We’ve been installing commercial sized ATAG boilers for some time, in fact, you will find some others on this blog.

ATAG have recently relaunched their domestic offering in the UK, and now offer 10 year warranties and 24hr technician support.   ATAG are a premium brand boiler manufacturer from the Netherlands, although a stake is now owned by Ariston MTS Group.

Kensington here we come

Our customer had selected an ATAG IC Economiser 39, which is a combi boiler augmented with ‘designed at birth’ flue gas heat recovery (rather than tacked on afterwards like most other manufacturers), and reputed to be the most efficient boiler of its type currently available.

ATAG domestic boilers are now sold direct through ATAG sales partner installers.  Our customer, who owns their apartment in a prestigious development in Kensington (London), was an engineer who had taken a great deal of time to research and choose their new boiler.  After selecting the IC39, they engaged one of these accredited partners to supply, design and install their heating system.

Unistrut in position (Bosch boiler from adjacent apartment in view)

The task was not straightforward, because the building was running on a district heating system, this was being discontinued in late 2017.  Each apartment owner had been given a deadline for the changeover, which was quite a complex task, each dwelling being the floor area of a large detached house.

The boiler and parts were delivered to site, and their chosen installer took payment for the boiler,  and a further 50% of the installation cost up front.  Unfortunately, our customer didn’t have much luck thereafter.  The installer made a few calls and emails, and clearly was somewhat fazed by the size and complexity of the task.  At one point, he was suggesting he would turn up with five ‘Facebook/Forum friend plumbers’, and knock the job out in one day.

Tight fit in cupboard

Sadly, that was the last our customer saw of this character;  he claimed to have fallen ill and be incapacitated;  their calls went unanswered thereafter.   But when they asked a friend to ring him, their call was answered immediately and he offered to pop over to do a quote.

This is where Hot Water & Central Heating Ltd got involved.  Normally, we’d ‘run to the hills’ if a customer wants to supply their own boiler and the job is half finished; but on this occasion, the customer was a friend of one of our best customers, and they were clearly in a jam not of their own making.

New flue system in lift motor room

We constructed a Unistrut support, fitted the boiler in a service cupboard, ordered the correct flue components (the previous installer had made some errors) and fitted the flue through a disused lift motor winding room on the roof.

The customer had made numerous schematics to show how the district heating system had connected into the apartment.  These were complex but thorough, and we found them to be 100% accurate.

Unfortunately, the ATAG One controller needed a wired connection from the boiler, which would have ruined the finished decorations, so we specified a Honeywell Evohome zoned system instead.


As the ATAG IC39 can use OpenTherm modulating controls, (the ATAG One is OT) we fitted an OpenTherm compatible Evohome.  This will modulate the boiler logic according to the number of radiators open, and the calculated heat requirements.  All clever stuff, just a shame Honeywell had no OpenTherm controllers in the UK, which was a drama we had not planned for.

NB: If you are technically minded, here’s a fact sheet on OpenTherm;


Lift room on roof, 5 floors up. Great view of London!

We hit a few hurdles along the way with missing parts that the original installer had opened and lost;  ATAG UK were superbly supportive in all cases and sent them by post the next day, gratis.

We’d also like to thank our customer and her son.  The boiler task was made especially difficult for them due to a bereavement in the family.  They pulled out all the stops to make our job as easy as possible; coffees and help were endless.

It was a pleasure, we even forgot about the horrible journey to Kensington each day!