Practical Ice Maker Troubleshooting Tips
May 29, 2006
Ice Maker
Troubleshooting Is Easier If You Take It One Step at a Time
Ice maker troubleshooting is always easier when you have the service manual for the machine. Since you're already online,
why not visit the ice machine manufacturer's Website and get the service manual for your machine?
You'll find
The service manual provides crucial information about the ice machine
refrigeration system and electrical controls, so
there's no reason to hesitate about breaking it open during service calls.
If the customer asks what you're reading, show him or her the steps in the manual, and explain that following the factory recommended procedure step by step helps make sure you don't miss anything, helps you identify the problem quickly, and helps get the repair finished efficiently, which reduces labor costs.
If you can't get the manual, all of the newer machines I've worked on have
had a good set of explanations somewhere,
on the front cover, or in the control
panel area, about what the indicator lights mean with regard to what part of
the
operational cycle the machine is in, or what error code is being displayed.
If the indicator lights are working, and if you can find the legend that explains what they mean, they'll at least point you in the direction of what part of the machine is malfunctioning.
If your ice maker troubleshooting call is for a machine that isn't running
at all, be sure to ask the owner or operator what
type of problem they might
have been having with the machine before it stopped, then check the disconnect
or outlet for
power.
If there's no power at the disconnect or outlet, check the breaker or fuse
(or fuses). If the breaker tripped or a fuse blew,
you'll have to use an ohmmeter and check the wiring and electrical components for a ground or short.
If you find a failed part, good job! Replace the part, inspect the rest of the machine to see if it's actually in good enough condition to run, verify that the power supplied to the machine is correct, then give it a test run.
Otherwise, if there's power at the disconnect but it was turned off, or if the machine was unplugged, ask the owner why.
If the machine was disconnected because it just wasn't running right, the
next step of this ice maker troubleshooting call
will be to open the panels up and do a quick, thorough visual inspection.
VISUAL
CHECKS
You need to verify that the water supply to the machine is good, and you should
also inspect the water distribution
components in the machine. If they're
plugged with scale build up, the machine should be descaled, but make sure the
machine at least runs and starts freezing normally first.
If there are major problems with the compressor, metering device, controls,
etc., and the machine is old enough that the
owner wants to replace it instead
of paying for major repairs on an old machine, the descaling procedure might
turn out
to be a waste of time.
You'll also want to take a close look at the evaporator plate. If the
plating is severely discolored, or if you see a lot of
copper color showing through, the plating might be worn off to the point where ice won't drop off the evaporator during harvest. You also want to be sure there's no scale build up on the evaporator.
Check the condenser and make sure it's clean, make sure the condenser fan
blade turns, and verify that nothing is
interfering with the airflow through
the condenser. If it's a water-cooled condenser, verify that there is water
pressure
available to flow through the condenser when the unit runs.
Attach your gauges and make sure there's pressure in the machine; and if you can, verify that it's the correct refrigerant.
If there's nothing else visibly wrong with the machine, turn on the power
and verify that it is the correct voltage for the
machine. If there are solid state controls, see if there are any error code indications, and note down what they are. We'll go over possible problems and their causes shortly.
By this stage of any ice maker troubleshooting call you will have verified
that the water and power supplied to the machine
are correct, that the condenser is clean and the fan is good. If it's a water-cooled condenser, you'll have verified that there's water available to flow through the condenser, and you'll have verified that the evaporator plate and water distribution components are clean and scale free.
If there are no error indications, or if the machine doesn't have solid
state controls, turn the machine on to “ice,” and see
if it will run.
Keep in mind that different makes of ice makers start out differently.
Hoshizaki units start by defrosting until the suction line thermistor warms up;
Manitowoc’s start a couple of different ways, depending on the type of machine;
and Ice-O-Matic’s
also start a couple of different ways, depending on the type
of machine. So give the machine a couple of minutes to cycle
into its full freeze mode.
If your ice maker troubleshooting call is for a
wait at least 10 minutes to see if it drains, re-fills, and starts rinsing again.
If it does, someone switched it to “clean,” and it won't cycle into “freeze” until it finishes the complete clean cycle.
If your ice maker troubleshooting call is for a Hoshizaki unit, pay close
attention to the strength of the water flow during
the fill cycle when it
starts up. These units require a strong water flow for optimum harvest
efficiency, so if flow looks
weak, check the pipe size, filter, inlet screen, and distribution nozzles.
COMMON
ICE MACHINE PROBLEMS
The rest of this article will cover common ice machine problems, and what
symptoms to look for during your ice maker troubleshooting calls.
