Freezer "Anti-Sweat" Heater Controller
Freezer: Humidity Responsive Controls vs. Always On
A controller that turns off anti-sweat heaters when not needed on reach-in supermarket refrigerated cases.
Synopsis:
Anti-sweat heaters (ASH) are electric resistance heaters that are installed in the frames and doors of refrigerated cases to reduce condensation and prevent fogging. Condensation can lead to frost and ice build-up on door gaskets, mullion chambers and electrical raceways. An ASH prevents fogging on the doors when open, which precludes customers from clearly viewing the food products. A ComEd (Commonwealth Edison Company) fact sheet indicates that about 80% of supermarkets and grocery stores run the anti-sweat heaters constantly. Anti-sweat heater controls monitor relative humidity and are programmed to ensure that the doors and frames are heated only when necessary.
ASH controllers save energy by adjusting the heater duty cycle in response to relative humidity (RH) and dew point. When air is dry and dew point is low, the heaters operate with a low duty cycle and surfaces are allowed to get colder as condensation will not form. When air is more humid (i.e. 55% RH,) the ASH controllers operate with a 100% duty cycle.
Typical case construction requires three heaters: case mullion heaters (to keep doors from freezing shut), door frame heaters (also to keep doors from freezing shut plus transfer some heat to the glass), and glass heaters (to prevent condensation). Anti-sweat heater controls work only on the glass heaters and save energy in two ways. First, they reduce the amount of time the anti-sweat heater needs to run. Second, because the anti-sweat heater runs less often, the refrigeration system does not have to remove the additional rejected heat. Case studies indicate annual energy savings of about 1,400 kWh to 2,500 kWh per controlled case.
Energy Savings: 30%
Energy Savings Rating: Extensive Assessment
What's this?
| Level | Status | Description |
| 1 | Concept not validated | Claims of energy savings may not be credible due to lack of documentation or validation by unbiased experts. |
| 2 | Concept validated: | An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles. |
| 3 | Limited assessment | An unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline. |
| 4 | Extensive assessment | Additional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions. |
| 5 | Comprehensive analysis | Results of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications. |
| 6 | Approved measure | Protocols for technology application are established and approved. |