This guide explains what the common alarm codes on Carel's ir33 range of controllers mean, what a site owner and staff may check, and when to call an engineer. A Carel controller is the small electronic display fitted to many cold rooms, freezer rooms and display fridges; it reads the temperature probes and shows an alarm code when something is wrong. At Climate Flow Limited we install and service Carel controllers across London and surrounding areas.
What does a Carel controller do?
A Carel controller takes readings from its temperature probes. The set point is the temperature the installer chose for what is stored. On the ir33 range, probe S1 is the room probe. Probe S2 is the defrost probe. Our guide to cold room defrost cycles and controller adjustments explains what defrost does and how it is set. Carel's alarm table for the ir33 smart instruction sheet names both probes.
Carel makes several ranges of controller, and they do not all use the same codes. Carel's MasterCase manual, for example, gives E0 a different meaning from the ir33. Everything below refers to the ir33 family unless it says otherwise. If your display shows something else, check the instruction sheet for your exact model before acting on it.
How do you read a Carel controller display?
On an ir33 smart, pressing SET for more than one second shows the set point and lets it be changed. Other models use a different keypad, so check the sheet for yours.
When something is wrong, the controller shows an alarm code. Write the code down before anyone presses a key, because the engineer will ask for it first.
What do the common alarm codes on a Carel controller mean?
These are the codes Carel's ir33 documents describe that a site is most likely to see:
- E0: a fault on the room probe (S1).
- E1: a fault on the defrost probe (S2). According to the ir33 platform user manual, the controller then runs a timed defrost of the length set in parameter dP1. The unit can keep defrosting on a timer, but the probe still needs an engineer.
- HI: the high temperature alarm. Carel's MasterCase user manual describes it as the control probe reading more than the value of parameter AH above the set point.
- LO: the low temperature alarm, which works the same way below the set point, using parameter AL.
- dor: the door open alarm. The cold room or cabinet door has been open too long, according to the ir33 smart instruction sheet (Italian edition).
- HA and HF: some ir33 models have HACCP functions, which record temperature alarms. On those models, HA records a high temperature during operation and HF records a high temperature found after a power failure. The controller keeps the most recent events for review, as the ir33+ user manual explains.
The thresholds and delays behind HI and LO are set by the installer, so two units with the same controller can alarm at different points. A code not listed here, or any code on another Carel range, needs the sheet for that model or an engineer.
Why do temperature alarms matter for food safety?
The Food Standards Agency says chilled food must be kept at 8°C or below, a legal requirement in England, Wales and Northern Ireland, and recommends setting fridges at 5°C or below. An HI alarm on a chiller means the stored food may be moving out of that range. The set point is how a site aims to hold the right temperature, but it does not hold it on its own: the probes, the door, the airflow and the refrigeration system all have to work.
What can a site owner check on a Carel controller?
Some checks need no tools and no access to the refrigeration system. They are worth doing before calling, and they tell the engineer what has already been ruled out:
- The temperature on the display, against the set point and against what the stored food needs.
- The door: fully closed and nothing propped against it, especially after a dor alarm.
- The set point, changed only within the range your installer set for the food you store.
Carel's ir33-family manuals also describe a manual defrost started from the keypad by holding a key for about five seconds, but only when the temperature conditions allow it. The key differs between models and manual versions, so follow the sheet for yours.
Which Carel controller settings need an engineer?
Carel puts the configuration parameters on ir33 controllers behind a password, separate from the set point a user can change. We do not print the password here, and changing those parameters is a job for an engineer.
Replacing a failed probe is also an engineer's job. Anything on the refrigeration circuit is a matter of law: under UK F-gas rules, installing, servicing and maintaining refrigeration systems, checking them for leaks and recovering refrigerant all need F-gas qualifications. The GOV.UK register of regulated professions states that it is against the law to work on equipment containing F gases without the correct qualifications. Reading the display is for your staff; work on the system is for a qualified engineer.
When to call an engineer
Call an engineer when:
- the display shows E0 or E1;
- an HI or LO alarm comes back after the door has been checked;
- an HF alarm appears after a power cut, alongside your own food safety checks;
- the unit keeps alarming and nobody can say why.
Our refrigeration repair and maintenance engineers look at the controller, the probes and the refrigeration system together.
We also fit controllers as part of cold room installation and work on the controllers in display chillers.
If a Carel controller on your cold room or display fridge is showing an alarm, Climate Flow can help. We install and service Carel controllers across London and surrounding areas, our engineers are F-Gas certified, and we offer 24/7 emergency callouts.
This guide is general information, not a survey or a quote for your site; every system is different, so an engineer needs to see yours before any work is priced.