Before we begin the basic operation, let's look at some of the features and benefits that make Hoshizaki machines so dependable and serviceable. Regular maintenance checks and servicing are made easier with the KM Cuber's removable panels. The component sections are divided into separate compartments, free from the damaging effects of moisture. Separating the evaporator, or wet section, from the dry electrical components of our machines helps eliminate many problem areas. Dividing these compartments also helps insulate the heat generated by the compressor from the cold section, making the KM Cuber more energy efficient.
Unlike other ice makers on the market, the KM Cuber's pump motor is housed in a separate insulated compartment away from the moisture of the evaporator, reducing corrosion, bearing, and winding failures. At the heart of our pump assembly is a more efficient, permanent split capacitor motor. This assembly can be easily removed and rebuilt in the field. The sealed evaporator section has a smaller ice drop zone than other ice makers. During operation, positive air pressure helps to reduce the air flow around the evaporator, keeping airborne bacteria out and reducing algae growth.
Many manufacturers build evaporator plates in welded sections of copper, which are plated with nickel or tin. Plating the copper is necessary for sanitation and to allow the ice to harvest properly, but it may flake and peel from the copper with age, contaminating the ice. The unique plate design of Hoshizaki's evaporator with its stainless steel freezing surface and oval-shaped serpentine tubing produces a crystal clear, crescent-shaped hard cube of ice which displaces more liquid than square or diced cubes. Since pure water freezes first on the evaporator plate, minerals are left to run off into the reservoir, reducing scale buildup and saving frequent and expensive cleaning.
Some of the benefits of the KM Cuber that help make your job easier include removable panels, separate compartments, an insulated evaporator section, a rebuildable pump assembly, a small ice drop zone, and a unique stainless steel evaporator.
Now, let's look at the basic sequence of operation of the Hoshizaki KM Cuber. When the power switch is turned to the "Ice" position, the inlet water valve opens, allowing water to enter and fill the reservoir. The one-minute fill cycle assures that the ice machine will not start until there is sufficient water, eliminating overheated pumps and compressor problems. After one minute, the controller board checks to see if the float switch is closed, and if not, repeats the fill cycle until the water level is sufficient. The float switch check also occurs at the end of each harvest cycle to ensure continuous, automatic low water safety. When the switch is closed, the controller starts the initial harvest cycle which runs approximately 2-3 minutes depending on ambient air and water temperature.
First, hot gas from the compressor enters the serpentine coils of the evaporator, while the inlet water valve remains open to assist in the harvest. This causes any ice remaining from the previous cycle to be released from the plate, while water continues to fill the reservoir. Starting the compressor in the harvest cycle with the hot gas valve open provides a no-load start, better efficiency, and longer life of the compressor and components. When the thermostat senses that the evaporator temperature has reached 48 degrees Fahrenheit, the solid state defrost completion timer on the circuit board takes control of the remainder of the harvest cycle.
During the harvest cycle, the inlet water valve brings water through the supply tube and down the center of the evaporator plates. This water flow also helps transfer heat from the serpentine coils to the stainless steel plates and pre-chills the water flowing into the reservoir. During the freeze cycle, water is pumped to the outside of the plates through the distributor tubes. In the freeze cycle, the hot gas and water valves are closed. As the self-contained condenser fan and pump motor starts, water is circulated up and across the outside of the evaporator plate and back down into the reservoir. The circuit board controls the freeze cycle for the first five minutes, providing short cycle protection. The float switch then assumes control to initiate the next harvest. If power to the machine is interrupted, the unit will always restart in the one-minute fill cycle.
Before the second harvest, a 10-second pump-out cycle occurs. As the hot gas valve opens, allowing gas to warm up the evaporator, the pump motor stops for two seconds then begins again in reverse. This pumps out the water containing concentrated minerals from the bottom of the reservoir through the check valve and out the drain. At the same time, water is used to power flush the float switch.
