Going smart on my central heating - advice start to finish welcomed

[danlightbulb]

Hi all,

New (to me) house has a Worcester Bosch Greenstar 25Si combi boiler, controlled via a wireless Drayton thermostat which is interfaced to the boiler via a wireless receiver box. TRVs throughout the house all old, bit stuck and yellowed.

I want to go smart. Ideally looking at a Google Nest, with smart TRvs in the rooms for zonal control.

What do I need to do to upgrade this system please, I'd like to do it DIY.

Here are photos of what I currently have:

Boiler:

Wireless thermostat:

Wireless thermostat receiver box wired to boiler:

Room TRVs:

 

[muggles]

You'd be better off going for one system rather than Nest as a master thermostat and some other brand of smart TRVs which won't talk to each other properly. Have a look at the Salus Smart Home system.

Those TRVs on your radiators are ancient and will probably need to be replaced as part of the job

 

[danlightbulb]

@muggles thanks. I took a look at their product range and it seems promising. Not as eye catching as the Nest device though.

I see that the starter pack comes with a programmer, boiler interface device and the required universal gateway.

However I've been reading about potential loss of the boiler modulation feature with these types of devices. Does the Salus system retain boiler modulation?

 

[muggles]

The boiler will modulate with any control including the one you have now. If you're talking about OpenTherm then Worcester boilers don't support that

 

[mcprinter]

I have looked into this quite a bit. Still undecided.
Evo Home, Tado and Wiser seem the best systems.

3-4 Bed House, you are looking £700-£1K. Maybe more now
No guarantee that you will save anything on gas.

Your TRVs look like Danfoss RAS C. Evo are compatible so the others probably are as well. Do check though.

A programmable stat made a big difference to the comfort in our house.
Different temps at different times rather than just on and off periods

 

[danlightbulb]

The boiler will modulate with any control including the one you have now. If you're talking about OpenTherm then Worcester boilers don't support that

I've read there is an adapter that I would need, an EMS to opentherm interface made by WB? But I can't find alot of detail about it.

EasyControl Adapter | Worcester Bosch

Bosch EasyControl Adapter for boiler heating control allows the EasyContro to work with our Greenstar oil boilers and our range of regular boilers

www.worcester-bosch.co.uk

 

[danlightbulb]

@muggles Im Confused about the modulating function of my boiler.

Im aware that OpenTherm can modulate boilers. But my boiler isn't compatible with OpenTherm, so all a Nest or other type of smart thermostat can do is switch it on and off. Unless i get some kind of adapter but the information isn't clear.

Am looking at the Drayton Wiser website and it says this:

What is the Wiser HubR?
You will also find a HubR in the Wiser Thermostat packaging.
This will be hung near the boiler. The HubR connects to your thermostat wirelessly or via the existing thermostat wires. If you increase or decrease the temperature on your thermostat, this will be communicated to the HubR, which can switch the heating on or off or control it in a modulating manner.
The HubR now uses OpenTherm technology to modulate your HR condensing boiler.

So this suggests that I won't get boiler modulation because the HubR uses OpenTherm? Unless the boiler does it itself without the need for external thermostat? Is that what it means, that the thermostat won't be able to control the boiler modulation but the boiler itself will still do it?

If so, what is the benefit of having a smart thermostat control the modulation rather than the boiler itself?

 

[karlbbb]

If so, what is the benefit of having a smart thermostat control the modulation rather than the boiler itself?

The modulation via OpenTherm is a two-way street. You need both ends of the system to talk OpenTherm. Data is sent back and forth - set point, current temp, current flow temp, modulation level etc etc.

If your boiler doesn't support OpenTherm (or the thermostat system doesn't support a boiler's proprietary modulation system), it won't work, you will only get on-off operation.

 

[danlightbulb]

The modulation via OpenTherm is a two-way street. You need both ends of the system to talk OpenTherm. Data is sent back and forth - set point, current temp, current flow temp, modulation level etc etc.

If your boiler doesn't support OpenTherm (or the thermostat system doesn't support a boiler's proprietary modulation system), it won't work, you will only get on-off operation.

Ok so still confused then:

Does my current configuration modulate? (with the standard WB boiler, Drayton wireless thermostat)?

Can I keep/obtain a modulating function with some sort of OpenTherm adapter? I believe 'EMS' is WB's proprietary solution. Does my current setup use this?

 

[karlbbb]

Ok so still confused then:

Does my current configuration modulate? (with the standard WB boiler, Drayton wireless thermostat)?

Can I keep/obtain a modulating function with some sort of OpenTherm adapter? I believe 'EMS' is WB's proprietary solution. Does my current setup use this?

Your current Drayton control system doesn't have any OpenTherm capability so your thermostat simply calls for heating on, and your boiler maintains whatever flow temp is set on the controls on the front.


