Central Heating cannot be turned off! Potterton EP2002 timer

[rjsdavis]

Hi to all

I've got a problem that I think I've diagnosed, but not 100% sure.

At the moment, our hot water / central heating systems cannot be turned off! They continue to operate at the hours set by the Potterton EP2002 timer controller that is in the airing cupboard with the hot water tank.

I'm assuming that the fault lies with this Potterton control unit, as usually, when it gets warmer in the Summer, we simply turn off the C/H channel completely as it's just not needed, and then bring back in the Winter when it's colder etc. However, no matter what position the lower slider is on (either Off / Timer or Cont), the heating simply comes on at the programmed times no matter what!

My expectation is to simply get a new EP2002 control unit, unplug the old one, put the new identical unit in it's place, and expect it to work properly - but I just wanted a quick sanity check in case I should be fixing / checking something else?

Also - we've got an old Switchmaster wired thermostat in the hall, which controls the central heating temperature of the whole house - I've been toying with the idea of updating this, and wanted a slightly cooler digital display in it's place.

I'm considering replacing it with a Siemens RDH10 (non RF) unit, and simply unwiring the old Switchmaster and wiring in the new Simens unit. Is swapping over these thermostat units as easy as I'm envisaging it to be? Any help / guidance would be very much appreciated!!

 

[45yearsagasman]

What makes you so sure that the programmer is at fault?
By not describing all your system controls, it gives us little chance of giving accurate advice. I refer to boiler, motorised valves stats etc.

 

[rjsdavis]

What makes you so sure that the programmer is at fault?

...because the Central Heating and Hot Water tanks come ON (irrespective of whether the main control slider is set to either OFF / TIMER / CONT) ONLY at the programmed times that are set in the DAY/CLOCK settings on the programmer! (My gut is that the slider controls on the EP2002 unit are the specific fault...)

Is my logic faulty?

What I mean by this, is that the central heating is set to come ON on a standard weekday at 1830 and go off at 2330 - this continues to happen, even when the programmer Central Heating slider on the EP2002 unit is set to OFF. As far as I' concerned, this shouldn't happen - when the central heating slider is set to OFF, the central heating should not come on at all - ever.

I couldn't really see how any other part of the system could make this happen, and effectively trigger an over-ride - but am happy to be wrong. What other parts of the system should I describe?

I'm no expert by any means, but basically we've got:

1 - Airing Cupboard containing hot water cylinder and Potterton EP2002 programmer
2 - Switchmaster mechanical thermostat in the hall (wired)
3 - Boiler in the garage

Any input - much appreciated.

 

[45yearsagasman]

View media item 44939 View media item 38425 Got any thing like these, and maybe a thermostat on the side of the cylinder?

 

[matt1e]

Is my logic faulty?

What I mean by this, is that the central heating is set to come ON on a standard weekday at 1830 and go off at 2330 - this continues to happen, even when the programmer Central Heating slider on the EP2002 unit is set to OFF

No, not at all mate, if the above is true then yes it is the programmer at fault

Matt

 

[rjsdavis]

Thanks Gasman

Yes, there is a device that looks like this just beside the hot water cylinder - it's pretty awkwardly fitted, so cannot see the top - can only view the writing on one end of it:

V4073A1038
230-240v-50mhz
6W .04A Motor Load
1.0 (1.0)A Switch Load
T50 Brass Ts88
Made in Canada
For Head Replacement
USE 40003916-003

Don't know what it is / does though. Seemed pretty warm to the touch though when I just looked at it. Not burning hot - just very warm....

 

[rjsdavis]

No, not at all mate, if the above is true then yes it is the programmer at fault

Matt

Thanks Matt - like the reassurance. Am looking for one on Ebay right now....

 

[45yearsagasman]

Am looking for one on Ebay right now....

Good luck with that. The ep2002 is obsolete,I think, but there are some for sale on ebay.

 

[rjsdavis]

Am looking for one on Ebay right now....

Good luck with that. The ep2002 is obsolete,I think, but there are some for sale on ebay.

Thanks Gasman - there are loads on Ebay, both new and used right now... Think it would be easier to get the exact same model and pull the old one off, and pop the new one straight on with (hopefully) the minimum of fuss - reprogram the new one - and fingers crossed that the job's a goodun!

Agree with the logic that it's likely to be the Potterton programmer causing the problem?

 

[mysteryman]

It is the most likely cause, but it COULD be a sticking diverter valve.

 

[gas112]

If its only coming on at the times you have set and not at any othertime then it certainly sounds like the timer but by turning room stat down that should stop heating coming on in this weather.
If its coming on at other times its probably faulty motorised valves


As for new roomstat use the honeywell dt90 its a better stat than the siemens

 

[rjsdavis]

If its only coming on at the times you have set and not at any othertime then it certainly sounds like the timer but by turning room stat down that should stop heating coming on in this weather.
If its coming on at other times its probably faulty motorised valves


As for new roomstat use the honeywell dt90 its a better stat than the siemens

Hi Gas

Thanks - but am now confused, as the heating IS only coming on at the times that are set on the Potterton programmer, BUT turning down the only thermostat that is in the house (in the hall), makes no difference at all - it still comes on regardless.

Does this suggest something other than the Potterton programmer being at fault?

 

[rjsdavis]

It is the most likely cause, but it COULD be a sticking diverter valve.

Thanks mysteryman - how do I tell if it is the the/a diverter valve, and either eliminate it as a cause or isolate it?

I'm not a particularly knowledgable central heating person - so where / what is it?!

 

[45yearsagasman]

You read the numbers from it and posted them above, and you still want to know where and what it is?

 

[Felix247]

If you are going to replace the Potterton EP2002 controller and you haven't yet done so, my advice would be to replace it with the EP6002. The back plate is the same on both so its a simple swap if the old one isn't faulty. I speak from experience.

The EP6002 provides three timed periods per day and allows the CH to be switched on/off separate to the hot water.

Having said all that, if you are going to replace the old stat with a modern, programmeable one, then you will probably leave the CH set to be on all the time on the controller (with the stat now controlling the on/off times). If that is the case the EP6002 doesn't really offer any benefits over the EP2002.