Honeywell Evohome - Multiple Bindings

For a while now each evening there's been a Comms Fault message on the Evohome Controller. But the heating has been working fine, so I've pressed on the checkmark and ignored it, thinking that some random external interference had interrupted communication between the Controller and the heating BDR91 wireless relay in the airing cupboard.

But looking at the system log this fault was happening at exactly the same time every evening, which made the chances this was random very slim.

Some searching on the internet brought up some advice from Richard Burrows at the Evohome Shop, which suggested that the Controller and BDR91 could have multiple duplicate bindings. Thinking back I did have to rebind the BDR91s after a power cut, and I've probably got the system into a situation where the Controller and BDR91s are bound to each other twice. So the solution is to clear the bindings, and rebind the Controller and BDR91s afresh. However the key is clear the bindings at both ends, i.e. not just at the BDR91s.

So first use the long press on the Settings button on the Controller to get into the system settings. Then set the System Devices and set the Boiler Demand and Sundial Valves to None.

The inconsistent naming in the Evohome Controller really annoys me. "Boiler Demand" on the System Configuration page becomes "Boiler Heat"...

... and "Sundial Valves" becomes "Hot Water Configuration".

Both Boiler Demand and Sundial Valves set to None.

With the two BDR91 bindings cleared at the Evohome Controller, now pop off the front fascia and remove the batteries.

To clear the bindings at the BDR91s in the airing cupboard, hold the button on them down for about 15 seconds. After about 5 seconds the lower red light will "long flash", and then after 15 seconds the red light will "short flash". Once in "short flash" the binding has been cleared.

Back at the Controller I replaced the batteries and fascia, confirmed the date and time settings, and then long pressed the Settings button to get to the system settings and the System Devices page.

I rebound the hot water BDR91 first by setting it to Stored Hot Water. The first thing to rebind is the CS92 storage cylinder water temperature sensor. Hold the button down on the CS92 for about 5 seconds, when the button/light will start alternating between green and red. Then press the button again, and the controller should detect the CS92.

Next the Controller asks whether you've got a "2 or 3 port valve" or a "hot water valve". Our system is a Sundial Y-Plan, so the correct setting is a "hot water valve", but it is a little confusing as it has a mid-position valve, which is a valve with 2 ports. Anyway, a 5 second press on the hot water BDR91 to get it into binding mode, and then a press on the Bind button on the Controller and the two are paired again.

Likewise the Boiler Demand is set back to Boiler Relay, and a 5 second press on the heating BDR91 and a press on the Bind button on the Controller, and everything is re-binded (rebound?). Hopefully this has done the trick, and regular Comms Fault messages are a thing of the past.

Honeywell Evohome - Multi-Room Zones - Step-by-Step

I found the evohome Installation Guide uninformative for setting up a multi-room zone. Here's what the Guide says:

Verbose it is not, so here's a step-by-step guide.

The starting point is that there is already a zone set up with one HR92 bound to that zone. First get into the System Settings by pressing and holding the Settings icon for a few seconds. Then select the Zone Settings icon in the top row:

Select the Edit Zone option:

Then select the zone you want to add a radiator or room to. Use the arrow in the bottom right of the Controller to get to the Application Settings option, and select it:

You can then use the Single/Multi Room Zone option to change the type of zone:

Select the Multi Room Zone option, then press the green tick icon in the bottom right hand corner of the Controller: 

Use the arrow in the bottom left of the Controller to get back to the Zone Configuration screen, and the select the Radiator Valve option:

The next step is non-obvious, use the arrow in the bottom right of the Controller to bind an additional HR92 to the current zone:

You'll then be presented with the standard Binding screen, so press and hold the button on the HR92 to get to the Bind function, then a short press of the button on the HR92 to initiate binding to the Controller in the current zone. On the Controller press the green icon in the middle:

When bound successfully you'll get a message on the Controller of the form:

In this case there are 2 HR92s (2 actuators bound) bound to the zone, with bi-directional comms (2-way). You can continue to add more HR92s to the same zone by using the arrow in the bottom left of the Controller, or complete the zone by using the green tick in the bottom right of the Controller.

