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