- Heat pumps
- Air-to-water heat pump
70
Hitachi alarm 70 on a Yutaki S heat pump: water flow or pump
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On Hitachi Yutaki S and S Combi units, alarm 70 means no water flow is detected in the hydraulic circuit or the pump is faulty. Note the alarm and whether P70 appeared first, and call the service contractor: Hitachi does not want you to service it yourself.
Safety first
Stop and check this first
- Hitachi says not to carry out service or inspection tasks yourself, not to open the service cover without disconnecting the main power supply and not to touch the internal safety devices. If the breaker or unit fuse trips often, stop the system and call your service contractor.
Safe checks you can perform
- Alarm and retry code
- Indoor unit model
- Flow and pump
Leave these tasks to a qualified professional
- Do not attempt this professional task: Measure flow against the model table
- Do not attempt this professional task: Test the pump before replacing it
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.
Measure flow against the model table
What they doThe technician measures flow and compares it with Hitachi's minimum and maximum for your unit.
They must show youflow in m³/h against your model's minimum and pressure against 0.1 to 0.3 MPa.
In writingthe cause found and what was corrected.
Test the pump before replacing it
What they doWith the circuit full and open, the technician tests the pump before proposing a replacement.
They must show youthe pump under test and the resulting flow.
In writingif the pump was replaced, its part number, and the test without alarm 70.
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.
Alarm and retry code
- Who:
- you.
- How:
- note what the controller shows: P70 or alarm 70.
- Result that matters:
- P70 is the retry code; alarm 70 is the stop.
- If you only saw P70 and the unit carried on:
- flow recovered; note the date.
- If it stayed on alarm 70:
- the unit is stopped; call the service contractor.
- Evidence to keep:
- a photo of the controller with the alarm.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
Indoor unit model
- Who:
- you.
- How:
- look at the indoor unit rating plate and note the model, for example RWM or RWD and its HP size.
- Result that matters:
- Hitachi gives different minimum and maximum flows for each model.
- If you have the model:
- the technician knows which minimum flow to compare against.
- If you cannot find the plate:
- do not open the unit to look; the technician will find it.
- Evidence to keep:
- a photo of the rating plate.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
Flow and pump
- Who:
- a qualified service person.
- How:
- they check circuit pressure against 0.1 to 0.3 MPa, measure flow and compare it with your model's minimum and maximum, and test the water pump.
- Result that matters:
- measured flow against the minimum in Hitachi's table for your model.
- If flow is below and the pump runs:
- the cause is in the hydraulic circuit.
- If the pump does not move water with the circuit full and open:
- the pump is confirmed.
- Evidence to keep:
- a job sheet with pressure, flow in m³/h and the pump test result.
Hitachi says not to open the service cover without disconnecting the main power supply. Qualified service personnel only.
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 Yutaki alarm 70
- Yutaki 70
- Yutaki P70
What it means
Hitachi defines alarm 70 as a hydraulic alarm for flow and water pump malfunction: water flow is not detected in the hydraulic cycle or the pump is defective. It has a retry code, P70, before the stop. The manual gives minimum and maximum flows per model, for example 0.5 to 1.9 m³/h on the R32 Yutaki S 2 HP and 1.0 to 2.9 m³/h on the R410A 4 HP, and an allowable pressure of 0.1 to 0.3 MPa. The code does not separate low flow from a faulty pump.
Warnings and stop conditions
- Highsource verified
Hitachi says not to carry out service or inspection tasks yourself, not to open the service cover without disconnecting the main power supply and not to touch the internal safety devices. If the breaker or unit fuse trips often, stop the system and call your service contractor.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
Symptoms and causes
Probable causes · in order
- Flow below the model minimumCommon
The circuit does not reach the minimum flow Hitachi gives for your model. Measuring flow against the table separates it.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
- Faulty water pumpPossible
Hitachi lists a defective pump as a main factor. It fits if the pump does not move water with the circuit full and open.
Evidence: Hitachi YUTAKI series and YUTAKI cascade controller installation and operation manual PMML0575 rev.1
Virtual technician
Does 70 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
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