HOSHIZAKI CARE TECH-TIPS
Danny Moore Hoshizaki America, Inc. Volume 125
Editor 618 Hwy. 74 South
Peachtree City, GA 30269
COMPRESSOR REFRIGERATION DIAGNOSIS
Diagnosing a compressor refrigeration problem on an ice machine requires several preliminary checks. These
checks must be done prior to condemning a compressor and will help avoid a mis-diagnosis.
Before we look at the pre-checks, it is important to understand what the compressor is designed to do in the
refrigeration system. The compressor pumps a specified refrigerant through the system providing a
specific ratio of suction to high side pressures. The other components are sized to balance the system
providing the desired refrigeration effect. If this compression ratio changes, the net effect is inefficient
operation. This will be evidenced by improper operating pressures.
A clean evaporator and condenser (water or air cooled) is necessary to achieve proper heat transfer. Scale or
dirt build-up on either component can affect the operating pressures and cycle times of an ice machine.
Assure proper refrigeration load by checking the water pump for adequate water flow. Also check the
condenser fan or the water regulating valve to affirm a consistent condensing median.
The refrigerant charge is critical for proper operation (reference Critical Charge article Tech Tips Volume
121 Sept. 95). Always assure that the charge is weighed in according to the nameplate type and
amount before condemning a compressor. Once the correct charge is evident, check for proper
operation of the TXV. It should open and close as the evaporator load varies from warm to cold. Placing
ice on the TXV bulb should result in closing the valve. Likewise, warming the bulb should open
the valve allowing an increased refrigerant flow. Check for any restrictions in the refrigerant system that would
affect the operating pressures. Look for temperature differentials across the liquid line drier, refrigerant
header or distributor, line valve, and any refrigerant check valves in the system.
An increase of load on the evaporator can influence operating pressures and cycle times. Make sure the
insulated evaporator covers are in place so that warm air cannot enter the evaporator compartment.
Check the inlet water valve operation. If the inlet water valve leaks, the load on the evaporator will increase
causing longer freeze cycles. Once these items have been checked, if improper
pressures and cycle times still exist, the compressor is suspect. You will find that faulty compression can be
caused by internal mechanical problems or valves that are weak, cracked , or broken.
A mechanical failure could be anything from a dragging rotor to tight bearings. Anything that could slow down
the compression stroke can reduce the compression ratio affecting basic refrigeration. These failures
generally show up with symptoms of excessive noise, vibration, improper amp draw, breaker trips, or
shutdown on internal overload. Bad valves also produce pressure problems in the
system. Broken valves, either suction or discharge, will cause higher suction and lower discharge pressures. The
pressures usually balance out in this situation. Cracked or weak valves will result in
higher low side and lower high side pressures and a lower discharge temperature. You will still have a
compression ratio in this case, although it will be lower than normal. You may actually have limited ice
production however, the harvest times will be longer than normal due to the lower discharge temperatures.
The amp draw will decrease and the compressor temperature likely will increase. As the valves become
weaker the ratio decreases to the point that basic refrigeration is not possible.
Remember that bad compressor valves could be the result of liquid floodback. Since floodback can be
caused by a bad TXV, a severe freeze-up or a refrigerant overcharge, a thorough system check should
be performed. Operating with an undercharge can also damage the valves due to an increase in the compressor
temperature which causes carbon build-up and overheated valves. To determine weak valves some
suggest conducting a vacuum check first. Copeland however, recommends checking the amp draw of the
compressor against the compressor specifications. The reason for failure must be determined and corrected
before the unit is restarted.
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HUGE CUBES
When diagnosing an ice machine, there are many obvious symptoms that will point you in the right
direction. One such symptom can be found by inspecting ice in the bin. Odd shaped ice cubes
generally point to water related problems. By inspecting the shape of the cubes, you can know which area to
check first.
Here’s an example: A customer calls to complain of running out of ice (low production). Upon arriving at the
site, you question the owner and find that the ice drops about once an hour. The owner also mentions that the
cubes appear bigger than normal. Looking in the bin, you find larger than normal or huge cubes. These
cubes are thicker and taller than they should be and may roll up on the edges.
You remember that KM series control boards styles B, C, and Alpine have a 60 minute back-up freeze
protection timer. This timer will automatically switch the unit to harvest, if the float switch does not open within
60 minutes. A 60 minute freeze time will utilize all the water in the reservoir to make ice and possibly cause
the pump to suck air or cavitate towards the end of the cycle. Adding two and two together, 60 minute cycles
plus huge cubes equals a float switch stuck in the up or closed position. Likely, the float switch is sticking
due to scale build-up. You should clean the float switch with ice machine cleaner and check the
operation with a quality ohm meter. Simply replace a float switch that doesn’t check properly after you clean it.
There is another rare possibility in this case. This should be checked after you eliminate the float switch. Check
to see if the inlet water valve leaks a little additional water into the reservoir. Just enough to cause a 60
minute cycle and huge cubes. You will find that in most cases, if a water valve leaks, it adds so much water to
the reservoir that the ice bridges together on the entire evaporator. If the water valve is stuck wide open, the
reservoir water temperature is tempered so much by the incoming water that no ice is produced. You will detect
either ice bridging or a fully open water valve immediately.
