Improving my heating controls - going smart - advice welcomed

[danlightbulb]

Hi all,

I currently have a Worcester Bosch Greenstar 25Si combi boiler located in the kitchen with a wireless Drayton Digistat thermostat wall mounted in the hallway. All rads except the bathroom towel rail have a Danfoss TRV.

The boiler with its rotary manual timer:



The Drayton thermostat (no programmable functionality):



The wireless receiver unit which seems to be wired into the boiler:



The TRVs:




I would like new TRVs anyway, as the current ones are stiff, yellowed, and covered in paint splashes. I could go for smart TRVs to give me some zonal control.

I would also like a Google Nest thermostat or similar to replace the existing controls.

I want to DIY this if possible.


Any advice on what I need to do, compatibility issues, would be appreciated.

 

[danlightbulb]

Ok perhaps I ditch the idea of smart TRVs then.

On the thermostat side though, I'm currently trying to find out how to get a device compatible with Worcester Bosch's EMS bus to get proper boiler modulation functionality.

My research so far has pointed me to the Tado system which I've read can communicate via EMS protocol. Has anyone done this or OpenTherm and got good results?

 

[danlightbulb]

Effectively I have the same as the "tado° Wireless Smart Thermostat Starter Kit V3+ with water controls", an small internet bridge, a remote room thermostat/control and the boiler/hot water interface box.

Could you elaborate on your configuration please?

I've discovered that the UK version of the v3 wireless interface doesn't support bus control but I can order the EU version which does have it. I believe they used to make a separate bus connection interface, which might be what you have, but this is now discontinued.

I'm particularly interested in how you made the connection to the boiler EMS interface please.

 

[danlightbulb]

turn the heating off upstairs and I guarantee the kids will want to play up there!

Isn't that the point though? In a normal system if your heating is off and someone wants heat in a room just turning up the trv won't do anything, you'd have to turn the heating on as well. Whereas with a smart trv you can use it directly to activate the boiler for that room without touching the main programmer.

 

[danlightbulb]

It looks like a well-balanced system with a sensible schedule is the best way to save money. Not possible for everyone, of course, but for most it'll likely work out.

As long as I invest in a control system that can accommodate smart TRVs in the future then I can start with the thermostat and app control and see how that goes.

The frontrunner at the moment is the Tado system but Im really keen to hear more from @Demon because it sounds like he has done exactly what I want to do in terms of making a Tado to EMS connection on the boiler. Don't let me down Demon!

 

[danlightbulb]

I have full tado too.
I did it all myself.
Every radiator bar towel rail and downstairs hall has one.

Caveat. I have a tank.

I removed our control unit and replaced with tado unit (wiring was provided by app)

I removed old analogue wall thermostat and bridged the wires (always on)

Now the Tado control unit calls for CH or HW as a direct replacement to the old one.

Any one TRV can turn the boiler on.
HW is obviously same method. If it's requested it comes on.

I bought a V2 box from ebay so I get the geofencing for free!

What boiler do you have and did you wire into the flow modulating functionality?

 

[danlightbulb]

A quick Google suggests these models don't have OpenTherm capability so it'll just work in an on/off fashion @danlightbulb

@danlightbulb Also, it's flow temperature modulation via OpenTherm. The heating pump is what would modulate flow rate, be it the one in the boiler or elsewhere on the heating loop.

Yeah Ive developed my understanding of it over the past couple of days.

What I need to do is decide whether its worth trying to get a device, likely the Tado, to connect to the EMS bus on my Worcester Bosch boiler. To do this I need to buy the EU version of the device and get it shipped here. Or I can buy the UK version which doesn't support EMS bus link so I'd have to wire it using switched live approach. To connect via EMS I would also have to open my boiler case to make the connection. That's why im interested in @Demon and what he did to wire this up.

Its £200 for the EU version or £100 for the UK starter pack currently on screwfix.

 

[danlightbulb]

They don't do that extension kit anymore, but I see what you mean, the EU version of the V3+ kit has the same connections as I have, the UK version has some cut down version without the "A | - | +" connections..

Mine works a treat and added hot water control as well (although I don't need that) the TADO app and installation method through a lovely wizard is 10/10 from me!

The other tip is I removed the DT20RF programmer from the boiler previously and found loads of installers sell the little blank covers for a few quid on ebay, they must have left over from installs, this neatens up the boiler with no ugly controller on show.

Thanks for replying that sounds perfect to what I want to do.

