CH always on: Potterton EP2002

[AmateurImran]

Hi Guys,

I was wondering if anyone could help with an issue regarding my CH and HW system (Potterton EP2002). Unfortunately I have no knowledge in this area and am looking for advise.

NORMAL OPERATION:
Prior to the issue, we used have the Potterton system setup as:
* CH on timer
* HW always on
* CH Thermostat (Honeywell) adjusted as necessary

MALFUNCTION:
During the winter months I noticed that the CH (alongside the HW) stayed on all the time even though nothing was changed. This left me no option but to switch the system off (using the fused ON/OFF switch) and switch it back on as and when necessary. Also I noticed that adjustment of the thermostat ceased to function and the heating temperature, when on, is always on full (judging by the temperature on the radiators) even though it may be set to the lowest.

I didn't want to tamper with the system during the winter so I used to wake up at 04:00 to switch the system on ready for the morning showers etc! It also meant that we came home to a cold house until we switched the system on! The same issue in the summer means that I have no option but to have the heating on (without thermostat functionality) just to heat the water - still waking up at 04:00!

INVESTIGATION STEPS TAKEN:
Having read some relevant forums, I have not come across anyone who has had this same issue, so have tried the following as per some suggestions:
* Reset the system by holding down + and - buttons
* Removed the control panel and reset the battery connections on the back of the panel (but this just reset the clock display)

QUESTIONS:
* Is the EP2002 faulty or thermostat; or both?
* Should I replace the EP2002 and if so which model will be compatible with the existing back wiring plate?

I would really appreciate any answers to my questions or any further advise offered to resolve the issue.

Many Thanks,
Imran
PS: I think a picture of my system can be accessed here:

 

[Boilerman2]

Has this problem started suddenly, or was something else done to the system to cause this problem? It sounds like either the programmer has been set to "Gravity" setting - (assuming you don't have a gravity system) instead of "Pumped" setting - (assuming you have a fully pumped system) if this is not the case I suspect that the 2 opert Heating valve - or 3 port mid- position valve (as applicable) is letting by around the heating circuit..more info on your heating layout would be helpful

 

[twgas]

Did you remove the programmer when you started decorating?

 

[Whitespirit66]

Hold your horses!

Is this an oldish system, where you can have H water on its own, but if you want CH, the H water also has to be on? Also, the room stat now has no control over the rad temperatures?

This may well be a motorised valve problem, and nothing to do with the programmer.

What motorised valve(s) have you got? If it is the old system you have, then you may just have a single 2 port valve, controlling the heating only.

Poss the valve is stuck open. If this is possible, I can tell you how to diagnose it.

Now, lets have a nice snap of your valve(s)