Replacing ST699 with ST9400C

[exfi01]

Hi, All I am replacing below ST699 (currently connected with Thermostat and Kingfisher Potterton Gravity boiler) with ST9400C . Need some help with Wiring Diagram.

Currently
There is a loop between 5 & 6 >> This need to be discarded ?
From L there is loop to 6 >> Should I use feed from L to connect to 3(in ST9400C) ?

While swapping:

ST699 - ST9400C
L - L
N - N
3 - 4
6 - 3
7 - 1
8 - What should I do with this ?

Any help would be much appreciated.

Attachments​

 

[gas112]

https://www.free-instruction-manuals.com/pdf/pa_458238.pdf

 

[exfi01]

https://www.free-instruction-manuals.com/pdf/pa_458238.pdf

Morning, I have followed the instruction and connections as below by not using "8" (isolating by insulation tape), then lights come on on the unit but heating and hot water does not start.

 

[CountryFan]

In the St699 I see a black wire in with the yellow for hot water off, I can't see it in the new photo. Can you take a clearer photo? All demands calling?

 

[exfi01]

In the St699 I see a black wire in with the yellow for hot water off, I can't see it in the new photo. Can you take a clearer photo? All demands calling?

Hi, Just to make sure I have not mixed up the wires, I have connected with old unit ST699 and both heating and water works. Below is the wiring diagram with numbers corresponds to where they will go in ST9400.

- There is a loop between 5 & 6 >> This need to be discarded ?
- From loop from "L" to 6 >> Should I use feed from L to connect to 3(in ST9400C) ?
- 8 >> What should I do with this ?

 

[CountryFan]

There is a loop between 5 & 6 >> This need to be discarded ?

Yes as the internal parts provide this

- From loop from "L" to 6 >> Should I use feed from L to connect to 3(in ST9400C) ?

No, not required

- 8 >> What should I do with this ?

If it's fed from L, it should be a link and disregarded

It's in the instructions that @gas112 provided. I have screenshot this and cropped to help minimise confusion and hopefully make it easier

 

[exfi01]

Yes as the internal parts provide this

No, not required

If it's fed from L, it should be a link and disregarded

It's in the instructions that @gas112 provided. I have screenshot this and cropped to help minimise confusion and hopefully make it easier

Very helpful, but then how should I feed (3 in ST9400), since in old setup (6 takes feed from Live).

 

[CountryFan]

Very helpful, but then how should I feed (3 in ST9400), since in old setup (6 takes feed from Live).

You don't, if you look at the diagram it shows it's made internally

 

[stem]

Very helpful, but then how should I feed (3 in ST9400), since in old setup (6 takes feed from Live).

Terminal 6 appears to have two wires in and if as you say one of them is linked to L, I believe you may have an old system with only the central heating being pumped and the hot water cylinder heated by natural gravity circulation, instead of the more usual system with motorised valve/s

Whilst you have given details of the controller, you haven't given details of the system to connected to it, the wiring can vary considerably according to the type of system you have connected to the other end of the wires.

Unfortunately, if my suspicions are correct the old and new controller aren't compatible as the 'COM' terminals are not available with the ST9400c, and you need to use them with the older type systems, because the central heating can't be on without the hot water being on at the same time. The 'COM' terminal allows the interlocking between the HW (boiler) and CH (pump) to ensure the HW is on whenever CH is required.

EDIT:
Having looked at the ST9400c instructions, if part gravity / part pumped is the type of system you have. It appears that it may be possible to configure the ST9400c as a Mini-Programmer to make it suitable by changing the Installer Parameters to select it. However, the wring will need to be changed so the function of each of the cables you have will need to be identified. Here's the comment from the ST9400c instructions:

"3. It is recommended that gravity circulation hot water systems are fitted with a suitable hot water control valve as shown in the Sundial C-Plan system. For systems installed without this valve, ST9400can be configured as a Mini-Programmer. This is done within the Installer Mode (see page 3 for details). Refer to Honeywell for details of suitable wiring schematics."

 

[exfi01]

Terminal 6 appears to have two wires in and if as you say one of them is linked to L, I believe you may have an old system with only the central heating being pumped and the hot water cylinder heated by natural gravity circulation, instead of the more usual system with motorised valve/s

Whilst you have given details of the controller, you haven't given details of the system to connected to it, the wiring can vary considerably according to the type of system you have connected to the other end of the wires.

Unfortunately, if my suspicions are correct the old and new controller aren't compatible as the 'COM' terminals are not accessible with the ST9400, and you need to use them with the older type systems, because the central heating can't be on without the hot water being on at the same time.

I have very old Potterton Kingfisher (Gravity), and you are right when CH is switched on is it also heats up the HW in cylinder. While going through the other threads found this (similar to mine). https://www.diynot.com/diy/threads/honeywell-st699-to-st9400c-wiring-issues.603919/

 

[stem]

Some controllers have a switch on the back to allow them to select between "fully pumped" and "gravity / part pumped". Where this is the case, the programmer makes sure that whenever the CH is on the HW is also on as well.

Other, usually older programmers don't have this facility and the changeover contact utilising the COM makes sure that when the HW is turned OFF by the programmer, but CH is required an alternative live when the HW is OFF is made available to keep the boiler going.

 

[stem]

I have very old Potterton Kingfisher (Gravity), and you are right when CH is switched on is it also heats up the HW in cylinder. While going through the other threads found this (similar to mine). https://www.diynot.com/diy/threads/honeywell-st699-to-st9400c-wiring-issues.603919/

Well found I'd completely forgotten about that thread. If I had remembered it would have saved me some typing

 

[exfi01]

Some controllers have a switch on the back to allow them to select between "fully pumped" and "gravity / part pumped". Where this is the case, the programmer makes sure that whenever the CH is on the HW is also on as well.

Other, usually older programmers don't have this facility and the changeover contact utilising the COM makes sure that when the HW is turned OFF by the programmer, but CH is required an alternative live when the HW is OFF is made available to keep the boiler going.

As you have mentioned , I can try changing setting in 'installer mode', but before that how will I feed port 3 in ST9400C and should I still discard port 8 in ST699

EDIT:
Having looked at the ST9400c instructions, if part gravity / part pumped is the type of system you have. It appears that it may be possible to configure the ST9400c as a Mini-Programmer to make it suitable by changing the Installer Parameters to select it. However, the wring will need to be changed so the function of each of the cables you have will need to be identified. Here's the comment from the ST9400c instructions:

"3. It is recommended that gravity circulation hot water systems are fitted with a suitable hot water control valve as shown in the Sundial C-Plan system. For systems installed without this valve, ST9400can be configured as a Mini-Programmer. This is done within the Installer Mode (see page 3 for details). Refer to Honeywell for details of suitable wiring schematics."

 

[stem]

There should be 3 cables entering the programmer, but you need to confirm where they go. I have come across all sorts of bizarre wiring arrangements in the past. I would expect to see.

1. Mains Supply
2. Cable to Boiler
3. Cable to Pump

Once you have identified the cables

1. The mains supply is quite obvious N & L
2. The Live in the cable to the boiler goes to HW On (3)
3. The Live in the cable to the pump goes to CH On (4)

The earths and neutrals of all the cables are connected together respectively. (earths omitted for clarity below )

Some boilers require a permanent live (shown by the dashed line) if yours needs it, it will be connected already and shown in the boilers installation instructions.

I suspect the pump cable will contain a live wire that originally went to ST699 'Heating On' (Terminal 3) and the cable to the boiler will have a live wire connected to 'HW Com' (Terminal 8.) But check to make sure.