Will Tado work with Trianco Oil Boiler / pumped CH / gravity HW which has a Honeywell valve

flyingchorse

Hello,

Tado is arriving today and I’m looking to replace the Howneywell programmer. The heating configuration is an oil boiler downstairs then HW tank upstairs. There is a motorised valve just before the HW tank. So I am able to turn on the CH or HW independently. there’s a thermostat on the HW tank and there’s NO thermostat for the CH.
The current wiring is an absolute mess so I have run two new 5 core cables between the boiler and HW tank as that’s where the current controller is.
So first off is this a configuration that compatible with the Tado? Secondly can I then add smart radiator valves to control individual rooms?

Thanks

Dave

flyingchorse

Ok on further investigation/googling I would say my heating system is a C-Plan. Would that mean I follow the wiring instructions as per a S-Plan but omitting the CH valve? And then which configuration should it be set to? As the HW is Gravity fed.

davidlyall

I believe that should work OK but someone with more experience than me will be able to advise

Tado will give you customised install instructions if you tell the app what controls you currently have in place but it does support gravity fed systems and the fact you have an oil boiler shouldn't matter

You will be able to add smart TRVs later. What type of dumb TRVs do you have at the moment?

Bazly

To add to an older thread I own a Mistral gravity oil fired boiler and had problems tracking down a wiring diagram for a gravity system. I finally did and it works as it should with the on choices of heating and water or just water.

The Tado instructions do go through how to set up the controller for a gravity boiler (blue light) but then doesn't actually provide a wiring diagram in their literature.

Wiring diagram attached.

policywonk

The charity has a facility which operates three oil fired boilers, all of which are twin flow units, like yours.

Would you clarify if your boiler powers the pump, or whether the pump is always turned directly by the programmer?

If your pump is directly turned on by the programmer, right now, then please consider the following:

There are inherent obstacles with firing a boiler and pump on the CH side with a Tado, because both the boiler, and the pump will, at the switching point, initially draw more than 3 amps , more than a Tado controller is meant to handle (its max is 3 amps). Honeywell programmers although rated at 6amps can actually handle 10amps of switching current.

This obstacle can be overcome, in the following way. It may be a pain, but it also saves money in the longer term and makes the boiler more reliable.

• I presume you will be fitting a Tado Wireless Receiver (aka Extension kit) and then deciding seperately whether you want to use a wired thermostat or Smart TRVs.
• So, unless your boiler has a special slave port to drive its CH pump, this is likely to be the minimum change you need to make.
  • Fit a motorised valve before the pump on the CH side. Have the pump wired so that it is only switched on by the motorised valve after it has completed the task of opening the flow of CH heat.
  • This means that a Tado wireless centre can trigger the motorised valve to open (it needs less than 3amps) and then the motorised valve can seperately source power to the pump.
  • Then wire the system as though it is an S plan with a proper wiring centre. That wiring will ensure that the Tado Wireless Receiver does not have to handle more than 3amps when switching.

However, would recommend you also consider also making the following change, if you intend to keep that boiler for at least three years:

2. Convert it all into a genuine S plan system, with two pumps and two motorised valves. Most gas boilers do not have twin flows. Some oil boilers, like yours, and ours, actually do.

• Move your existing CH pump (likely to be a switched speed one, ie basic), presently on your CH side; installing it between the two port motorised valve and the HW tank, dedicating it to the HW tank feed.
• Purchase a Wilo differential pressure pump on the CH side, and also a two port motorised valve. Fit these on the CH output side replacing the old CH pump. The Wilo will reduce pressure as your radiators come up to temperature down individually (assuming you have TRVs, smart or dumb) and reduce heat waste by at least 18% pa.
• Fit a proper wiring centre for an S Plan. Makes it easier to fix if you have a problem.
• Wire in Tado wireless controller as though it is the programmer for an S Plan.
• The cost of these changes will be recovered within 2 years.

Wiring diagrams for the port valves are easy and can be found here - Central Heating Controls and Zoning - DIYWiki.

If this does not phase you and you want specific advice, come back.

@davidlyall . Need your review. I know this is an electrical switching limitation of the controllers.