For improved cleaning, the pump-out timer on the circuit board may be adjusted to lengthen the cycle to 20 seconds. It can also be adjusted to occur every 1, 2, 5, or 10 cycles. These adjustments provide the service technician with the flexibility to overcome some problems associated with the high mineral content present in some local water supplies. When the pump-out cycle is completed, the pump motor stops and the inlet water valve opens. Just as in the initial harvest, the evaporator is warmed by the hot gas defrost and water assist, clearing any ice left frozen on the plate as the reservoir then refills in preparation for the next freeze cycle. The water level in the reservoir always overflows the stand pipe at the end of the harvest cycle. On top of the stand pipe is a displacement cap, which pulls additional minerals from the bottom of the reservoir and flushes them. This cleaning action can be extended by lengthening the defrost completion timer setting. When the bin is filled with ice, the machine automatically shuts off until more ice is needed.
Let's review the basic sequence of operation: the ice maker always starts with the one-minute fill cycle. The initial harvest cycle clears ice from the plate, assures a full reservoir, and allows quick and easy compressor starting. After five minutes in the freeze cycle, the float switch assumes control to initiate the next harvest. The 10-20 second pump-out cleans the reservoir every 1, 2, 5, or 10 cycles. The normal harvest is the same as the initial harvest and allows the flush to clean the reservoir at the end of this cycle.
For Tech Support, call 1-800-233-1940.
Hoshizaki KM Cubers are designed to be efficient, sanitary, and easy to maintain. Stainless steel evaporator plates, a rebuildable pump assembly, and a small ice drop zone are just a few of the many benefits to these cubers.
The following preventive maintenance checks will help keep Hoshizaki KM-series cubers dependable and serviceable for many years. Clean the removable air filter. Service the water filter and check the water valve screen. Visually inspect the loose wires, oil spots, water drips, etcetera. Clean the exterior with a soft cloth and neutral cleaner. Clean and sanitize the water system and bin. Annual cleaning and sanitizing of the water system is recommended. More frequent cleaning may be required depending on local water conditions. Cleaning the water system is an easy procedure with the KM cuber. The complete cleaning instructions are listed on the reverse side of the front panel. First, drain the reservoir by removing the stand pipe on M-models or drain plug on S-series models. Mix the cleaning solution according to directions on the panel and then pour it into the reservoir. Hoshizaki recommends Hoshizaki Scale Away or Economics Lab’s Lime Away. However, the durable stainless steel evaporator plate will not be harmed by any commercialized machine cleaner. Set the control switch to wash and turn the evaporator cleaning valve to the “open” or “wash” position. With these controls set, the pump circulates cleaner inside and outside of the evaporator plates. Since the inside pass does not collect heavy mineral deposits, allow the cleaner to circulate through the cleaning valve for about 5 minutes. Then, turn the cleaning valve back to the horizontal position. This allows all the cleaner to flow on the outside of the plates where more cleaning is needed. Once the flat surface is clean, pull the distributor tubes out 3/8” to allow the cleaner to flow down the evaporator ribs. When cleaning is completed, flush the rudder system thoroughly with clean, fresh water. Turn the control switch to the “ice” position. The ice maker will restart in the normal sequence of operation. The same procedure should be used to sanitize the water system. Mix the commercial ice machine sanitizer as per directions on the panel or a 5 1/4 percent sodium chloride solution. Circulate this solution for 5-10 minutes over the evaporator surface and ribs. Flush the solution from the machine with clean, fresh water before restarting the ice maker. We hope this video has helped you better understand the basic sequence of operation and check-out procedure for Hoshizaki KM Cubers. Call our toll-free hotline for further information on KM cubers or other Hoshizaki products. Remember, the name Hoshizaki stands for dependable and serviceable ice makers, designed with the service technician in mind.
Learn how to properly clean and sanitize your Hoshizaki KM cuber in just a few simple steps with this instructional video!
