What's Yellow?

[PlumbersMate]

unfortunately going on courses will still not teach you much about a situation like this its a process of educated guess work to work out what goes where orange is the wire that fires boiler or boiler and pump so that leaves just 2 cables to sort out i used to sit down and write what was going where and mark each cable with tape to differentiate between them but now a picture or two on your phone does it take a look in the roomstat will often allow you to match it to one of the remaining cables by putting a meter across the wires you think and switching the stat on and of to confirm this is where the buzzer on the meter comes in handy
actually thats quite a good junction box as often there in a single box and covered in three rolls of insulation tape

By meter do you mean manometer as this is what I need just some basic training in at least. Think I will do the Baxi course as said above and also Honeywell

 

[Barry98]

Disconnect the lot do continuity tests and start again , I've wasted many a hour messing with a rats nest like that

 

[AlexGas]

By meter do you mean manometer...

a multimeter

 

[PlumbersMate]

Lol I meant a multi meter not a bloody u gauge lol

 

[Leo21]

As a rule of thumb, it's red to red and blue to bits.

 

[peteheat]

I have to agree colour doesn't mean much often times they only make sense to the person who installed them.

To get a basic idea of system wiring it may help to take a look at [DLMURL="http://www.ephcontrols.com/products/categories/5"]this page[/DLMURL], click on the package and you can download the wiring diagrams the difference is using a pdf you can increase the size and see where the links should go.

The best and probably only way to get familiar is buy a kit hopefully to install on a job or make a board using a light to see if you get it right, that is wired properly the light comes on (thinking it's a boiler).

Once you get the basics you will know what to look for next time.