Honeywell st9100s to 9400s

[Mick4441]

Hi
Is it possible to change my st9100s to the 9400s so I can operate hot water and heating?
As far as I can tell it's an s plan set up with x2 2port valves for the upstairs and downstairs heating and another on the hot water cylinder coil. We have solar water heating also but it looks like that uses the other coil in the cylinder and and is separate to the boiler side of things.
Currently the 9100s only operates the heating but it looks like all the components are there for water heating just not the control

 

[stem]

The ST9100s is a single channel programmer for control of the heating only, designed for use with Combi Boilers

The ST9400s a dual channel programmer for control of heating and hot water where the hot water is stored in a cylinder.

So here's the question. You say you have an 'S Plan' but you presently have a single channel programmer designed for a Combi, how do you presently control the 'on' and 'off' times for the hot water?

 

[Mick4441]

Facility isn't there from the programmer it's supposed to be done with the solar (but it isn't good enough) so at the minute over ride the cylinder 2port valve and run central heating which in turn heats the water but obviously this then bypasses the stat so not ideal. Think I need to bell the wiring out to the 10 way junction box from behind the programmer

 

[stem]

It is normal for the solar controls to operate the entire hot water system, so that the use of solar is maximised, and the boiler is not used unless necessary to top up a shortfall. When you said that the solar was separate to the boiler side of things, I thought it was unusual that they would have separate independent controls.

If the solar system currently controls the motorised valve between the boiler and the cylinder, then it is the solar control system that needs rectifying. Exchanging your current single channel programmer for a dual channel programmer won't help, because the wiring for the hot water control should still go to the solar control system, and if you modified the wiring you would find that the boiler heated the cylinder first thing every morning and then the heat produced by the solar couldn't be used and would be wasted.

I have no experience of working on a solar installation, but on a base level, is the motorised valve between the the boiler and the cylinder coil working? If it remains permanently shut you will only be getting solar heating which I imagine doesn't amount to much at the moment.

 

[Mick4441]

As far as I can see the solar has a separate control incorporated in the heat exchanger/pump unit next to the cylinder and pipes in to the primary coil on the storage tank having a separate stat. The boiler heated side of things is all Honeywell wired through the 10 way junction box I'll get my head in the wiring diagrams when I get a minute see if I can figure it out.