Pipestat wiring - Honeywell 4360 F/stat to H/well 641B 1004

[corkyboy]

I know there are several old threads on this topic but I would appreciate your advice.
Curently I have a 4360 f/stat wired T1 live/T3 neutral. I have a 641B pipe stat I want to connect up and I need to know exactly where I need to connect the feed from the pipestat to the f/stat.
Looking at the diagram T1 on the pipestat goes back to T3 on the f/stat, but where exactly does the feed from C on the pipestat go? Is it to the f/stat or the boiler wiring terminal block. If it is the latter it is a job for the professionals, not me.
TIA,

Colin

 

[D_Hailsham]

I have a 4360 f/stat wired T1 live/T3 neutral.

The blue/black wire is not a neutral, it is a switched live.

Where are the other end of these two wires connected? If it's to a junction box, which terminals? Can you post a pic of the box with the lid off, so we can see the wiring?

 

[corkyboy]

Thanks for your reply. The wires feed back to a terminal box and I have uploaded a picture to an album called (what else?) terminal box.
The permanent live from the f/stat on T1 comes in at first terminal from the left and the switchable live (thanks for that clarification) comes in at 4th from left. Hope this helps.

 

[D_Hailsham]

Thanks for the pic.

I can see two grey wires connected to terminal 6, which tells me you have two motorized valves (see pic). Is one in the HW circuit and the other in the CH circuit, or do you have two heating zones?

View media item 11762

 

[corkyboy]

Yes, one is for CH and one for HW.

 

[D_Hailsham]

Yes, one is for CH and one for HW.

OK

Which terminal, in the junction box, is the Brown wire of the CH valve connected to?

 

[corkyboy]

Reading from the left I have 2 browns going into 7 & 9 but visually it is not possible to confirm which is the CH or HW. However the terminal on 9 becomes live when I trip the f/stat and the CH valve opens while T7 remains dead. Hope this helps.
I also have a brown wire looping bottom T1 to top of T6 but guess we are not interested in this one?

Colin

 

[D_Hailsham]

OK. Here's what you do.

Turn the power OFF
Disconnect wire from Frost Stat 3 and connect it to Pipe Stat C
Connect Frost Stat 3 to Pipe Stat 1 - with a new length of wire.
Turn Power ON

The Frost Stat should be set to about 5C and the Pipe Stat to about 20C. The Pipe Stat is fixed to the boiler return pipe.

 

[corkyboy]

OK. Here's what you do.

Turn the power OFF
Disconnect wire from Frost Stat 3 and connect it to Pipe Stat C
Connect Frost Stat 3 to Pipe Stat 1 - with a new length of wire.
Turn Power ON

Just so I understand correctly, these connections/disconnections are to be made in the terminal box not on the actual stats?

 

[D_Hailsham]

Just so I understand correctly, these connections/disconnections are to be made in the terminal box not on the actual stats?

The connections in the terminal box are to be left as they are; the changes are to be made at the actual stats. This diagram shows how the stats are wired. You have an S Plan system, so the diagram shows the wire from pipe stat C connecting to terminal 5 in the junction box. But this assumes the wiring follows the "Honeywell standard", which you system does not.

View media item 27048
The "official" wiring is a bit messy as all wires are single and adding a pipe stat will probably mean extending one wire to reach the pipe stat. There is an alternative method, but it depends on there being a spare unused terminal on the frost stat. Here's what you do - all changes are made at the stats

Turn power OFF
1. Disconnect wire from Frost stat 3 and connect to a spare terminal
2. Run a 2 core cable from frost stat to pipe stat.
3. One core connects to Frost spare (same terminal as in 1) and Pipe C
4. Other core connects to Frost 3 and Pipe 1.
Turn Power ON

 

[corkyboy]

Thank you very much for all your help and advice. It's all up and running just fine now.
I might add that our local boiler service engineer had 2 goes at installing the p/stat and could not get it to work........doh!

Thanks again,

Colin