This video will demonstrate the proper way to perform the 10 minute check-out procedure for a system diagnosis of the KM cuber. Before we see how to diagnose electrical and component failures, let’s review the KM cuber’s sequence of operation. First, the unit always starts in the 1 minute fill cycle. Sixty seconds later, the initial harvest begins. Three to four minutes later, the freeze cycle begins. Longer harvest may occur in colder climates. After an average freeze time of approximately 30 minutes, the pump-out cycle occurs. Ten to twenty seconds later, the normal harvest begins. The KM cuber will continue to cycle until the bin control opens to stop the ice production. The first step in the 10 minute check-out procedure is to make sure there is adequate water and power supplied to the unit. When trouble shooting for system failures, remove the front panel, turn the ice maker off, and remove the control box cover. Now turn the unit back on. Remove the evaporator cover and make sure water is entering the reservoir. If there is no water coming in, check the bin control. The bin control contacts supply power to all the other controls in the unit. To check the bin control, flip the unit switch to the “wash” position. In the pump starts, it indicates that the bin control is closed. Next, check the cleaning valve micro switch. Flip the unit switch back to the ice making position. If there is still no water entering the evaporator, check the position of the cleaning valve handle. This handle must be in the horizontal position in order for the micro-switch, located behind the handle, to close. This micro-switch supplies control voltage to the control board. The cycle will not start without control voltage. A quick check of the control transformer secondary will verify that control voltage is present. If the 1 minute fill does not begin after you have checked the bin control and cleaning valve, check for 115 volts to the water valve. Check the terminals of the inlet water valve. If you have voltage, you can assume there is a problem with the water valve. Before replacing the water valve, check the inlet stream for debris. To do this, shut off the water and unscrew the thumbnut behind the water valve. Push the water line aside and inspect the screen. Clean or replace the screen as necessary. Check the water valve coil and diaphragm for problems and replace the water valve if necessary. After correcting the water valve problem, turn the machine on. The ice maker should cycle through the 1 minute fill and start the initial harvest cycle. If the initial harvest cycle does not start after 1 minute, check the float switch. Unplug the float switch and check for continuity with your own meter. If it is not closed and water is in the reservoir, the float switch is either dirty or defective. Clean it and check it to assure proper operation. If the float switch is good, the control board timer is defective and the board should be replaced. If the ice maker cycles into the initial harvest, the float switch is closed and the 1 minute timer works. A minute or so into the harvest cycle, the inlet to the evaporator should feel warm to the touch. As the hot gas circulates, the thermistor at the evaporator outlet reaches 48 degrees. The length of time it takes to reach 48 degrees depends on the ambient conditions and the water temperature. The length of harvest will automatically adjust to be longer in the winter and shorter in the summer. If the evaporator is not warming up, the first place to check is the hot gas valve. Lightly touch the discharge line to see if it is hot. If the discharge is not hot, then there is an obvious refrigeration problem and you’ll have to troubleshoot the system using basic refrigeration practices. If the discharge line is hot, but there is no heat coming from the outlet of the hot gas valve to the evaporator, you should check for coil voltage. To check for voltage, pull the tin pin connector out about 3/8” and check from the pin on the pink wire, which is the hot gas valve, to a neutral white wire. If you get proper voltage, the control board is working. If not, the problem is the control board. If you do get voltage, check the coil to be sure it’s energized. To do this, lay a metal paperclip on the coil. If you can feel a magnetic pull, the coil is energized. If the coil is in fact energized, it is possible that the hot gas valve is stuck. A stuck valve should be replaced using proper refrigeration practices. With normal operation of the hot gas valve, the evaporator will warm. At 48 degrees, the thermistor will start the defrost completion timer. The average harvest cycle and average ambient temperatures will range from 2-4 minutes. Longer harvest will occur with colder supply water or if the defrost completion timer is adjusted longer. If the harvest cycle does not end within 10 minutes, leave the machine running and unplug the thermistor. Check the resistance with your