Huge cubes will generally harvest properly unless combined with a dirty evaporator or low water flow.
If all cubes do not fall during harvest, a freeze-up could occur. In this case a thorough preventative maintenance
cleaning and external filter check should be completed.
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INLET WATER VALVE SCREEN
This is just a reminder that Hoshizaki inlet water valves have an 80 mesh screen in the inlet. This water screen
catches the big trash that might enter the ice machine so that it does not plug the water distribution system. This
is an important check point when conducting a preventative maintenance cleaning. A plugged screen
will reduce the water flow which could affect harvest and production.
The water valve screen is replaceable. The replacement part is #SP9200010. Be sure to replace the screen if it
gets damaged because it definitely serves a useful purpose.
DCM ICE
DCM stands for Dispenser Cubelet Machine. The ice produced by this auger style unit has a unique shape and
falls in the 90% hardness range. This harder cubelet dispenses easily and has less problems with bridging in
the small, air tight DCM storage bin. A Hoshizaki flaker can be converted to produce the cubelet style ice,
however the converted cubelet will fall in the 85% hardness range. The DCM ice is generally preferred in
health care applications because it is easy to chew than cubes.
The evaporator and auger in the DCM series is slightly different from that of a flaker. The difference in the
evaporator is two short keys that are welded vertically to the inside of the cylinder. The smaller DCM-240 has
a single key. The purpose of the keys is to cause the ice to pack tighter on the auger as it moves upward. This
squeezes more water out of the ice and provides a harder cubelet as it is extruded. The auger on the
DCM-450 & 700 units has two keyway slots cut vertically down the flight or screw of the auger.
It is important to remember that all DCM models have these cylinder keys welded inside. This makes auger
removal different from typical auger type units. You cannot lift the auger straight out like you do on a flaker
unit. When removing the auger for inspection on the small DCM-240, you must lift upward on the auger and
turn it clock wise to “unscrew” it past the key in the cylinder. To remove the auger from the larger DCM’s, you must
align the keys with the auger slots. Do this by lifting the auger up slightly until the spline at the bottom of the
auger clears the coupling. Next, rotate the auger to align the keys with the slots. Once they are aligned , lift
it straight up and out of the evaporator cylinder. You may find it necessary to
remove the extruding head in order to visually see the keys and slots. Keeping upward pressure on the auger
as you rotate it clockwise will allow the auger to come out as the slots reach the keys .
Service Tip: Cleaning the water system on a flaker or DCM before you pull the auger allows for easier removal.
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HEAD PRESSURE CONTROLS
Proper head pressure is very important to remote ice machine operation. The head pressure must fall into an
acceptable range so that basic refrigeration can occur. It is also important for adequate hot gas defrost. Head
pressure is generally not a problem for warmer climate applications. In colder climates however, some type of
head pressure control is needed. The choices are limited. A fan cycling device can be
used to cut off the condenser fan for a period of time. Some type of air flow control, like a damper system,
can be used to restrict the condenser air flow. Lastly, a three way valve can be used to back up liquid in the
condenser and divert discharge gas directly to the receiver. Hoshizaki remote systems use a head pressure
control valve typically called a headmaster valve. The headmaster valve is preferred in our application
because it normally provides a 5-10 PSI operating range for the head pressure. Air flow and fan cycling
devices can vary the head pressure as much as 40-50 PSI. For our application, the narrow range provides
better operation. The headmaster used on KM- 500~1200 models is a Sporlan LAC-4 190 PSI valve.
KM-1600 & 2000 Models use a 157 PSI setting and the KM-2400 uses a LAC-5 140 PSI setting.
The headmaster valve is a modulating valve that limits the flow of liquid from the condenser while at the same
time regulating the flow of hot gas around the condenser to the receiver. This mixing of liquid and hot gas creates
a high pressure at the condenser outlet which causes liquid to back up in the condenser. This reduces the
effective condenser surface causing a rise in condensing pressure and maintaining a more constant receiver pressure.
Proper refrigerant charge is imperative for correct operation of a head master. Always check for the
correct charge before condemning a headmaster.
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SERVICE Q & A
Question: The freeze cycle is longer than normal, what should I check?
Answer: by Keith Johnson This is a common question asked by service technicians and is relatively
easy to diagnose. First, remember that there are backup timers incorporated in the solid state control board.
This includes a five minute short cycle protection timer and a sixty minute maximum freeze timer. The board
has the freeze cycle under control for the first five minutes. This is the short cycle protection timer. After
five minutes, the board waits for the float switch to open contacts. This occurs when the water level in the
reservoir drops to a certain point. In order to determine what the freeze cycle should be
running, check the reference material. This information is found in the Tech-Specs or individual service
manuals. By referring to the production charts, determine approximately how long the freeze cycle
should be. This time will be affected by ambient conditions and water temperature and should be used as
a guideline. If it has been determined that the freeze cycle is too
long, there only a few things that could cause this. Here is a list of what to check.
