3 channel setup with OpenTherm

chmi17

Hi I wanted some help to understand whether I can have a 3 channel setup and OpenTherm. I have an Ideal Logic Heat2 H18 boiler and Therma TQX0027 controller with 2 Therma wired thermostats, 1 for upstairs CH and 1 for downstairs CH. The controller also controls the HW which is a hot water cylinder.

I have read through the community and this post suggests the setup is possible using the wireless receiver and an additional thermostat.
https://community.tado.com/en-gb/discussion/21799/replacing-3-channels-programmer-2-zones-rads-ufh-and-hot-water/

My question is whether this can all be modulated through OpenTherm or would OpenTherm only work for the CH

wateroakley

hello @chmi17 welcome. Sorry, my opentherm knowledge is very limited, perhaps @Andreplusplus can best advise?

policywonk

Your boiler can modulate with Opentherm, however you will need to get Tado to agree to give you the full migration steps to move from dumb on-off switching of your boiler to an opentherm modulated setting.
This boiler does not seem to engage its opentherm features if the programmer switches via dumb on-off live relay controls, which your current programmer and stats are set to use.

Tado may have to clarify whether the EU extension kit is more appropriate in this instance.

It is possible to find opentherm thermostats for cylinders, thereby making the process of keeping the temp on the cylinder more efficeiently maintained. Tado don't have a cylinder smart stat and don't know yet if they will integrate with an opentherm stat on that side.
Presume @Andreplusplus can chime in

chmi17

Understood. So it sounds like I cannot use OpenTherm to modulate CH + HW.

I have read about priority hot water, is this the next best thing, to modulate CH and make calls for hot water a priority? If so, can I do this through Tado or do I need to keep my current controller for hot water

policywonk

Not true. Chances are that it is possible to have Opentherm control both. Would be surprised if your boiler couldnt control both with Opentherm. We need to wait for @Rob or @Andreplusplus to chime in. In mainland Europe opentherm and digital controls are more commonly used, so more expertise needs to be pulled in.

Rob

Opentherm can control CH+HW. For HW, you can set a schedule and set the temperature for the HW per timeblock.

This is in general though. It assumes the boiler allows this. If the specific boiler does not support OT, this discussion is over. But let's assume that it does.

Is your boiler a system boiler or a combi? If it is a combi, great. If it is a system boiler, is the HW controlled via the boiler?

The issue I see here is replacing the 3-channel relay programmer with an Opentherm system. This is where my lack of knowledge kicks in, I am team continental Europe from an experience point of view. Meaning I have no experience with the concept of 3 channel programmers. I am assuming your 3-channel programmer is used for 1x HW and 2x CH, with each separate CH relay not only activating the boiler but also their own zone valve? Is that a correct guess? Now, it will not be super straight forward to replace this with an Opentherm system.

First you'd need an Opentherm-capable tado device wired to the boiler. This will do DHW (assuming your boiler controls HW) and it can start/modulate the boiler for CH. But that's CH/Heating in general, not a specific zone.

Second, we have to think of the two zone valves for each of your existing CH zones that are currently controlled by the 3 channel controller. I see two options;

• You could wire a separate tado wired thermostat to each zone valve, or
• You could remove (/leave permanently open) the zone valves and use tado smart radiator thermostats to regulate which radiator should heat when.

Please note I made some assumptions in this reply. If my assumptions are wrong, my suggestions might be wrong too.

chmi17

Hi @Rob thanks for your thorough reply. Your assumptions are all correct:
- Boiler supports OpenTherm
- Boiler is a system boiler which controls HW
- 3 channel programmed is 1x HW and 2x CH
- Each CH relay is calling for the boiler and activating it’s own zone

The wireless receiver can control 1x HW and 1x CH which should work on OpenTherm. If I purchase another wired thermostat to control the remaining CH zone, will that also work on OpenTherm or would that be relay?

policywonk

Suggestions:

1. Contact Tado Sales. They should give you the full package to address this, where parts are concerned. According to the Ideal installaiton manual this is definitely an Opentherm boiler- but they must give you the specific instructions to enable access and to wire it in.
2. Have an electrician
   1. replace your three channel controller
   2. enable the HW side to be controlled with Opentherm
   3. wire access to the Opentherm connector on your boiler.
   4. replace the remaining CH thermostsats with Tado wired stats

About 3-5 hours work.

Rob

@chmi17

You can only wire 1 tado device to your boiler. This device can control it via Opentherm. All other tado devices wirelessly ask for heat at the device that is wired to the boiler. The way the wired device communicates with the boiler is irrelevant to all other tado devices.

