Replacing ST699 with ST9400C

[DP]

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

8 is taking 240 from L
When HW is on 6 runs the boiler and feeds live to 5 also. If CH slider on position then pump will run if HW time is calling
If HW is not calling, no CH either.

There is a better way to do this where ch operation starts the boiler and pump or hw only operates the boiler to heat hot water.
As said above, installing a 28mm MV improves the system

 

[exfi01]

del

 

[exfi01]

8 is taking 240 from L
When HW is on 6 runs the boiler and feeds live to 5 also. If CH slider on position then pump will run if HW time is calling
If HW is not calling, no CH either.

There is a better way to do this where ch operation starts the boiler and pump or hw only operates the boiler to heat hot water.
As said above, installing a 28mm MV improves the system

Hi DP, Is there a way where I can use ST9400C where I just need thermostat and Boiler & pump functionality as currently working OR even with limited capability. Also found diagram of my installation.Thx

 

[DP]

Hi DP, Is there a way where I can use ST9400C where I just need thermostat and Boiler & pump functionality as currently working OR even with limited capability. Thx

As far as I can comprehend, your programmer limitations is due to the fact that C terminal connections is internal. This setup is ideal for fully pumped. For gravity you need access to C terminal. St9100 gave you access to all the terminals but that programmer is now discontinued



Gravity hot water is also old hat and prone to boiler recycling ( wasteful) needlessly. As a stop gap fit a motorised valve and thermostat on the cylinder which will give you the facility you are after or ditch the ST9400 and get the set I mentioned earlier

I suspect using a 3 pole relay and ST9400 might give you what you need. Will need to look at that option.

 

[exfi01]

As far as I can comprehend, your programmer limitations is due to the fact that C terminal connections is internal. This setup is ideal for fully pumped. For gravity you need access to C terminal. St9100 gave you access to all the terminals but that programmer is now discontinued



Gravity hot water is also old hat and prone to boiler recycling ( wasteful) needlessly. As a stop gap fit a motorised valve and thermostat on the cylinder which will give you the facility you are after or ditch the ST9400 and get the set I mentioned earlier

I suspect using a 3 pole relay and ST9400 might give you what you need. Will need to look at that option.

Hi DP/ @stem ,
I can do the basic plumbing & electrics but not expert enough to install motorised valve.
Please see the link below where someone is able to successfully able to configure with my setup (except Thermostat) with Mini Programmer settings.
The only thing which I need is

In ST699
7 (Yellow from Thermostat + Pump Live) - do I need to connect to Terminal 4 (in ST9400C) ?
Red wire from Thermostat (currently in 3- Where it will go ?

For the time being I don't mind if CH on then HW also on as system is working for many years (agree it's a waste of energy, which I need to probably fix later )

S

Thread 'Honeywell ST699 to ST9400C Wiring Issues'

15 Jan 2023

Afternoon all, I'm hoping someone can help here as we are now without heating!

Bit of background - I had a ST699 programmer controlling our heating and hot water. It has worked flawlessly for 20 odd years, but last year, it started playing up. First thing that happened was that we couldn't have the heating and water on at the same time. Then, just before Xmas, it started to switch off (the display disappeared) and either the heating or hot water just went off. If I switched off the power and then switched it back on again, it would fire back up. It's hit and miss as to how often this...

• SPayne
• Replies: 23
• Forum: Plumbing and Central Heating

 

[DP]

Hi DP/ @stem ,
I can do the basic plumbing & electrics but not expert enough to install motorised valve.
Please see the link below where someone is able to successfully able to configure with my setup (except Thermostat) with Mini Programmer settings.
The only thing which I need is

In ST699
7 (Yellow from Thermostat + Pump Live) - do I need to connect to Terminal 4 (in ST9400C) ?
Red wire from Thermostat (currently in 3- Where it will go ?

For the time being I don't mind if CH on then HW also on as system is working for many years (agree it's a waste of energy, which I need to probably fix later )

S

Thread 'Honeywell ST699 to ST9400C Wiring Issues'

15 Jan 2023

Afternoon all, I'm hoping someone can help here as we are now without heating!