I do have to open up the boiler front cover though, which strictly speaking is not allowed. Was this easy to do and access the terminals?

Did you have to go through the setup menu to activate a certain mode on the Tado stat?

Thanks for the tip to blank off the mechanical rotary timer with a blanking plate, that sounds ideal as well. Would you know what to search for please?


Do you think its worth £100 extra to get the EMS interface?

 

[danlightbulb]

Assuming yours is similar to mine, the TADO app wizard is very detailed, it gets you to power off, it takes you through taking the front panel off, dropping the control section down etc, where to route the cable, how to connect.. Fairly easy.

It's absolutely fine to take the front cover off IMO, the Worcester Bosch is really well designed for service, the control panel is hinged so it all comes down and is easy to access. I don't think TADO would offer the installation guide in the App if it wasn't appropriate.

Thanks, really helpful. Do you wire in the 'normal' 230V switched live as well as the EMS connections, or only the EMS connections?

Do you know if I can access the app instructions for my boiler model without purchasing the device to see what it says?

 

[danlightbulb]

No, if using the Digital +/- connections on the Tado smart wireless receiver, you only wire those 2 connections to the boilers BB or EMS connections, it gets power from that as well, no mains at all (switched or not).

I've just changed model to a Greenstar 25si of your vintage (its says 2011-2013) and picked any controller (e.g. DT10), the installation is identical to mine, turn off power, remove front cover, remove the cap holding the programmer in, remove programmer with ribbon cable/connector, pop in a blanking cap (optional!) and wire to the BB connections internally, then to the +/- digital on the wireless receiver..

Obviously you'll then get rid of your Drayton Digistat and it's wireless module, so less clutter.

TRV Wise, you'd need to remove one of the Danfoss TRV Tops (all mine unscrew, but not sure with Danfoss) there is a compatibility guide on the Tado site showing the valves underneath it's compatible with:

Spoiler: danfoss excerpt

Excellent thank you. Just need to source the bits now then.

 

[danlightbulb]

Looking like a standard TRV head replacement for the existing Danfoss RAS-C ones will come in at circa £15 a unit.

Anyone know whether I can swap the TRV head for any other brands or do I have to stick with Danfoss?

 

[danlightbulb]

Going by this page for a RAS-C2 head:

Danfoss Randall RAS-C2 Replacement Head

www.heatingcontrolsonline.co.uk

It states "Can also be used to replace heads on RAS-C TRVs" and has a picture of the head which looks like yours, so definitely not generic.

The RAS-CK (first image in that picture above) with the basic 30mm x 1.5mm thread is how all mine are (from about 4 different manufacturers), I've replaced 2 by buying new cheap TRVs for £6 (The local plumbing supplies 'contract' range that was recommended by a plumber) and swapped the heads over and all seem interchangeable.

Yeah I found the Danfoss Randall range C2 as part of my search, but didn't know if I could go for Drayton TRV4's.

I tried taking off the TRV last night on one radiator and couldn't get it off, so not sure if I need a set of pliers for more power or if Im not trying to take it off correctly. I thought the black knurled section at the bottom would just unscrew counter clockwise, but it wouldn't turn.

 

[danlightbulb]

Ah ive got some of them off now.

These are the TRV valves and the pin seems to be moving ok.



Some are horizontal, some vertical:




So am I locked in to Danfoss Randall C2 if I replace with standard non-smart TRVs? The Danfoss ones are more like £17 each though.

 

[danlightbulb]

You could buy the RAS C2 complete TRVs for £17.99 from screwfix

Yeah that's the conclusion I came to as well.

Tado website says that the smart TRVs come with the right adapter for the valve as well.

 

[danlightbulb]

Still undecided on whether to go full on EU version Tado or not.

My boiler manual says set the temperature dial to 1 or 2 to maximise efficiency. This would be 47-50 degrees C according to the manual which I guess maintains condensing mode.

I don't know how the Tado would choose to set the flow temperature. Would it choose to set a lower temperature and bring the house up slowly, or would it choose to set a high temperature and bring the house up to temperature quickly before leveling off.

I suppose this is the crux with smart stuff isn't it - you've got to hand over the control to the device rather than doing it yourself. Is the device smarter than me adjusting the dial on the boiler when it gets colder.

 

[danlightbulb]

I successfully acquired Danfoss RAS-C2 TRVs, brand new unboxed, for £7 a unit off Ebay. Fitted no probs and look loads better than the battered originals.

Now trying to source new lockshield valve covers but can't get the original ones for the valves that are fitted.