Viessmann Vitodens 111-w Storage Combi with Hive

[mattdiyuk]

I recently had a Viessmann Vitodens 111-w storage combi boiler installed in my property but the electrician did not connect up the hive thermostat correctly. The central heating has 3 circuits, a UFH circuit for the kitchen (where the boiler lives), a zone for downstairs rads and a zone for upstairs rads. The system has 3 TRVs motorised valves installed and 3 Hive receivers. The UFH is connected to a single channel receiver but the rad zones are both connected to dual channel receivers. The wiring appears to be the wrong way around for the central heating, so I have to switch on the hot water channel to get central heating, and the thermostats therefore don't work. I have the thermostats paired directly with the receivers rather than through the hub as I'm not interested in any of the smart home features.

My question is, which type of receiver should be installed for this system? I was going to change them all over to single channel receivers but then I realised that the hot water timer might actually work? If a dual channel receiver can control a timer for the DHW I would like this to be connected but preferably shared with the UFH receiver as this thermostat will live in the kitchen nearer the boiler and the hot water time can be controlled from the thermostat.

 

[ericmark]

The first thing I did was hunt for the manual and type into the "find in page" OpenTherm, and it seems it is an OpenTherm boiler, and Hive does not have OpenTherm so seems the wrong type of thermostat for that boiler.

However the only thermostat I know of which with work with zones and Opentherm is EPH, and you would need three thermostats one set as master and two as slave, but really you want one type of control, either use zone valve or use TRV's they are both designed to do the same thing, so either you fit the Hive TRV heads (or what ever make you select) or you use motorised valves, I hesitate hear as TRV's with electronic heads are motorised valves.

I am sure you can use Hive, but not and use the complex system already built into the boiler, likely Drayton Wiser would work better, it is designed for three channels, but you would need four as it does not allow you to use third for anything but DHW.

The people who design central heating systems are called heating and ventilation engineers, and engineer to me at least means educated over level 3, if I as an electrical engineer was asked to design a central heating system so complex I would sub contract to some one who knows what they are doing, I have not got the skill required, but also know my limitations.

Making central heating work, is not the same as making central heating work efficiently, the idea is not to turn anything on/off, digital control causes hysteresis, what you need is analogue control, where each TRV slowly closes depending on that room temperature, and the boiler slowly reduces output to suit the demand and gains the latent heat from the flue gases.

As said you can likely make it work, and the boilers built in algorithms will try and do its best, but to my mind two motorised valves don't work with a modulating boiler, with my oil yes, but with gas looking at either more motorised valves or move to TRV control.

 

[mattdiyuk]

@ericmark I mis-spoke, It's a 3 zone system with 3 motorised valves (not TRVs). There are TRVs on all the rads except there is an open rad on each zone in the hallways where the thermostats intend to be. But yes I have read some things about hysteresis with these thermostats. Might be time to call a better heating engineer.

 

[ericmark]

As DIY using Hive is great, it is simple, and works, as a professional it is not really the correct selection. This is the Drayton Wiser which is the same as Hive for wiring

but also has a three channel version, and also an extra

for connecting the OpenTherm which is missing from the Hive version. But the first diagram shows terminal 3 is DHW and terminal 4 CH so moving one wire from 3 to 4 should cure your problem, it will then work.

 

[Mister Banks]

Looks like the electrician may have wired all the backplates the same which is wrong. Ideally you would have 1 two channel and 2 single channel Hives, you can then have the UFH and DHW wired to the two channel and the radiators zones wired separately into the 2 single channels.