Ice Machine Refrigeration
The major way that ice machine refrigeration is different from most other vapor compression systems is that during the harvest cycle, discharge vapor by-passes the condenser and metering device.
It's used to warm up the evaporator so the ice will drop off, so it goes straight through the evaporator and back to the compressor without condensing or evaporating.
Another difference you'll eventually notice after you've worked on a few ice machines is that none of the manufacturers mention superheat or subcooling in their service manuals.
What they do mention is weighing in the exact specified charge, comparing operating pressures to factory specified pressures, and timing freeze and harvest cycles.
Otherwise, ice machine refrigeration systems run according to the same principles as other vapor compression systems.
You'll find that ice machine refrigeration systems differ slightly from manufacturer to manufacturer, and you'll also find design differences between the models of the same manufacturer.
What I'm leading up to is that the most efficient way to troubleshoot ice machines is with the factory service manual.
Since you're already on-line, why not visit the web site of your ice machine's manufacturer and download the service manual for your machine?
You'll find Hoshizaki manuals at
you'll find Manitowoc manuals at
you'll find Iceomatic manuals at
and you'll find Scotsman manuals at
The Hoshizaki manuals have good information about the performance characteristics you should look for when troubleshooting their machines.
The Manitowoc manuals have Manitowoc's classic troubleshooting worksheet, specifications on the performance characteristics of their machines, and some good information that can be used on other makes of similarly designed machines.
The Iceomatic manuals have information about their ice machine refrigeration operating characteristics, troubleshooting flow charts, and some basic information and troubleshooting tips about TXVs and other components that is applicable to other types of equipment too.
I haven't taken a look at a Scotsman service manual in a long time, but if I recall correctly, they had good information about how to troubleshoot and repair their machines.
When you troubleshoot an ice machine refrigeration system, you need to check the ambient temperature of the condenser entering air, the temperature of the water entering a water cooled condenser, and the temperature of the supply water to the cuber.
The operating characteristics of the ice maker will vary depending on these temperatures; and the service manual can tell you what pressures to expect, and how long an ice making cycle will take, depending on what these temperatures are.
Once you've verified that the condenser is clean, and that the water distribution system is clean and not scaled up; attach your gauges, measure the ambient and entering water temperatures, start the machine, and take note of the time and starting pressures.
It's a good idea to note the pressures every two minutes during the cycle, and use a small mirror to watch the ice form on the evaporator.
Take notes on what's happening so you'll have an accurate record of the machine's operating characteristics.
I always check the hot gas solenoid temperature about 5 minutes into the freeze cycle to see if it's getting too hot and indicating a leak; and I also keep an eye on the drain for steady draining water.
If the drain line from the dump valve is the clear see-through type, I'll open the panels to keep an eye on the drain line to verify the dump valve doesn't leak during the first freeze cycle, and at the start of the next freeze cycle.
During and after the first ice making cycle the main questions to answer when troubleshooting an ice machine refrigeration system are:
Is ice formation on the evaporator normal?
Do the freeze and harvest pressures match the service manual specifications?
Does the freeze cycle time match the service manual specifications?
Does the machine cycle into harvest normally?
Does the harvest cycle time match the service manual specifications?
Does the ice drop off the evaporator plate normally?
Does water fill normally, and at the right time in the operating cycle?
Does water drain normally, and at the right time in the operating cycle?
I've found that troubleshooting an ice machine refrigeration system is easier when I can check these readings against the factory specifications in the service manual.
Another way the factory manual helps is that no matter what a customer might say about the performance of a machine; if all of these operating characteristics match the factory specifications, then the machine is working fine.
If the customer complains that the machine just isn't making enough ice, you can show them the operating specifications in the service manual, and explain that the machine is making the quantity of ice it was designed to produce.
Once you identify a failed refrigeration component, the best thing to do is use a factory replacement part.
And while we're on this topic, when you troubleshoot an ice machine refrigeration system, or any refrigeration system, verify that all components in the system are correctly sized for the system's capacity.
You don't know who worked on the machine before you did, and what kind of parts they installed; so take the extra time to be sure all the parts are correct.
If you absolutely must use a non-factory txv, be sure the capacity and temperature range of the replacement matches the original exactly.
This means you'll have to identify the factory original txv and find the performance specifications for it.
If you have to use a non-factory compressor, be sure the electrical requirements, oil, refrigerant, capacity, and temperature range match the factory original compressor.
Once again, identify the original compressor, and find the performance specifications for it.
If you're a professional, why guess or experiment?
Why wouldn't you want to be sure you're installing the exact, correct txv or compressor?
For more information on ice machine refrigeration systems, it would be a good idea to download a service manual from Iceomatic, and one from Manitowoc.
Pick a model in the 400 to 600 pound range.
The manuals from both companies explain ice machine refrigeration systems, but each has a slightly different approach, so combined, they provide a good explanation of how ice makers work.
There are also some good diagrams and troubleshooting tips, and best of all, the manuals are free!
I hope this page has helped, and please, feel free to contact us with any specific HVAC questions you might have, including questions about refrigeration on Guam, or air conditioning on Guam.
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