- Heat pumps
- Air-to-water heat pump
02
Hitachi alarm 02 on a Yutaki heat pump: high pressure cut
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
Alarm 02 on a Hitachi Yutaki means the high pressure protection device in the outdoor unit has tripped. Note the alarm, check from outside that nothing is blocking the outdoor unit and call the service contractor.
Safety first
Stop and check this first
- Do not open the outdoor unit or touch the refrigerant circuit: Hitachi says not to carry out service tasks yourself or open the service cover without disconnecting the main power supply, and refrigerant is for qualified personnel only.
Safe checks you can perform
- Note the alarm and whether it repeats
- Look at the outdoor unit from outside
- Check the heat pump breaker position
Leave these tasks to a qualified professional
- Do not attempt this professional task: Diagnosis of the high pressure cut
- Do not attempt this professional task: Refrigerant circuit check by a certified installer
- Do not attempt this professional task: Check the outdoor unit power supply
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Diagnosis of the high pressure cut
What they doThe technician checks the high pressure switch, the fan and its motor and the outdoor unit operating pressures.
They must show youthe measured pressures, the fan running and the high pressure switch test.
In writingthe cause found, the part checked or replaced and a test run without alarm 02.
Refrigerant circuit check by a certified installer
What they doIf excessive refrigerant, inert gas or clogging is suspected, an F-gas certified installer checks the charge and the circuit.
They must show youthe measured charge against the rating plate charge and the leak tightness test.
In writingthe amount of refrigerant recovered or added and the technician's certificate number.
Check the outdoor unit power supply
What they doA professional measures the outdoor unit supply and checks the phases and the power wiring.
They must show youthe voltages measured at the outdoor unit supply.
In writingthe measured values and what was corrected.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Note the alarm and whether it repeats
- Who:
- you, on the Yutaki controller.
- How:
- take a photo of the controller with the alarm and the time. Then go to Operation Information and Alarm History and see how many times 02 has appeared and whether alarm 100 is listed.
- Result that matters:
- knowing whether it is a one off or repeating; three 02 alarms within 6 hours lead to compressor protection alarm 100.
- If alarm 100 appears or the outdoor unit shows EE:
- stop resetting the unit and call the service contractor.
- If 02 appeared only once:
- note the date and time for the technician and watch whether it returns.
- Evidence to keep:
- photos of the controller and of the alarm list with dates.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
Look at the outdoor unit from outside
- Who:
- you, without removing panels.
- How:
- check that the coil and the air outlet of the outdoor unit are not blocked by leaves, grown grass, paper or other objects, as Hitachi asks in its maintenance section. Only remove loose items around it and never put your hand or tools through the fan grille.
- Result that matters:
- knowing whether air can flow freely through the outdoor unit.
- If there were obstacles:
- remove them from outside and note whether the alarm comes back.
- If it is clear:
- tell the technician, who will check the fan and the circuit.
- Evidence to keep:
- photos of the front and back of the outdoor unit.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
Check the heat pump breaker position
- Who:
- you, from outside the consumer unit.
- How:
- see whether the heat pump breaker in the consumer unit is off, without opening the consumer unit or the heat pump. Hitachi says to stop the system and contact the service contractor if the breaker or unit fuse trips often.
- Result that matters:
- knowing whether there is also a power supply problem.
- If it has tripped or trips often:
- do not keep resetting it; stop the system and call the service contractor.
- If it is on:
- note it for the technician together with the alarm.
- Evidence to keep:
- a photo of the breaker and how many times it has tripped.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Heat pumps
- Brand
- Hitachi
- Product type
- Air-to-water heat pump
Known code variants
- Hitachi alarm 02
- Hitachi alarma 02
- Hitachi Yutaki alarm 02
- Yutaki 02
- Yutaki alarm 02
- Yutaki alarm 2
- Yutaki alarma 02
- Yutaki corte por alta presión
- Yutaki high pressure cut
- Yutaki outdoor unit protection device
What it means
In the outdoor unit alarm table of the Yutaki manual, Hitachi describes alarm 02 as activation of the protection device by high pressure cut. It lists the high pressure switch (PSH), a locked motor or an abnormal power supply phase, failure of the fan motor, PCB or a relay, pipe clogging, excessive refrigerant, inert gas mixing or a fan locked in cooling. If 02 occurs three times within 6 hours, compressor protection alarm 100 appears (EE on the outdoor unit). The code on its own never proves that a part is faulty.
Warnings and stop conditions
- Higheditorial warning
Do not open the outdoor unit or touch the refrigerant circuit: Hitachi says not to carry out service tasks yourself or open the service cover without disconnecting the main power supply, and refrigerant is for qualified personnel only.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1 · Hitachi YUTAKI S COMBI series RWD-(2.0-6.0)(N/R)W1E-220S(-K) indoor units instruction manual PMML0573 rev.3
Symptoms and causes
Probable causes · in order
- Outdoor fan locked or faultyPossible
Hitachi lists fan motor failure and a fan locked during cooling among the causes of alarm 02, both of which stop the outdoor unit from shedding heat.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
- Problem in the refrigerant circuitPossible
Hitachi mentions pipe clogging, excessive refrigerant and inert gas mixing. Only an F-gas certified installer can check this with gauges.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
- Abnormal power supply phasePossible
Hitachi includes abnormal operation in the power supply phase among the causes. It is checked by measuring the outdoor unit supply, which is a job for a professional.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
- Locked motor, PCB or relayLess common
Hitachi also lists a locked motor and failure of the PCB or a relay. These are only confirmed by the technician's diagnosis, never by the code alone.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
Virtual technician
Does 02 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
Johnson Controls-Hitachi Air Conditioning · 2021 · manual
- 2
Johnson Controls-Hitachi Air Conditioning · 2023 · manual
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