Rewiring

[MANDATE]

It would be worth having a look at the cylinder stat. For a 'y' plan which is basically what you appear to have the cylinder stat should have 3 terminals and 3wires and one of these may well be the 'blue'
Other than that the cylinder stat may just have two terminals and two wires.

 

[Steelmasons]

Term 2 will be used when using motor open motor shut valves. Maybe hot water mv is spring return.

 

[Fayrana]

so with the 3 wires as shown in photo, where would they go on new timer?

 

[Hugh Jaleak]

Cant say without knowing where they go to. Wrongly connected, at best it may not work, at worst you could fry the programmer.

Current wiring needs tracing and each wire identified ideally, allowing all connections to be made properly. Very good Y plan explanation here: http://octaveblue.co.uk/c_heating/index.htm

 

[D_Hailsham]

Term 2 will be used when using motor open motor shut valves. Maybe hot water mv is spring return.

The OP appears to have a mid-position valve (though it could be a diverter). The MoMo version of a mid-pos is wired exactly the same as the spring return; it's only the MoMo zone valve which uses the CH OFF terminal.

My guess is that the original installer got confused between terminal 1 (HW OFF) and terminal 2 (CH OFF). However we need to know where the Blue wire goes to in the terminal box.

Q for the OP
How many wires are there in the black cable from the valve to the junction box? If there are five, you have a mid position valve; if only three you have a diverter valve.

Assuming you have a mid-position valve (which is more likely), trace the grey wire to its connection in the junction box. Are there two other wires connected to the same terminal (they are in pairs, top and bottom)? If so, is one of them Blue? If yes, this is probably the blue wire connected to terminal 2 of the timer. If you can confirm this, we are halfway there.

 

[Steelmasons]

The OP appears to have a mid-position valve (though it could be a diverter). The MoMo version of a mid-pos is wired exactly the same as the spring return; it's only the MoMo zone valve which uses the CH OFF terminal.
.

I'm well aware of that.

We didn't know what controls the OP had (i still don't) , seen many S plans using motor open/motor shut zone valves , i've also seen plenty systems whereby the MO/MS HW zone valve has been replaced with a spring return leaving term 2 of programmer 'active' for CH valve , you said term 2 should not be used which is wrong depending on what controls are used , i've also seen MO/MS used on CH whareby HW was gravity

Where does the OP state the system is a Y plan (mid -position) ? I do this for a living DH.

 

[Steelmasons]

I need to know where the blue wire in terminal 2 goes to (it shouldn't be there!). Can you find out?

Just noticed the OP has uploaded some pics although you comment was made before the pics were uploaded.

 

[Fayrana]

Yes there are 5. Orange ,Grey Blue, White and Earth. The Grey wire goes to the top of a connector in the terminal block but there are no other wires to the same terminal either top or bottom.

 

[Steelmasons]

Yes there are 5. Orange ,Grey Blue, White and Earth. The Grey wire goes to the top of a connector in the terminal block but there are no other wires to the same terminal either top or bottom.

There should be 3 cores into that terminal , grey mv/cyl stat term 2/programmer term 1.

 

[Steelmasons]

twice,

 

[MANDATE]

Yes there are 5. Orange ,Grey Blue, White and Earth. The Grey wire goes to the top of a connector in the terminal block but there are no other wires to the same terminal either top or bottom.

There should be 3 cores into that terminal , grey mv/cyl stat term 2/programmer term 1.

Regarding the wire to feed the 'grey' which comes from the HW OFF terminal of the programmer. It will depend which programmer is used.
On the mini minder.
HW OFF is terminal 1.
HW ON is term 3.
CH ON is term 4.
On the horstman 425 tiara.
HW OFF is terminal 3.
HW ON is term 1.
CH ON is term 4

 

[Steelmasons]

A moot point mandate as we were discussing the mini-minder.

 

[MANDATE]

Well I know your talking about the mini minder, the OP wants information regarding the new timer, so better if it's clarified.

 

[D_Hailsham]

Yes there are 5. Orange ,Grey Blue, White and Earth. The Grey wire goes to the top of a connector in the terminal block but there are no other wires to the same terminal either top or bottom.

Do you have a cylinder stat (see pic)?

View media item 10596
We need to know why the blue wire is in programmer T2. Have you managed to trace it to the junction box? If so what else is connected to the same terminal in the JB?

 

[matt1e]

Op your system is most probably y-plan although it looks as though the original programmer was wired incorrectly, Hence

nobody has touched the system. Believe this is how it was installed prior to us moving in. I've been here 8 years.
No I can't have heating without water. I can have water without heating though.

Because the programmer is/was wired incorrectly and always has been

some easy instructions

connect the new backplate as follows
black to N
brown to L
yellow to 1
blue to 3
red to 4
now get two short lengths of suitable cable core and connect the links between L&2&5
job done,test it and you will probably find you can now also have central heating without hotwater (depending on the rest of the system being ok of course)

Matt