27 Jul Turn your faults into virtues. Understand and optimize refrigeration control faults versus alarms for energy savings and improved operation
Utilizing the full capabilities of your control system is one of the most cost-effective ways to save energy. We find very few facilities maximize the full capabilities of already installed systems. Nowhere is this more detrimental than in grocery stores where controls operate the commercial refrigeration systems which make up the lion’s share of energy use.
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It’s easy to think energy management is the reason controls systems exist. But in grocery stores, the real day-to-day work of those systems is proper food storage and keeping customers and staff comfortable. Ensuring that food stays within FDA guidelines, is appealing, and that you’re keeping customer’s happy is essential to grocery store success.
When the food isn’t cold enough, or store occupants aren’t comfortable, someone complains. Store technicians or facility maintenance (FM) staff receive those complaints and hopefully track down the problem and fix it. In stores with a lot of deferred maintenance or old equipment this means that FM staff attention can be frequently distracted by resolving complaints. It’s far more valuable for staff to proactively prevent equipment failures and optimize performance of the very expensive assets control systems are designed to protect.
Those assets have a much higher value than is typically recognized if you include all the impacts. In a grocery store these assets are expensive compressors, condensers and fixtures, not to mention the food itself. A single frozen food case can hold tens of thousands of dollars’ worth of Ben and Jerry’s! Then there’s also the valuable customer relationship to protect. If they have a bad impression, it can do long term damage to your business.
So, minimizing complaints is a big deal. Stores use alarms in control systems to minimize complaints. Unfortunately the inherent nature of alarms can result in excessive alarms causing technicians to be overwhelmed.
Alarms apply simple logic to notify users of an immediate issue. Any control system can issue alarms. For example, you can get an alarm on a refrigerated case that can’t meet or hold temperature (which could result in product loss) or compressors that are running at high head pressures (warning “it’s gonna blow”). So being alerted of potentially problematic conditions is valuable.
“Alarm fatigue” is problematic
When the number of alarms become excessive it causes “alarm fatigue”. Especially in older systems, or those with persistent problems, too many alarms can make it difficult to 1) separate the important ones from the unimportant and 2) solve root causes rather than symptoms. So, when there’s too many alarms, attention to optimal operation flies out the window.
What’s the difference between “faults” and “alarms”?
We make a subtle distinction between alarms and faults in controls systems. The concept of alarms is fundamental to controls systems – you want to know when something is operating “out of bounds” and alarms do just that. However, they typically have very simple logic. Faults, on the other hand, dive deeper into system-level data and can support complex logic.
Fault detection and diagnostics (FDD) lets you design sophisticated algorithms to identify fundamental issues. More importantly, new FDD systems allow custom fault detection logic, so they can focus on what’s important and reduce the number of alarms rather than scrambling to address symptoms.
Think of fault detection as “smart alarms”
We’re now using advanced fault detection and diagnostics (FDD) in grocery stores to bring the focus back to root cause analysis instead of fighting daily battles with alarms. But sometimes, when describing FDD to clients FDD can sound like you’ll be adding to their list of alarms, rather than help reduce it. In fact, the correct use of FDD can reduce alarms and bring focus to what’s important. To understand that, it’s really import to understand the difference between “faults” and “alarms”.
For example, in grocery stores we use FDD to monitor daily compressor operation to ensure compliance with the sequence of operations. We can have the system automatically analyze performance over time checking for proper suction pressure float, head pressure float, and filter case temperature alarms only to those that persist over time. This identifies real impacts on performance and eliminates “nuisance alarms” that might be tripped by stocking a walk-in with product that needs to be pulled down to temperature.
Using Automated FDD to Augment Commissioning
There’s a great benefit to augmenting commissioning with FDD. If you’re commissioning a new system, tight commissioning budgets often dictate that only a sample of similar equipment gets a detailed functional test – it’s assumed that other similar units respond the same. But with automated FDD you essentially cut and paste the commissioning rules you want to enforce, ensuring the sequence operates correctly on every piece of equipment, not just the ones you have time to sample.
However, FDD doesn’t eliminate the need for onsite commissioning. For the foreseeable future, we anticipate there will be a need for engineers and technicians to perform tests onsite. There are a multitude of implementation details that need a human touch to make sure what’s seen in the controls and trends represents reality, and that installation is done correctly.
Fault detection is one area where market and technology trends allow us to manage the energy use of multiple facilities more effectively at lower cost. Costs of sensors have come down, processing power is greater and cheaper than ever, and internet connectivity makes it easier for controls and software to communicate and analyze data. Better connectivity reduces travel time and decreases down time since we can do more remotely.
We’re encouraged by our work to date using automated FDD on test sites in Utah. We’re excited to expand this work through our upcoming NYSERDA pilot program applying these techniques under our Remote Energy Monitoring program in New York State. We’ll be sharing more information and data from those pilot stores as that program is rolled out in the coming months.
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