FLOAT SWITCH: The float switch initiates the KM
cuber harvest. If in 60 minutes, the float switch failed to open its contacts, the board will automatically put the
unit into harvest. The symptoms of a stuck float switch is a consistent 60 minute freeze cycle. The cube will be
larger than normal. Also the reservoir may run short of water before 60 minutes expires causing the pump to
suck air. When the freeze cycle is started, the board starts the maximum freeze timer. If the contacts stick
closed, this would cause a long freeze cycle. The float switch can be checked by using a simple ohm meter. If
the float is in the up position, the switch is closed. If the float is down, the switch is open. The float switch could
be dirty. Clean it and recheck the contacts. If the float switch is still reading closed when it should be open replace it.
WATER VALVE: Another cause of a long freeze cycle may be a leaking water valve. The water valve should
shut completely off when de-energized. If it fails to do so, it will continually let water in the reservoir. This will
lengthen the freeze cycle. The actual increase in cycle time will depend on how much water is seeping past the
water valve diaphragm. If the water is flowing excessively, no ice will be made. In this case clean the
bleed port in the valve diaphragm, replace the diaphragm, or replace the water valve. The symptoms
would be up to a 60 minute freeze cycle if the valve was leaking excessive water into the reservoir.
CONTROL BOARD: The control board could cause a long freeze cycle. To check this disconnect the float
switch from the board after five minutes in the freeze cycle. The machine should go directly into the harvest
cycle. If this does not occur, the board should be replaced.
Each of these problems will produce an oversized cube. Long cycles can also be caused by a refrigeration
problem. A long freeze cycle that produces a small cube or no cube at all will most likely be linked to a weak
compressor, expansion valve, or some other refrigeration problem. Use basic refrigeration principals
to diagnose these areas.
TXV Diagnostics
Thermostatic Expansion Valves (TXV) are utilized on all present production Hoshizaki Machines.
Misdiagnosis of the TXV is common because the symptoms of a bad TXV are: low or no ice
production, possible freeze-up, deformed ice cubes, partial or improper freeze pattern on the evaporator,
long cycle times and flooding or starving of the evaporator.
Since the symptoms are similar to other failures these items should be checked thoroughly before condemning
a TXV: check the water system to assure that the evaporator and distribution system are clean.
Remember that lime or calcium scale is transparent when wet, so check the evaporator to assure a smooth
clean freezing surface. Also check the inlet water solenoid for leak-by during the freeze cycle. This would
add additional water to the reservoir and more evaporator load. The air cooled condenser must be
clean and have proper air flow. A water cooled condenser must be clean and have adequate water flow
and proper operation of the water regulating valve. Other refrigeration system components should be
checked. A liquid line valve which leaks by during harvest, a partial restriction in the system, a bad
condensing pressure regulator valve (headmaster) or a low capacity compressor can cause symptoms similar to
a bad TXV.
The refrigerant charge must be correct in order to properly troubleshoot the TXV. The refrigerant charge
is critical and a high or low charge can cause the TXV to operate improperly. The proper refrigerant type and
charge should be weighed in according to the name plate rating on the unit. Now
that we have covered items with similar symptoms, lets discuss the thermostatic expansion valve. The TXV
operates as a metering device and feeds refrigerant to the evaporator. There are three factors which act
together to open and close the TXV to supply the proper amount of refrigerant to the evaporator. These
three factors are the sensing bulb pressure, the evaporator pressure and the valve spring pressure.
The sensing bulb contains a type “C” gas charge and is attached to the evaporator outlet using stainless steel
clamps. The bulb should be mounted between the 10:00 and 2:00 position on the suction line. Always
check the mounting and clamps to assure good thermal contact. A loose TXV bulb could cause liquid flood
back, long freeze cycles or a possible freeze up. This could also cause a high pressure safety switch trip at the
beginning of freeze. This would be due to excessive refrigerant in the harvest loop because the TXV does
not close down properly during harvest. This excess refrigerant could cause a high pressure “spike” at the
beginning of freeze to shut the unit down on the high pressure safety. This could occur intermittently
depending on the operating conditions. Hoshizaki uses non-adjustable TXV’s which are factory
set by the manufacturer. In normal operation, as the water flows down the evaporator and is cooled and
finally begins to freeze, the load on the evaporator decreases. As the load decreases, the suction line
temperature will decrease which in turn allows the bulb pressure to decrease. This decrease in bulb pressure
allows the upward spring to begin closing the diaphragm, thus maintaining proper refrigerant flow.
This is why suction pressure is higher at the beginning of the freeze cycle, then
gradually decreases as the cycle continues. If the TXV valve does not open enough, long cycles, and low
production may occur. If the valve opens too much or does not close properly, flood back and possible
compressor damage may occur. On a KM cuber, check the frost line, freeze cycle time
and ice fill on the evaporator to assure proper TXV operation. The frost line at the end of the freeze cycle
will range from the suction line compressor connection to 1/2 the distance from the evaporator to the
compressor. The normal freeze cycle time is found on the performance data chart in the KM service manual.
You must know the exact inlet water temperature to read the chart correctly. Suction pressure (5 minutes
into freeze cycle) and head pressure readings are also found on this chart. The normal ice fill will be from top
to bottom and at the end of the freeze cycle. The last two passes will have slightly smaller ice cubes if the
refrigerant charge is correct and the TXV is feeding properly.
