Evohome step-by-step

Controls technology has developed rapidly over the last five years with a big increase in demand for smart heating controls. Steven Hancock, Director of Mere End Consultants and Director of Plumb Arena provides a guide to installing the Honeywell evohome system.

Here at Mere End Consultants we get a lot of customers with medium to large properties asking about the benefits of installing smart heating controls, and our answer is simple – the benefits are huge!

We always like to go through the property specifications with the homeowners to find out what they already have and what they would like to get out of smart heating controls. Once this is agreed, we then go through our system builder checklist as it is essential to know what products are needed.

This particular home had two separate heating zones – upstairs and downstairs – and they wanted to control up to 12 zones. As they also wanted to control their hot water (Megaflo hot water cylinder) we decided that the best product in this case was the Honeywell evohome system.

Before going in to install the system, we like to carry out a functionality check to ensure the new control system will work in the home. Once this is done and we are happy with the best place to install the controller, we go through each zone to determine timings and temperatures for the system. Then it is time to draw up the heating plan.  When the customer is happy with this we source the products and get a date booked in for the installation.”

The products needed for this installation were: one evohome controller (and wall mounting kit), 17 wireless radiator controllers and a hot water kit.

(1) Before we start dismantling the boiler and the old controls in the home, we do a signal strength test using a wireless kit consisting of a wireless thermostat and a BDR boiler relay. We move to the furthest points throughout the house to check that the controls signal from the proposed controller location is received loud and clear.

(2) Once we are happy with the signal, we move on to checking out the existing wiring at the boiler, the programmer, room/cylinder thermostats and also the main wiring centre and zone valves located in the airing cupboard.  Before proceeding, it’s important that we establish that the existing system is operating correctly.  Carrying out routine electrical checks makes life easier and is also important for safety. We trace the wires by

exposing the timer and look for the switches live signal to the boiler. For best practice we label all the wires at the boiler and wiring centre adjacent to the hot water cylinder.

Note: Before any smart control installation, installers should check the manufacturer’s installation instructions for the boiler and research the specific wiring requirements, especially where permanent live supplies for pump overruns are required. Also, any specific requirements for a hydraulic system bypass must be observed.

(3) Moving to the Megaflo hot water cylinder, the existing system has three zone valves: One for domestic hot water (which remains operational) and two heating zone valves.We make the latter valves redundant (and locked in an open position) so that the evohome system can operate to its full potential as new radiator controllers now cater for multi-zone control. We electrically isolate the heating zone valves them to keep the system safe.

To allow integrated hot water control, we remove the existing redundant hot water cylinder thermostat and insert a new evohome NTC sensor in the Megaflo’s dry sensor pocket.

Note: Unvented hot water cylinders such as the Megaflo also have an integrated overheat thermostat wired in series with the cylinder thermostat. This de-energises the hot water zone valve in the event of an overheat fault. It is vital that we maintain the functionality of the overheat thermostat and it should be rewired in exactly the same way.

(4) Now it’s time to fit the hot water sensor transmitter, which provides the wireless transmission between the cylinder and the evohome controller. We also install wireless BDR relays to switch the boiler live supply and to operate the hot water zone valve. For ease of installation and appearance, we use single gang pattress boxes for transmitter and BDR relays. It’s important to keep transmitters and BDR relays at least 30cm apart to avoid any signal interference.

The great thing about evo, is that it simplifies the whole wiring system. Trunking the wires and labelling them keeps the install neat and helps to make life easy if any future work needs to be carried out on the system.

(5) Once all the wiring in the system is complete, we move onto the radiators and fitting the wireless radiator controllers. It’s always important to check whether the radiator controllers need additional adaptors or if they can simply be screwed onto the existing TRV using the standard M30 adaptor supplied with each radiator controller. It’s certainly worth checking out this requirement at the survey stage!

(6) Once all the radiator controllers are in place, they are ready to bind to the main evohome controller. Consulting the heating plan and the homeowners, we name the zones in the home. It is

best to clear the evohome controller of all pre-programmed zones and replace them with the ones that you have agreed with the customer.

(7) Once this is all programmed in, it’s simply a case of pairing the zone with the relevant radiator controller. It’s always best to refer to the heating plan to cross reference.

In seven simple steps we have retrofitted a two-zoned, four bedroom house into a 12 zoned, heating solution with a controllable hot water system as well. And the best bit? The

installation of the evohome system will aid in achieving up to a 40% saving on their energy bills leaving us with a very happy customer.