Replacing ST699 with ST9400C

[exfi01]

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."

Later I would configure ST9400C as Mini-Programmer

 

[stem]

Hi, Since Last time my existing ST699 worked after cleaning terminals, now it's not working. I have attached complete wiring diagram. Can someone please confirm if it's correct.

I' a bit puzzled by your post. If it's been working for the last year and it's just stopped, why will there be a wiring issue? Wires don't move themselves.

 

[exfi01]

I' a bit puzzled by your post. If it's been working for the last year and it's just stopped, why will there be a wiring issue? Wires don't move themselves.

I meant the old ST699, which had been working intermittently, but it has now stopped working completely. I am therefore planning to replace it with an ST9400C.

 

[CountryFan]

I' a bit puzzled by your post. If it's been working for the last year and it's just stopped, why will there be a wiring issue? Wires don't move themselves.

What I deduce is the St699 was left in fully working after cleaning the contacts. OP now wants to replace with the St9400c.

 

[CountryFan]

Hi, Since Last time my existing ST699 worked after cleaning terminals, now it's not working. I have attached complete wiring diagram. Can someone please confirm if it's correct.

Not the best diagram to follow

 

[exfi01]

Not the best diagram to follow

Please see updated diagram

 

[CountryFan]

Please see updated diagram

I don't know why 8 is boiler, when it should be Com. Have a look at this attachment

 

[exfi01]

I don't know why 8 is boiler, when it should be Com. Have a look at this attachment

 

[exfi01]

I have checked the wiring in Boiler and located back to the controller before marking in my previous post

 

[CountryFan]

I am not entirely sure then, because if you look at the wiring diagram on the ST699 8 clearly states Com and number 5 - which is linked to 6, which is NO for hot water. Unless 8 is a live from the boiler?

 

[exfi01]

I am not entirely sure then, because if you look at the wiring diagram on the ST699 8 clearly states Com and number 5 - which is linked to 6, which is NO for hot water. Unless 8 is a live from the boiler?

Yes, even that is puzzling me. rechecked the wiring in boiler

 

[CountryFan]

Yes, even that is puzzling me. rechecked the wiring in boiler

Yes, but at the boiler end, you have a LNE and brown (usually Live) going to that red (live) which goes to the St699. Maybe wire as per instructions, disconnect or place in a wago/terminal block and reconnect if not functioning properly?

 

[exfi01]

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 )

View attachment 397575

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.

Hi Stem, Going back to this thread, I have identified all the cables as below and just need to confirm 2 points
Is PUMMP(L) & Yellow from Thermostat go in 4 (ST9400C)
Existing 3 (Red from Thermostat) - where does it go in ST9400C

 

[exfi01]

Hi Stem, Going back to this thread, I have identified all the cables as below and just need to confirm 2 points
Is PUMMP(L) & Yellow from Thermostat go in 4 (ST9400C)
Existing 3 (Red from Thermostat) - where does it go in ST9400C
View attachment 423909
View attachment 423910

 

[DP]

You can have gravity HW by purchasing a single channel programmer ( it will have C, NO, NO) and replace the thermostat with programmable battery operated thermostat with three terminals.

With this set up timer will control HW and thermostat the heating. Have done this a few times.

Danfoss FP 715 allows gravity HW option

Alternatively install a 28mm motorised valve which will allow gravity circulation and temperature control of hot water

ST699 did not have Gravity hot water option but the C contact availability allow this to happen.