The Sequence of Ice Machine Operation-Electrical
The eTech Professional Ice Machine Technician electrical certificate course centers around the circuitry, controls, and components finishing with the electrical sequence of operation, aka sequence, directly related to the commercial ice machine. Remember that the ice machine follows a set of sequences of operation in an automated and robotic fashion repeatedly. Why is the sequence of operation unique to the ice machine? Simple enough, but what happens when something interrupts the sequence? How can the sequence be restored without a significant loss of production? Here are some examples.
Effect of the Loss of Water
A momentary loss of water pressure in the building. The loss of water pressure negatively impacts the elapsed time it takes to fill a water reservoir. In many ice machines, the filling of the reservoir is a timed event. E.g., when the operation sequence calls for the water valve to open and flow water, the control system begins a timed sequence that eventually expires and then shuts the electric water valve. What happens if inadequate water is in the reservoir. Among other things, the machine could run out of water during the freezing sequence. A loss of water capacity is not a good thing, since some machines can be substantially damaged due to freezing damage to components.
In most cases, the ice machine control system locks out, preventing operation until the operator performs a specific task, such as cycling the power switch. In other machines, such as the flake and nugget machine, the reservoir can be emptied, resulting in the control circuitry temporarily shutting down the ice machine to restart after a set time interval automatically. The execution of the control sequence is further complicated by issues such as how many times the machine is allowed to restart automatically and what the control system should do when the low water condition is not resolved after several attempts to restart?
The storage bin is full
What happens when the storage bin is full? At least twelve control configurations manage the sequence of operation affected by the storage bin control, varying between manufacturers and models. The most important concept is ‘what happens when the bin is full’ and ‘what happens when the bin level decreases.’ Of more complexity, what happens when the ice machine storage bin is ‘nearly full’ and still running, with the next batch of ice harvested likely to overfill the bin?
The good news is that this is not a factor in some ice machines, such as the flake and nugget machines. The fun part is that the same ice level mechanism in these two machines also sometimes serves the double function of detecting ice jams.
What happens, it takes too long for the ice to fall off a vertical evaporator during the harvest cycle?
Sometimes interruptions in the water supply or a leak in the cubed ice machine’s closed water loop create a freeze-up condition, causing malformed ice to bind to the evaporator. This ice cannot be ejected during the harvest cycle, but the machine does not ‘know’ it. The issue with this situation is that an excessively long hot gas harvest cycle could overheat the compressor. The effect of an overheated compressor can be similar to what happens when a radiator hose breaks and cause engine overheating in our cars. The control system needs to detect an excessively long harvest cycle before the compressor shuts down one of its overload systems.
Dozens of Operational Scenarios
By now, we have demonstrated a few of the dozens of possible scenarios that the ice machine’s electrical and control system is responsible for managing normal operations and minimizing the damage caused by abnormal conditions. As you continue your studies, it becomes more evident that the sequence of operation varies significantly widely between manufacturers, models, and types of ice machines. Specific models provide extensive feedback to the maintenance personnel, and others provide none other than the current inoperative ice machine.
Ice Machines and YouTube
We frequently are asked how technicians ‘get by’ with YouTube videos and rules-of-thumb. The short answer is that they don’t. As with everything else, a trained expert succeeds, and the YouTube parts blaster barely gets by; a mastery of refrigeration, electricity, and sequence of operations is a given. Not to state that all YouTube videos are wrong because there are fantastic resources if you know how to separate fact from fiction.
The eTech Professional Ice Machine Technician certificate course also explores the added complexity of control systems when the ice machine head has a remote condenser. In other words, the head section needs to monitor and control the remote condenser up to 100 feet away, possibly on the roof. Can this be more complex (hint-yes, it is)?
Troubleshooting
Acquire the manufacturer’s service manual that outlines the sequence of operations.
- Be sure that you can identify the components in the ice machine.
- Before proceeding, ensure the machine is clean with no scaling, mold, or obvious contamination on the freezing surfaces. Check the air-cooled condenser to make sure it is clean.
- Watch at least one complete cycle (preferably 2 if needed), including the start, freeze, harvest, and purge (when the purge is separate).
- Using the factory sequence of operation chart and outline, observe and ensure that each step completes.
- Identify any failures and troubleshoot each using the factory troubleshoot instructions for that component(s)
