A01, A02, A07, A08, A09: the alarm codes on MTA TAEevo process chillers, explained in plain English.
What each code means, what usually causes it on site, and whether it is safe to reset. Covering the TAEevo range, including units supplied and badged as ICS chillers.
Quick answer
On an MTA TAEevo chiller, A01 is high pressure or a phase monitor trip, A02 is low pressure, A07 is the antifreeze alarm, A08 is the flow switch or pump thermal overload, and A09 and A10 are compressor thermal alarms. Codes beginning with P are probe faults. The alarm is shown flashing on the bottom of the display, alternating with the temperature.
To see the active alarms, press the menu key to enter the Function menu, select ALrM and press SET. The alarm code appears at the bottom of the display. Scroll with the up and down keys.
If the top of the display shows rSt, that alarm can be reset from here: press SET. If it shows NO, the alarm cannot be reset because the condition causing it is still present.
The alarm history is under ALoG in the same menu and stores up to 50 events, oldest first. That history is often more useful than the live alarm, because it shows whether a fault has been recurring for weeks.
The buzzer silences automatically when the cause clears, or you can silence it manually by pressing any key, which does not clear the alarm itself.
A note on controllers. The TAEevo range uses the IC121C controller, which runs MTA’s own alarm set: the A-codes below. The newer MTA iC range uses the IC121CX or IC208CX, which show a different style of code altogether, such as AEFL, b1HP or C1tr. Same controller family, different code set, which is why an engineer used to one can be caught out by the other. For the CX versions see our Dixell iCHILL alarm codes guide.
| Code | Meaning | What usually causes it | Who can deal with it |
|---|---|---|---|
| A01 | High pressure switch, or phase monitor trip | Two very different faults share this code. High pressure: dirty or blocked condenser coil, failed condenser fan, high ambient, or recirculating warm air around the unit. Phase monitor: incorrect phase sequence or a phase failure, often after electrical work. A blown transformer fuse in the panel can also show A01. If A01 appears before the compressor has even started, suspect the phase monitor or the fuse rather than pressure. | Site team can check the coil, fans and airflow. Electrician or engineer for phase and fuse faults |
| A02 | Low pressure switch | Usually refrigerant loss through a leak. Also a blocked inlet water filter, a failing expansion device or ice on the evaporator. The alarm is delayed after compressor start to ignore normal suction fluctuations, and resets automatically until it has tripped too often, after which it goes manual. | F-Gas engineer needed |
| A07 | Antifreeze alarm | Water leaving the evaporator has dropped close to freezing. Low flow, weak or missing glycol, a setpoint below what the system can safely run, or a faulty probe. The factory freeze protection setpoint is 4°C, adjustable on parameter Ar03, and lowering it means adding the right glycol concentration. Note that closing both the chiller’s inlet and outlet valves will also trip this alarm, by design. | Site team can check flow, valves and glycol. Engineer if it repeats |
| A08 | Flow alarm, or pump thermal overload | The most common call-out on these machines. No flow or not enough flow: blocked inlet strainer, closed valve, airlocked or failing pump, or inlet and outlet connected the wrong way round on units without a pump. As a pump thermal alarm it means flow is too high, the pump’s cooling air grille is blocked, or the pump is failing. The compressor and pump stop. | Site team can check the strainer, valves and pump. Engineer if it repeats |
| A09 / A10 | Compressor 1 and compressor 2 thermal alarm | Compressor motor protection has tripped: high load combined with low refrigerant, an electrical fault, or on three-phase units a scroll compressor running backwards after a phase change. A compressor that is very hot and restarting after a few seconds points here. | Engineer needed |
| A03 | Low ambient air temperature | Ambient below the configured limit. More relevant in winter on outdoor units. | Engineer needed if it stops production |
| A05 / A06 | High or low temperature, pressure related | Triggered from the ambient probe against a set value. Usually a siting or seasonal issue rather than a failure. | Engineer needed |
| A13 / A14 / A15 | Compressor 1, compressor 2 and water pump maintenance | Running hours have passed the maintenance threshold. A reminder, not a fault, cleared by resetting the hours. | Raise at next service |
| A20 / A21 | Low and high water temperature at evaporator outlet | Process water outside the configured band. Often load related, or a sign the chiller is undersized or struggling. | Site team can check load, engineer if it persists |
| AEUn / ACUn | Evaporator or condensation unloading | Not a fault. The controller is shedding capacity because the water returning to the chiller is too hot, typically on a summer start-up after a shutdown, to avoid tripping on high pressure. | No action, normally clears as the water cools |
Not sure whether it is safe to reset? Send us a photo of the display and the data plate and we will tell you what it needs before anyone travels. Call 0121 820 8946.
| Code | Meaning | What usually causes it | Who can deal with it |
|---|---|---|---|
| P1 / P2 / P4 | Probe faults | P1 is the evaporator outlet probe, P2 the tank outlet probe and P4 the ambient probe. A damaged probe, a broken cable or a reading outside the expected range. The unit may keep showing odd temperatures or nuisance alarms until it is replaced. | Engineer needed |
| rtC / rtF | Clock needs setting, or clock failure | rtC usually appears after a long power cut and just needs the clock setting. rtF means the clock itself has failed. | Site team can set the clock. Engineer for rtF |
| EE | EEPROM error | The controller has lost its stored data. The machine will not run and the controller usually needs replacing or reprogramming. | Engineer needed |
| ACF2 to ACF6 | Configuration alarms | The controller’s configuration does not match the machine, for example two digital inputs set the same way. Normally follows a controller replacement or parameter changes. Switching the unit off and on again is worth one attempt; after that it needs someone who knows the parameter set. | Engineer needed |
| AFr | Mains frequency alarm | Supply frequency outside limits. Usually a supply problem rather than a chiller fault. | Site electrician |
| ALOC | Generic alarm | Whatever the machine builder wired to the generic alarm input. Check the wiring diagram for that unit. | Engineer needed |
| noL | No link to the remote terminal | Remote keypad unplugged, or a cable fault. | Site team can check the connection |
Behaviour varies with model, software version and the options fitted, so treat this as a guide alongside the manual for your unit. We service and repair MTA and ICS-badged chillers across the Midlands: see our MTA chiller service, repair and spares page.
We hold common TAEevo spares on our vans and at our Oldbury depot, and maintain over 300 MTA and ICS-badged chillers. Send us a photo of the display and the data plate and we will tell you what it needs.
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