Replacement of Landis & Gyr RWB2 + Honeywell T6060

[jguibert]

Hello,

I have currently the following installation:

- Vaillant Turbomax VUWGB 242E combination boiler, controlled by:

- Programmer Landis & Gyr RWB2
- Thermostat Honeywell T6060
both units are on the small wall, distant of 2cm from each other.

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I have no experience in wiring, but reading through some previous forums, I thought about replacing the Landis & Gyr RWB2 by a Siemens RWB29 (as using the same backplate as the L&G).

As far as my T6060, it has 2 wires, a red one connected to 1 (Live In?) and a black one connected to 3 (CH ON?). I would like to replace it with a digital thermostat. On some forums they recommended the Honeywell CM907 (7-day programmer) or a non-programmable, the Honeywell DT90E.

Isn't it redundant to combine a Siemens RWB29 programmer with Honeywell CM907 programmer? Should I rather consider the non-programmable one (DT90E). In terms of wiring, how to connect the two wires of the T6060 (connected to 1 & 3 respectively) between the A & B connections (either to the CM907 and DT90E)?

However, wouldn't it be a better solution to replace my existing combined Programmer Landis & Gyr and Honeywell Thermostat with one single unit? If so, would you recommend some products (Honeywell?) However, I believe in that case, I should ask for a professional to carry out the works, as I have no idea how to connect the 3 wires of the L&G (as shown in the picture) and the 2 of the T6060 into one single unit.

Many thanks in advance for your advice and recommendations.

 

[mikely]

You are right, I think the best solution would be to dispose of the programmer and fit a programmable room stat. The Honeywell CM907 would be a good choice. Fitting it should be straight forward. The CM907 would simply connect to the same two wires as the T6060, either way round. The programmer can be removed and its wires simply connected. However, from your low res image it looks like the wire on terminal 4 of the programmer is the green/ yellow sleeved earth wire of the twin and earth cable. If it is then you should really get the wiring sorted out because an earth wire should never be used for a live circuit.

If the thermostat is not in the optimum location then you could fit the wireless version of the 907, the CM927.

 

[jguibert]

Mikely, thanks a lot for your prompt answer.
If I may, I have some follow-up questions.

Does it mean that the CM907 also enable to program separately Central Heating and Hot Water? In practice, I would like to program my central heating (especially weekday and weekend separately), while hot water be available anytime (when you turn the hw tap).

Sorry for the low resolution of the photos. I you get to this link, is it better? :

//www.diynot.com/network/jguibert/albums/7171/28342

Could the red and black wires connected to the T6060 be the same as the ones connected to the RWB2 programmer on terminal N & L ? If so, could I either decide to connect the CM907 to the same wires currently connected to the RWB2 or to the T6060? Should I understand that it does not matter whether the black or red wire is connected to A or B of the CM907?

About removing the programmer, and simply connected its wires, do you mean to connect them together (i.e. the red and black together? with a butt splice or a choc block). In the case I could fit the CM907 in lieu and place of the RWB2 (rather than to the T6060), does it mean that I will then connect together the black and red wires of the T6060?

About the green /yellow wire, should I thus disconnect it, fit a choc block to the end and then tuck it away?

Thanks a lot in advance.

 

[mikely]

Does it mean that the CM907 also enable to program separately Central Heating and Hot Water?

No, the CM907 will only control the heating, but as you say HW is available anytime from the combi. So you don’t need the programmer. The CM907 can be set to have different programmes for every day of the week and, having set one day, those settings can be copied to another.

It does not matter which way round the wires are connected to the CM907.

The red and black wires connected to the programmer are live and neutral, so you certainly must not connect those together. They are not the same wires as the red and black to the thermostat. Your photo confirms that the earth wire of the cable connected to the programmer (on terminal 4) is being used to supply the CH circuit. It should not be and this should be corrected.

Terminal 4 is the CH switched output which will connect to the thermostat, but it must be interconnected somewhere to the wires going to the thermostat and boiler. This all assumes that the programmer and thermostat do both currently control the boiler?

You need to find where the wires from the programmer and the thermostat are interconnected with the boiler. Is there a wiring box in an old tank cupboard or near the boiler?