit of Virtjoule’s automated alerts on cycle maximums.

This is the chart of a different Heatcraft HyperCore that we’re monitoring and it’s prototypical of what we see with most walk-in condenser units. It’s quickly apparent that this unit is not cycling as many times as the one above.

Virtjoule chart of a normally operating Heatcraft HyperCore

Is it time to make the call?

When do you know it’s time to call someone to repair the machine? They had not lost control of the temperature in the cooler. In this case it really is a business decision since there is no imminent crisis. But consider this, a newly installed compressor for a Heatcraft Hypercore has cost this customer $2,200 on a different unit. They do have a serious financial incentive to avoid a $2,200 replacement and whatever interruption it causes to their business or distraction it creates for their store managers.

I consulted with a local commercial HVAC and refrigeration company in Boulder County, Timberline Mechanical. Timberline does commercial HVAC and refrigeration for some of the larger food manufacturers in Boulder County. Founder and president, John Kuepper, was able to validate that this behavior is detrimental. One of their rules-of-thumb is that if a machine is cycling more than five times per hour then it’s short cycling. If it’s cycling six times an hour then it’s probably not worth a trip.

In this case this unit was cycling 18-20 times per hour. It was turning on for about a minute and shutting down for about two minutes before coming back on again. Start-to-start cycle times were averaging about three minutes and runtimes during the cycle were averaging about a minute. Timberline is saying that start-to-start cycle times shouldn’t really go much less than 12 minutes.

With that rule-of-thumb in mind, this condenser unit was cycling four times more than it should have been.

What does it mean to the owner/operator of this unit?

This unit might continue to operate for quite a while into the future without needing a repair, but when it does it’s going to be a huge bill. It’s quite possible that if this unit was cycling normally that the customer may never have to replace the compressor while they’re leasing the space. While under their lease they are contractually responsible for maintenance and anything that happens to those machines. A 10 year lifetime machine is reduced to just two to three years, easily within the time span of a commercial lease. If they have inherited this machine with time already on it, the expensive failure could come at any time and would be their problem, not the landlord or the previous operator.

The Problem

Enough with the suspense of what was actually happening. Timberline Mechanical was called to take a look after the current service had just given the unit a clean bill of health after months of this behavior while Virtjoule was still saying it was short cycling. What was found was hair raising for any refrigeration technician. This unit did not have a thermostat or defrost clock installed. Instead someone had gotten a Johnson Controls bulb thermostat, set the set point to 35 degrees and then embedded it into the evaporator part of the split system in the cooler. The idea was as soon as it got cooler than 35 degrees it would shut down the evaporator.

I don’t know where to start with this one. It worked only because the condenser unit was still running well. It worked only because it was an extremely clumsy and inefficient way of getting what amounted to a nearly continuous defrost cycle. Of course this worked at the expense of a very expensive compressor. Timberline had a more colorful opinion of this approach. Do we even need to speculate that there could be many more installations like this?

But why the short cycle?

Let’s go deeper into why this caused a short cycle. First and foremost, in a medium temperature cooler you might try to hold temperature in the cooler at 38 degrees. To achieve 38 degree temperatures, temperatures out of the evaporator would have to be about 20 to 24 degrees. If this poor man’s defrost cycle thermostat is sitting in the evaporator set at a cutout setpoint of 35 degrees then 20-24 degree cooler air is going to satisfy that set point really fast. The evaporator will only be on for a little while.

20-24 degree evaporator air is blowing on the embedded thermostat set at 35 degrees. It is satisfied quickly and the evaporator is cut off. Let’s say 38-40 degree walk-in air continues to circulate through the evaporator. At some point the thermostat will notice it’s more than 35 degrees and the evaporator comes back on. The condenser unit on the roof is still working correctly as is the evaporator itself and cold air is coming out which is why they never lost temperature control. The store manager is happy because there is no health problem. But that cold air quickly satisfies the thermostat and everything shuts down again. It’s a nasty short cycle that has continued, perhaps, for the entire life of this unit. The people who pay the bills long term should care a lot about this behavior.

What needs to happen here is to install a basic control system of thermostat and defrost cycle clock in the cooler, not a simple thermostat buried in the evaporator.

