- Heat pumps
- Air-to-water heat pump
P3-01
Daikin Altherma P3-01: outdoor unit abnormal direct current
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Daikin Altherma P3-01 means the outdoor unit stopped after exceeding its direct current limit value, with an automatic reset configured in the controller. Note the exact operating mode in menu [11] Malfunctioning, check for repeated automatic restarts, and call an installer if P3-01 returns.
Safety first
Stop and check this first
- Do not open the outdoor unit switch box or touch internal PCBs. High-voltage capacitors inside the inverter section require turning off all power supplies, waiting more than 10 minutes, and confirming less than 50 V DC before any contact.
- Do not turn off the unit circuit breakers repeatedly to force restarts when P3-01 recurs; turning off outdoor power disables freeze protection and repeated overcurrent starts can damage the inverter power module.
Safe checks you can perform
- Review menu [11] Malfunctioning to see if P3-01 cleared automatically or keeps cycling
- Check your home electrical panel and other high-load appliances during the trip window
- Verify sensor temperatures in [6.3] and configure [5.23] Emergency selection if heat is lost
Leave these tasks to a qualified professional
- Do not attempt this professional task: Measure inverter DC bus current, compressor winding insulation and DC current sensor accuracy
- Do not attempt this professional task: Discharge the DC link for over 10 minutes and test outdoor inverter PCB and ACS PCB harnesses
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 inverter DC bus current, compressor winding insulation and DC current sensor accuracy
What they doThe technician must test compressor winding resistance and insulation to earth, monitor the inverter DC current value during compressor ramp-up, and determine whether the DC limit exceedance comes from the load or a faulty inverter PCB sensor.
They must show youThe compressor megohmmeter and winding resistance readings alongside the logged DC current during a supervised test run.
In writingCompressor phase-to-phase resistance (ohms), insulation resistance to ground (MOhm), and written confirmation that P3-01 and P3-04 do not recur.
Discharge the DC link for over 10 minutes and test outdoor inverter PCB and ACS PCB harnesses
What they doA certified technician must isolate mains power, wait more than 10 minutes, verify less than 50 V DC across the inverter capacitors before touching components in the outdoor switch box, and inspect the wiring and connectors between the Control PCB, Inverter PCB and ACS PCB.
They must show youThe meter verification of less than 50 V DC after 10 minutes and the physical inspection of the Control, Inverter and ACS PCB connectors.
In writingMeasured residual DC voltage (V DC), condition of internal board harnesses, and incoming AC supply voltage under load (V AC).
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.
Review menu [11] Malfunctioning to see if P3-01 cleared automatically or keeps cycling
- Who:
- You, checking the indoor user interface display.
- How:
- Navigate to [11] Malfunctioning to read the extended fault text, and enable the advanced end user permission level to inspect the malfunction history timestamps.
- Result that matters:
- Whether P3-01 logged once and recovered via its automatic reset or is repeating every time the heat pump attempts to start.
- If P3-01 appeared only once during a utility voltage flicker and normal heating resumed, that points to a transient mains disturbance.
- If P3-01 repeats in the history log or escalates to manual-reset codes such as L5-00 or L8-05, that confirms a persistent outdoor DC current fault requiring a technician.
- Evidence to keep:
- Photograph the [11] Malfunctioning description and the timestamped malfunction history entries.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C · Daikin Altherma 4 H F+W+ECH2O operation manual 4PEN773378-1C
Check your home electrical panel and other high-load appliances during the trip window
- Who:
- You, inspecting the indoor distribution board without opening any equipment enclosures.
- How:
- Verify that the dedicated heat pump circuit breakers and residual current device (30 mA RCD) are fully on, and note whether large loads (EV chargers, ovens, pumps) started when P3-01 occurred.
- Result that matters:
- Stable breaker position and correlation between household electrical demand and the P3-01 timestamp.
- If P3-01 coincides with whole-house voltage sag or flickering lights, that suggests supply voltage instability (related to U2-07) affecting the inverter DC bus.
- If the household supply is steady and no other load switched on, that rules out domestic load drops and points to the outdoor inverter or compressor circuit.
