The mystery of intermittent ice production

April 10, 2000
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In the business of refrigeration service, most problems are resolved effectively with systematic, procedural diagnostic techniques. However, every so often we experience situations that cannot be diagnosed by traditional methods. I call these situations intermittent problems.

A technician who works on ice machines and other refrigeration equipment will occasionally experience a similar situation. The customer calls and reports, “My ice machine is not making enough ice. It keeps shutting off and I have to reset it.” The tech goes to the job and resets it, or begins checking the machine that has already been reset and finds that it runs just fine. Everything checks OK.

What do you do now?

The customer usually will not accept the diagnosis that the machine is fine, then sign a service invoice for $100 or more. Let’s investigate and see what we can do about this dilemma.

Don't reset it

When we encounter a recurring intermittent type problem, I will sometimes visit the jobsite with the technician. The first thing we will do after arriving on the job is to leave the ice machine as it is.

We don’t want to reset any switches or begin adjusting anything until we have had an opportunity to view the machine “as is.” This also means telling the customer not to reset any switches before we get there.

First we inspect the installation and general operating environment. We’ll check the basics, such as proper condenser airflow, water pressure, drain connections, level of the unit, etc. We will then ask the customer many questions, such as:

  • “When do you notice low ice in the bin?” We are trying to establish a timeline; a pattern may develop (only at night, on the weekends, etc.).
  • “Has anything changed recently with regard to the utility services coming into the building (water, electric service, etc.)?”
  • “Can you describe exactly what the machine is doing when it malfunctions?” (“I hear clicking from here, the unit is very hot, no air is coming from it, it makes a loud noise, etc.”)
  • “Has anybody else been working on the machine lately, or have you made any adjustments? What switches did you flip, and how did you flip them? What happened next?”

Then we will take a look at the ice in the bin. Are there any abnormal ice formations or colors, such as thick pieces of ice, or very white ice? Both could be indicators of low water pressure or another malfunction that causes low water flow over the evaporator.

Performance analysis

Now is the time to begin analyzing the system performance.

First, we will turn the unit off and back on to see if there is a safety limit stored in the memory of the control board. If a safety limit is noted, we will refer to the appropriate checklist in the handbook and begin systematically checking for causes that fit the scenario we have.

We will then check and analyze the following:

  • Voltage supply;
  • Water pressure;
  • Cycle time;
  • The ice fill pattern on the evaporator plate; and
  • Refrigerant pressures.

We compare our data with the manufacturer’s specifications. We are looking for anything out of tolerance that may signal a potential problem.

If we do not find any leads on the problem to this point, we will take the symptom and begin theorizing potential causes of the problem. For example, we may know that the unit is occasionally shutting off for no apparent reason. Situations that can cause this include:

  • The unit lost electrical power. Check the circuit breaker and the wiring to the unit. Check the wiring inside the unit, there may be a loose electrical connection. Is the unit on a dedicated electrical circuit?
  • The bin switch may be malfunctioning; let’s ohm it.
  • Is the ice-thickness sensor dirty and/or not properly adjusted? If so, we will clean and/or adjust it.
  • And let’s check the operation of the high-pressure cutout to verify that it is cutting out at the proper pressure (if the machine is tripping on the high-pressure cutout).

It also may help to call the manufacturer of the unit. The manufacturer can usually point you in the right direction.

You may find it necessary to attach a temperature or pressure recorder (refrigeration or water) to the unit to find out what is happening while you are not there.

In a nutshell

In summary, I suggest following these steps.
  • Gather as much information as possible.
  • Compile a history of the problem and the machine.
  • Write down the information as you gather it.
  • Thoroughly check the unit’s installation, noting anything that does not meet the manufacturer’s specifications.
  • Note any unusual occurrences that may happen while you are checking the unit, even if it only happens once during the sequence of operation.
  • Know the sequence of operation of the unit, and theorize the potential causes of the problem’s symptom (e.g., list what can cause the machine to shut off on the high-pressure switch).
  • Call the manufacturer of the equipment, with as much information in hand as possible, to get their advice on what to do next.

These situations can be challenging for both the technician and the customer, but with some patience and properly directed investigation, they can be solved effectively.

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