Replace BDR91 with tado smart thermostat

[ConcreteMan]

Hello. New to the site and would like some advice please.

I am replacing a Honeywell BDR91 controller with a tado smart thermostat and have run into a problem. My existing wiring doesn’t match either of the examples in the tado instruction. My boiler is an Ideal Logic C30

There is a bridge between the two terminals L and A. However there are other wires that aren’t shown on the Tado diagram.

I have two wires in L, two wires in N, two wires in A and finally one in B.

Could you kindly advise on where these wires go. Presumably I don’t need the bridge wire? Which position does the jumper need to be in?

Please see attached photo of existing wiring.

Many thanks for your help.

 

[CBW]

Transfer both N from BDR91 to N on Tado
Transfer both L from BDR91 to L on Tado
Transfer both A from BDR91 to Com on Tado
Transfer B from from BDR91 to NO on Tado
Leave Earth terminated

Have a celebratory drink once complete

 

[ConcreteMan]

Many thanks for your reply. It does mention in the instructions that the loop wire between L and A isn’t needed to run the tado? Should I leave it in anyway? Also, what position should the jumper be in?

I really appreciate your time on this. If I disable our heating my wife really isn’t going to be impressed!

 

[mcprinter]

I am DIY but have installed Wiser and other stats.

Your BDR is switching Live
I would suggest:
Tado in Mode 2
L+N
BDR B to Tado 4

Tado Mode 1 is for when the Boiler supplies the COM to the stat.
I guess you could link L to COM in Mode 1

Wait for Chris (CBW) or another pro to confirm.

 

[ConcreteMan]

Thank you for your input. I am planning to do this job next weekend so I am in no rush to get the advice I need,

I’m the first to admit that electrics aren’t my area of expertise!

 

[ConcreteMan]

Hopefully Chris will be able to confirm later today. Thanks again.

 

[CBW]

Nope, relay 2 is for hot water and heating, relay 1 layout is for what OP wants, which is a thermostat for a Combi boiler. The link is there because it’s been wired like this instead of taking the Com from the boiler, so it’s going to be required. Not entirely sure what you mean by the jumper, can’t see one.

 

[ConcreteMan]

Thanks for your reply Chris. The jumper is either put in position 1 or 2 on the tado? It's over on the right hand side of the unit shown on the photo.

I think it says set to 1 for "potential free" or 2 for "switched live" - that doesn't mean much to me though.

Just to confirm, the loop wire between L and A is required?

 

[CBW]

Set jumper for position 1 and yes link will be required. Try wiring without, as I don’t know why there’s wire coming from it either,

 

[ConcreteMan]

Thanks Chris.

So, one last time to confirm, I am leaving the link in between L and A?

Then .............

Transfer both N from BDR91 to N on Tado
Transfer both L from BDR91 to L on Tado
Transfer both A from BDR91 to Com on Tado
Transfer B from from BDR91 to NO on Tado
Leave Earth terminated

Then set the jumper to position 1.

 

[stem]

I don’t know why there’s wire coming from it either,

My guess would be that there is an incoming 230V supply (probably from the 3A FCU) and an outgoing 230V supply to the boiler, so 2 lives and 2 neutrals.

Then, as there is also a link required between L and A, there wouldn't be enough room to get a 3rd wire in L, so it's been put into A to pick it up for there instead.

EDIT
As we posted at the same time, I didn't see your last post, but what you have said looks good to me, and I'm sure Chris will confirm.

Transfer both N from BDR91 to N on Tado
Transfer both L from BDR91 to L on Tado
Transfer both A from BDR91 to Com on Tado
Transfer B from from BDR91 to NO on Tado
Leave Earth terminated

Then set the jumper to position 1.

 

[ConcreteMan]

Thanks fellas. I’ll have a go at this over the coming weekend