System Puzzler

[satchmolips]

Been working on my folks heating system (sludged up radiator) but can't understand what's going on. 1990's professionally installed oil Worcester Boiler system with gravity header tank. Hostmann Tiara Controller. One single two way Honeywell diverter valve. No roomstat but stats TRV's on radiators. What puzzles me is that there is no stat anywhere on hot water tank or the lines and nothing obvious feeding back to the diverter valve? The Tiara controller has two sliders but you can operate Hot water only, or heating with hot water; not heating only. Big dial on front of boiler to turn hat up, but that will increase heat of hot water also?! So what is the diverter valve actually doing, any suggestions? And how simple would it be to convert this system to a Y plan so I could have sep heating and hot water............

Any explanations very welcome please

 

[tamz]

It would be straightforward enough to convert your system if the hw is pumped but if it is on gravity there will be a bit rejigging of pipes needed.
Gravity hw systems were still quite common in the 90's

 

[satchmolips]

It would be straightforward enough to convert your system if the hw is pumped but if it is on gravity there will be a bit rejigging of pipes needed.
Gravity hw systems were still quite common in the 90's

Sorry, should have said there is a pump one side of diverter, but a header tank feeds whole system by gravity

 

[tamz]

How many pipes come off the boiler

 

[satchmolips]

Two pipes