Tag: ice machine

This article is written by Austin Higgins, an experienced commercial service tech from Iowa. Thanks Austin!


 

Ice machines and Limescale

Any seasoned Refrigeration technician knows that ice machines can be extremely finicky contraptions. Modern commercial ice makers have become a complex symphony of tubing, valves, pumps, and water directed by advanced microprocessor control boards. Newer technicians are often overwhelmed by the sight of all these different components somehow working together to produce something most people take for granted: frozen water. Ice machines have become a showcase of engineering and human ingenuity. However, no matter how technologically advanced the ice making process becomes, new and old designs alike have a common enemy: Scale buildup.

 

What is limescale?

 

Limescale goes by several names, such as calcium deposits, calcium carbonate, or simply “scale”. It is caused by hard water which contains higher concentrations of dissolved minerals such as magnesium and calcium. These minerals, when not filtered out by quality water filters, cause severe problems for any appliance or equipment exposed to the water supply. Fortunately, limescale is not harmful to humans- in fact, it is the main ingredient in many over-the-counter antacids. It is, however, harmful to ice machines and the pocketbooks of negligent owners.

Scale buildup and discoloration on an Ice Machine water distributor and ice thickness probe (photo by Austin)

 

How limescale can affect an Ice Machine

Commercial ice makers are akin to a symphony of different parts working in harmony with one another. Like an orchestra, one wrong note can ruin the entire piece. Limescale buildup in an ice machine is like replacing half of the London Philharmonic with 8th-grade band students from Nebraska and expecting them to play Tchaikovsky perfectly. It’s probably not going to work very well.

Limescale has the unfortunate quality of adhering to the plastic and metal components of ice machines and never letting go. Once scale begins to build up, it tends to have a ‘snowball’ effect- more and more piles on until it becomes nearly impossible to remove. Trying to remove limescale with abrasive material such as emery cloth or a knife is effective, but only makes the problem worse- as you’ve created more micro-crevasses for it to take hold. Scale buildup becomes apparent in all parts of the water distribution system: the inlet screen on the water fill valve can become restricted or clogged causing low water pressure and slow fill times. The water trough tends to collect a layer of white/chalky deposit which can build up over time and reduce the amount of water allowed into the sump; this is a particular problem with smaller Manitowoc machines, as they rarely have much water to spare at the end of the freeze cycle to begin with. From the water trough, the limescale is then sucked up by the water pump and brought to the water distributor and circulated over the evaporator grid. With enough time, the impeller can become laden with scale, causing higher amp draw and a hotter motor. In severe cases, the pump will become seized. The water distributor holes will clog, causing low water flow over the grid and forming ice that looks like a frozen waterfall. A small, hard to see layer of scale buildup on the ice grid itself can cause longer freeze times and longer harvest times.

Ice thickness probes and water level probes are especially susceptible to buildup.

Manitowoc water level probe caked in limescale (photo by me)

When this occurs, the limescale is often enough to ground or “short” the probes and the control board will then react accordingly. When a water level probe touches the water in the trough, it sends a signal to the control board telling it to shut off the water inlet valve. With enough scale buildup, it will short to itself instead of the water, and the water inlet valve will not open. The same goes for the Ice thickness probe (often used by Manitowoc Model Q and later as well as Scotsman Prodigy) and the freeze cycle will terminate before enough (or any) ice is allowed to form.  

 

Last, the dump valve and drain line. Common problems include clogged drains and leaking dump valves. Clogged ice machine drains often cause much more buildup in the water trough since the minerals cannot be carried away, thus compounding and causing many of the aforementioned issues. A faulty dump valve that won’t open will present the same issues as a clogged drain. Another way that the dump valve can be affected is when small flakes of scale become lodged in the valve, holding it open. This can cause low water pressure in the distributor and the water in the trough may run out before the freeze cycle is complete.

 

Prevention and Mitigation

The ball is in the customer’s court on this one. You can advise them to get a water softener, talk to a qualified water quality technician, install a good water filtration system dedicated to the ice machine (I like the Everpure InsurIce), and to schedule regular ice machine cleanings depending on the severity of the hard water. Ice machines should be cleaned a minimum of every 6 months; but every machine is different and developing a unique cleaning schedule with the customer based on water quality, usage, and age of the machine is recommended. I have seen some machines go years without proper cleaning, and I have seen machines in towns with terrible water require almost weekly cleaning. Follow the manufacturer’s recommendations on specific ice machine cleaning chemicals and concentrations, as well as their instructions on how to properly clean the machine. Be aware of whether the ice machine cleaner you carry is nickel-safe. If it isn’t, and you use it on a nickel-plated evaporator it will strip the nickel from the grid and render it useless.

