I turned the power off and when I turned it back on again, the clock of my Potterton EP3000 was reset, and now the heating comes on at the wrong time. I dont have a manual for it, so I was wondering if anyone could tell me how to change the time on the clock. I've searched the internet for hours and haven't found anything specific to the EP3000.
Having just asked my own question about an EP3000, I think I know the answer to this one. The current time (and all your programmed on/off times) are preserved during a power outage by a little rechargeable battery that's kept topped up by the mains. But like any rechargeable battery, it's got a finite life. Yours may have died some time ago - you just didn't notice until you switched the power off.
I didn't bother trying to prise the battery out of mine (which is also dead), but based on this discussion it's almost certainly a Varta 250DK. It's an oval about 30x40, 70mm long, containing 8 x 1.2 NiCad cells (9.6 volt total).
You need a bit of confidence (and brute force!) to prise the programmer off its back-plate which is screwed to the wall. It's "half-hinged" on the top, but there's a moulded "retaining latch" on the bottom right. Look from underneath and you'll see a 5mm "slot" about 5cm in from the bottom right. Push a screwdriver hard up there to free the latch, and simultaneously pull/prise the bottom edge of the programmer outward and upward.
I can't say exactly where you'll get a replacement (I doubt Varta still make them). The important thing is it should be an 8-cell 9.6v NiCad (don't use Li-ion or whatever). If you take the old one in to Maplin or similar they might be able to supply something compatible.
Other options are: Expensive - pay an electrician/gasman to come and deal with it; Cheap - just live with it and get used to reprogramming the thing whenever you've had a power cut or turned it off for some reason.
This may help. It's not your exact model, it's a 3002.