S-plan with intellistat?

[Flambo]

Have a Baxi 133HE combi boiler with an intellistat.

Currently in the process of installing some underfloor heating which requires I install an s-plan configuration.

The problem is that I will not be able to use the intellistat as per the s-plan diagram below and was wondering if I could perhaps use the live pump feed from the boiler to power the Zone valve? Unless anyone has any better ideas?

S-plan - follow the link to see the diagram

http://digital-magic.tv/digitalplanet/resources/38_motorised-zone-valve.pdf

Baxi wiring - follow the link and go to 9.1 Electrical Wiring Diagram

http://www.partsarena.co.uk/baxi/System/DATA/Dx/DS1/installation/2671/I44-2671/I44-2671.htm

 

[D_Hailsham]

Have a Baxi 133HE combi boiler with an intellistat.

Currently in the process of installing some underfloor heating which requires I install an s-plan configuration.

Do you want to have separate time/temperature controls for the UFH zone and the rad heated zone?

 

[Flambo]

Yes. I have a polypipe underfloor heating system and thats how they have told me to configure it.

Thanks.

 

[D_Hailsham]

Yes. I have a polypipe underfloor heating system and thats how they have told me to configure it.

Just to make sure I have got you requirements 100% right!

1. A new programmer and zone valve for the new UFH
2. Existing Intellistat and new zone valve for the old radiator circuit.

The only problem I can see is that the new programmer and the Intellistat will "fight" for control of the boiler. There are ways round it, but it would mean ditching the Intellistat and having controllers which work together to control separate zones, e.g Honeywell CM921 or CM927. You would need to go wireless.

It might be worthwhile talking to Baxi.

 

[Flambo]

That is correct and thanks for the information.

Just spoke to Baxi and they have told me to ditch the Intellistat - which is a little annoying as it cost around £80 at the time - and to simply install a two channel programmer like the EP2002 with two separate thermostats.

I did ask what the purpose of the Intellistat is, and if I understood him correctly it regulates the heating instead of running the boiler flat out, which to me sounds like something I would rather be doing but seems have no choice to.

 

[D_Hailsham]

Baxi ... have told me to ditch the Intellistat ...and ... install a two channel programmer like the EP2002 with two separate thermostats.

Agree with the ditching of Intellistat, but not about replacing it with an EP2002.

the purpose of the Intellistat is ... it regulates the heating instead of running the boiler flat out, which to me sounds like something I would rather be doing but seems have no choice to.

Oh yes! you do have a choice.

The Honeywell CM921 and CM927 Wireless Programmable Thermostats can do what the Intellistat does and do it better. They can also be connected to control up to 4 zones and you only need two.

Honeywell CM921/7 Spec Sheet

I suggest you get in touch with Honeywell's Technical Help Desk (08457 678999) and tell them what you want to do.

 

[baxpoti]

Thermostats can do what the Intellistat does and do it better.

They most certainly cannot!

 

[D_Hailsham]

Thermostats can do what the Intellistat does and do it better.

They most certainly cannot!

So how is the Intellistat better?

 

[baxpoti]

The main advantage of the intellistat is that it lowers the flow temp whilst still maintaining the desired room temp!

It is also acccurate to ±0.25°C.

 

[D_Hailsham]

The main advantage of the intellistat is that it lowers the flow temp whilst still maintaining the desired room temp!

So it must modulate the boiler directly. Didn't know that, thought it was a straightforward PI controller which turned the 240v on and off.

It is also accurate to ±0.25°C.

Impressive, but how many people will register such a small change? The temperature the other side of the room could be varying more than that.

I still think a pair of CM921 or CM927, set up in zone mode, would give the OP what he wanted, even if if does not have the modulation capabilities or temperature control of the Intellistat.