- Evidence to keep:
- Write down the breaker ratings, the time of the trip, and any simultaneous appliance activity.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
Verify sensor temperatures in [6.3] and configure [5.23] Emergency selection if heat is lost
- Who:
- You, operating the indoor user interface.
- How:
- Check [6.3] Sensors to see if water and tank temperatures are dropping due to repeated stops, and check [5.23] Settings > Emergency selection if you need backup heating while waiting for service.
- Result that matters:
- Current leaving water and domestic hot water temperatures and the configured emergency backup heater mode.
- If water temperatures are holding steady after an automatic reset, that confirms the heat pump resumed normal operation after a one-off P3-01 event.
- If tank and room temperatures keep falling because the outdoor unit stops on every start attempt, that indicates an active DC limit lockout requiring professional diagnosis.
- Evidence to keep:
- Record the [6.3] sensor readings and your dealer contact details from [6.2] Dealer information.
Evidence: Daikin Altherma 4 H F+W+ECH2O operation manual 4PEN773378-1C
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
- Daikin
- Product type
- Air-to-water heat pump
Known code variants
- Altherma 4 H F P3-01
- code erreur Daikin Altherma P3-01
- codice P3-01 pompa di calore Daikin
- código P3-01 bomba de calor Daikin
- Daikin Altherma error P3-01
- Daikin Altherma Fehler P3-01
- Daikin heat pump code P3-01
- Daikin P3-01
- Daikin Wärmepumpe Fehlercode P3-01
- défaut P3-01 pompe à chaleur Daikin
- error Daikin Altherma P3-01
- errore Daikin Altherma P3-01
What it means
According to chapter 14.4.4 of the Daikin Altherma 4 H F installer reference guide (4PEN773391-1C), code P3-01 (alongside P3-04) is titled Abnormal direct current, triggered by a malfunction decision when exceeding the direct current limit value in the outdoor unit. Upon detection, the heat pump stops operating and uses an automatic reset once the DC reading returns within limits. A P3-01 event alone never proves the inverter PCB or compressor must be replaced: transient mains voltage dips, heavy compressor starting load, or internal transmission disturbances between the Control PCB, Inverter PCB and ACS PCB can also push the DC rail or current sensor across its threshold.
Warnings and stop conditions
- Highsource verified
Do not open the outdoor unit switch box or touch internal PCBs. High-voltage capacitors inside the inverter section require turning off all power supplies, waiting more than 10 minutes, and confirming less than 50 V DC before any contact.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C · Daikin Altherma 4 H F+W+ECH2O operation manual 4PEN773378-1C
- Mediumsource verified
Do not turn off the unit circuit breakers repeatedly to force restarts when P3-01 recurs; turning off outdoor power disables freeze protection and repeated overcurrent starts can damage the inverter power module.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C · Daikin Altherma 4 H F+W+ECH2O operation manual 4PEN773378-1C
Symptoms and causes
Probable causes · in order
- Direct current spike in the outdoor inverter section under heavy load or voltage sagCommon
A sudden dip on the incoming mains supply or a high-pressure compressor load burst causes the DC bus current in the outdoor inverter stage to exceed its limit value.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
- Internal transmission or sensing disturbance between Control PCB, Inverter PCB and ACS PCBPossible
Electrical noise or a loose internal harness inside the outdoor unit (related to P1-00 transmission and imbalance checks) corrupts the direct current feedback signal.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
- Inverter PCB current sensor drift or power module faultPossible
Degradation of the DC current sensing circuit on the outdoor inverter PCB (or a developing fault that also triggers manual overcurrent codes L5-00 or L8-05) causes repeated P3-01 trips.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
- Increased compressor mechanical or winding loadLess common
Abnormal compressor motor impedance or refrigerant circuit restriction elevates the direct current draw required by the inverter drive during ramp-up.
Evidence: Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C · Daikin Altherma 4 H F+W+ECH2O operation manual 4PEN773378-1C
Virtual technician
Does P3-01 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
Daikin Altherma 4 H F installer reference guide — 4PEN773391-1C
Daikin Europe N.V. · 2026 · official_doc
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