First, check the cuber and bin drains for steady running water. If you see
this, the dump valve might be leaking, the fill
solenoid or float valve might
be leaking, the drain siphon pipe might be loose or adjusted incorrectly, or
the sump pan or
the machine might not be level. This will cause long harvest
cycles, can trip the solid state controls on “long cycle time”
errors, and will increase the cost of making the ice.
If there are no water overflow problems, let's move on to other possibilities.
If your ice maker troubleshooting call is for a machine that immediately
trips off on high pressure, put your gauges on and
verify that the pressures are actually high and that the safety hasn't failed.
If the pressures stay normal but the high pressure safety opens, the safety
has failed and you need to replace it. If the
pressures are high, verify that there are no isolation or service valves closed on the high side of the system, double-check
the condenser coil to see if it's plugged, check to be sure the
condenser fan is running and that it's the right size and turns in
the right direction, and make sure no other appliances are blowing hot air directly into the condenser coil.
If this ice maker troubleshooting call is for a water-cooled machine, verify
that you have water flow and that it's not hot
water, make sure the head
pressure regulating valve hasn't gone out of adjustment or totally failed, and
if you can,
disconnect the water lines and inspect the inside of the condenser for scale or dirt buildup.
If there are no mechanical problems that would cause high pressures, it's
possible the system is overcharged or
contaminated with noncondensibles.
To check for noncondensibles, leave the machine off for a few minutes so
pressures will equalize. Check your pressures,
and check the temperatures of
the evaporator plate and condenser coil. If your saturated temperatures aren't
equivalent to
these pressures, it's very likely that the system is
contaminated. You'll need to recover the charge, replace the drier,
evacuate the system, and weigh in the factory specified charge.
If the saturated temperatures are equivalent to the evaporator plate and
condenser coil temperatures, and you suspect the system is simply overcharged,
it's still a good idea to recover the charge, replace the drier, pull a vacuum
to 500 microns,
then weigh in the factory specified charge.
You don't know who worked on the machine before you did, so you'll want to
be sure that you don't leave the machine
running with an overcharged and possibly contaminated system.
OK, what about an ice maker troubleshooting call where the machine trips off
on the low pressure cutout instead of the
high pressure safety?
Once again, check the pressures to be sure the suction pressure is actually
low enough to trip the cutout. If the cutout
opens but the suction pressure hasn't dropped to the cutout point, the cutout has failed and should be replaced.
If the suction pressure is lower than normal and you also have low discharge
pressure, suspect a low charge and check
for a leak. If you find a leak, make the appropriate repairs.
If you don't find a leak during this stage of the call, charge in two to
four ounces of refrigerant to see if your suction
pressure increases. On large machines you may need to charge in a little more to see an increase in suction pressure.
If suction pressure and discharge pressure increase, it's very likely an
undercharge; so you need to find out how the
charge was lost if possible, make the appropriate repairs, then charge in the factory specified amount of refrigerant.
If you suspect a leak and absolutely can't find it, charge in enough
refrigerant to get the machine to make ice, charge in the correct amount of
fluorescent leak detection dye, leave the machine running and making ice, and
make plans to come
back and find the leak in a day or two. Return in a couple
of days and, using an ultraviolet light, you should be able to
locate the leak. Make the appropriate repairs, and get the machine up and running.
What about a similar ice maker troubleshooting call with the machine
tripping off on low pressure, or running with low
suction pressure, but you don't find a leak, and when you charge in refrigerant, the pressures don't rise?
First, check for a restricted drier or liquid line. If the drier is
restricted, the outlet will be several degrees cooler that the
inlet, and the
drier itself might even be sweating or frosting. If the liquid line is
restricted, you might see frost or
condensation at the location of the restriction, and the outlet side of the restriction will be cooler than the inlet side.
If the drier and liquid line aren't restricted, check for a restricted or
failed metering device. If the metering device is a
capillary tube, you might
have to strip off some insulation, but if it's restricted you'll see a spot of
frost at the restriction.
If the metering device is a TXV, and if you're sure
the machine is fully charged and the evaporator plate is only freezing
about half way or maybe even less, then the TXV has failed.
· After five minutes of the freeze cycle, measure the temperature of the inlet and outlet copper lines of the evaporator.
· If the temperatures are not within 5° of each other, the TXV has failed.
· For a double evaporator machine, measure the temperatures of the TXV outlet lines as close to the TXVs as possible.
· If the temperatures are within 5° of each other, both TXVs are good.
