Boiler Brands We Service Across London

Viessmann Climate Solutions became part of Carrier Global in January 2024, and Viessmann UK now carries "a Carrier company" on its own site. Its distinguishing feature at a service is the Inox-Radial stainless steel heat exchanger used across the Vitodens range, which Viessmann covers with a separate ten year guarantee against leakage caused by corrosion — a promise sitting underneath the boiler warranty rather than part of it. The boiler warranty itself is shorter than people assume: two years as standard, extending to seven free of charge if the installation is registered within 30 days, with paid extensions beyond that depending on model. Viessmann is explicit that annual servicing is what qualifies each subsequent year of cover, so a missed service does not just risk the warranty, it stops the clock advancing.

Glow-worm is a trading name, brand and registered trademark of Vaillant Group UK Limited, operating from the same Belper site as Vaillant itself. That relationship is genuinely useful rather than trivia: Glow-worm warranty repairs are carried out by Vaillant service engineers, and Glow-worm uses the same F.xx fault code convention as its premium sibling, so an engineer who knows the ecoTEC platform is not starting from scratch. Warranty lengths run by range — the Energy at seven years, the Ultimate at five, with longer periods available through the group installer scheme — and the same hard rule applies as on a Vaillant: register within 30 days or it reverts to twelve months. Glow-worm’s terms require an annual service by a Glow-worm or other Gas Safe registered engineer, and note the service cost is not included.

Potterton is one of the most recognisable names in British heating, but the domestic brand has largely been absorbed. Its own domain now redirects to Baxi, and Baxi’s current brand listing carries Potterton Commercial under commercial heating rather than domestic. What survives on the domestic side is a small number of Potterton-badged products within Baxi Heating, including the Potterton Titanium Heat, published at seven years parts and labour. In practice most Potterton boilers we are asked to service are older appliances in unmodernised London properties, where the visit is about safety, condition and honest advice on parts availability rather than warranty paperwork. Being group products, they use Baxi’s E-code fault convention.

Vokèra trades as Vokèra by Riello, and its corporate home has just changed: Ariston Group completed its acquisition of the Riello business from Carrier on 1 July 2026, and Vokèra’s own site now states it is subject to the direction and coordination of Ariston Holding. That makes Vokèra, Ariston and ATAG stablemates, which matters mainly for parts and technical support routes rather than day-to-day servicing. The current range runs Pinnacle, Synergy, Vibe MAX and Easi-Heat, with published warranties from five up to twelve years by model. The Pinnacle uses a stainless steel heat exchanger with a wide modulation range. We could not verify on a Vokèra-owned page whether annual servicing is a hard warranty condition, so if that matters to you, confirm it with Vokèra directly rather than assuming.

Alpha is part of the Italian Immergas group and has been selling in the UK for around sixty years, with its head office in Kent. It is most often specified where installed cost is the deciding factor, which puts it firmly in the London landlord and developer segment. Alpha publishes warranties in the seven to ten year range depending on model, with the E-Tec Plus NX carrying ten years as standard and extensions available when its wall-mounting jig is fitted, and registration required within 30 days. Alpha is blunter than most about servicing: it states that failure to have the boiler annually serviced during the guarantee period will invalidate the warranty. Current ranges are the E-Tec NX, E-Tec Plus NX, Evoke NX, InTec and ProTec NX.

Ariston Group is an Italian manufacturer listed in Milan, and its portfolio has grown considerably — it already owned ATAG Heating, Elco and Wolf, and completed its acquisition of Riello, and with it Vokèra, in July 2026. The distinctive engineering feature on its UK combi range is the patented Xtratech stainless steel heat exchanger, a single-coil design with substantially wider waterways intended to resist debris blockage, which is a sensible thing to know on a system with any history of sludge. Ariston requires registration within 30 days from commissioning and states the product must be professionally serviced every twelve months by a competent person. We are deliberately not quoting a headline warranty length here: Ariston’s UK product pages would not yield one reliably, and the figures circulating on merchant sites are not something we are willing to repeat as fact.