Some units utilize multiple TXV’s. In this case each circuit should be treated individually as a single pass
circuit when troubleshooting. On a flaker, the TXV maintains a constant suction
pressure and evaporator temperature because the evaporator load is constant. The frost line will be
consistent and within the same range as the KM cuber. A quick check for a TXV that is suspected bad is to
check the valve swing. To do this, check the suction pressure 5 minutes into freeze. Remove the TXV bulb
and hold it securely in the palm of your hand for 2 minutes. Check the suction pressure and place the bulb
in an ice bath for 4 minutes to check to see if the suction pressure swings at least 10 to 25 psi. A swing of 5 psi
or less would indicate a weak TXV which should be replaced.
Hopefully the information provided here will help you understand TXV operation, symptoms and trouble
shooting procedures, and assist you in future diagnosis on Hoshizaki equipment.
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KM Pump Assembly
You Get What You Pay For!
How many times have you heard this statement. Well, taking a good look at the KM pump assembly will
definitely bring this statement to mind. The KM pump assembly utilizes a Permanent Split Capacitor (PSC)
motor. The capacitor is located in the control box. Using a PSC motor provides better starting torque and
better running efficiency. The capacitor along with the dual winding also give us the capability of reversing the
pump motor for the pump -out cycle. The motor has a thermal overload protector built into the windings and
uses sealed stainless steel roller bearings which do not require lubrication.
The front end of the assembly is completely rebuildable. Four bolts or screws can be removed to access the
replaceable impeller and mechanical seal. These parts are available individually for replacement if failure
occurs. This is definitely not a throw away assembly, however, in case of a failed motor, the complete
assembly should be replaced. Providing this quality pump assembly and mounting the
assembly is a dry compartment away from the damp/moist conditions in the evaporator section have
proven to extend the service life of the KM unit.
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Service Seminar Results
This is just a quick update on the 1994 Hoshizaki Training Season. We have completed out Spring
Training sessions for this year. It is obviously hot outside and your Service Techs are working fast and furiously.
This year the Hoshizaki Care Department conducted total of 64 service seminars which included 2,760
Service Techs. We are presently gearing up for the Fall by updating our seminars and material. We look
forward to seeing you at the next service seminar held near you. Contact your local Hoshizaki Distributor to
get your name on the seminar list.
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Compressor Checkout
By David Brown
The heart of the refrigerant system in the Hoshizaki Ice Machine is the compressor. The compressor pumps
refrigerant through the system. A bad or inefficient compressor means low or no refrigerant flow.
Since proper diagnoses of an inefficient compressor can be very difficult, all other components must be checked
first for proper operation. The condenser and evaporator must be clean. Check the water distribution
system and be sure the water solenoid valve is not leaking-by during the freeze cycle. Confirm TXV
operation and that the refrigerant type and charge is correct.
The symptoms of an inefficient compressor are high suction and low discharge pressure, longer than normal
cycle times, and hot running compressor. The manufacturers have a Full Load Amperage (FLA) rating
for each of their compressors. An inefficient compressor will be drawing considerably less than FLA.
The older method of testing for an inefficient compressor was done by closing off a liquid line valve and pumping
down the refrigeration system into a 10” to 15” vacuum. This method is no longer approved by compressor
manufacturers, and is not recommended by Hoshizaki. If you suspect an inefficient compressor, check system
pressures and amp draw. For cubers, also check the complete cycle time. A border line compressor may
have “decent” pressures and a normal freeze time but the harvest time will be longer than normal.
In cases where the compressor will not run, the first thing to do is check the voltage at the compressor which it is
attempting to run. The voltage should be within 10% of the rating on the compressor tag.
If the compressor will not attempt to start, the thermal overload may have opened. If the crankcase is hot, cool
down the compressor. restart and check the amp draw. If amperage exceeds 40% of FLA, check for an
overcharge of refrigerant, excessive or no evaporator load, an over feeding TXV, or a high side restriction.
The overload could also be stuck open. A malfunctioning TXV can cause extensive damage to
the compressor if not corrected. An over feeding TXV will cause flooding of the compressor which can wash
the lubricating oil from the crank case causing the bearings to seize and resulting in Lock Rotor Amps
(LRA). Flood back can cause the compressor to pump liquid refrigerant causing the valves to warp or break.
Along with flooding comes high amp draw, and a cooler compressor.
An under charge of refrigerant can cause the compressor to overheat and the valves to warp. An indication of an
undercharged system is low pressures, long cycles and the amperage draw will be less than FLA.
If the compressor will not run, trips the breaker or hums, check for voltage across the run and common motor
windings. If the proper voltage is found, the compressor needs to be ohmed to see if there is an open
or shorted winding. Most Hoshizaki compressors utilize an internal thermal overload in the windings which could
also open not allowing the compressor to start. In order to ohm out the compressor; disconnect the
power to the ice machine, remove the compressor terminal leads and set your multimeter on the ohm scale.
Read the resistance from terminal to terminal recording the resistance. The least resistance will be from run to
common, start to common will have more resistance, and start to run will have the most resistance. Make
note that this applies to single phase compressors only. Three phase compressors will have equal resistance
between all 3 terminals. Also check each terminal to the crankcase for a grounded condition. A readable
resistance from any terminal to ground is a shorted condition.