Be cautious of terminology here - your boiler is modulating, in that it can reduce its output power in an attempt to maintain the flow temperature set on the front of the unit, but that flow temperature is fixed. What OpenTherm/EMS does is actively modulate the flow temperature, overriding the front of the boiler. So when a suitable thermostat calls for 20C room temp, and the current temperature is 15C, it'll demand a higher flow temperature. As the room heats up and approaches the set temperature, it'll tell the boiler to reduce that flow temperature.

From a cursory Google, it looks like you'd need some kind of interface to sit between the Nest system and the boiler. However, I'd have to defer to someone with experience with that.

 

[danlightbulb]

Be cautious of terminology here - your boiler is modulating, in that it can reduce its output power in an attempt to maintain the flow temperature set on the front of the unit, but that flow temperature is fixed. What OpenTherm/EMS does is actively modulate the flow temperature, overriding the front of the boiler. So when a suitable thermostat calls for 20C room temp, and the current temperature is 15C, it'll demand a higher flow temperature. As the room heats up and approaches the set temperature, it'll tell the boiler to reduce that flow temperature.

I think I get you.

My understanding is that modulating is desirable because it can keep the boiler in the most efficient condensing mode for more of the time when the unit is running. I want to keep/obtain that because obviously I want to be as efficient as possible.

It seems that the OpenTherm solution is better because it dynamically changes the flow temperature as well, presumably keeping the boiler in its most efficient mode for even longer than in the standard setup. I.e when a flow temp of 70 degrees isn't needed, OpenTherm dials this back so the boiler doesn't need to heat the water as much. This sounds desirable to me from a gas usage perspective.

So I would like to find out what adapter I would need and how to wire it, to gain smart thermostat control over boiler flow temperature.

 

[karlbbb]

I think I get you.

My understanding is that modulating is desirable because it can keep the boiler in the most efficient condensing mode for more of the time when the unit is running. I want to keep/obtain that because obviously I want to be as efficient as possible.

It seems that the OpenTherm solution is better because it dynamically changes the flow temperature as well, presumably keeping the boiler in its most efficient mode for even longer than in the standard setup. I.e when a flow temp of 70 degrees isn't needed, OpenTherm dials this back so the boiler doesn't need to heat the water as much. This sounds desirable to me from a gas usage perspective.

So I would like to find out what adapter I would need and how to wire it, to gain smart thermostat control over boiler flow temperature.

Modulation in the sense you first mention is internal to the boiler, so is always there, and so you won't lose it as it's an internal function, so don't worry about that. Think of this as basic cruise control on a car - you set 65mph, and the car modulates the throttle to maintain that set speed. Can you imagine if the car could only do full throttle or no throttle? It'd be constantly jerking you backwards and forwards, and you'd always be fluctuating around the requested speed.

Modulation in the sense of OpenTherm (a desirable control) is an external function, though one that must be supported by the boiler, and is not the same as the modulation already internal to the boiler described above. Think of this in terms of smart cruise control - some cars these days will start to reduce the cruise control speed for you as you approach a roundabout or junction. You don't need the full 65mph anymore, so it'll slow down the cruise control to say 30mph so you can get over the roundabout.

 

[danlightbulb]

Modulation in the sense of OpenTherm (a desirable control) is an external function, though one that must be supported by the boiler, and is not the same as the modulation already internal to the boiler described above. Think of this in terms of smart cruise control - some cars these days will start to reduce the cruise control speed for you as you approach a roundabout or junction. You don't need the full 65mph anymore, so it'll slow down the cruise control to say 30mph so you can get over the roundabout.

Thanks I understand now what the difference is.

So lets say I want OpenTherm/EMS control. How do I get this? EMS is WB's proprietary system however I guess my basic thermostat is not using this even (does my model of boiler even have it?).

If I don't have EMS capability at all, I guess I won't be able to get any form of OpenTherm adapter anyway as the functionality is not present on the boiler. If my boiler does have EMS, I would need to either use an EMS thermostat or get an OpenTherm adapter.

 

[danlightbulb]

The wiring diagram in the boiler installation manual seems to show an EMS connection plug, although I can't see any indication of it on the boiler front panel.

 

[danlightbulb]

Tado stat + wireless kit + 7 smart TRVs = £665.
Evohome stat + wireless kit + 7 start TRVs = £866.
Drayton Wiser stat + wireless kit + 7 TRVs = £477 (but these TRVs don't have a temperature readout)
Google Nest stat only - £190 would need to find compatible smart TRVs.

I like the look and price of the Wiser kit but the TRVs don't display the temperature unfortunately. 2nd preferred option is the Tado kit currently.

The Google Nest would be winning if it was easy to find compatible smart TRVs.

However Bosch have their own Easy Control smart system as well including TRVs, and this would use EMS. If my boiler has the ability to be controlled with this it might be the better option.

I think the adapter I would need for OpenTherm use is the Nefit EMS OpenTherm converter, provided I have the EMS capability on the boiler. Not sold in the UK though.