own meter and compare it against the temperature resistance chart in your tech specs book. For example, if your meter reads 6K ohms of resistance, the sensor temperature is 32 degrees. However, after 10 minutes in the harvest cycle, the temperature should be much warmer. This would tell you that there is a refrigeration problem. In another example, if your meter reads 2.5K ohms then the suction line temperature is 70 degrees. Since that temperature is well above the normal 48 degrees needed to start the defrost completion timer, the control board is not responding and there is a problem with the board. Once the harvest cycle ends, the freeze cycle begins. The hot gas valve and water valve de-energize and the pump motor and self-contained fan start. After the ice maker is in the freeze cycle, the evaporator inlet should feel cold within about 3 minutes. If it does, you have basic refrigeration occurring. If the evaporator is still warm after 3 minutes, there is a possible refrigeration problem. This problem might be caused by 1-hot gas valve not closing, 2- coil still energized because of a control board problem, 3- thermostatic expansion valve not opened properly, or 4- insufficient refrigerant. These items should be checked using normal refrigeration diagnostic practices. Next, let’s make sure the ice maker is purging properly by checking the pump-out system. After 5 minutes in the freeze cycle, unplug the float switch to initiate harvest. This will cause the unit to go into a 10 second pump-out that will flush the dirty water and sediment through the check valve and down the drain. You can also squeeze the pump supply hose tight enough to force the water down the drain. This would empty out the reservoir and allow the float switch to open by itself. It is important to understand the control components of the KM cuber. These components include the control board, the float switch, the thermistor, and bin control. First, let’s look at the bin control for any suspected problems or adjustments. A quick check of the bin control can be accomplished by switching the pump to the “wash” position. The unit will not start if the bin control is stuck open. When the bin control is stuck closed, the machine will not automatically shut off. If the bin control is not adjusted properly, it could cause the unit to shut down prematurely or allow ice to back up into the evaporator, causing a freeze-up condition. To check the adjustment of the bin control, access the thermostatic bulb, turn the switch to the “wash” position. Next, place a small amount of ice on the thermostatic bulb. Count the seconds and listen for the pump to shut off. If the pump shuts down within 6-10 seconds, the bin control is adjusted properly. Adjustment can be made with a screwdriver in the bin control slot. The float switch has two primary functions; it provides low water safety protections and initiates harvest. If the float sticks in the down position, which is open, the unit will switch to the one minute fill cycle and run water continuously. If the float sticks in the up position, which is closed, the unit will remain in freeze for 60 minutes. The cubes will be larger than normal and the pump will cavitate before harvest begins. If either of these symptoms exists, the float switch needs to be cleaned and checked. First, take the float switch apart and clean it with ice machine cleaner. Once you’ve cleaned the float switch, check it with an ohm meter to be sure it operates properly. The thermistor monitors the outlet temperature of the evaporator. At 48 degrees, it starts the defrost completion timer. At 127 degrees, it automatically shuts down the machine on the manual reset high-temperature safety. There are only two ways a thermistor can fail: open or shorted. An open thermistor will cause a consistent 20 minute harvest cycle. A shorted thermistor will shut the unit down on the high-temperature safety. When you switch the power off and back on, the safety will not reset. The thermistor should be checked using an ohm meter as previously discussed. Now, the control board. The control board processes information to supply the voltage that allows the components of the ice maker to cycle properly. Many things can affect the control board, but if you have proper supply voltage, proper control voltage, a good float switch, a good thermistor, and good pin connections, and the machine is not cycling properly, you can assume that you may have to replace the control board. Remember, when servicing any Hoshizaki ice maker, always refer to your tech specs guide for detailed information or call the Hoshizaki service hotline on your screen. Understanding these symptoms and the operation of these simple controls will help you diagnose sequence problems on a KM unit using the 10 minute check-out procedure.
Properly diagnose electrical and component failures with your Hoshizaki KM cuber system by using this 10 minute check-out procedure!