A run capacitor can fail causing the compressor to draw excess amperage while the pressures are correct.
Failure of a start relay or capacitor will cause high amp draw or failure to start. Check both start and run
components thoroughly. Most compressors fail due to other component failure. Action must be taken to
correct this or you will loose another compressor. Inspect the system completely to determine the cause of
the problem and replace the compressor and components as necessary.
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Front Panel Insulation
Effective on June production, a change has occurred on the KM-500 and KM-30 front panel insulation. The
polyethylene foam which was attached to the lower panel has been changed to a one piece molded ABS
separator that fits inside the edges of the front panel. This separator provides an air gap which insulates the
front panel from the ice drop and pump compartment. This reduces the possibility of condensation. It can also
be removed for cleaning if necessary. This change will likely be implemented on the 30” “M” models in the future.
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KM-2400 Part Change
Effective on the June production for the KM2400, a change was made in the Discharge Line Gas Valve. The
original Fugikoki valve part number 2U0131-01 is being replaces with a Sporlan Valve part number 4A0582-01.
If a discharge line gas valve is ordered for the KM-2400, the Sporlan Valve will be shipped. Don’t get
excited when you see the new valve because it looks a little different from the original. The inlet is stamped
“IN” and should point towards the compressor when installed. Be sure to use a good
heat sink to protect the valve body from overheating during the brazing process.
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CFC Update
Time is quickly slipping away on the phase out of CFC Refrigerants. I’m sure you are also aware that
November 14 is the date that Technicians must be EPA Certified to handle refrigerants. If you are not prepared,
you won’t be able to purchase refrigerant after that date!!
When we look at HCFC or HFC options to replace CFC’s we find some controversy as to the best choice.
In the ice machine industry, some have chosen to go directly to the “new” HFC refrigerant R404A (SUVA
HP62). Some have chosen “HP81” which is another “new” HCFC refrigerant. While others are using the
“old stand by” HCFC R-22 which has been utilized in the refrigerant industry since its introduction in 1936.
Hoshizaki chose R-22 as an interim refrigerant due to its compatibility with our ice machine application, the vast
industry acceptance and experience, lower price and excellent market availability. Also when you look at its
potential to destroy the ozone (0.05 ODP) you will find it 4.6 times less that R-502 at 0.23 ODP. Refrigerants
are also rated on their effect during production and use on Global Warming or Global Warming Potential
(GWP). The GWP for R-22 is 0.3 as compared to R-502 at 3.75. The new
HFC HP62 has a 0. ODP and a GWP of 0.94. Since we expect GWP to be the next “Hot Issue” with EPA,
we made the R-22 choice. Who knows, in the near future, someone may develop the perfect refrigerant
which will resolve all our problems and drop in to existing units. Yeah right! Meanwhile, we have a few
years while using R-22 to thoroughly test all the new alternative refrigerants and chose the best one to the
environment and our customers.
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Ice Machine Refrigerant Charge
The refrigerant type and charge amount for all Hoshizaki ice machines is printed on the model nameplate. This
nameplate is located in 2 places on the machine; on the rear panel, upper right hand corner and inside the
compressor compartment on the wall, base of control box cover.
From a factory standpoint, the charge amount is critical and must be correct for proper operation and production.
The standard Hoshizaki policy for a sealed system repair is to recover the existing charge, replace the drier,
evacuate the unit and weigh in the correct refrigerant type and charge as per the model nameplate information.
Topping off the refrigerant charge or guestimating the additional refrigerant needed to make the unit operate
properly, commonly known as the “S.W.A.G.” method is not an acceptable practice. Also, installing a sight glass
on a system for charge purposes is not recommended for Hoshizaki applications.
Most likely the question in your mind now is what is so critical about this charge. The answer is simple. The
Performance Data which is provided in the service manual is used for refrigeration system trouble-shooting.
This data is taken from detailed test conducted under varying water and ambient conditions with the exact
factory charge in the system. When the charge is varied from the factory recommendations, this data will not hold
true. The charge amount is also calculated to provide maximum production and efficiency from the sealed
refrigeration system. This critical factory charge extends for all models
including remote applications. While it is true that the receiver included in a remote system will hold additional
refrigerant, the proper receiver level is important for proper operation throughout the wide yearly condensing
temperature range. There is only one application when the factory charge should be altered. This is in the case
of a remote installation where the line set length is over 66 feet long. In this case additional refrigerant should be
added to fill the liquid line for the additional length over 66 feet up to a maximum of 100 feet. Add .5 oz. for each
additional foot of 3/8” liquid line. You should always mark the total charge on the name plate labels for future
reference if additional charge is added. This information is covered in the installation instructions for remote
applications.
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The Hot Gas Valve Diagnosis By Perry Maxwell
The hot gas valve is installed between the discharge line and expansion valve outlet. It is used to divert the
discharge gas from the condenser directly to the evaporator. to harvest ice from the plate. Hoshizaki KM
model ice machines utilize an electro-mechanical snap action valve. There are three different sizes of hot gas
valves. Each valve is sized to match the size of the ice maker. For field replacement of the valve body you must
use the correct size. For field replacement of the coil you can utilize one universal coil thus reducing the
amount of parts stocked. The universal coil replacement part # is 440353-01.
