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Do any central heating controls actually do this fancy shizzle if you add a new boiler to an older set up ie have zone valves for hot water Tank and central heating rather than running the two separately from the boiler.
Ummm... not quite sure I understand the question but opentherm controls the boiler itself, not the other stuff. It doesn't matter what kind of system you have: https://theevohomeshop.co.uk/content/21-What-is-OpenTherm-and-why-use-Honeywell-evohome-with-it
If you're getting a new boiler then any of the modern controls should be able to make use of opentherm. I've got Nest at home and it works great. Been in a couple of years and it's just about paid for itself in reduced gas bills. I've installed the Honeywell one as well, looks a lot more involved than the Nest but not had any complaints.
As I understand it, a new boiler has the ability to vary the temperature that it heats the water to rather than just being on or off. So on a colder day it heats to a higher temp than a warmer one.
When a controller tells the boiler to adjust the water temp it does this via opentherm. If there’s no opentherm the controller just turns the boiler on or off.
However, you only want this to happen to the radiators - hot water needs to be heated the same regardless.
From what I can see not many smart controllers actually do opentherm They Still just do on/off it’s just you can control them via your phone.
I was sold a Viessmann 100w System boiler which will do weather compensation and a wiser controller. I thought that the two would work together but it seems the wiser system only does open therm for combi boilers and not when controlling both hot water and heating. I also saw an article that Seems to suggest the evo home system doesn’t actually use the outside temp either.
I can t just attach the temp probe to my boiler since it doesnt know when it’s doing hot water or heating, since I’ve got zone valves. Which would mean that If the Boiler does its own temp adjustment it would do it all the time. Which would mean at times the boiler wouldn’t be supplying water hot enough to heat the hot water in the cylinder.
So wondering what will work.
Nest definitely uses Opentherm and regulates the boiler temperature and looks after the hot water too. You connect the Nest wiring centre to both your heating and hot water zone valves and it does the rest. With ours I haven't bothered with the boiler's external temperature sensor because the Nest is internet connected and it can just check online what the outside temp is.
Just had a look at the Drayton stuff you have and unless you've been sold the Combi-specific version or the installer hasn't wired it up properly then it should do everything you want, including weather compensation - no need for the external temperature sensor.
What model do you have?
@theflyingox I have the 2 channel version- as I’ve a system boiler assume the combi wiser unit wouldn’t work.
According to wiser only the combi version (1channel) does opentherm
No idea if that link will work!
The link works but I don't get it. All the Wiser options on the Drayton website - whether they're for Combi boilers, system boilers, multi-zone set ups - all of them specifically mention that they come with an Opentherm module. I think if you've got the Thermostat Kit 2 then you're good to go: just plug in the Opentherm module to the back of the wiring centre. If you're still not convinced then I can 100% guarantee that the Nest 3rd Gen will control central heating and hot water, uses Opentherm and is weather compensating.
A bit more reading and I'm seeing some potential issues. I've used mainly Ideal boilers and apparently they use the DHW satisfied connection to allow Opentherm to take over, so you may need to wire up the HW zone valve as normal (inc orange wire to boiler). Not sure if Veissmann do the same as I'm seeing various questions online about Opentherm and S plan. Again though, the Nest allows you to set your system up with Opentherm CH and either Opentherm or simple on/off DHW so I don't see why it wouldn't work. Maybe that's the bit in the manuals about not working with external DHW controls?
Thanks TFO. I don’t get it either. Seems odd for Drayton to do it on one and not the other. The Only reason I can think of might be because the hot water shouldn’t have open therm applied but it surely is simple enough For the controller to apply opentherm to central heating and not hw, as the nest seemingly does.
Although where are you seeing opentherm advertised for the 2 channel version? I couldn’t see so asked Drayton and they pointed me to that link.
My set up is S plan.
Can't find the actual Drayton webpage now, but the 2-channel version on Screwfix mentions Opentherm module being included: https://www.screwfix.com/p/drayton-heating-2-channel-wiser-thermostat-control-kit/9575v#product_additional_details_container