Summary

Panasonic's Aquarea range is one of the established heat pump brands on UK domestic Boiler Upgrade Scheme (BUS) installations, sold in monobloc (single outdoor unit, water pumped directly to the heating circuit) and bi-bloc/split (separate indoor hydro-box and outdoor unit, linked by a refrigerant circuit) configurations. The fault code architecture is broadly consistent across recent generations (F, J, K, L, and All-in-One/T-CAP series), using an "H" prefix for a first family of faults (largely communication and sensor-related) and an "F" prefix for a second family (largely refrigerant-circuit and pressure-related), though the exact digit meanings can shift slightly between generations.

The fault code and its history are shown on the indoor unit's wired remote controller display, with a fault log accessible through the service/history menu — always check this log for a pattern of recurring codes rather than diagnosing a single occurrence in isolation, particularly for intermittent communication faults.

As with all UK heat pumps, refrigerant circuit work — recovering, leak-testing, or recharging refrigerant — is restricted to F-Gas certified engineers under the Fluorinated Greenhouse Gases Regulations. Many Aquarea F-series codes point toward the refrigerant circuit but also have simpler explanations (blocked outdoor unit airflow, a tripped isolator, a loose sensor connector) that a competent heating engineer can check first.

This guide covers the fault codes with the most consistent documentation across current Aquarea generations, with particular focus on H90 — by far the most frequently reported fault on UK installations.

Key Facts

Quick Reference Table

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Code Likely meaning Most likely cause Competent-engineer checkable?
H90 Indoor/outdoor communication error (>1 min after start) Damaged/loose communication cable, connector fault, PCB fault Yes — cable and connector check first
H12 Capacity/model mismatch Incorrect model setting after PCB replacement Yes — check configuration setting
F12 (indicative) Refrigerant pressure/sensor fault Blocked outdoor unit airflow, sensor fault, genuine refrigerant issue Partial — airflow check is DIY-safe; refrigerant diagnosis is not
No code, unit runs but poor heat output Possible undersized emitters or wrong weather comp curve Commissioning/design issue, not hardware Yes — check design and settings first
No code, outdoor unit heavily iced beyond normal defrost Defrost cycle fault or blocked airflow Blocked outdoor unit, failed reversing valve Partial — visual airflow check is DIY-safe
Any code not listed Unconfirmed for this specific generation/model **** —

Detailed Guidance

Diagnosing H90 (indoor/outdoor communication error)

H90 displayed (fault after >1 min from start)
        |
        v
Isolate power at BOTH indoor and outdoor
units simultaneously for several minutes
        |
        v
Restore power and observe start-up
        |
   ----FAULT CLEARS AND STAYS CLEAR----> Log as resolved, monitor
        |                                 fault history over next visit
       FAULT RETURNS
        |
        v
Inspect communication cable along its full run
for damage, chafing, or water ingress at glands
        |
   ----DAMAGE FOUND----> Repair/replace cable, re-test
        |
     NO DAMAGE FOUND
        |
        v
Check terminal connections at both indoor
and outdoor PCBs are tight and correctly wired
        |
   ----LOOSE/INCORRECT----> Correct wiring, re-test
        |
      CORRECT
        |
        v
Suspect PCB fault at indoor or outdoor unit —
refer to Panasonic technical support for
board-level diagnosis

H90 is by far the most commonly reported Aquarea fault on UK forums and independent trade documentation, and the pattern is consistent: it is a communication-link fault, not (in the great majority of cases) a refrigerant or compressor problem. The most productive first check on any callout is the physical condition of the cable run between the indoor and outdoor units — these often run externally for some distance and are exposed to UV degradation, rodent damage, and water ingress at cable glands, especially on installations more than a few years old.

Monobloc vs bi-bloc — why the fault means something slightly different

On a monobloc Aquarea system, the entire refrigerant circuit is sealed within the single outdoor unit, and heated water is pumped directly into the property's heating circuit — there is no indoor refrigerant-carrying pipework. An H90-type communication fault on a monobloc system therefore points to the control/data cable between the outdoor unit and the indoor wired controller (and any cylinder/zone controls), not a refrigerant-side connection.

On a bi-bloc (split) system, refrigerant pipework runs between the outdoor unit and an indoor hydro-box, alongside the control communication cable — a communication fault here can sometimes accompany refrigerant-side symptoms, but the two are diagnosed separately: the communication link electrically, the refrigerant circuit only by an F-Gas certified engineer.

Frequently Asked Questions

Why does my Aquarea keep showing H90 even after I've reset it?

A fault that clears briefly and then returns points to an intermittent connection rather than a one-off event — check for a loose terminal or a cable with damaged insulation making intermittent contact, particularly at any point where the cable is exposed to weather or has been disturbed during other work near the outdoor unit.

Can I fix an H90 fault myself without an F-Gas qualification?

Yes, in most cases — H90 is a communication fault, not a refrigerant fault, so cable and connector checks fall within the scope of any competent heating engineer. F-Gas certification is only required if diagnosis points to the refrigerant circuit itself (relevant on bi-bloc systems), which is a separate and much less common cause of this specific code.

Is an F-series code on my Aquarea always a refrigerant leak?

Not necessarily — many F-series faults are triggered by conditions that mimic a refrigerant problem, most commonly a blocked or restricted outdoor unit (leaves, debris, snow, or an enclosure built too close to the unit restricting airflow). Check airflow and clearances around the outdoor unit before assuming a genuine refrigerant leak, which would need an F-Gas certified engineer to confirm and repair.

Does the fault code mean the same thing on a monobloc and a bi-bloc Aquarea?

The code numbers are broadly shared across the range, but what the fault implies for diagnosis differs — see the Detailed Guidance section above. Always confirm which configuration (monobloc or bi-bloc) is installed before assuming which pipework or cable run is implicated.

Regulations & Standards