Summary

LG's Therma V range (monobloc and split, R32 and earlier R410A refrigerant models) is a significant presence in the UK domestic air source heat pump market, particularly in the price-competitive segment. Like other heat pump brands, Therma V units display numbered error codes on the wired controller rather than relying on symptom-only diagnosis, but the specific numbering and groupings differ from other manufacturers (Daikin, Mitsubishi Ecodan, Vaillant aroTHERM, Grant Aerona, Panasonic Aquarea, Samsung — covered in their own dedicated fault-finder articles on this wiki).

The most practically useful grouping for on-site triage is by fault category rather than memorising individual numbers: sensor faults (a sensor reading out of range or disconnected — often the single most common category, and sometimes resolvable by checking a connector rather than replacing a part), water-side faults (flow rate, air in the system, blocked strainer — very common in the first two weeks after a new installation as trapped air works its way out and residual debris from pipework is caught by the strainer), and more serious PCB/refrigerant-circuit faults that require manufacturer-level diagnosis.

As with all heat pump brands, always cross-check the exact error code and number against the specific model's installation/service manual before acting, since LG has used slightly different code numbering across generations (R410A vs R32 models, monobloc vs split) and a code number alone without model context can be misread.

Key Facts

Quick Reference Table

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Error code Fault category Typical cause First check
1 Sensor Remote room air sensor fault Check sensor connection/wiring before replacing
2 Sensor Refrigerant inlet-side sensor fault Check sensor connection/wiring
6 Sensor Refrigerant outlet-side sensor fault Check sensor connection/wiring
8 Sensor Water tank sensor fault Check sensor connection/wiring
10 Water/pump BLDC water pump lock (stalled/obstructed) Check pump for obstruction, air lock
14 / CH14 Water flow Flow switch/insufficient flow — very common in first 2 weeks post-commissioning Check strainer for debris, bleed air from system
16 Sensor General sensor fault group Check relevant sensor connections
17 Sensor Water-inlet sensor fault Check sensor connection/wiring
18 Sensor Water-outlet sensor fault Check sensor connection/wiring
19 Sensor Water-interim sensor fault Check sensor connection/wiring
53 PCB/electronics PCB program (EEPROM) fault Manufacturer-level diagnosis/board replacement — not field-repairable
Code persists after sensor/wiring check Possible refrigerant circuit Refrigerant sensor or circuit fault Refer to F-Gas certified engineer

Detailed Guidance

Triage by fault group, not just the number

Before diving into a specific numbered code, identify which broad category it falls into — sensor, water-side, or PCB/refrigerant — since this determines both the likely cause and who should be doing the work. Sensor faults are the most common and most often resolved by a competent heating engineer checking a connector or wiring run rather than condemning the sensor itself. Water-side faults are mechanical/hydraulic and generally within a heating engineer's normal scope. PCB and refrigerant-related faults should be escalated to manufacturer technical support or an F-Gas certified engineer respectively, rather than attempted as a general repair.

Diagnosing early-life flow faults (CH14 / Error 14 pattern)

If a Error 14/CH14 flow fault appears within the first couple of weeks of a new installation, start with the strainer — residual flux, jointing compound, or debris from the installation process is a very common and easily resolved cause, and clearing a blocked strainer followed by re-bleeding the system resolves the large majority of these early cases. If the fault persists after the strainer is confirmed clear and the system has been properly bled of air, move on to checking the actual flow rate against the manufacturer's minimum specification for the unit's output, and confirm the circulation pump itself is operating correctly (not stalled — see Error 10 below) and that any zone valves affecting flow to the unit are open.

Diagnosing a pump lock (Error 10)

A BLDC (brushless DC) pump lock indicates the pump motor has stalled, which can be caused by a genuine mechanical obstruction (debris trapped in the pump impeller, again more common shortly after installation), an air lock preventing the pump from establishing flow, or — less commonly — a genuine pump fault. Check for obstruction and air first, as these are both more common and more straightforward to resolve than a pump replacement.

When to escalate beyond a general heating engineer's scope

Any fault that persists after sensor wiring and water-side checks are confirmed sound, particularly where the code relates to refrigerant-side sensors or shows signs of a genuine refrigerant circuit issue (reduced heating output alongside the fault, unusual outdoor unit noise, visible frosting beyond normal defrost patterns), should be escalated to an F-Gas certified engineer or LG's technical support line rather than investigated further by a general heating engineer without the appropriate certification and equipment.

Frequently Asked Questions

My new LG Therma V installation is showing Error 14 after two weeks — is this a serious fault?

Not usually. This is a well-documented pattern on new installations — check the strainer for installation debris and re-bleed the system for trapped air before assuming a more serious fault. If the error persists after both checks, investigate flow rate and pump operation next.

Can I reset an LG heat pump error code myself without a qualification?

Clearing/resetting a fault code on the controller itself doesn't require special certification, but you should only do so after addressing the underlying cause — resetting repeatedly without fixing the fault simply masks the problem and risks equipment damage or a nuisance callback. Any work on the refrigerant circuit requires F-Gas certification regardless of how the fault is cleared on the display.

Does working on a grant-funded heat pump (Boiler Upgrade Scheme) require any special registration?

Yes — installations funded under the Boiler Upgrade Scheme must be installed and maintained by an MCS-certified installer to remain compliant with scheme rules; non-MCS repair work can have warranty and scheme implications. ****.

Are LG Therma V error codes the same across all models?

Not necessarily — R32 refrigerant models and older R410A models, and monobloc vs split configurations, can use different code numbering for broadly similar faults. Always confirm against the specific model's installation or service manual rather than relying solely on a general reference.

Regulations & Standards