Strange new CH problem

[dpluxor]

Hi all, my old Drayton ACL lifestyle programmer starting playing up a bit, like bringing the HW on at 11pm when its not even set to do that in the timer. Decided to do a straight swap with a new Horstmann C27.

Now I have a baffling problem, HW and CH both set to come on at 4pm, HE set to go off at 6pm and CH at 10pm, my old programmer handled this no problem. The C27 does not seem to be working proplerly IMO. When 6pm comes, the HW light goes out, the pump stops, the boilers stops (if it was on) and the valve stays in its mid position, slowly the rads start cooling down of course. I havent left it any length of time to see if it suddenly strikes back up a few mins later, I switched it off at the wall and when I turned it back on, the CH light was on and the boiler/pump struck up straight away. All was fine until 10pm

I thought it might have been a one off but this is the 3rd day it has done this at 6pm everytime the HW time ends.

Could it be a dodgy programmer or was it really not a straight swap with the Drayton. Both showed the same wiring diagram (i.e. LN1234)

Thanks

David

 

[stem]

Whilst I don't know your specific programmer, it may be that the microswitch in the motorised valve that runs the pump and boiler when central heating is required may not be operating properly. (the hot water operates the boiler by the cylinder thermostat so wouldn't be affected)

Or it could be that the connection to the programmer for 'hot water off' is missing. The 'hot water' off connection keeps the boiler & pump going if required by the central heating when the hot water is switched off by the programmer. Although, I don't think the manual switching you describe would help in this instance, if I understand what you mean correctly.

If you need a wiring diagram search the internet or the forum under "Y plan wiring diagram"

I'm assuming that the room thermostat is calling for heat when the 6pm cooling occurs.