In diagnosing hot gas valve problems there are a few different problems that can occur. The most obvious is
an open solenoid coil. When the solenoid coil has an open winding the valve will not open when energized.
Another possibility is a sticking valve. The valve can stick fully open, causing hot gas to be supplied to the
evaporator continuously throughout the cycle This will allow heat to build up in the evaporator and possibly
cause a high temperature safety shutdown. A valve that is stuck fully closed will do just the opposite. It will not
allow hot gas to be supplied during harvest. This will cause a self-contained air-cooled machine to trip on the
high pressure safety. A water cooled unit will frost the evaporator and drop ice strictly on water temperature
thus prolonging the harvest cycle. A remote system will pull into a vacuum if a line valve is present. A valve can
also stick in any position in between. The symptoms will vary depending on where the valve sticks. If the valve
sticks partially open, but not enough to overpower the refrigerant supplied by the expansion valve, the machine
may make ice but will have a long freeze cycle. One of the best ways to diagnose a valve stuck partially open. is
to check the temperature at the valve outlet. A bullet strainer is installed ahead of the hot gas valve to
protect the valve from contaminants. A plugged strainer will resemble a partially closed valve and not supply
enough hot gas to harvest the ice. The coil on the hot gas valve could also cause a problem
if the windings are weak. A weak coil will open the valve when voltage is first applied. As the valve warms,
the coil’s magnetic field will start to weaken and the valve will start to close. As the valve closes, hot gas will
be diverted back through the condenser. The symptoms of a weak coil will vary with the different types of
machines. For example:
1) An air-cooled machine does not run the condenser fan motor during the harvest cycle. As the gas valve closed
down the head pressure will climb and the machine will trip the high pressure safety switch during the harvest
cycle. This could occur in 30 seconds to 3 minutes depending on the weakness of the coil.
2) On a remote unit, as the coil weakens, the gas is diverted to the condenser. Since the remote condenser
fan runs all the time, the unit will not shut down on high pressure safety. It will however, pull into a vacuum due
to the liquid line valve being closed during harvest. On early model units without a liquid line valve the expansion
valve will be forced open and start feeding the evaporator. In both cases, the harvest is extended. The
common complaint related to a weak coil is “the pump motor will not run in the freeze cycle.” This is because
the unit remains in harvest. You will continue to have voltage applies to the coil even though it is not opening to
divert the gas.
3) A water-cooled unit will also leave you with the impression that the pump is not running in the freeze
cycle. When the unit is in harvest, with a weak coil, hot gas in not diverted to the evaporator. The pressure
increases in the condenser, the water regulator valve will open to cool the condenser and maintain a constant head
pressure. This will force the expansion valve to open and frost the evaporator coil on units with no liquid line valve.
The result here is also and extended harvest. These failures would be considered the most common
problem associated with hot gas valves.
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Pre-Chillers Pro’s and Con’s
To chill or not to chill, that is the question. There are several different manufacturers of water pre-chillers who
state that their product will increase ice machine production and efficiency. This increase promises a
quick return on investment which will mean free ice at some time in the near future.
There are 2 basic types of pre-chillers available. (1) refrigerated pre-chiller utilizes a separate compressor
system and water jacket to cool incoming water. (2) A mechanical pre-chiller employs the unit and bin drain
water in a water jacket to cool the incoming water. Typically a mechanical pre-chiller will give only a 10° to
15°F drop in water temperature at best. A refrigerated pre-cooler will provide a 40° to 50°F drop, however,
there are definite energy costs, as well as, a high initial equipment costs.
Let’s take a quick look at a KM-1200MAE to see what chilled water will do for production. Keep in mind that
there are 2 major factors which effect ice machine production, they are ambient air temperature and
incoming water temperature. At a 90°F ambient temperature and a 90°F water
temperature, the production will be 1052 lbs. per day or approximately 2.7% more ice production.
Chill the water to 50°F and your production is 1127 lbs. per day, another 4.4% increase. The total increase in
production by pre-chilling the water 40° us 7.7% or 75 lbs. per day. The increase in production would vary
somewhat depending on the model. The only way to chill enough water needed for a KM-1200M by 40° is to utilize a refrigerated water chiller. Considering the cost of such a system, plus the energy to
operate i.e., a 7.1% increase is not worth the effort. I’m sure you get the picture here. A pre-chiller will
increase production, however, over all it is probably not a cost effective measure.
HOSHIZAKI CARE TECH-TIPS
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KM ICE QUALITY
Recently, in the state of Florida, a federal agency conducted a test on bagged ice. Bag ice was tested
from different locations across the state for ice quality and purity. The testing agency noted the different ice
shapes and inspected the cleanliness of the machine, that produced the ice .
The results showed the KM crescent shaped cube to be clearer and purer than some ice cubes. Some of the ice
inspected had traces of bacteria and minerals. The KM units inspected had a clean sanitary appearance. This
prompted the testing agent to question our local distributor “Why?”. In answer to this question I submit
the following reasons.