· If the temperatures aren't within 5° of each other, the TXV with the higher outlet temperature has failed.
Keep in mind, this is only one step in the overall ice maker troubleshooting procedure.
LONG
CYCLE TIMES
The next ice maker troubleshooting call we'll discuss will be a machine that's
running, but takes too long to make ice, and is possibly tripping off on “long
freeze cycle.”
You should have already verified that the dump valve, fill solenoid, and
float valve aren't leaking, that the drain pipe isn't
loose or adjusted incorrectly, and that the sump pan and machine are level.
If there's no water flow problem, check the temperature of the defrost/hot
gas solenoid about five minutes after the freeze
cycle starts. The inlet will
be hot, but the body and outlet should be cool enough to hold. If the body and
outlet are too
hot to hold, it's probably leaking, which will increase freeze cycle times.
During your ice maker troubleshooting calls you should keep an eye on your
gauges, and take notes on what's happening.
Are pressures normal? If you have a high discharge pressure, check the condenser, and check for noncondensibles.
What's happening with the suction pressure? A few minutes after starting the freeze cycle, the suction pressure and head pressure should both start gradually dropping until the machine harvests.
If pressures start out normal on this call, and the machine starts making
ice with a good fill pattern on the evaporator, but suction pressure doesn't
drop and the ice takes way too long to build up, it's possible that the TXV has
failed and no
longer responds to superheat changes. Verify that the bulb is
strapped securely to the suction line, and that the contact
between them is clean. Use the TXV troubleshooting method described earlier in this article.
If you replace the TXV, make sure the replacement is an exact match for the
capacity and operating range of the machine.
I'd recommend using factory replacement parts.
Let's say we're on this ice maker troubleshooting call and there's no water
flow problem, discharge pressures aren't too
high, it doesn't look like the TXV has failed, and the pressures look very close to normal.
What does the ice pattern on the evaporator look like? Is the ice thickness
good all the way up the evaporator? Or is the
ice thin on the last few rows of the plate?
If the ice is noticeably thinner on the last few rows of the evaporator, and if the suction and discharge pressures are slightly lower than normal, check for a low charge.
Charge in two to four ounces of refrigerant and see if the ice now builds
the rest of the way up the evaporator. If it does,
the problem was a low charge, which can cause long cycle times. Find the leak and make the appropriate repairs.
Other possible causes of long cycle times are hot supply water, hot
condenser water, an air cooled condenser recirculating
its own air, ice
thickness control set too thick or failed, too much water flowing into the
sump, failed harvest pressure
regulating valve, inefficient compressor, or someone might have installed the wrong compressor or TXV.
ICE
WON’T DROP
What about an ice maker troubleshooting call where the machine makes ice, but
it won't drop off the evaporator during harvest? You should have already
verified that there's no scale build up on the evaporator, and that the plating
looks good.
On this type of call the service manual will be a lot of help. It will tell
you what the pressures should be during both the
freeze and harvest cycles.
If your pressures are good during the freeze cycle, but not as high as the
factory specifies during harvest, check for a low charge, restricted hot gas
solenoid, or inefficient compressor. Once again, the manual for your specific
machine will give
you more detailed guidance on how to troubleshoot it.
If harvest pressures are normal during this call, but the ice doesn't drop
off the plate, the evaporator plate is clean and scale free, and the machine is
level, there's a strong possibility the plating has worn off the evaporator,
which will make the ice
stick even during harvest.
Pull the curtain off and take a close look at the ice slab during harvest.
If you can look through the ice slab and see the
water running down between the slab and evaporator, but the ice simply sticks on the evaporator and doesn't drop off, the plating is gone, and the evaporator has to be replaced.
On a Hoshizaki ice maker, you don't have to worry about plating because they
have all stainless evaporators. But if ice
seems to drop off the evaporator too slowly, and harvest pressures are good, check for strong water flow into the machine during harvest, and make sure the water distribution nozzles are clear.
There are separate sets of nozzles in some Hoshizaki machines, so during the harvest cycle be sure there's good water flow through the nozzles that fill down between the plates. This water flow helps warm up the plate during harvest.
NOTHING
HAPPENS WHEN MACHINE IS TURNED ON
Let's try an ice maker troubleshooting call where there's good power to the
machine, and overall it looks in good enough condition to run, but when you
turn it on to make ice, nothing happens.
Again, check for any LED error indicators, and troubleshoot according to the schematic and legend on the machine.
· Check for a high pressure switch that needs
to be manually reset. If you find one tripped, use the method described
earlier in this article to determine why it tripped.