Bit of background - I had a ST699 programmer controlling our heating and hot water. It has worked flawlessly for 20 odd years, but last year, it started playing up. First thing that happened was that we couldn't have the heating and water on at the same time. Then, just before Xmas, it started to switch off (the display disappeared) and either the heating or hot water just went off. If I switched off the power and then switched it back on again, it would fire back up. It's hit and miss as to how often this...

• SPayne
• Replies: 23
• Forum: Plumbing and Central Heating

In that case HW NO to boiler and CH NO to pump

Switch hw zone will fire the boiler to heat water
To get heating hw will need to be on also

 

[exfi01]

In that case HW NO to boiler and CH NO to pump

Switch hw zone will fire the boiler to heat water
To get heating hw will need to be on also

Thanks , Is below correct and how do I feed 1- Live input to Thermostat

 

[exfi01]

Update - I was able to configure ST9400C as a Mini-Programmer by just connecting L, N, Pump(L) - 4 , Boiler (L) - 3 and removing all thermostat cables although not ideal but at least CH & HW working as before.
Thank you very much @CountryFan @DP @stem for all your help.

 

[ericmark]

I am really not sure what is going on, there seems to be old and new all mixed up together.

Gravity boiler

I also have a DHW system which uses gravity or therm-syphon, and to install Nest Gen 3 I found com goes to boiler not N/O as with most systems. It seems at first glance that the contacts are wired the wrong way around.

But only way I sorted it was to draw it all out, so I could follow the wiring, and it seems some bits have been removed from this thread, the diagram to use Nest Gen 3 with gravity is not included in the book. But it has the same contacts as you show, so maybe this will help?

Many seem to call things gravity, when to my mind they are not, so being careful as may be not singing from same song sheet, what I have shown is called C Plan.

 

[exfi01]

Hi @ericmark , in my old setup, I had a Kingfisher Potterton boiler, a Honeywell T6360 thermostat, a Honeywell ST699 programmer, and a Grundfos TPE UPS pump.

When the ST699 stopped working, I replaced it with a Honeywell ST9400C (configured as a mini programmer). However, I couldn't get the T6360 thermostat connected to the new setup, possibly because it's not compatible. As a result, I'm currently running the system without a thermostat.

 

[DP]

I am really not sure what is going on, there seems to be old and new all mixed up together.

I also have a DHW system which uses gravity or therm-syphon, and to install Nest Gen 3 I found com goes to boiler not N/O as with most systems. It seems at first glance that the contacts are wired the wrong way around.

But only way I sorted it was to draw it all out, so I could follow the wiring, and it seems some bits have been removed from this thread, the diagram to use Nest Gen 3 with gravity is not included in the book. But it has the same contacts as you show, so maybe this will help?
View attachment 424372
Many seem to call things gravity, when to my mind they are not, so being careful as may be not singing from same song sheet, what I have shown is called C Plan.

OP has Honeywell programmer that does not have access to C contacts.
Had already suggested change room stat to programmable roomstat will allow gravity HW with chosen Honeywell programmer or to install a motorised valve with 6 wires ( 28 mm MV allows that or Honeywell head, or a relay)

 

[DP]

Hi @ericmark , in my old setup, I had a Kingfisher Potterton boiler, a Honeywell T6360 thermostat, a Honeywell ST699 programmer, and a Grundfos TPE UPS pump.

When the ST699 stopped working, I replaced it with a Honeywell ST9400C (configured as a mini programmer). However, I couldn't get the T6360 thermostat connected to the new setup, possibly because it's not compatible. As a result, I'm currently running the system without a thermostat.

Connect the red rhermostat wire to CH no where you have got the pump wired to and yellow to pump.
You will only get central heating when hot water is on

Replace your Honeywell roomstat ( EPH Controls 1-Channel Wired Battery-Operated Programmable Room Thermostat) will move this task forward and tick all the boxes. EPH is just one example. Any thermostat that is battery operated and has access to three terminals will do the job. All that is required, even now, is three contacts ie C, NC, and NO. and system will work as before

Present thermostat already has blue, red and yellow wires that will allow suggested thermostat change to work