Stainless steel is known for its durability and sanitary qualities. The flat freezing surface of the KM stainless
steel evaporator offers no restriction to the water flow. Water flows quickly and smoothly down this flat
surface. Pure water freezes first and the contaminants are “washed” out in this freezing process. The speed at
which the water flows down the plate will directly effect ice purity, clarity, and hardness. Consider that any
restriction which slows the water flow allows time for the contaminates to freeze into the cube. Water which
must flow into a grid cell, or across a restrictive separator or barrier , can be slowed to the point where
cube purity suffers. At the end of the freeze cycle, the reservoir contains a
high concentration of contaminants. If these contaminants are not removed , they mix with the
incoming water and the next batch of ice will suffer in purity. To reduce contamination, Hoshizaki units
clean the reservoir twice during the harvest. KM units pump out these contaminants at the beginning of
the harvest cycle and flush the reservoir by overflowing the stand-pipe at the end of the harvest cycle. The
pump-out can be adjusted to occur every cycle or to skip 2, 5, or 10 cycle to reduce water usage in good
water areas. The flush removes additional contaminants and can be lengthened to provide additional cleaning of
the reservoir. A small ice drop zone also helps to prevent algae growth. Most ice machines have a large ice drop zone
which allows air to circulate from the bin upwards and around the evaporator. When the bin door is opened to
remove ice, air-born bacteria enters the bin cavity. As the ice releases and drops into the bin, the air circulates
up around the evaporator and the air-born bacteria adheres to the wet surfaces of the evaporator. This is
what causes“slime”growth in the water system. The KM evaporator section is insulated and sealed to
provide a pressurized cavity. The small ice drop zone and this positive pressure helps to eliminate air flow
around the evaporator reducing the possibility of contamination by air-born bacteria.
These exclusive features provide Hoshizaki customers with hard, crystal clear, purified, KM crescent shaped cubes.
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CONTROL BOARD MIX-UPS
We have established through previous issues of Tech Tips that there are four different control boards in the
field. Consequently, the possibility exists that the wrong board could be installed in a KM cuber. Let’s
explore the possibilities, symptoms, and solutions, should this occur. Misapplication 1: Older model units (KM-451/601/
631/1201) came from the factory with an “A” or “B” board. If an attempt is made to install a “C” or Alpine
board in one of these units, you will find that the unit will not operate. The unit has a 9 pin connector and the
board has 10 pins. The K-2 connector on the board cannot be connected because there is no separate
control voltage transformer. Your only choice here is to order a “B” style board for this application.
2: The unit you are servicing was manufactured with a “C” board. You have a “B” board on the truck and
decide to give it a try. Guess what, it won’t work. The 10 pin unit connector will slide over the 9 pins on the
board but it doesn’t match up properly. There is no place on the “B” board to connect the control voltage
transformer. You have two choices here, you may still find a “C” board in the distributors inventory or you can
use the Alpine replacement board. Both are direct replacements.
If you use an original Alpine board or an Alpine universal replacement board with the RO65 jumper wire
cut, the unit will not start for 3 minutes and then will not have the correct sequence. The jumper must be in
place when using an Alpine board to replace a “C” board.
3: The unit you are servicing was manufactured with an original Alpine board part # 2U0127-01. This original
board is now available as a service part or you can use a universal Alpine part # 2U0139-01 if you cut the
black jumper wire across resister RO65. It is important to note that if you fail to cut the jumper wire
the unit will work fine until you cut the power switch off. At that time the contactor will remain energized to keep
the compressor on. This is not good! Always check to assure the contactor de-energizes when you flip the
power switch to off, before you leave the site. To avoid board mix-ups follow these simple rules.
1. If the unit came originally with an “A” or “B” board, replace it with a “B” board.
2. If the unit came originally with a “C” board, replace it directly with a universal Alpine board.
3. If the unit came with an Alpine “original” board, replace it with an “Alpine original” or a universal
Alpine with the jumper cut.
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WATER SYSTEM SANITATION
Sanitation is a vital step in the process of cleaning an ice machine. It is important to remember that ice is a food
product. Since this food product goes directly into the customers cup or glass, it is critical to assure that it is
clean and bacteria free. A good water filter system will help neutralize waterborn
bacteria and slow mineral build-up. Even with the best filter system, routine maintenance, including
cleaning and sanitizing , is a must. Cleaning the ice machine with an acid based scale
remover gets rid of the mineral build-up which forms on the evaporator. A clean freezing surface provides better
efficiency. Once the system is de-scaled or de-limed, it should also be sanitized to inhibit the growth of air-born
bacteria. This will retard algae or slime growth in the ice drop zone and evaporator compartment.
Algea growth is common in a business that bakes bread or has open beer bottles sitting close to the ice machine
due to yeast spores in the air. The use of a commercial sanitizer will definitely extend the time between cleanings.
Frequency and scheduling of preventative maintenance cleaning and sanitizing will depend on the
local water conditions. Sanitizing can be considered a health issue. Service technicians should make
recommendations and sell the customer on the benefits of this important service.
REVERSE OSMOSIS
There are many different types of water treatment systems available today. Due to the increased concern
over the quality of water, Reverse Osmosis " R O " systems are more prevalent.