· Check the manual on-off toggle.
· Check the bin switch.
It could be a magnetic switch on the water curtain, a thermal element that opens when ice in the bin cools it down to its set point, an infrared beam and sensor assembly, a push-rod that the curtain activates, or a lever that the curtain activates.
If you find that there's no water in the sump on this call, and if it's a
machine that cycles on a float switch or water level
sensor, verify that the
fill solenoid is energized. If the top of the armature doesn't feel magnetized,
check for voltage at the
leads to the coil. If the voltage to the coil is correct but it isn't energizing, the coil has failed and needs to be replaced.
Let's say that on this call the fill solenoid is energizing, but no water is
getting into the machine. Crack open the inlet fitting
to the fill solenoid to
see if there's good pressure available, then crack open the outlet. If there's
water pressure on the inlet
side but not on the outlet side, the solenoid is
restricted and needs to be cleaned or replaced. If there's no pressure even
on the inlet side, you need to check the water supply to the machine. After you take care of the water problem, the sump should fill to the point where it satisfies the float switch or level sensor, then the machine should cycle into freeze.
If the machine doesn't cycle into freeze when the float switch lifts or when
the water reaches the level sensor, you'll need to check the operation of the
float switch assembly or level sensor. The problem might be dirt, sludge, or
scale buildup, or
the part has failed.
Whether or not the machine cycles into freeze at this stage of the call,
keep an eye on the fill water flow and make sure it
stops. Some machines will
continue to fill a little more water after the machine cycles into freeze, but
if the machine
continues filling to the point where you have a steady drain out
of the sump, check the fill solenoid. If it's de-energized
but fill water
is still flowing, it's probably being held open by some debris, and you'll need to disassemble the valve and clean it out.
Continuing this call, if you didn't find any of the previous possible
problems, check the wiring and connections in the
machine for a loose
connection or broken wire, and check for a blown control fuse or a failed
relay, contactor, or time
delay.
You might even have to trace through the controls wire by wire to see if a
control wire is connected to the wrong place.
This would be another call where the service manual for the machine will save you a lot of time and frustration.
COMPRESSOR
DOESN'T RUN
What about an ice maker troubleshooting call where the machine turns on, the
water pump runs, and water is flowing
over the evaporator, but the compressor doesn't run?
First, if you hear the compressor humming and tripping off on its overload,
turn the power off. Remove the leads from the compressor terminals, and ohm out
the compressor windings. If the windings ohm out OK with no indications to
ground,
the next thing to do is make sure the leads aren't grounded or shorted
to anything, then turn on power and verify that
there's good power at the compressor leads. If there's good power at the leads, replace the start relay, start capacitor, run capacitor, and external overload (if installed), reconnect the leads to the compressor, and turn the machine on and see if the compressor will run.
At this point in the call, if you have good voltage at the compressor, and new start components, but the compressor simply won't run, but just hums and trips the overload, you can be pretty sure the compressor is locked up and has to be replaced.
Otherwise, if you're on a call where the compressor doesn't run but it's not humming and tripping off:
· Verify that the contactor has pulled in.
· If it hasn't, check the voltage at the coil.
· If you have control voltage at the coil but it doesn't pull in, the contactor has failed and needs to be replaced.
· If you don't have control voltage at the coil,
you need to trace back through the circuit to see if there's an open safety,
broken or loose wire or terminal connection, or a failed control relay.
At this stage of the call, if the contactor has pulled in, check the voltage
on both the line side and load side, and check
across the contacts to see if
one set has failed and isn't conducting. If you have good voltage on the load
side of the
contactor, check the voltage at the compressor terminals and start relay.
If you don't have good voltage at the compressor terminals and start relay, look for a broken or loose wire or terminal connection. If you have good voltage at the start relay and compressor terminals, ohm out the compressor windings (and external overload if installed).
By this stage of the call, if the compressor is three phase, or single phase
with a potential start relay arrangement, you'll
have already found the failed part.
If this is a small compressor with a current relay and external overload,
and the windings ohm out OK with no indications to ground, you'll probably find
that either the overload has failed open, or the current relay has failed. If
you replace the
failed part, the compressor will probably run, and I'd recommend replacing all three parts.
That about covers the most common ice maker troubleshooting calls.
Mike Taitano is a technician with 20 years of experience troubleshooting,
repairing, and maintaining air
conditioning and refrigeration equipment. He
also operates Air-Conditioning-and-Refrigeration-Guide.com.
For more information, visit www.air-conditioning-and-refrigeration-guide.com.
Publication date: 05/29/2006
