Questions people ask

If the system has stopped itself, leave it stopped until you know why. A protection code means a measured value moved outside a safe range, and forcing the system back on repeats the condition that triggered it. If you smell burning, see scorching, or hear grinding, switch it off at the isolator and call a technician.

It clears the display on most systems, and on a small number of one-off electrical glitches that is genuinely the end of it. If the code returns, the condition is still present and the reset has only removed the evidence. Note the code before you cut power, because some systems do not store history.

Because there is no industry-wide code standard. Each manufacturer defines codes for its own control platform, and often changes them between generations. That is why every reference on this site names the product family the definition came from.

Usually not. Heat pumps run a defrost cycle that briefly reverses operation to melt frost from the outdoor coil, and the steam is that frost evaporating. Heating pauses for a few minutes and the fan may stop. It becomes a problem if the unit ices over completely and does not clear, or if defrost runs constantly.

Most systems hold the indoor fan until the coil warms up, and some run a short delay after any start or mode change. Cool air for a minute or two at start-up is expected. Cool air that continues once the system is running is not.

That is condensate and defrost meltwater leaving the outdoor coil, which is normal in heating. Water appearing from the indoor unit is not normal and points to the condensate path, the filter, or a frozen coil.

Manufacturers of ductless systems typically specify cleaning the washable filters every two to four weeks in regular use, and more often in dusty homes or with pets. It is the single maintenance task with the largest effect on capacity, energy use, and coil icing.

No. Refrigerant is not consumed in normal operation, so a system that loses charge has a leak. Repeated top-ups without finding the leak are both expensive and, under UK and EU F-Gas rules and US EPA regulations, not an acceptable substitute for repair.

Long run times at low outdoor temperatures are how heat pumps are designed to work. Steady low-output operation is more efficient than short bursts. It becomes a concern when the system cannot hold the set temperature, or when auxiliary or immersion heat is running far more than in previous seasons.

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