Summary

This unit was built with a good refrigeration system. Heatcraft HyperCores, in our experience, have been some of the most reliable condenser units we’ve monitored which was part of the reason this setup poked out like a sore thumb. The design of this system did not include a thermostat in the cooler with a defrost clock in series to manage a proper defrost cycle. There was a very bad choice made by the installation technician(s) that short cut basic refrigeration control design.

We may never know the real reason this unit was designed without the proper temperature and defrost controls, or for that matter how many more installations there are like this one. However, with the current setup the customer could have to replace a compressor prematurely only to have to do it again and again, perhaps even blaming Heatcraft products, and never know why they have such a lemon. The lemon in this case was the control design which affected everything about how the system operated.

Virtjoule was quickly able to pinpoint the short cycling behavior of this unit and fixing it could easily add years to the lifespan of this machine, avoiding large expenses, compared to its previous operation.

Virtjoule monitored Heatcraft HyperCore condenser unit for walk-in refrigerator

Apr

Catching a Niwot Market refrigeration failure

Posted by randy at 3:49 pm

Summary

If there’s one thing that we know for sure when monitoring for refrigeration failures, it’s that finding behavior changes in the compressors or condenser unit will give you hours, if not days, of notice that your equipment needs attention…before you’ve lost control of the temperature of your walk-in or refrigerator or freezer cases.

In this article, we’ll cover a recent shutdown of a bank of two large Copeland compressors that served a low temperature refrigeration circuit at Niwot Market, Niwot, CO. Notice was given to the owner, Bert Steele, within minutes, well before he knew that anything was wrong, giving him time to correct the problem before there were any temperature problems in the freezer cases.

Niwot Market is an independent small grocery store in the town of Niwot outside of Boulder, CO. It is owned and operated by Bert Steele. The market has two refrigeration circuits in the store. One for low temperature freezer cases and ice cream and one for medium temperature refrigeration cases for products like meat, milk, and produce.

If there is one thing Bert worries about it’s an unexpected failure of either of those refrigeration systems. With enough lead time on the problem, he can move frozen products to his back room walk-in freezer which has more capacity to stay cold for hours while the problem is getting fixed. If he doesn’t get that lead time, several large display cases of food are at risk of total loss.

Failures tend to be in two categories, power failures and compressor failures. Weather in Colorado can be unpredictable and violent. Afternoon thunderstorms can take out the electricity for minutes to hours at a time. Winds in the area can exceed 80 mph several times a year, often occurring at night time after the market has closed, and he can lose electricity for several hours. Although this particular case did not represent a power failure across the whole store, it was a type of power failure in the low temperature compressors that caused the problem.

Below is a picture of the compressor rack for the low temperature system. It has three Copeland compressors. The one on the right is permanently out of service and not needed due to lower demands on refrigeration as Bert has updated his units in the store.

Low temperature compressor bank for Niwot Market

You’d think this might be an April Fools prank it it were not such a serious problem. Right before 8 am on April 1st, the low temperature compressor rack shut down after running continuously for months.

Niwot Market refrigeration failure

Virtjoule’s servers were monitoring this with automated rules that required that in the previous 25 minutes that the compressors had to have run for at least 10 minutes. Soon after 8 am the Virtjoule alert was sent out. Since a non-operation fault is pretty rare, I looked at the charts and it was clear that both compressors had shut down. It was highly unlikely to be a sensor error since both sensors were reporting the same thing. There were no other good explanations except that the units had shut down.

I gave Bert a call on his cell phone and then at the store where I reached him. I explained the situation and he said he would go check on things. I got a call back at 8:28 am from Bert saying he thought things were okay. He had put his hand into the freezer cases and the fans were still running and cool was still coming out. The fact that the compressors had shut down had not quite reached the freezer case yet, but it’s a great example of the fact that a serious problem had not yet surfaced on a temperature probe.

I was a bit puzzled since nothing would explain why the readings flatlined near zero. Fortunately Bert decided to go on down to the basement where the compressor racks are and check the source. Sure enough, I got a call at 8:40 from him saying that the compressors had shut down. He was able to reset them and they have been running ever since.

Bert’s comment at the time was, “You just paid for yourself for the next three years.”

It was obviously very gratifying to hear that and stories like this make all the work we’ve put into the company very worthwhile. Whether it’s a story of saving thousands of hours of HVAC time, energy, and money, or helping a small grocery avoid a very expensive loss of products, we really get a kick out of helping businesses find these very tangible problems.

