Tado X and 2-zone Central Heating

Cald

Hello, my current place has 2 heating zones. Upstairs and downstairs. How will it work when installing Tado X? Do I need to remove valves or can I wire so it operates as a single heating zone, which then is split between thermostats / TRVs?

Also interested to know if this kind of setup would cause issues with OpenTherm which my boiler supports.

Thanks.

policywonk

Bear with me. I dont have experience of the X series, but the principles should work for you.

A decision to install two central heating zones is one which installers take when they calculate the burden on the pump and the boiler. It also helps when fixing leaks and handling breakdowns. If you are sure your boiler has the wellie to handle both zones and then some… we can move onto your question.

1. First you have to decide whether you want to introduce TRVs in most of your radiators, ideally smart TRVs. You can do this by adding one every month so it doesnt wear out your bank account, but it is important to ensure that your boiler is not spending its time pumping heat everywhere, especially when it isnt needed.
2. Assuming that the two CH zones, upstairs and downstairs are opened through two twin-port valves, you can do the following:
   1. You can temporarily force the slider on the side of the valve open and lock it open- but only for a few weeks. Longer than that and the motor inside the valve can burn out. However to get Opentherm fully efficient you have to dismount the valves- specifically removing their role in the way in which the boiler is triggered.
   2. So when decommissioning use this guide: to understand the logic Central Heating Controls and Zoning - DIYWik.
   3. When you've got the time and money, work out how to drain the system, remove the valves, putting in a bridging pipe where they once were. Then decommission their wiring - be careful because these valves normally have a role in passing on the request for heat to the boiler so you will need to be clear on how to amend the wiring in your wiring centre.
      1. If it confuses you, do get a sparkie in to apply the changes so the zone valves have no role in determining how the boiler is fired. Needs about 2 hours work from someone who knows what they are doing.
      2. You may need a plumber too - and when removing the valves, ask them to fit a decent automatic bypass valve set carefully. It will reduce boiler cycling, saving expense, when the radiators are not asking for heat. May need about 4 hours work including removing the zone valves and fitting and trimming the bypass valve.
3. In this mode, you have fewer parts failing and things will be a lot more efficient, two physical CH loops, running as one logical loop, handled by one Opentherm controlled pump (which will be a lot more efficient) and a simpler, more reliable, wiring system. Once you've replaced at least a half of the rad feed valves with TRVs and have spent time refining your temperature settings for each room, you'll find that your costs go down rapidly.
4. Need to check. Is there a zone valve pointing to a hot water tank or is you boiler a combi? If there is a hot water tank is the thermostat an Opentherm one, or dumb on-off type? That affects a few things.
5. Opentherm? Arrange that once you've completed Step 2 as a whole. Have you checked whether Tado handles your specific boiler model on X? Best to check. Tado Sales should give you the position on that, as well as instructions, when you give them the boiler and thermostat arrangements you want. The fact that your boiler can run in Opentherm means that the pump is set to operate efficiently and

Does that help?

Cald

That is really helpful. But also seems very complicated and quite out of scope for what I was aiming for, I was hoping to do this in steps, so once it's all working I could then remove redundant stuff like the valves.

I wasn't aware that manually leaving valve opens could damage them, but would I not be able to wire so both valves open whenever heating is requested by thermostats /trv?

The boiler is an Assure Combi 36. So no hot water tank. The valves are Horstmann Z222 if it helps.

Also seems you cut off something at the end of point 5.

policywonk

The valves are interesting, involving a small motor which when triggered opens the valve. When it completes the process of turning open it throws a microswitch, which relays power on to the boiler and causes it to fire. So yes it is possible to do two things
1. Use the slider to push open the valve.
2. Change the wiring in the wiring centre to ensure that the valve's electrics are bypassed when there is a call for heat.
It may take you about an hour to research what this involves and to get it working. If unsure get an electrician to do it for you.

policywonk

Here's a simple workaround if you are sure you can handle electrics. DONT DO THIS IF YOU'RE NOT.
1. Find the wiring centre. double check that it's logic looks like the S Plus Plan in this webpage
http://wiki.diyfaq.org.uk/index.php/Central_Heating_Controls_and_Zoning
and ensure you grasp the logic even if there are differences. If you don't, do not take another step in this plan.
2. Trace the grey and orange wires from each two port valve back carefully back to its origin in the wiring centre.
3 Kill all the power to the system and triple check that the wiring centre is dead.
4. Locate the points where the first zone valve's grey feed and orange feed are clear to you. Place a bridging wire between the two pins in the wiring centre. Repeat for the other valve.
5. Go to the valves and set the sliders to 'Open'.
6. Now go back and double check the wiring centre. Have someone else with you checking if possible.
7. Power on. The valves should be open and you need to double check that both zones are pushing heat.
Come back when you've done this. Need to know all is well.