Warranties differ, so read the one registered for your install. Work that commonly takes a system outside cover includes DIY work on the refrigerant circuit, pairing an indoor unit from one brand with an outdoor unit from another, and skipping a service when the warranty makes that service a condition. The service point applies only if the warranty says so. Ask the installer to show you the clause. This is a hedge, not a ruling on your paperwork.
Registration, serial numbers and the commissioning sheet
A manufacturer warranty, an installer warranty and an extended scheme are different documents. Cover often starts when the commissioning company registers the models, the serial numbers and the address. A unit bought online and connected by whoever was free that weekend may never have been registered. Keep the commissioning sheet, the model codes and the name of the F-gas company. A later claim without those is already harder, even before anyone argues about cause. Read your warranty. Do not rely on a forum list.
Some warranties demand an annual service by a competent person and a record. Missing it can limit or void cover, because the clause says so. Other warranties do not mention service. In that case a missed anniversary does not, by itself, invent a void. If you are unsure, ask the manufacturer or the registering installer to point at the sentence. A missed service voids or limits cover when the warranty makes service a condition. If the document is silent, ask the manufacturer rather than assuming you are uncovered. Using a different service firm is often allowed. Using no one, when the clause requires someone, is the risk.
Mixed pairs, neglect and the service sentence
Opening the refrigerant circuit is for a certified company. A DIY charge, a mix of gases, or a joint made by someone who is not certified is both an F-gas problem and the sort of event warranties are written to refuse. DIY work on the refrigerant circuit is a common exclusion and is unlawful. If you top up the gas yourself, you are outside that common exclusion and outside lawful F-gas work. Replacing a failed part with a board or a fan from a different brand, or hanging one maker's indoor unit on another's outdoor unit, leaves you without a system the maker described. That mix is commonly outside the manufacturer warranty, and it may not work as a matched system. Check the wording before anyone splits the pair.
Physical damage, a blocked coil you never cleared, a cover left on a heat pump through winter, and filters left solid for years can also be argued as neglect. Whether that defeats a claim depends on the wording and on what actually failed. Ask, and keep photos of maintenance you did do. Energy Saving Trust will not adjudicate the claim. The warranty text will.
Core buying guides
Start with these high-intent guides, then dig into the rest of the library.
Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.