Electrical Wiring for Refrigerated Cases

This video is a training session on Electrical Wiring for Refrigerated Cases we will cover common refrigerated case components for reach-in grocery refrigeration equipment, including electrical controllers and components working with building automation. This video focuses heavily on Sporlan components and controls (including the S3C).

The S3C controller is a compact computer specifically designed to control refrigerated cases. Like a computer, it takes inputs from sensors and has outputs that control operations at the equipment. In some cases, a few inputs and outputs may go unused, such as occupancy sensors for unlit cases or defrost in medium-temp refrigeration applications that don't have electric defrost.

In many cases, we use terminal blocks for several terminations in one location, which eliminates the need for several individual terminations directly at the controller. Terminal blocks are useful for part replacements, as using a screwdriver at the usual termination point could damage the component, whereas terminal blocks isolate terminations from the components. To remove wires from terminal blocks, you will need a precision screwdriver to open up the mechanism that holds wires in place.

Relays are common devices that can be used in several different applications; they open or close when voltage is applied to a solenoid. Relays allow you to use a safe voltage for control wiring. They come in general-purpose (often rated for a higher current) or control (for controlling a sequence of operations) varieties. Relays have a solenoid, armature, and contacts; they contain a coil wrapped around an iron core, and voltage is applied to that coil to magnetize the iron core. The armature is pulled toward the coil when the core is magnetized, which pushes a rod toward another contact (essentially switching the current path). In many cases, there are normally open and normally closed relays, but there may be Form A or Form C relays, too. Relays can also protect components by isolating the controller from potential issues with the circuit.

Liquid line solenoids open and close to control the flow of refrigerant; they are normally closed, meaning their respective circuits need to be energized to open them and allow the flow of refrigerant. Closing the valve to stop the flow of refrigerant except when energized is advantageous, especially during a power outage, as that state will help keep liquid refrigerant from getting into the compressor. As a result, liquid line solenoids are also closed during the defrost cycle.

Temperature sensors provide inputs that the controller uses to send outputs to the equipment. We use resistors as temperature sensors because resistance helps with voltage regulation and because temperature changes impact the electrical resistance of the sensor material; that is why we sometimes need to perform adjustment factors on wiring based on the ambient temperature. On S3C controllers, temperature sensors may be color-coded to help with ease of installation.

Electronic evaporator pressure regulators (EEPRs) maintain pressure in the evaporator coil at predetermined setpoints. This component will modulate based on outputs from the controller, which are based on inputs from the discharge air temperature or pressure transducer; temperature and pressure have a direct relationship.

Electronic expansion valves (EEVs) are metering devices that modulate to control the flow of refrigerant, much like a TXV. Unlike TXVs, the modulation is controlled by the controller, not by mechanical sources of pressure. Stepper EEVs open and close at multiple fixed positions, and pulse EEVs open and close rapidly for variable durations. Stepper and pulse EEVs have different terminals on the S3C. EEVs may work in conjunction with a pressure transducer (to monitor superheat), which may also help control an EEPR.

RH/ambient temperature (RHT) sensors typically help control anti-sweat heater controls. They may also use pulse-width modulation (PWM).

Display modules allow users to access system settings and perform local system controls; they allow users to communicate with the equipment. These may be on the controller(s) or in a remote location.

When we hook up power to an existing or retrofit application with multiple circuits (including lighting, anti-sweat, and fan circuits), we may only want to control a few of them with our S3C. We need to verify that the circuits that need to be unswitched are unswitched. Otherwise, we may interrupt power to the other circuits, which can cause the refrigeration system not to function properly.