Is defrosting your commercial freezer the key to better performance?

Have you noticed your commercial freezer’s performance slipping lately?

The true problem could be right in front of you: frost.

It can creep up slowly making it easy to overlook. After all, freezers naturally experience frost build-up...right? 

Be this as it may, when this situation escalates, frost stealthily drains energy, this reduces cooling efficiency, effects energy bills and can even compromise your food quality.

Understanding the science behind why frost forms in commercial freezers is a great first step. You can then look to manage this more effectively, keeping your freezer running smoother for much longer.

How frost effects performance and why it forms

Frost occurs in commercial freezers when air moisture freezes directly onto the unit’s cold internal surfaces. The process begins in the situation where humid warm air enters the freezer, most commonly through frequent door openings or inadequate seals. The moisture in the air condenses onto the coldest surfaces, once inside the freezer, such as the walls, back and shelves, and then freezes, and this forms frost.

In commercial freezers, the primary sources of moisture are:

 

• Air – warm, moist air enters every time the freezer door opens. Even despite good seals, the temperature difference can still create a negative pressure that draws in humid air from the surroundings.
• Food – unpackaged or improperly sealed food is more likely to release moisture into the air inside the freezer. This moisture then condenses and freezes on the cold surfaces around it.
• Humidity – hot kitchens and food preparation areas are usually humid by nature. Moisture can enter the freezer through gaps or vents. This can also occur when the freezer is filled or unloaded.

As frost accumulates, this acts as an insulating layer, making it harder for the coils to absorb heat. This means the compressor must work much harder, and over a more prolonged period, to maintain the ideal temperature. This leads to increased energy consumption and possible overheating.

The refrigerant system in your commercial freezer works in the following way: 

The refrigerant in the evaporator coils (within the freezer) absorbs heat from inside the unit. When the compressor activates, this sends this heat outside the freezer through the condenser, and this is why freezers and coolers give off heat.

So the fact is, frost’s impact on performance is measurable. Some studies show that frost build-up can increase energy use by up to 20% as well as reduce cooling capacity by up to 30%.

Warning signs that your commercial freezer needs defrosting

Your commercial freezer will need defrosting more often than a domestic unit. In the meantime here are some of the signs to watch for.

First, and most obviously, check how thick the frost (ice) build-up is. If it’s anything more than ¼ inch (5mm), it’s time for a defrost cycle. You don’t need to be too precise with your measurements here.

Use a ruler or tape measure if you like, but a visual inspection usually tells you all you need to know.

Second, monitor the thermostat’s cut-in time (the duration the compressor stays off before restarting). As frost accumulates on the evaporator coils, it gets harder for the refrigerant to absorb the heat, causing the compressor to run longer and the off-time to shorten. If the cut-in time shortens by a significant amount (say about 30%) – or the time the compressor runs increases by a similar amount – then frost may be impairing its efficiency. It’s time to look at defrosting.

Finally, monitor temperature fluctuations. Of course, this is far simpler if your unit has a digital thermostat on the outside. Check and log the temperature regularly across a few days. That way, you’ll have a good dataset from which to work. However, note that when your freezer isn’t working, you’re more likely to see greater energy bills than obviously fluctuating temperatures, unless the frost build-up is extremely severe or the freezer is on the way out.

How often should you defrost your commercial freezer? 

There’s no ‘one-size-fits-all’ in this situation. That’s because every shop, premises, business and workplace are different. The trick here is to find the right sweet spot for your business and operations.

The frequency of defrosting depends on all sorts of things. Here are just a few: 

• Type of freezer
• Use pattern
• Ambient conditions
• Energy bills
• Condition and age of your freezer
• Produce you store 
• How busy your staff are 

However, be aware of one thing: you should defrost your commercial freezer far more often than its domestic equivalent. A typical home freezer typically only needs a manual defrost once per year, or once you notice significant frost build-up. In contrast, commercial freezers may need defrosting every few weeks.