Technician Help Center

Hoshizaki flakers have a unique feature with the automatic periodic flush system. This feature has also been added to the latest DCM products. The purpose of the periodic flush is to clean the water system daily to provide better efficiency, reduce preventative maintenance, and give longer life to the auger bearings.

The basic periodic flush shuts down the refrigeration system for 20 minutes every 12 hours to allow the water system to drain. This draining action completely empties the water system to drain away impurities. The reservoir is then re-filled with clean fresh water. The flush is accomplished by using a mechanical flush timer and a gravity flow flush valve. A manual flush switch is also included to allow manual draining of the water system for service.

There are two models that do not use a mechanical timer. They are the F-300B and the F-500B series under-counter flakers. These models drain the complete water system each time the unit cycles down. This is considered an off cycle drain down and provides the same result as the timed flush.

It is important to remember the flush timer if you are diagnosing a problem on a unit that will not start. Rotating the cam wheel clockwise will advance the timer. This will allow the unit to start if it was off on a periodic flush. The timer motor runs continuously when the power switch is ON. There are no adjustments to the length of the flush time. The flush period however, can be adjusted to occur at a specific time each day. This can be done by rotating the cam wheel until the micro-switch opens. The unit will flush every 12 hours from that specific time.

Recently there have been several inquiries concerning the provision in our icemakers to prevent back flow from the icemaker into the potable water supply. If there is not a provision to prevent this, during a period of negative pressure of the potable water supply, water from within the icemaker could be siphoned back into the potable water supply, causing contamination.

All of our KM series units (Including KML, KMS, KMD, etc.), Flaker, DCM, and AM model icemakers are listed by NSF International under NSF Standard 12, Automatic Ice Making Equipment. As part of getting listed by NSF, an icemaker must comply with section 5.28 “Backflow Prevention” of NSF 12. Section 5.28.1 states “Units intended to be connected to a water supply system under pressure shall have one of the following:

“-an air gap at least twice the diameter of the water supply inlet and not less than 1.0 in (25 mm): Or”

This clause goes on to state several other methods of meeting this requirement however, the first method is how all of our models meet the requirements.

KM-Models

For the KM models, the water passes through the solenoid water inlet valve to the top of the KM evaporator plates. The water falls by gravity between the evaporator plates and over the refrigerant tubing sandwiched between them. It then falls further through the cube guide and into the reservoir tank. The space between the two stainless steel plates is open to atmosphere, so once the water leaves the water spray tubes, it is in an air gap the height of the evaporator plates. The height of the KM evaporator plates is minimum 11.5 inches, which easily meets the NSF requirement.

Flaker and DCM-Models

For the Flaker and DCM models, the water passes through the solenoid water inlet valve and through a 3/8” ID plastic fitting attached to the water valve outlet. The water then falls through the air into the water reservoir through a small hole. There is an overflow pipe in the reservoir that is 1 1/4 inches below the hole that the water enters through. The overflow pipe is connected to an open drain pan, therefore no water can siphoned back to the potable water supply.

AM-Models

For the AM models, water passes through the solenoid water inlet valve, it exits through a plastic tube that is vertically oriented and is held in position by a clamp attached to the icemaker wall. After exiting the tube, the water passes through a vertical air gap of more than 1.0 inch before it drops into the water tank. So even if some malfunction causes the water tank to overflow, the water will drop into the ice bin below it, and cannot reenter the vertically oriented water supply tubing above the water tank.

In all of our ice maker models, the built in air gap described above are secondary back up to the water solenoid valve. The water solenoid valves are normally closed and in most situations prevent any back siphonage from happening.

When the machine beeps once every 3 seconds it indicates the HIGH TEMPERATURE SAFETY switch has been triggered.

The HIGH TEMPERATURE SAFETY is activated, when the thermistor which is mounted on the suction line reaches a temperature of 127° F. When this occurs it will shut the unit down, trigger the alarm, and lock it out on a manual reset safety.

Some of the reasons for a High Temperature safety alarm are as follows. You will find these possibilities included on the control board diagnostic label located in the compressor compartment. Follow the instructions provided on the label to reset the alarm and check these areas to locate the problem.

1. Check to see if there is a mechanical problem with the hot gas valve sticking open or with the control board relay sticking.

   1. Check for a temperature differential across the hot gas valve.

   2. To check for a sticking relay, use a volt meter to check for voltage on pink wire, pin # 2 on the K1 connector.

2. Hot water migration can also cause this. This typically happens at night when the only piece of equipment requiring water flow is the ice machine.

   1. Hot water migration is a tough problem to find and to prove to the customer. The best way to determine that this is happening is to place a temperature recorder on the inlet water line of the ice machine. The recorder will show when migration occurs.

   2. Usually hot water migration is due to a defective mixing valve in the existing plumbing. A good place to check is the pre-wash area at the dishwasher.

3. A stuck head master on a remote air cooled condenser unit operating in a high ambient condition.

   1. The best way to check for this is to carefully touch the liquid line connection at the rear of the unit. Also, check for heat at the inlet pipe to the receiver tank. If these areas are hot, the head master is likely stuck in the bypass mode.

4. Check for a shorted thermistor. If the thermistor reads approximately 500 ohms or less the control board will lock out on this safety.

   1. A shorted thermistor will signal zero ohms and cause repeated shut down on HIGH TEMPERATURE SAFETY.

First, let me say that 9 out of 10 callbacks on a new unit are related to the machine not being installed according to the factory specs. This problem is no exception. When we receive calls about this problem the solution usually lies in the external drain circuit. When installing a Hoshizaki ice machine, the technician should refer to the Instruction Manual that comes with the machine. You can also find information on installation in the Hoshizaki Technician’s Pocket Guide.

