Honeywell Evohome Questions..

[*Dan*]

I’m thinking of going for the Honeywell Evohome in my house and while I understand the logic behind it I’m struggling in what I need for it to work seamlessly in my house with my current heating and water setup.

I have an unvented water cylinder in airing cupboard and a potterton promax SL boiler in cloak room downstairs. The water cylinder has two Honeywell zone valves (one for downstairs and one for upstairs heating). There is also another valve as you would expect for the water system. I see you need the relay box which comes in the kit to connect to the zone valves - would I then need two of these to connect to each of my valves?

For the hot water Evohome kit I see you can get a sensor that actually goes in the cylinder - there seems to be a blanking plug on the side of my cylinder in the picture below. Is this to allow for something like an extra sensor to be immersed in the tank?

The zone valves at the moment are controlled by danfoss controllers (one downstairs and one upstairs). The downstairs controller also has a temperature sensor in the lounge as the controller itself is right by the boiler in the cloakroom. Just trying to get my head around how it would be set up (understand the TRV side of things on the radiators) with my system and if it is even possible as it’s not cheap but if it worked properly would be very beneficial in our house and for our lifestyles.

Here is the unvented setup in airing cupboard upstairs and in second picture you can see a brass blanking plug (I think) - is this where I could locate the sensor for the water probe?

Thanks for looking

 

[Dan Robinson]

Apart from not knowing what set up you are aiming for, all I can deduce from your post, is that you definitely don't understand the logic of it.

 

[*Dan*]

I’m looking at individual room temperature control for all my rooms and getting rid of my old controllers in the house.

 

[ericmark]

I think I has answered else where, but

I’m looking at individual room temperature control for all my rooms and getting rid of my old controllers in the house.

was not said on the post I answered, so I will say what happened to my attempts which may help, we found enough heat gets upstairs so only worried about down stairs where at the time my late mother was living.

I did not want to spend too much money, so I went for Energenie MiHome eTRV heads, and had all big ideas of adding Nest after as it would work with Nest. However the problem was not the eTRV heads, it was the house, we had not realised how long the house took to cool down, heating up is all down to how big the water heater is and how big the radiator is, plus how the anti hysteresis software in the heads works plus in my case problem of getting water heater to fire up at right times. With EvoHome you will not have the last problem. I set the times to allow heating to go off at night at least until the lower limit of 16°C was reached, but in the morning at 6 am when heating was due to come on again, 90% of the time the house was still over 16°C. The fabric of the building stored too much heat.

My big idea was to set the main living room for example over night 16°C then 6 am 20°C 6 pm 22°C and finally 9 am back to 16°C I set the eTRV head to do that, however in real terms at 6 am 17°C but took to 11 am to get to 20°C unless morning sun warmed room, when it could easy hit 24°C by midday it was stable but at 6 am the room started to heat up however was still only at 21°C by 9 am when due to return to 16°C.

Setting the temperature to 22°C at 6 am then back to 20°C at 8 am the room was at 20°C at 8 am, clearly not the radiator or water heater at fault, but the anti hysteresis software in the eTRV heads. It became clear any idea of using the geofencing was not going to work, it just takes too long to adjust temperature.

We also miss calculated how much heat will move room to room, on mothers death we used her old bedroom down stairs to store furniture, as we combined what was in three houses ready to go into a new one. So since the eTRV was fitted I turned it down to 16°C all day long, it will not allow one to set it any lower, however the room never seems to drop below 17°C as the hall radiator is on the wall between hall and her old bedroom and the heat simply goes through the wall.

In fact don't know why we bother with internal walls, as there seems to be nearly the same variation between rooms as to different points within the same room. I have tested a set of thermometers and they are within 0.3°C of each other, three thermometers in different places in same room can record up to 6°C variation in the room.

My old house before we moved back in with mother had a Myson radiator which is fan assisted, not a lot of air flows the fan is turned right down, but that fan does ensure all the room is the same, without the fan you will get hot and cold spots within the room.

If I was doing it all again either I would go whole hog or really cheap, the stand alone eTRV heads would have done just as well. I looked at going whole hog, and just could not find a unit cheap enough, the new Myson radiator unlike mine has an automatic multi-speed fan, so as the room cools the fan speeds up, and as it warms up fan slows down, this is all build into the radiator. Seems great, but how do you control the central water heater? Most water heaters will auto regulate so heart of Winter every thing will work A1, where the problem arises is as Winter approaches, and as summer approaches, what tells the water heater to shut down or start up again.

I think now best option is two or three wall thermostats all wired in parallel, I have one in hall and one in kitchen, not the best rooms, but if any room with a wall thermostat in needs heat water heater fires up, and if all hot enough it closes down, so in my house three thermostats one in each regularly used room, with stand alone radiator thermostats, would work A1. Problem is running wires to thermostats. You want cheap programmable thermostats hard wired, and cheap eTRV found some for £20 plus £20 for wall thermostat so £40 per room for main rooms at £20 for bedrooms and rooms not used much. It is the wiring that puts me off.

Warning I tried to use a cheap wireless wall thermostat, it lost signal and found room at 28°C, if using wireless you need expensive types, and the expensive types have anti hysteresis software which you don't want, so cheap wired is the way to go.

Note that would not be my advice if your water heater was OpenTherm enabled, then I would say EvoHome best option, but your water heater is not OpenTherm so EvoHome can't modulate the boiler, it can only switch it on and off.