Understanding Honeywell wiring centre connections

[Alexnh]

Hi, while fitting a new tado thermostat I have damaged my honeywell sundial wiring centre. Therefore I am replacing it with a new one (same model) with the intention to swap over all the connections.

I am puzzled by two things. One is that link L1 has been soldered despite the instructions saying that it should be cut if a programmer is fitted rather than a simple clock (there was a honeywell ST6300A - replaced by tado extension kit. It seems that the system is all working correctly and so I planned to swap the connections directly as they are currently. However, I don't see why L1 has been reconnected and secondly a terminal block has been added connecting some other wires (live connections).

I have attached some pictures. (NB - the brown connection jumping from mains live to the programmer is one I have added as it is this link that I damaged on the board).

 

[Alexnh]

Here's a better picture of the terminal block. It connects wires 3 and 4 coming from the programmer (tado extension in this case) to wires going to the HW/mid plan valve and the hot water cylinder thermostat.

I don't understand why these wires bypass the wiring centre rather than being connected to the appropriate terminal?

 

[Alexnh]

No one knows.

 

[Alexnh]

So, L1 connects C on the cylinder stat terminals to 1 on the room stat. Nothing is connected to C so didn't matter if L1 is cut or joined.

 

[ianmcd]

So, L1 connects C on the cylinder stat terminals to 1 on the room stat. Nothing is connected to C so didn't matter if L1 is cut or joined.

If nothing connected to C then how does it work ?

 

[Alexnh]

If nothing connected to C then how does it work ?

It's getting live from the programmer output via the additional terminal block.

Similarly the other output from the programmer is connected to the boiler wire in the same way, again bypassing the wiring centre. There doesn't seem any good reason for it. I could just connect those wires to the appropriate terminals on the wiring centre and cut L1. On the other hand it is working correctly at the minute...

 

[ianmcd]

The wires shouldnt be connected to the boiler, the orange wire from the mid position valve tells the boiler to come on, the mid position valve needs a HW off and a CYL stat satisfied connected to it, your system is not wired correctly

 

[Alexnh]

You're quite right, I have described it wrong. The wire goes to the valve. But I think you're not correct about needing a HW off.

 

[ianmcd]

But I think you're not correct about needing a HW off.

Of course you need a HW off and a HW satisfied in the same terminal along with the grey from the mid position valve, or have you got mixed up and it is not a three port mid position valve but two x 2 port valves

 

[Alexnh]

I never said whether it was two or three port so I cannot be mixed up between the two

I don't know, maybe you can tell from the picture. No HW off in the tado wiring diagram.

 

[CBW]

Do you know who soldered the joint back together? Was a basic time clock used at any point?

 

[D_Hailsham]

I never said whether it was two or three port so I cannot be mixed up between the two

I don't know, maybe you can tell from the picture. No HW off in the tado wiring diagram.

There is no white wire on the cable to the "Mid position or HW valve" terminal block, so it cannot be a mid position valve. It must be an S Plan with separate CH and HW valves.

The cylinder stat will not work without a connection to C terminal.

 

[ianmcd]

I never said whether it was two or three port so I cannot be mixed up between the two

to wires going to the HW/mid plan valve and the hot water cylinder thermostat.

Who wrote that then if it wasnt you ?

 

[Alexnh]

There is no white wire on the cable to the "Mid position or HW valve" terminal block, so it cannot be a mid position valve. It must be an S Plan with separate CH and HW valves.

The cylinder stat will not work without a connection to C terminal.

Who wrote that then if it wasnt you ?

That is how it is labelled on the wiring centre. I thought the backslash meant "or"?

 

[Alexnh]

Do you know who soldered the joint back together? Was a basic time clock used at any point?

I do not. I inherited it from the previous owners.