First, you have to pick a tado generation. Either X or V(2-3+) and stick with that, as they are not compatible with each other.

In the UK market not all our devices support Opentherm. So, the device that is wired to the boiler will have to be Opentherm-compatible, and thus it will have to be one of the following:

• Wired thermostat (V2-V3+ or X), EU/UK market irrelevant
• Wireless Receiver V3+, EU market. Serial number starting with BR
• Extension Kit (discontinued wireless receiver) V2-V3+, EU/UK market irrelevant, serial number starting with BU
• Wireless Receiver X, EU market. Serial number starting with TR

What will NOT work with Opentherm:

• Wireless Receiver V3+, UK market. Serial number starting with BP
• Wireless Receiver X, UK market. Serial number starting with TP

The wireless receiver can control 1x HW and 1x CH which should work on OpenTherm. If I purchase another wired thermostat to control the remaining CH zone, will that also work on OpenTherm or would that be relay?

I think you misunderstood me, or I was unclear.

A wireless receiver BU/BR/TR (or a thermostat wired directly to the boiler) can control heating + hw via opentherm. Using Opentherm, it cannot also control a zone valve. So the water for your heating is exiting your boiler via 1 pipe. Later, I presume, this one pipe is split in two; one for each zone/floor/whatever, with zone valves controlling the flow. If you want to keep those zone valves, they need a wired thermostat each. So, in the end, you'd have 3 wired tado devices. 1 wired to the boiler via Opentherm and number 2 and 3 wired to a zone valve each, via relay. The communication between the Opentherm device wired to the boiler and the other devices is wireless-only.

There is a lot of rewiring involved, and you need a good and pragmatic person who knows what he's doing (=professional) to set this up. Be sure to discuss this in detail before he shows up at your house as I imagine some might refuse or be hesitant.

Please also read what policywonk wrote. His and my expertise are on different fields of this setup, so they complement each other.

chmi17

@Rob not sure if I 100% understand but just to clarify what I have understood:
1. Need to choose a thermostat that is OpenTherm compatible (e.g. wired thermostat)
2. Wired thermostat has 2 channels, 1 for HW and 1 for CH in general. This would work on OpenTherm
3. Purchase an additional 2x Wireless thermostats to control the 2x CH zones. These would communicate to the boiler via the OpenTherm thermostat already installed

For #3 I am guessing this would be to open/close the valves, however will the boiler modulate heat to these zones depending on what is set on the wireless thermostats?

policywonk

@chm17

Rob was setting out three three hurdles to be crossed.

1. At the simplest level, you stated you have two central heating zones, which we believe are controlled by individual motorised valves, which are in turn switched by wired thermostats. Now assuming you dont want to remove those valves and include more complex controls, the first thought would be, that to introduce a Tado system you'd need to replace those wired thermostats with Tado smart wired thermostats. These would handle the motorised valves easily and support Opentherm if needed. However there are a few more hurdles.
2. The second hurdle is to remove the three channel controller and rewire the wiring centre so that it operates with one CH channel (with two zones), and one HW channel. This really isnt difficult.
3. The third is to reconfigure the wiring to the boiler so that the following can occur. This is best done by an electrician recommended by Ideal.
   1. Either leave your boiler in dumb on-off switching mode, in which case you would need to also install a Tado UK extension kit. This would then handle the HW and both CH zones with ease, once the wiring in (1) and (2) is done.
   2. Or migrate your boiler to Opentherm mode for central heating and and optionally for hot water. To take another step in this direction it is necessary to contact Ideal and ask them the following:
      1. Do they know of a wiring solution which enables their boiler to operate in full Opentherm mode even though there would be three zones, ie 2 X CH, 1 x HW?
      2. Please pose the question to them and come back with their response. We can help you take it forward in simpler steps. However there is a good chance that Ideal will offer a different solution - and you'll need to consider that as well.
      3. Not putting you off. Some technical input is needed from Ideal.

chmi17

Thanks @policywonk. Ideal are not being very helpful - they will not provide any wiring solutions or general advise unless I am a gas safe engineer, which is a catch 22 as I need to understand what needs to be done so I can explain it to them.

But what you have said makes sense and I will try to find a gas safe engineer who understands

policywonk

Try this. First get a sparkie to rewire your wiring centre so that it operates with two CH channels and one HW channel. Keep using your boiler in relay on-off mode.
Second, write to Tado sales, identifying the boiler model, the layout in zones, how your hot water is handled, and ask for a plan to migrate to their products with opentherm engaged.
See what they recommend. Come here if you are troubled. They have a team who should know all this.