Feb

HVAC and refrigeration monitoring projects

Posted by randy at 11:48 am

Summary:

As a young company, we’re still learning the range of things that are possible with the Virtjoule solution. In the last year and a half, we’ve discovered that not only has the technology met our original vision of functionality and price, the types of projects that can be accomplished are even more varied than we thought. The Virtjoule solution has been installed on everything from beverage coolers to a 6,000 ton cooling system on a major Las Vegas hotel.

We often get asked, “What kind of projects can you do?” In the earlier days of the company, the answer was in the form of suggestions of what we ought to be able to do. After all, we had a device that could pick up vibration and the ability to track that vibration over time and see patterns emerge.

These days, the answer is educated by field experience with the problems and the economics of solving those problems for our customers. At the highest level, the answer is “If it vibrates, we can monitor it.” As a company, we’ve done work in the various segments you’ll see in the list below.

To get a handle on the range of applications, perhaps it’s useful to take a scan across the types of units that we’re currently tracking.

Function	Model
Beverage Coolers	Micro Matic MMPP4301
Walk-in refrigeration	Numerous models of Harford Duracool Harford Duracool – H1984A8 Trenton – TEHA025L6-HS2A-F – 2.5 hp Trenton – TEHA006E6-HS2B-B – .6 hp
Air conditioning – Split systems	Ducane – 2AC13L60P – 2A – 5 ton
Package units	Trane YSC048A3EMA2U – 4 ton Trane YSC060A3EMA3 – 5 ton Rheem RKKA-A073CL10E – 6 ton Carrier – 48TCEA07A2A5A0A0A0 Bard PH13062 Bard PH1060-B – 4.6 ton York D1NA042N05625C – 3.5 ton York D1EB048A25B – 4 ton York D2NA060N09025D – 5 ton York DM090N10A2AAA4B – 7.5 ton York BP090C00A2AAA4A – 7.5 ton York D1EB060A25B – 5 ton Johnson Controls – J05ZJN10D2AAA1C – 5 ton Johnson Controls – J07ZHN15P2AAA4B – 7.5 ton Johnson Controls – J10ZHN20S2AAA4B – 10 ton Johnson Controls – J25ZJN32S2BZZ10001 – 25 ton York ECO2 50 ton Carrier 48P5 Horizontal VAV 100 ton McQuay 40 ton McQuay 70 ton
Heat pump packages and split systems	Heil Tempstar – NHP060AKC1 – 5 ton Coleman/York – HP060X1021A, 5 ton split system Goodman CKL60-1 – 4.75 ton Goodman CPLE60-1 5 ton Goodman GPH1324M41AB 2 ton York 20 ton
CRAC-(Computer room air conditioners)	Liebert
Evaporative Coolers – Water pumps	Can’t divulge manufacturer at this time
Air handlers	Goodman AH120-00
Commercial Refrigeration Compressors	Copeland Copelametic 4RA3-100A-TSK-800 Copeland Copelametic 6RA4-200A-TSK-800 Copeland Discus 3DB3F33KE-TFC-800 Copeland Discus 4DL3F63KE-TSK-800
Chillers	York – 18 ton Carrier 30GTN090 90 ton
Cooling towers	Baltimore Air Coil, 125 hp electric pump and 100 hp VFD fan – 2,000 ton

One of the most satisfying things that we’ve seen is that this is a huge range of equipment, all being monitored by the same Virtoule Sense technology.

If you’re familiar with some of the pieces on this list, you’ll know that some put off so much noise and vibration that you need ear protection. Other pieces are so quiet and smooth that it’s very difficult to tell if they’re running when standing right next to them or even putting your hand on the machine. I’ve been particularly impressed with the Trane series (YSC060A3EMA3) as very smooth operators in package units.

Because the Virtjoule sensor is self-calibrating, once it’s installed it can start off as a very sensitive device and self calibrate to the point where it can handle large magnitude vibrations. This self-calibration means that the installation is roughly the same for all of these installations, stick it on, power it up, and start getting data. An operating signature will always emerge that can be analyzed, reported on, and alerted on.

