Heating Controls for multiple source system (Oil Boiler, Back Boilers and Solar Thermal)

[JohnDean]

I've recently moved into a old property that has two sources for heating and three for hot water. The previous owner had a terrible system set up with two separate honeywell controls (timers) - one just to switch the oil fired boiler on and off, the other seemingly just operating the valves and pump(s). There's an additional proprietary controller for the solar thermal and I'm not 100% certain what that is doing other than controlling the pump for that closed circuit.

This system is a nightmare, the Worcester Bosch boiler randomly comes on even when there is no call for either heating or hot water and needs to be manually overridden. Only one of the two controls has battery backup and in the event of a power cut they end up out of sync. For whatever reason it also seems to want to fire the boiler even when the back boilers (wood fired stoves) are in operation.

I've fitted heating controls before in my previous houses, and thought I had a pretty good understanding of the architecture but these were much simpler single boiler systems. Can anyone recommend any heating controls that can manage multi-source systems such as this efficiently? I'm not really sure what I'm looking for and while I've found systems such as the Vaillant sensoComfort, it repeatedly mentions working with Vaillant Solar Thermal, Vaillant Boilers etc giving the impression it may _only_ work with their own products.

I may still ultimately get a pro in to connect it up, but I really want to know what I'm getting and not end up with a plumber recommending something that's simply unsuitable.

 

[Swwils]

Probably worth doing a paper based exercise to ensure you aren't falling into a sunken cost fallacy.

 

[JohnDean]

In so far as simplifying the system to use just one source? Maybe I'm just lacking imagination but given the astronomical costs of fuel right now, I can't see how giving up alternative solutions or having them re-installed will work out cheaper than just installing an appropriate programmer/control (<£200 + labour)? Best I can tell everything is plumbed in logically it's just the strange combination of multiple controllers that needs sorting as they currently seem to working independently*

*Another option would be to just re-wire this existing combo 'correctly', but that still leaves the power cut issues and an untidy collection of devices on the wall.

 

[Exedon]

Without knowing how your system is configured re how boilers are interconnected its difficult to advise.
Pictures of existing pipework pumps cylinder would be useful. Also a sketch of pipework runs.
Your first priority is safety the wood fired stoves are a uncontrolled heat source need to have been installed correctly.
Assuming the solar thermal has been correctly installed its controller should look after that.

 

[oldbutnotdead]

It's very likely there won't be an off the shelf solution to your controller problem.

As someone above mentioned, the wet solar should look after itself- it's controllers will presumably monitor panel and tank temperature and only pump when panel temp is above tank temp.

The back boiler should have minimal control gear (a loading valve if you are lucky) but must not rely on a pump to dissapate heat from back boiler to cylinder. Some loading valves have pumps built in but they run a bypass so gravity circulation still works.

You may want to install one or more extra thermostats- for instance a flue stat on the back boiler- to inhibit the oil boiler if the flue is above 150 Deg C.

Again as suggested, a sketch schematic of what you've got will make it much easier to suggest useful options.