Wiring help please

[so1o]

Hi people

Finally got my act together and have got myself a sundial rf pack 2.

ST9420C and DT92E.

Now i managed to replace my ST6300A with the ST9420C as it was a direct replacement, it fitted perfectly over the previous base plate.

Now the hot water worked when i switched it on but the heating would not work. The red light on the ST9420C would come on indicating that its working etc but the heating would not fire up. The old thermostat was left in situ so i disconnected the wiring for this but still had the same fault. What wiring needs to be changed so i can make use of the wireless thermostat and get rid of the old thermostat.

If you need more information please let me know.

 

[Agile]

Just because something fits a backplate does not mean the contacts are necessarily match.

You should check that.

The timeclock may have adjustments on links or DIP switches which need setting.

You may have a faulty motor valve!

Tony

 

[D_Hailsham]

The old thermostat was left in situ so I disconnected the wiring for this but still had the same fault.

You need to link the old thermostat live and switched live together.

If you have only two wires, that's easy. But if there are three wires post a pic showing the wiring and we will tell you what to do.

The wiring of the ST6300A and ST9420C are identical, so there's no need to make any changes on the back plate, and the ST9420C doesn't have any links or dip switches. (I'm surprised Tony didn't know that. )

 

[so1o]

Thanks for the replies guys.

The old thermostat in the hallway has three wires.

The hot water tank also has a temperature knob/switch on it.

I should mention in my haste i disconnected the thermostat from the wiring block to see if that would fix the problem i was having. It did not fix the problem so i put the old timer back on and connected the thermostat back up but i think i may have done it wrong. If someone could be kind enough to look at the wiring for the block connector i would appreciate it, when i disconnected the old thermostat im 99% certain i put it back to how it was but im just trying to be doubly sure. BTW my thermostat in the hallway is now broken thanks to visiting nephews and nieces they have somehow managed to break the control knob on it. The reason why i think it may be wrong is even with the central heating and hot water switched off the boiler fires up, i think i may have wired it wrong???

If you need more pictures showing the wiring better please let me know and i will try my best to show it as clear as i can.

 

[so1o]

The pictures are not clear so i checked and can confirm where each of the wires go in the wiring block for the old thermostat.

Brown wire is in the same place as the other 3 brown wires.

Blue wire is in the same place as the blue wire from the boiler.

green/yellow wire is in the same place as the white wire which comes of the 3 way motorised valve.

Can i just disconnect the old thermostat completeley or do i have to use it?

 

[D_Hailsham]

Brown wire is in the same place as the other 3 brown wires.

Do you mean the left end of the connector block? I would expect only two: one to the room stat and one to the Programmer. What do the other two connect to?

Blue wire is in the same place as the blue wire from the boiler.

Won't be required with the new stat

green/yellow wire is in the same place as the white wire which comes of the 3 way motorised valve.

This is the switched live. The installer has used the earth wire as a voltage carrying wire, which is contrary to regulations.

Can i just disconnect the old thermostat completely

When we have sorted out the other two brown wires, you should be able to get rid of the old stat and the cable to it.

Could you let me know the make and model no of the motorized valve? That's the silver box above the red pump in pic 10.

 

[so1o]

Thanks for the help, appreciate it.

In reply to your first question
Yes the left hand side of the connector block. In total including the brown from the thermostat are three other brown wires. I know one definitely goes to the programmer as you mentioned, when i get home will confirm where the other three go.

Make and model of the motorized valve is Honeywell F5 9923.

The only thing i cant get my head round is.......

When i removed the old programmer and put on the new one. I did not change no wiring whatsoever, fitted straight onto the old backplate.
I disconnected all the wires for the old thermostat. The new programmer worked, the water was being switched on and off as normal. The problem was the central heating, The led would light up to indicate the heating has been turned on but the boiler would not fire up. The new wireless thermostat was working i could use it to switch on the heating etc but obviously it was not firing up the boiler.

 

[Steelmasons]

There appears to be only 1 core into term 4 of terminal strip whereas in the other pics it shows 2 cores? , I would 'think' this black core would be CH ON from programmer , where is the other core? (room stat live term 1).

 

[so1o]

I will confirm this later but its definitely the one core in terminal 4, i think because of the pictures and masses of wire it looks as though it has more than one in the same location.

"room stat live term 1" what colour wire/core you referring to?

Sorry dont know much about this stuff.

 

[D_Hailsham]

Yes the left hand side of the connector block. In total including the brown from the thermostat are three other brown wires. I know one definitely goes to the programmer as you mentioned, when i get home will confirm where the other three go.

I can see a total of four wires!

1. Programmer
2. Room stat
3. ??
4. ??

Make and model of the motorized valve is Honeywell F5 9923.

I think that's a batch number. There should be a label on the other end with a V number

The only thing i cant get my head round is.......

Maybe this diagram will explain it to you.

Untitled

• D_Hailsham
• 11 Sep 2013
• 1

You have to short out the old stat, which we should be able to do at the junction box - when we know what all four brown wires are for!

 

[so1o]

1. Programmer
2. Room stat
3. Boiler
4. Switch on the right as in picture no 9 turns off power to everything.

Motorised valve number is V4073A1039.

Thanks to everyone helping out.I appreciate it.

 

[twgas]

Room stat should not have a direct connection to the boiler or main iso switch, I suspect the room stat brown should be in no4 with the black but need confirmation of what the other end of the black is conned to.

 

[so1o]

The black wire in no 4 comes from the programmer. However there are two black wires coming from the programmer. One in slot 4 as mentioned and one goes to slot 6 which also has a brown wire which comes from the cylinder temperature switch picture no 8

 

[twgas]

The black to no6 will come from no3 in prog, both the no4s will be connected to one another. The brown to room stat should be in 4 in junction box.

 

[Steelmasons]

Wasn't this covered in an earlier post.