scale Archives - HVAC School

If you don’t use a scale every time you add or remove refrigerant I would suggest you begin doing so immediately if not sooner. Weighing in while charging is fairly obvious and is useful so you can keep track of what you are using and how much to charge a customer.

When you have a system that has just been repaired it is a good practice to weigh in the charge to factory specs plus or minus adjustments for the line-set if it is a split system. This is all pretty evident, but why would you weigh a charge out? There are many reasons but one good example is whenever you have a failed compressor, weighing out the charge can help indicate whether possible undercharge or overcharge may have contributed to the failure. With any significant failure on an older system, weighing out the refrigerant can indicate whether a leak is likely. When possible on major failures you could even weigh out the refrigerant at the time of diagnosis just to ensure that a leak or a compensatory overcharge may be at play.

Using refrigerant recovery as a means to find possible cause or even diagnose leaks on non-functional systems is next level diagnosis in my book. Use your scale.

Weigh in when adding charge

Weigh out as a diagnostic aid and to ensure you don’t overfill your tank.

— Bryan

Tech Tips

Ice Machine and Scale (Limescale)

January 23, 2019 By Bryan Orr No Comments

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