Common heat pump problems and what usually causes them
Most heat pump complaints are not equipment failures. They are design, commissioning or expectation problems: a system running hotter than it should, an emitter that is too small for its room, controls set up like a boiler, or a household that was never shown how the system is meant to behave.
Three different kinds of problem
There is a distinction that gets lost in most discussions of heat pump problems.
A fault is something broken or outside its operating range: a failed component, a leak, a blocked strainer, a sensor reading incorrectly, a protection cutout triggering.
A design issue is a system working exactly as it was built to work, where what it was built to do was not right for the house. An undersized radiator in a north-facing bedroom is not a fault. It is a decision made at design stage.
An expectation issue is a system performing correctly where nobody explained what correct looks like. A heat pump running for hours at low output is doing its job. To a household used to a boiler firing hard for twenty minutes, it can look wrong.
Conflating the three is why some owners spend a winter unhappy without anyone diagnosing anything. Airwarm’s complaint process explicitly distinguishes a comfort expectation from a technical fault.
The problems people report most often
| What is reported | What usually causes it |
|---|---|
| One or two rooms never get properly warm | Usually the emitter cannot deliver that room’s heat loss at the system’s flow temperature. Sometimes it is a balancing problem, so the room gets less flow than the design intended. Occasionally a stuck valve. Bathrooms with standard towel rails are a very common example. |
| The house is warm but electricity use is higher than expected | Most often the system is running hotter than it needs to, either because weather compensation was never configured properly or because someone raised it to solve a symptom. |
| Hot water runs out | Usually a cylinder sized for a smaller demand than the household actually has, or a reheat schedule that does not match the routine. Occasionally a failing coil, immersion or thermostat. |
| The unit is noisier than expected | Noise usually comes from position and mounting rather than the equipment: vibration through a wall bracket or hard surface, discharge air reflecting off a nearby wall or fence, or a unit sited near a bedroom window. Some increase is normal in very cold weather and during a defrost cycle. |
| The system short cycles | Common causes are an oversized unit, insufficient water volume, too many zones closing at once, or excessive flow restriction. |
| It stops and shows a fault code | Codes are manufacturer-specific and usually point to a protection function rather than a failure: low flow, low pressure, a sensor out of range. Note the code before resetting, because the code is the diagnosis. |
Why it matters for your home
For anyone still choosing an installer, almost every item above traces back to a decision made before installation.
Room-by-room heat loss prevents undersized emitters. A correctly derived compensation curve prevents unnecessarily high flow temperatures. Honest hot water demand assessment prevents cylinder disappointment. Careful siting prevents most noise complaints. Correct sizing prevents short cycling. And a proper handover prevents the expectation problems entirely.
That is why Airwarm’s proposition is survey-led rather than product-led. A good heat-pump installation begins with the home, not the product. Airwarm checks the building, emitters, hot-water requirements, controls and practical installation details before making a recommendation.
What Airwarm does about it
Before installation: room-by-room heat loss, an emitter schedule checked against it, a design flow temperature stated explicitly, hot water demand assessed from actual household use, siting checked for air flow, clearances, condensate and noise, and a design review before a proposal is issued.
At commissioning: the system is flushed, the pressure test recorded, filters and strainers checked, controls configured, weather compensation set, emitters balanced, hot water tested, noise checked, photographs and serial numbers saved, and handover completed. Each is a recorded item rather than an assumption.
Afterwards: contact at 48 hours, a comfort review at two weeks, seasonal optimisation where required, and an annual service including error history and weather compensation.
When something is reported: establish the facts, distinguish comfort expectation from technical fault, agree the next action, document the outcome and review the root cause. What we learn from genuine faults feeds back into future designs.
Airwarm does not offer a general public 24-hour or emergency call-out service. Existing Airwarm customers get a response within 24 hours, and where a genuine system fault cannot be resolved remotely, emergency support or attendance may be provided as appropriate; that is not a guarantee of attendance within 24 hours. Some third-party equipment falls outside Airwarm’s competence to diagnose. Where that applies, Airwarm will say so rather than take the work on.
Common questions
“Heat pumps are unreliable.” The equipment is generally reliable. The variation in reported satisfaction comes overwhelmingly from design and commissioning quality, which is why choosing the installer matters more than choosing the brand.
“Ice or steam from the outdoor unit means it is broken.” Both are normal. The outdoor coil frosts up in cold, damp weather and the unit periodically defrosts, producing vapour and meltwater. Ice that never clears, or meltwater freezing across a path, is worth reporting.
“A fault code means an expensive repair.” Most codes are protection functions responding to conditions such as low flow or low pressure, and the underlying cause is often simple. A reset clears the symptom, but if the same code returns the cause is still present.
“If it was installed badly, nothing can be done now.” Often a great deal can be done: correcting the compensation curve, rebalancing, cleaning and treating the system water, enlarging one or two emitters, or reconfiguring the hot water schedule.
Next step
If your heat pump is not behaving as you expect, note three things before contacting anyone: what the system is actually doing, when it started, and any fault code exactly as displayed. E-mail hello@airwarm.co.uk with those details and the make, model and approximate age.
If you are choosing an installer, ask how they calculate heat loss, what design flow temperature they propose, how they will set weather compensation and what their commissioning record includes. The answers tell you a great deal.
If you are at the start, begin with the Home Energy Assessment. A quick first step to understand whether a heat pump is worth exploring for your property.
Frequently asked questions
My heat pump runs almost constantly. Is that wrong?
Usually not. Steady low-output running is how a heat pump is meant to work in cold weather, and it is preferable to frequent starting and stopping.
Can a badly installed system be corrected?
Frequently yes, at least in part. Some issues, such as significantly undersized pipework buried under floors, are harder and more expensive, and Airwarm will be straight with you about which category yours falls into.
Should I keep resetting a recurring fault?
No. Note the code and report it. A repeating code is information, and repeated resets can allow a small problem to become a larger one.
Read next
Servicing and maintenance
What an annual service checks, and the four things worth doing yourself between visits.
Will I need new radiators?
The single most common design issue behind a room that never gets warm.
Contact Airwarm
Describe what the system is doing and get an honest answer about scope.
Start with your home, not a product
The Home Energy Assessment takes a few minutes, asks for no photographs at this stage and gives you an honest first view of whether an air source heat pump is worth exploring for your property.