Yet another "What is the right system configuration" post
Hello and sorry that I add one more (long) post on the matter, I'm hoping that someone with similar configuration will be helped by the answers to this:
I've moved to a new build, I have an Ecotec plus 835 (combi) and I have resigned that I will have to use relay and not something more clever like opentherm unless I want to forfeit the warranty on that brand new boiler.
Ground floor has a Honeywell wired thermostat at the entrance in front of a radiator without TRV, and controls Zone 1 for the living room area radiators with TRVs.
Top floor has a Honeywell programmer in the airing cabinet, and the same type of wired thermostat in the main bedroom, also with a radiator without TRV, and controls Zone 2 for all the rooms on the top floor, which thankfully have TRVs.
According to tado support, I need to replace the Honeywell programmer in the cabinet with the wireless starter kit, and add 2 wired thermostats, while also replacing the TRVs with the equivalent ones. I find this proposal both excessive (I end up with a wireless thermostat to control... the hallway?) and it doesn't solve my energy problem, which is that in order to heat up the other rooms on the top floor I need to overheat the main bedroom which has the thermostat, and that the temperature in the living room depends on the temperature of the hallway, both unacceptable design decisions that I have to live with.
Interestingly, they provide a blog post:
which suggests to install TRVs on the rooms that have the wired thermostats as well. This goes against the recommendations of every heat engineer I talked to, who insist (and I agree) that trying to control a room with two thermostats will lead to weird behaviours. To install TRVs on those rooms, the system needs to be drained, which means an added cost of a plumber.
So, what is the solution?
My current idea is:
- install non-smart TRVs on the radiators missing them (drain the system etc), in order to have the correct pin on the radiators for the followup.
- buy a wireless starter kit, a wireless add-on and tado TRVs
- install the wireless thermostats where the wired Honeywell thermostats are
- place one wireless sensor in the living room to control the existing radiators in Zone 1
- replace all TRVs on Zone 2 with the smart ones and the TRV in the hallway
- leave the Honeywell programmer in place and on the 'always on' setting (which makes it depending on the thermostats)
Do you see a problem with this plan? Any help is appreciated.
Comments
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I’m not familiar with ecotec boilers but why would you forfeit the warranty, especially if it already has Opentherm support? As far as I’m aware most manufacturers will only consider the warranty void if you’ve tampered with the internal workings or installed something unapproved by them.
What does the programmer in the airing cupboard do? Are you sure you don’t have a system boiler (with a hot water tank) rather than a combi? If Tado is recommending an extension kit there it sounds like it’s for hot water control.
The reason Tado recommends smart trvs and temperature sensors in the same room is because they can work in conjunction with each other if they’re all Tado. One device, usually the wall thermostat becomes the master sensor, controlling when the trvs should call for heat. The heating engineers are right that dumb trvs can work against a thermostat.0 -
Thank you for taking the time to read and answer!
Ecotec valliant boilers sold in the UK do not come with the Opentherm module. Buying it from another country and fitting it would fall under the 'unapproved' claim, despite being a fully compatible module produced by the same company. So, unfortunately, I have to stick with their relay mode - unless tado manage to reverse engineer their latest ebus protocol, which is not likely.
The programmer in the airing cabinet is basically opening the correct valves depending on which wired thermostat is calling for heat. Boiler is definitely a combi, no water tank. tado currently doesn't offer a wireless starter kit that doesn't include hot water control, which is the reason they proposed that.
Thank you for the insight regarding the mix of thermostat and TRV on the same room - it makes sense that tado's system is clever enough.
I'm assuming that the idea of adding TRVs to the ones missing them, and then switching them to tado, is the way to go. Other ideas welcome.
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Ah, got you. The UK’s lack of uptake of Opentherm is baffling to me but there you go. Tado can partially replicate modulation by cycling the boiler on 230v connections anyway.
You seem like you’re on the right track. However you’ll need the extension kit wired to the boiler so that the wireless thermostats and smart trvs can call for heat. Replace the programmer in the airing cupboard with it.
This will presumably take the existing wired thermostats out of the circuit as well. Bear in mind that the smart trvs also function as thermostats so you don’t necessarily need a wireless temp sensor as well, assuming you’re putting smart trvs on both upstairs and downstairs radiators. Sometimes wireless temp sensors can give a more accurate room temperature reading than the smart trvs though, depending on where they’re placed.0
