Opentherm with S Plan System

[Sim777]

If Tado is OT only for CH and has no separate SL then you will not be able to do it on a Logic. Get Nest.

 

[picasso]

Fit an x plan (pdhw with NO zone valve) then you will need a relay to short the OT terminals when hot water is called for, shorting the cables makes the boiler run at high temp, when the relay opens the OT takes control of the central heating.

 

[Sim777]

Fit an x plan (pdhw with NO zone valve) then you will need a relay to short the OT terminals when hot water is called for, shorting the cables makes the boiler run at high temp, when the relay opens the OT takes control of the central heating.

Are you sure? That boiler requires 2 separate switched lives?

 

[picasso]

No not sure forgot You have to open the dhw zone valve and power the relay.

 

[Sim777]

No not sure forgot You have to open the dhw zone valve and power the relay.

Yep, no need to short OT then. It will go to OY once it gets SL2. Right?

 

[picasso]

I would fit a separate 240v hot water timer and put a demand on the dhw thermostat/ zone valve connected to sl2, if the boiler stayed on low temp opentherm then short the OT terminals.

 

[Sim777]

I would fit a separate 240v hot water timer and put a demand on the dhw thermostat/ zone valve connected to sl2, if the boiler stayed on low temp opentherm then short the OT terminals.

No need to short OT, boiler ignored OT when it gets power on SL1 or both SL1 and SL2

With 7kw min modulation it’s is still not achieving very much though.

 

[vulcancontinental]

The cheapest way is for EPH controls to do it either PDHW or simultaneous reheat at the highest temp called for.

The most expensive is to buy a boiler available with a bolt on accessory that permits up to 4 temperatures, 3 mixed and 1 for DHW .

Thing is you have a working boiler and a control system, both reasonably expensive, what are your expectations for savings and is it money or ecological motivation that makes you considering changing?

Let's say you save 4% of a £2000 heating bill, £80/annum, or 4% fewer CO2 emissions. If either floats your boat then go ahead. If you're warm enough in the winter at the moment it will not be to improve comfort levels (perhaps tighten them a little).

 

[picasso]

I have never fitted an ideal boiler so will take your word on the SL1-SL2 ignoring the OT but at least I now know how to run a "plan" with opentherm on any boiler.