Customer and facility types

The table above is specific to equipment and equipment applications. But what sort of customers and markets does this represent? Here’s one look at the type of facility and customer:

Executive office buildings
Restaurants
Strip malls
Small market and convenience store refrigeration
Data centers
Hotels

Some are very high energy users where control problems or equipment degradation can cost thousands of dollars a year if the problem isn’t corrected. Some have equipment that might not burn a lot of energy, but the unit is serving high value contents. Food, pharmaceuticals, and computers are good examples of high value contents that need to be protected from catastrophic loss.

In a recent example, Virtjoule was able to give the owner of a walk-in refrigerator days of notice that their unit was degrading. The customer was able to get a refrigerant leak fixed before they lost control of the temperature of the cooler. One of my upcoming blog articles will discuss this “catch”.

If I were to sum up our results since we started, I would say we’ve helped customers save money by identifying control problems or system degradation that were racking up extended hours and energy bills. And we’ve helped some customers avoid serious loss of high value contents that were being refrigerated.

What new applications will we see this year? I can’t wait to find out.

[Randy Cox - CEO and co-founder of Virtjoule - He has been the software designer and analytics engineering for Virtjoule Sense sensors. He studied Chemical Engineering and Petroleum Refining at the Colorado School of Mines. You may contact Randy at: randy at virtjoule dot com]

Dec

Anatomy of a refrigeration condenser failure

Posted by randy at 10:53 am

Summary:

Refrigeration is a critical component of any restaurant for a variety of reasons, not the least is the health and safety of its customers. Keeping a close eye on how that refrigeration is working is key to avoiding health concerns and potentially the loss of all the contents of a walk-in cooler. In this article you will see how easy it is to notice that a walk-in refrigeration condenser unit is beginning to malfunction.

Key concepts:

Most any kind of fault will disrupt the observable common pattern of how the condenser unit operates.
Condenser faults may build up over time wasting energy and working equipment harder before a total failure occurs.
There can be adequate time to get a faulty unit fixed before it completely fails if the behavior change caused by the fault is detected.
Quick visual inspection of Virtjoule charts to compare patterns can easily identify changes in behavior that need to be investigated.

We recently notified a customer of a behavior change that we observed in the walk-in refrigerator for their restaurant. This is a critical unit for the restaurant as it’s the condensing unit for the only walk-in refrigerator that they have at this site. As you will see in this article, it’s not hard to figure out that something had radically changed in the operation of this unit despite the fact that the temperature in the cooler hadn’t risen. It was just a matter of time before this unit would have failed causing a big problem for the restaurant owner and the manager.

The walk-ins for this restaurant chain are made by Harford Duracool. Their labels don’t last in the sun and so I don’t have the exact model number for this condenser unit. The photo below is of the actual unit that failed.

Harford Duracool walk-in refrigerator condenser unit

What I want you to note in the following graphic is just how easy it is to determine that the unit has broken out of it normal pattern. This could be done visually or by using the Virtjoule cycle counter which would have shown a radical drop in the number of full cycles that occurred. The green and red highlights are mine.

You can see that just before 10:00 am on October 30, this unit stopped doing full cycles and ran continuously until about 4pm where it shut down for a few minutes and then started back up with an intense series of cycles only shutting down once every 5-6 hrs. Clearly this is much different than the cycles you see on the left hand side of the chart. The unit is working much more aggressively and constantly.

Harford Duracool Condenser breaking into failure pattern

The unit wasn’t fixed right away and luckily there was not a catastrophic failure that would have required moving or throwing away the food in the cooler. You can see this same failure pattern continued for quite some time.

Harford Duracool condenser in failure mode

Finally, about 9am on November 11th, the unit was shut down. It was thawed out, condenser cleaned, and then restarted just after 10:30 am. It ran continuously for a while in order to catch up on its cooling, but then settled back into its normal cycle rhythm about 6pm. It has been running normally ever since.

Harford Duracool condenser failure fix

In conclusion, you can see that it’s not at all difficult to notice that there was a problem developing and it was also quite easy to see when the problem was resolved. Virtjoule didn’t diagnose what the problem was, but it gave enough warning time for the unit to be looked at, fixed, and restarted before a catastrophic failure occurred. There was no other type of monitoring being done on this unit and it would have completely failed leaving the cooler to warm up at an inopportune time (night, food inspector dropping by, etc.). Compared to that inconvenience, a call to the Harford Duracool dealer and service was all it took to get things working well again.