Note that on the main screen of the Controller it will display the actual temperature from the first HR92 that was bound to the zone. In our lounge and dining room space we bound the lounge radiator to the zone first then the dining room radiator, and so the Controller shows the temperature from the lounge radiator. We've set up the local display on all of the HR92s to show the actual temperature, rather than the setpoint temperature, so I can always take a look at the dining room radiator if I'm interested.

[Whilst the HR92 can tell you on demand what position the valve is actually in, I'm geeky enough to have liked to see the valve position displayed on the HR92 all the time. But that's probably just me!]

Honeywell Evohome - Multi-Room Zones

When we installed the Honeywell Evohome central heating control system we fitted four radiators with HR92 temperature regulating valves (TRV). In the other rooms we left the manual TRVs fitted, and lived with the fact that whenever the Evohome system decided that any of the controlled rooms were getting a bit too cold, then the manual TRV rooms would be getting some heating. So recently we ordered another pack of four HR92s from JTM Plumbing, and have fitted them to the remaining radiators. We didn't do this originally purely because of cost, as the HR92s are not cheap, but the ability to add new HR92s to the system means you can fit out the whole house as and when we can afford it.

As our radiators already have the M30x1.5 valves, installation of the HR92s was as easy as before. Binding them to the Controller was also really straight forward. A long press on the Settings icon is required to get into the system settings menu. Then simply add a zone and give it a name, at which point the Controller will sit and wait for the HR92 to start the binding process. (The only thing to remember is to tell the Controller not to use the temperature sensor in the Controller itself for this new zone.) On the HR92 a couple of presses of the button are required to get it into binding mode, and within seconds the Controller was reporting that the two were bound.

We have an open plan L-shaped lounge and dining room, with a radiator in each 'room'. Previously only the lounge radiator had a HR92, but now both of them have HR92s fitted. We started by copying the temperature schedule from the lounge to the dining room, so that both radiators would be trying to keep this space at the same temperature. This is easily accomplished, by going into the schedule for the lounge zone, and using the icon in the bottom right of the Controller display to copy the entire week schedule to the dining room zone.

However this does mean that if we change a schedule or manually change the temperature setpoint in one of the zones, the other zone is unaffected and the two radiators will be trying to keep the one space at two different temperatures. So we set up a multi-room zone, using both the lounge and dining room radiators. The Controller now allows only one temperature setpoint and schedule for the space as a whole, but the two radiators work independently to achieve the desired temperature. This works really well at dealing with the different thermal characteristics of the space. Our lounge is on the south side of the house with big windows and a wood burning stove in it, while the dining room is on the north side of the house with very little natural warming getting in. Certainly when we fire up the stove, the lounge radiator pretty much shuts down as the stove warms up the lounge. We'll have to wait and see how the system deals with sunny days (I hope!).

Smart Central Heating

As I've been playing with the scheduling features of the Evohome Controller, I've been thinking about the various headline features that smart central heating systems are marketed on, and why they're needed.

Traditionally your central heating system had one job to do: ensure that your home is at a comfortable temperature. Now there's a second job for it: minimise overall energy use. Arguably, through the use of a well positioned thermostat and TRVs on each radiator you could achieve job number one. The recent explosion of smart central heating systems are all focussed on job number two: minimising energy use.

There appear to be two basic approaches to minimising energy use. The first is to turn off the heating when you're not at home. And the second is to only heat the spaces that you're using when you are at home. Different companies are tackling one or both of these approaches. For example Nest, Hive and Tado are using motion detection and geo-fencing to tackle the first approach, while Honeywell and Heat Genius are also zoning your house and controlling each radiator independently in order to tackle the second approach.

