Defrost schedules are important to knowing how to properly install and maintain a refrigeration system. A proper installation and defrost schedule will help you maximize system performance, keep thewalk-in at set-point temperatures, and, most important of all, keep your customers happy.
The importance of knowing what the refrigeration system will be used for
A good first step to determine when to defrost and for how long is knowing how the end user is going to use the cooler or freezer. The following are some good questions to ask which would help you determine this:
- When the peak usage time during the day occurs
- How they plan to load the box
- What time of day is the box is stocked
For example, a defrost should never be scheduled during a time period when the box is being restocked. During restocking,the door is open which allows moisture and warm air to infiltrate the space.
Setting the refrigeration defrost schedule based on usage and traffic
A good rule of thumb for starting out is setting the defrost schedule to four times a day. The amount of defrost schedules is based on the amount of traffic (door openings) in a day. More traffic leads to an increase in moisture that will collect on the coil surface. High traffic refrigeration systems may need 6 defrosts in a day. By contrast, low traffic, or long term storage boxes, may not be open for long periods of time. These low traffic refrigeration systems may be able to cut back to only two or three defrosts per day. Having no more than the required defrost time is a big energy saver.
The impact the defrost termination has on a refrigeration system
Defrost termination is another consideration to a successful install. Most of the smaller Heatcraft Refrigeration units come with a SPDT fixed defrost termination and a fan delay switch. The defrost switch will terminate at 55* and the fans will delay start-up until the temperature of the coil is below 35*. Keep in mind, after the ice melts from the coil there is still a coating of moisture on the coil surface. Having the fans to come on immediately would cause this moisture to be thrown from the coil through the fans and fan guards. This displaced moisture could potentially land on the product, the ceiling, the floor, etc. Adding a fan delay gives the refrigeration system a chance to run and refreeze any moisture left on the coil. This also helps prevent frozen droplets from appearing on the floor and ceiling of the box.
Heatcraft Refrigeration Installation and Operation Manual
Detailed instruction on setting defrost and defrost termination is provided in the Heatcraft Installation and Operation Manual on pages 4 & 5 shown below.
Click to view the entire Heatcraft Refrigeration Installation and Operation Manual
Looking for the most energy efficient systems? cfm Distributors, Inc. carries Beacon II Refrigeration systems and controls, Heatcraft Split System Controllers, and Smart Defrost Kits. Talk with your local cfm location about how you can take advantage of these products and improve your refrigeration system’s efficiency.
Visit Heatcraft’s website for more product information.
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