Cannot get boiler/timer/thermostat set up to only heat water

27 Apr 2013
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United Kingdom

I have a Vaillant Ecotec Plus 415 with a Potterton EP2002 timer. I cannot get the boiler to heat only the water for some reason. This is what i have tried so far:

1.I have tried putting the Water Slider to ON with Central Heating slider OFF on the Potterton timer, but i still get boiling radiators.
2.Putting Water ON and Central Heating OFF on the Potterton. I turned the Central Heating dial on the boiler itself down to zero, but the boiler doesnt fire up, thus no hot water.
3.Putting Water ON and Central Heating ON on the Potterton. Both Water and Central heating dials to max on the boiler but turning the thermostat down to zero on the wall. Radiators are boiling again

I cant figure out what i need to do? Can anyone help please
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If the system worked properly previously, I would think this is a motorised valve fault.

Unless you have Vaillant controls fitted, the hot water knob on the 415 does nothing. The heating knob controls the flow temperature for both hot water and heating.

Do you have two (or more) 2-port valves or one 3-port?
I moved into the house on november so havent needed to have the hot water running OK nits own without the radiators on.

Really sorry i really am a novice at boiler related mechanics. How do i check how many valves it is?
If you don't feel confident working on the system, I think it might be time to get someone in.

From what you said in your first post, it's clear that there is a fault. You seem to have a good handle on how to use the controls.

If you don't want or can't afford to get someone in I suggest starting in the Wiki, and plenty of googling, and maybe a book (or two) should tell you what you need to know, but you would need a basic knowledge of plumbing and electricals first. These things can be learnt but take some time to master.
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