Today we are in Sevenoaks, Kent, in a road where we now have installed at least three boilers, and three Evohome multi zone systems too!
Our customer knew about heating systems, and chose an ATAG i series boiler. He wanted a unit that was of high quality manufacture, and one that could use Opentherm controls, so that the house could modulate the boiler intelligently.
As the local ATAG and Honeywell Evohome specialists, we were asked to advise and quote for the job. A leaking Ideal condensing boiler was scrapped, and the plan was to fit the ATAG in the same position.
There’s a fair few things you can do with an ATAG that you can’t do with most other boilers. They understand Dutch, for one thing. Another is that if there is limited wall depth in your proposed location, the frame containing the expansion vessel can be jettisoned, making the boiler much slimmer.
As intimated earlier, you can use the clever ATAG ONE thermostat; but you can also use Evohome zone controls, because both rely on the OpenTherm protocol.
Most domestic boilers in the UK have used a simple 230V on/off control. On the continent, around 24 years ago, controls manufacturers agreed a common interface that would allow wall thermostats and the like to modulate the power of the boiler, using a data interface. Whilst not a standard, OpenTherm allows interoperability between any so equipped boiler and control.
In the UK the take up of OpenTherm hasn’t been great, whilst in mainland Europe it is difficult to market a boiler without it. Many boilers sold here as incompatible with OpenTherm, have almost identical twins abroad that are!
Our customer had his own existing unvented water cylinder and wished to retain this. Using a normally open, and a normally closed Honeywell motorised valve, we configured the system so that it now had hot water priority.
Honeywell’s Evohome can be used with their OpenTherm bridge interface; this automatically asks the boiler to ramp up to 100% in the event of a hot water cylinder recharge demand. When in heating mode the Evohome’s OpenTherm bridge modulates the boiler output according to the calculated number of radiator zones open, room temperature and external temperature. Clever stuff.
Our area technical representative from ATAG, Glenn Evans, was there to see the system commissioned; it was his first Evohome/ATAG installation.