 

Preventing limescale after installation of any new machine should be discussed with the customer before the first batch of ice ever drops. Informing yourself and your customers about the problems of scale buildup will save you from headaches and emergency calls, and will save them money over time if they invest in proper filtration and regular professional cleanings. Parts affected by scale are often not covered by warranty. When it comes to ice machines and limescale, diligence pays for itself.

–Austin Higgins

Note From Bryan:

Refrigeration Technologies makes an excellent Nickel safe ice machine cleaner that you can find more about HERE

There are several types of Ice Machines but in this article, we will focus on Cuber style and Flaker or Nugget style. Both types produce Ice but the process of freezing and harvesting is a little different. The application in which the Ice will be used will determine what style of machine is needed. I primarily work with Restaurants and Hospitals so my article will be geared in that direction.

Let’s start by simplifying the ice making process, if we take water and circulate it over an evaporator that is below freezing we will at some point start to freeze that water, once our Ice has formed we than harvest the ice and start our process again. That’s about as simple as it gets

The steps to make Ice seem simple take water and freeze it, but It’s not that simple. Making Ice cubes is actually a pretty complicated process, with several critical steps that must be met for the process to work correctly. The first step starts with properly cleaning the water that will be made into the ice to remove any impurities, water itself naturally contains minerals and those minerals are an Ice Machines worst enemy. The minerals lead to calcium buildup which causes issues with the ice machine. A quality ice machine install will have a high-quality water filter system installed that was sized properly and has the appropriate filters inside that are chosen after a water quality test has been performed. Once we have properly filtered water we bring the water into a reservoir inside the machine and the water waits until the machine is ready to make Ice.

Among all the ice machine manufacturers there are several methods that the machine will tell itself that the ice storage bin is low on Ice and to turn on, the most common methods are a thermostat and or some sort of mechanical control that is actuated by ice buildup, subsequently telling the machine that the ice is low and it’s time to turn on.

Cuber style ice machines

Assuming the machine is ready to turn on, most brands of ice machines will start in a pre-chill, which means we cool the evaporator with no water running over it, this is done to try and prevent slush from forming. Than by means of a water pump the machine will start to circulate the water over the evaporator, and that water will continually run over the evaporator and down into the sump than it will be pumped over the evaporator again, each time it passes over the evaporator the water will get colder and colder and eventually a little bit of the water will start to freeze to the evaporator plate, this process will continue over and over again until the ice is the proper thickness. The thickness can be determined by many methods including a thickness sensor, water level monitoring, and or a timer. Once it’s time to harvest the ice the most popular method is to introduce hot refrigerant from the discharge of the compressor into the evaporator and subsequently melt the ice off the evaporator from the inside out while running a little bit of water over the cubes to assist dropping the cubes off the evaporator. The harvest cycle is usually terminated by a timer that is in the circuit board. Each manufacturer has their own unique way of making and harvesting the ice. With all cuber style ice machines the harvest cycle is very dependent on maintaining an adequate high side pressure as their defrost depends entirely on it. When the machine is self contained and located indoors its not too hard to maintain the proper head pressure because the building will likely be conditioned, however on remote systems where the condenser is located outside we utilize head pressure control valves (headmasters) to back up the refrigerant in the condenser to reduce the condensing capacity of the condenser and subsequently raise the head pressure.

Flaker or Nugget style Ice machines

These machines have a unique way of making ice they utilize a round cylinder evaporator that has an auger inside of it that is turned by a high torque gear motor. The auger sits directly In the center of the evaporator with less than 1/16th of an inch clearance on either side and the auger is always spinning it has the shape of a corkscrew. The machine will have a water reservoir that supplies water to the evaporator whenever it gets low. The machine will start to freeze the water and as it becomes ice the continually turning auger will force the ice up to the top of the evaporator and out of a nozzle that will shape the ice into the desired style (Crushed, Flaked, and or Nugget). It is important to notice that with this style of ice machine the harvest cycle happens when the ice gets thick enough for the auger to scrape it off and it both freezes and harvests the ice at the same time.

— Chris Stephens

P.S. – we have a new podcast out on ice machines HERE enjoy

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