All Hoshizaki icemakers require a dedicated ¾” ID drain for the reservoir. This can be plumbed using either copper or PVC. On KM’s that use water cooled condensers, the outlet of the condenser should be ½” and piped separately from the sump drain. On all Hoshizaki KM units manufactured after 1988, the unit will start in the one-minute fill cycle. Within 60 to 90 seconds you should see water coming from the sump drain. This will assure us that the unit has good water volume to the machine. During the harvest cycle the water valve will remain open. This water is used to flush the bottom portion of the sump. The water coming in will help agitate the minerals that lie at the bottom of the sump tank and flush them down the drain.

Now we will address the problem, because of the flushing action in the harvest cycle, it’s important that the reservoir drain not be smaller than the required ¾”. The drain should also be vented; this is typically done using a tee at the back of the unit. The unit drain should never be tied in with the bin drain. Proper plumping practices should be followed when running the drain line to the floor drain.
The two items that most often cause this problem are:

• The sump drain is too small, or

• there is a restriction in the external drain circuit.

To find out where the restriction lies, cut the drain about 12” below the vent tee and place a 5-gallon bucket to catch the water during the harvest cycle. If the water stops overflowing inside the bin, the restriction is further down the external drain system. If the problem still occurs, then the restriction may be in the machine, between the standpipe and the drain outlet. Slime or other build up normally causes this type of restriction in the drain. You can usually blow nitrogen or CO2 through the drain to clear the restriction. If this restriction is found to be slime or algae build up the entire machine should be cleaned and sanitized. I hope that these suggestions will help you solve the problem of the reservoir overfilling and water falling into the bin.

Cuber Production Check

Spring has sprung and hot weather is on the way. Higher temperatures outside means more ice usage inside. A properly sized unit will provide adequate capacity in these peak periods of use. However, this is not always the case.

In the peak summer time, ambient conditions and inlet water temperatures are at their highest and unfortunately, the ice machine output will be at its lowest. This usually results in a customer complaint if the unit was not sized properly for peak periods.

At this time the unit should be checked thoroughly for proper operation. Be sure to check that the evaporator, condenser, air filter, water filter and water valve are clean before conducting a production check. Also utilize the 10 minute checkout procedure to assure proper operation. The steps for a cuber production check are as follows:

1. Time a complete cycle from the beginning of one freeze cycle to the beginning of the next freeze cycle.

2. Catch all of the ice from this freeze cycle and weigh the total batch.

3. Divide the total minutes in a 24 hour day (1440 minutes) by the complete cycle time in minutes to obtain the number of cycles per day.

4. Multiply the number of cycles per day by the cycle batch weight for the cuber production per 24 hours.

Once you calculate the production, check the incoming water temperature, and ambient condensing temperature of the cuber and cross reference the Data Specification Chart in the unit Service Manual to see if the calculation falls within 10% of the specification. If not within specifications, additional trouble shooting is required to find out why.

For the most accurate production check, a normal freeze cycle should be checked. If the evaporator compartment has been opened for service or if the unit has been cut off for a long period of time, the first freeze cycle will be longer than normal. Timing this cycle can result in an inaccurate production check.

To avoid this, start the unit and allow it to operate for 10 minutes in the freeze cycle, unplug the float switch lead and cause the unit to cycle into harvest mode. Start timing as soon as the next freeze begins. Also remember that the evaporator compartment must be closed during the production check. Removing the front cover to check the ice buildup during a production check will allow heat into the evaporator and will effect the total cycle time and actual production.

A complete inspection and production check on a KM Cuber can easily be completed in approximately 1 hour. This is an effective tool to help you prove to the customer that the unit is indeed performing according to specifications.

This is one of the most common questions asked Technical Support. Before we look at the possible causes we must understand two things.

1. The first is that the KM series goes into harvest by water level, and not by temperature. This occurs as the water level drops and the float switch opens.

2. The second is that the water level is controlled by the stand pipe in the reservoir and not by the float switch or control board. The reservoir of the KM series cuber fills with water one time during the ice making cycle. This occurs during the initial fill and harvest cycle only. The reservoir should fill and begin to over flow the stand pipe within about 90 seconds if proper water flow is available.

Now, we will look at the possible causes for a 5 minute freeze time. The first items to check are the float switch and control board operation. This is done by placing a jumper across the float switch connector and allowing the unit to sequence into the freeze cycle.

If the unit continues to sequence into the harvest cycle after 5 minutes, replace the board. If the unit remains in the freeze cycle, check the operation of the float and the following items. It is possible that the reservoir was not completely full at the beginning of the freeze cycle. This can be easily checked by watching the unit drain during the harvest cycle. Water should overflow the stand pipe and drain within the first 60 to 90 seconds of a normal harvest cycle.

If water does not overflow the drain, check for proper water line size and pressure. Also check for a plugged external filter system or inlet water valve screen, and check for proper operation of the water valve. If the reservoir fills properly, the next possibility is that the pump out check valve is stuck open. The easiest way to check for this problem is to see if you have water coming from the drain during the freeze cycle. This tells you that the check valve is stuck open, dirty, or has a weak spring. Disassemble the check valve housing and clean the valve seat. If the spring is weak, a temporary fix is to stretch it a little. This will get you by until you can replace it with a new one.

Checking these items should help you resolve a consistent 5 minute freeze cycle.