OpenTherm Installation Guide | The Smart Thermostat Shop.co.uk

[@DeclanLucas]

Do you need to leave the link cable(the one you normally remove when fitting on/off controls) in when fitting opentherm controls? I'm looking at a Drayton wiser system, on a Viessman 100. Or would you wire the controls such that the switched live is controlled by the Drayton wiser controller?

[@MWPHS]

Obviously this was an Intergas boiler in the video and manufacturers all have their own little ways of doing things, so its best contact the boiler manufacturer for exact guidance.

[@DeclanLucas]

@@MWPHS The answer was the Viessmann didn't come with a link cable, and you also don't need to add one if you are running OpenTherm controls. You do need to change a setting and tell the boiler you are using OpenTherm though!

[@45graham45]

What is the serial data protocol used? Eg RS485 or RS232 etc. Or does Opentherm use it's own unique protocol? If so so, what basically is it? Eg +-5V signal or 0-15V or even a mA signal etc?

[@MWPHS]

The V2 OpenTherm specification is available here to download - ihormelnyk.com/Content/Pages/opentherm_library/Opentherm%20Protocol%20v2-2.pdf

[@hamaadrana6191]

On a s plan where do you wire this in ? In the programmer with open therm ? And where do the zone valves go

[@MWPHS]

This is not for S Plan's. There are only a few systems that can do motorised zone valve control and OpenTherm. I'd suggest having a chat with a local heating specialist to understand what is possible with your heating system.

[@bimiuk4051]

May I ask if you have experience with TADO smart thermostat and Ideal Vogue Max to setup Opentherm and PDHW? Further more, do I have to travel two new cables (blue and brown) from unvented Tank down to the boiler? It be two different floors in my case.

[@MWPHS]

Unfortunately we don't, however all OpenTherm thermostats with a wireless receiver will be very similar to the one in the video.

[@jamilkrdi6282]

Nice

[@sanjayp2683]

What max flow temperature on the boiler do you recommend when using Opentherm thermostat?

[@MWPHS]

Ideally below 55 degrees C if its a combi boiler.

[@bimiuk4051]

Another question : Will OpenTherm or Weather Comp work on a system Boiler ONLY IF the SPlan is converted to XPlan??

[@MWPHS]

When we are trying to make condensing gas system boilers more efficient, we need to have low flow temperatures for space heating, but higher flow temperatures when recovering the hot water cylinder. We do this using what is becoming widely known as Priority Domestic Hot Water (PDHW). More details on this in an article I wrote here a few years ago - theintergasshop.co.uk/content/189-why-hot-water-priority-is-the-reason-s-and-y-plan-should-be-banned X Plan is something we developed (before Intergas Heating adopted it) and this is a heating design method capable of achieving PDHW. There are many other methods of achieving the same thing, BUT standard S Plan or Y Plan system will not achieve PDHW without clever wiring or additional relays removing power from the heating valves, when there is hot water demand.

[@bimiuk4051]

@@MWPHS my understanding is that you can make boiler condense by simply turning the max temp to 50c on the boiler. By doing do does that not mean the return will be something like 40c return ? And therefore condense? If true - then the problem is that the hot water tank will take days or weeks to reach Max temperature on cylinder stat 60c. In other words it seems possible to run Condensing mode on system boiler without a problem. It only would require me to increase the temperature back to 60c each time I am going to heat the tank. Am i understanding this correctly or am i missing something? As for PDHW: I am trying to find a diagram that I can follow. I got Ideal Vogue Max which seems to have two SL ports (L and In). Also got the NO valve handy for this. If you have a diagram to show how I need to connect wiring for my system pls let me know as I been trying to fix this past few months but no luck.

[@grimliver3498]

dose the ESi RTP6 Wireless Programmable Smart Thermostat come with the rf recevier? i have just had a main 30 combi fitted that accepts open therm

[@MWPHS]

Hi, yes the RTP6 comes with an RF receiver (it is the receiver featured in the video). thesmartthermostatshop.co.uk/product/6-series-wi-fi-wireless-programmable-room-thermostat-grey/

[@grimliver3498]

@@MWPHS brilliant thanks for quick reply,

[@dantronics1682]

I thought the idea of opentherm was to modulate the flame so that the boiler does not cycle on and off but run at as low a temp as possible, I have an esi esrtp but this doesnt seems to be doing that, its a heatline sargon wich is opentherm compatable, the manual doesnt mention openthem but the wiring diagram shows it, plus the fault codes will how on the esi display

[@MWPHS]

The thermostat can only use the OpenTherm communication to instruct what flow temperature it wants the boiler to run at. How the boiler operates at that flow temperature is at the mercy of the boiler itself. If the boiler is dramatically oversized to the property with a poor modulation ratio, then irrespective of what the controls try to do, the boiler is going to cycle. Different boilers and controls have different levels of OpenTherm compatibility based on how well the manufacturer has programmed them.

[@AdydeAdy21]

Opentherm is available on vaillant model of centrals?

[@MWPHS]

Vaillant uses eBUS and have some very good Class V & VI modulation controls. We will have a full Vaillant controls section on our The Smart Thermostat Shop website soon! thesmartthermostatshop.co.uk/product-category/vaillant-controls/

[@45graham45]

I have a nest learning thermostat. It knows the outside temp of it's location via it's internet link. Does it or can it use that info as weather compensation to determine boiler demand?

[@MWPHS]

It is possible for smart thermostats to use weather data either via the internet or a weather compensation sensor attached to the boiler via the OpenTherm connection within its algorithms. Obviously it is down the the thermostat manufacturer wether they use this information or not.

[@45graham45]

@@MWPHS Yes, that was my question, can / does the nest thermostat do this?

[@MWPHS]

@@45graham45 don’t know but the manufacturer claims to.

[@45graham45]

@@MWPHS thanks.

[@GTOOtt]

I've just installed a Drayton Wiser system to my Baxi 800 utilising OpenTherm. I've noticed that my radiators now get scalding hot even when requesting just a couple of degrees increase. Is this normal?

[@MWPHS]

Has the Baxi got the capability of controlling its maximum flow temperature once an OpenTherm controller is attached to it? If not, then this could very likely be the result.

[@GTOOtt]

@@MWPHS Emailed Baxi and they say "To adjust the temperatures on the boiler, it is done within the opentherm controller". Guess I need to call Drayton.

[@45graham45]

​​@@MWPHS Afaik, 2°C or more between target & actual temp will call for max boiler output. The Baxi cannot control max temp when using open therm. However, max temp can be set in the settings on many smart thermostats. The info should be in the thermostat instructions.