The pre-smart approach to turning off the central heating when you're not at home was to use a programmable timer. When you delve into the detail it feels like all of the smart central heating systems are really continuing that approach. Some of the systems still require you to program them with the times and temperatures that you want the central heating to work to. Even the ones that promote a 'learning' capability are just using motion detection and geo-fencing to work out your schedule without you manually entering it yourself. Some of the learning systems benefit greatly from you manually entering your schedule first, so they've got a baseline to start learning from.

So if your routine is entirely predictable then all of the smart central heating systems can ensure that your home is nice and toasty when you're in it. It's the unpredictable that some of them struggle to deal with automatically. Those occasions when the train is delayed, the meeting overruns, the motorway is congested, and the heating system kicks in when you're not actually there. In this case no amount of smart learning algorithm is going to be able to compensate and delay heating the house until you're actually going to arrive. As far as I can see, only the systems offering geo-fencing can automatically cope with the unexpected. The others will have to make do with manually controlling the heating system remotely via an app or the web.

When it comes to zoning the house there's very little differentiation between the smart central heating systems. All produce wireless TRVs that allow a central controller to independently adjust the heat output of the radiators. Some of these TRVs allow the temperature to be adjusted locally as well, and some have displays to report on room temperature or temperature setpoint.

Honeywell Evohome - Installation

We've started installing a Honeywell Evohome system in the house for our central heating and hot water. So far so good, although with some stumbling points along the way.

When we bought the house we inherited a gas-fired Potterton Suprima boiler hooked up to a Sundial Y-Plan system with a mid-position valve to heat up a storage tank for hot water, and water radiators in each room. There was a truly ancient 24-hour programmable timer, and the thermostat for the entire house was located behind a door in the entrance hallway. Consequently the house was simultaneously too hot and too cold, cost an arm and a leg to run, and within a month of moving in the whole system died just as the winter snow started falling.

The Evohome system comes in functionality packs, so we needed the Base Pack (a Controller and one BDR91 Wireless Relay), a Hot Water Pack (a CS92 temperature sensor and another BDR91 Wireless Relay), and a Radiator Multi Zone pack (four HR92 temperature regulating valves). We bought these in from JTM Plumbing, who provided an exceptionally quick delivery service and very keen pricing.

In the airing cupboard we removed the wired thermostat from the hot water cylinder, the 24-hour programmable timer from the wall, and unwired the mid-position valve and Grundfos Alpha2 water pump. To the hot water tank we fitted the CS92 temperature sensor, and ran the cable to the CS92 transceiver which was screwed to the wall. We then fitted the two BDR91 wireless relays to the wall, and proceeded to rewire the various components up according to the Y-Plan wiring diagram on page 47 of the Evohome installation manual (doc ref 50040745-201 A).

There were two issues with the wiring that we needed to resolve. The first was that the Honeywell wiring diagram has an error. The BDR91 for the hot water shows an unlabelled connection, which is actually to the C contact. The Evotouch was the Honeywell product that the Evohome Controller evolved from, and the manual for the Evotouch shows the same Y-Plan wiring diagram, with the connection to the C contact labelled correctly. I can only assume the cut-and-paste between manuals introduced the error.

The second issue was that the wiring for the Suprima boiler requires an always-on power supply, and then a switched live connection to get it to fire up. The boiler can also provide power to the Grundfos pump, presumably to ensure that water is circulating when the boiler is heating water. So we tapped into the power from contact 1 in the junction box, and used contact 8 for the switched live supply to the boiler. We also chose to disconnect the Grundfos pump from the boiler, and connect it to contact 8, as per the Y-Plan wiring diagram.

In terms of wiring, that's the extent of the work. Apart from a small bit of redecorating where we removed the old thermostat from the wall in the hallway, all of the work was in the airing cupboard and out of sight. The only other installation required was to fit the HR92 TRVs, which for us just required screwing them onto the M30x1.5 valves on each radiator. The HR92s separate into two parts, one of which is threaded for installing on the valves, and then the main body then just slides into place on top, with a sliding lock to keep them in place.

Now we just need to configure the system!