Navien is the UK arm of KD Navien of South Korea, established here in 2014 and based in Guildford. The parent company launched Asia’s first condensing gas boiler in 1982, which is a longer condensing pedigree than most of the brands it competes against in the UK. Navien publishes up to twelve years on its NCB500 and NCB700 combi ranges, and is unambiguous about the condition: all warranty lengths are subject to the undertaking of an annual service from the installation date. The NCB700 is rated to serve three bathrooms simultaneously with the appropriate controller, which is why it turns up in larger London houses where hot water demand rather than heating load drove the specification. Parts lead times are worth factoring in on any less common brand.

Intergas is the most genuinely different design on this list and worth understanding on its own terms. Its combis have no diverter valve, no valve motor, no auto air vent and no secondary plate heat exchanger — Intergas removes them by using a single two-in-one heat exchanger with two separate circuits that does both the heating and the hot water job. As Intergas puts it, the parts that tend to stick, leak or let you down are not there. For a servicing engineer that removes a whole category of the failure modes we spend most of our time on, and the Xtreme adds passive flue gas heat recovery on top. Registration must be within 30 days of commissioning or cover drops to twelve months, and fitting an Intergas system filter adds to the warranty period. We are not quoting a specific length because two Intergas-owned pages currently give different figures for the same range.

ATAG is a Dutch manufacturer acquired by Ariston in 2014, and it publishes the longest headline warranty in the UK: twelve years as standard with an eighteen year option. The upgrade is conditional rather than automatic, requiring a compatible smart control plus a water treatment pack built around a named magnetic filter — which is a consistent theme across this whole page, and on ATAG it is the difference between twelve and eighteen years. Underneath all of it sits the genuinely distinctive promise: a lifetime guarantee on the iCon stainless steel heat exchanger, regardless of which warranty tier the boiler is on. The condition is the familiar one, and ATAG states it plainly — the annual service by your installer is what keeps the warranty valid.

Ferroli Ltd operates from Walton-on-Trent in Derbyshire and is part of the Italian family-owned Ferroli group, founded in Verona in 1955. Its current featured domestic range in the UK is the Bluehelix HiTech RRT. Ferroli is worth reading carefully because it has the strictest filter condition of any brand on this page: seven years as standard, upgradeable to ten for a stated fee, registration required within 30 days, and a high-performance magnetic filter is mandatory — without one the warranty is one year only. Not reduced, not tiered down: one year. Ferroli also requires the appliance to be annually serviced to keep the warranty valid. If you have a Ferroli and no filter on the system, that is worth establishing before you need to rely on the cover.

Main by Baxi sits within Baxi Heating alongside Baxi itself, Megaflo, Heatrae Sadia, Andrews Water Heaters and Remeha. The standalone brand is being folded in — the old Main Heating website now states it has transitioned into Baxi, and the product is listed on Baxi’s own site as the Baxi MainEco Compact, published at five years parts and labour. Baxi describes Main as high efficiency boilers available exclusively through independent merchants, which is an unusual and quite specific route to market: it is why Main boilers tend to appear where a local installer sourced the appliance rather than where a developer specified it. Because Main sits inside Baxi Heating, the group’s approach to Benchmark documentation and service evidence is the right mental model, and it uses Baxi’s E-code faults.

Heatline needs a more careful answer than the other entries here, because the usual sources are wrong. It is widely described online as a Vaillant Group brand, but Heatline does not appear among the brands Vaillant Group currently lists, and the Heatline UK website is now a placeholder that serves no product content on any path. We are not going to assert an ownership or a warranty position we could not verify. What we can say descriptively is this: no current Heatline range is being marketed in the UK, the last widely installed model was the Capriz2 combi, and existing units are still serviceable through third-party spares. If you have a Heatline in a London flat — and plenty of buy-to-let properties do — it is worth booking the annual service on condition and safety grounds and planning for the fact that parts sourcing will be less straightforward than on a current brand.