An RO system produces almost pure water with a pH well below 7.0. This water has been forced through a
membrane under high pressure. The membrane serves as the filter media and has a pore size in the sub micron
range. Due to the small pore size, the amount of water that will pass through the membrane is reduced. The
rejected water is flushed down the drain. A ratio of three gallons of waste water to one gallon of processed
water is common in producing RO water. As the water is forced through the membrane, solids
larger than the pore size are deposited on the membrane surface. At some point , the membrane surface loads
up with solids and must be cleaned or replaced. In areas with a high mineral content in the water, more
frequent cleaning is required. The final purity of the processed water will depend on the quality of the
system and how well it is maintained. The water produced by an RO system is extremely
aggressive and is considered an active solvent. The low pH makes it highly acidic. RO water will attack most
metals and plated surfaces. The RO process increases the galvanic action of the water which will shorten the
life of rubber parts and can cause plastics to weaken. As you can see, this could cause problems in an ice machine.
Due to it's aggressive nature, Hoshizaki America Inc. does not recommend the use of RO water in
our ice machines. If RO water is used the following damage could occur : Over a period of time, RO water
flowing down the center of a KM evaporator could wash away the copper/stainless bond and cause
separation of the evaporator plates. If RO water is used in a flaker, premature bearing wear and damage to the
mechanical seal could result. Other ABS and rubber parts could also be effected. Any failures caused by RO
water would not be covered by warranty. Care should be taken in explaining the effects and
discouraging the use of RO water in ice machine applications. Please advise any customers now using or
planning to use RO water with Hoshizaki ice machines of these possibilities.
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COMPRESSOR DIAGNOSIS
In this issue, we will discuss the electrical aspects of diagnosing single phase compressors. Hoshizaki uses
CSCR type compressors in all single phase units. You will find the start relay, start capacitor, and run capacitor
mounted in the unit control box. A potential start relay is used. The start relay takes the
start capacitor out of the circuit when the motor approaches normal running speed. The coil of this relay
is parallel with the start winding. As the motor turns, additional voltage (back EMF) is generated by the start
winding. Since the amount of back EMF is directly proportional to the motor speed, as the speed increases,
so does the voltage. When the voltage reaches a certain point (motor approaches normal running speed ) the
start relay energizes. This opens a set of normally closed contacts to take the start capacitor out of the circuit.
The run capacitor is wired across the start and run windings and causes a phase shift between the two. This
phase shift improves the motor running efficiency, increases the power factor and reduces noise. Since the
run capacitor remains in the circuit continuously, it always has a much lower capacitance rating than the
start capacitor. Compressor electrical problems fit into one of four
categories. They are; No or low voltage, bad windings, improper wiring, and bad start / run components. To
find which category fits your problem you must look at the symptoms.
If the compressor does not start when the unit sequence calls for compressor operation, you should
first check for voltage across the common and run terminals. This voltage should match the name plate
supply voltage +/- 10%. If the voltage is low or zero, check your power supply and contactor or compressor
relay to assure the contacts are closed. Once you have establish proper voltage across common
and run, if the compressor still does not start, check the compressor windings for an open condition. This can be
done by checking the winding resistance using a good quality ohm meter. The compressor terminals (marked
C, S, & R) must be disconnected when checking the winding resistance. When disconnecting the terminals
make note of the wiring color code and check it against the unit wiring diagram to assure proper wiring. Check
for resistance across R & S with your meter on the high scale. If the meter reads infinity, the windings are open.
A hot compressor should be allowed to cool and checked again. This will determine if the internal
overload was tripped. If the meter shows e readable resistance, check between C & R, and C & S for
readings within the specifications provided in the Technicians pocket guide compressor data section.
If the windings or overload are not open and voltage is present, the compressor should either hum or start. A
compressor that simply hums will possibly shut off on internal overload or kick the unit circuit breaker. This
can occur immediately or within a short time after the compressor starts. In this case, the windings should be
checked for a shorted condition. With your ohm meter on the lowest scale, check each terminal to ground
(compressor case or suction / discharge line). Any resistance reading between a terminal and ground
represents a shorted condition. If the windings check OK and the unit continues to trip the overload or
breaker, it should be checked with a "Hi Pot" meter for a weak winding which breaks down under a load.
A partial short between the windings or a start / run component problem will also cause the compressor to
either hum or pull high amp draw and / or run sluggishly. A partial winding short would have been found when
checking the winding resistance. A bad run capacitor will generally cause high amp draw. Check the amp
draw with a clamp-on amp meter on the common lead. A bad start capacitor will cause the motor to hum or run
sluggishly. The amp draw will be high and the overload or breaker will finally kick. Both capacitors should be
checked on a capacitor checker to determine if they are weak or defective. A bad start relay may keep the start
capacitor in the circuit continuously or not at all. Either will cause the same symptoms as a bad start capacitor.
We have discussed the major aspects of electrical diagnosis. Hopefully this will help you troubleshoot any
CSCR compressor. Next month we will discuss the refrigeration aspects of compressor diagnosis.
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P M REMINDER
Winter time is generally a little slower than mid summer around the refrigeration shop. This is usually a good
time to conduct a few preventative maintenance checks for your flaker customers. Call them up and schedule a
PM check. Advise them of the benefits of an annual cleaning and bearing inspection. They get the benefit of
a more efficient operation and less down time when it is hot and heavy in the summer. You get additional service
work. Its a win~win situation.
