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My heating has developed a new and unwelcome quirk just recently, which is that it's sporadically failing to provide hot water. This is something that happened a few weeks back, but it seemed to go back to normal, but in the past couple of days it has happened again each day. We have a conventional setup with the following components:

Boiler: Vaillant Ecotec Plus 815
Programmer: Potterton EP2002 (pre-dates boiler)
Room stat: Danfoss Randall TP7001 (programmable)
Cylinder stat: Honeywell L641A
Diverter: Drayton Mid-Position Actuator MA1

The programmer has CH set to 'On' so that the room stat can take care of timings. The HW is set to 'Timed' and is on for something like 40 or 50 minutes in the morning and again in the afternoon, which is normally enough for our needs.

We've now had a couple of mornings where no hot water was available, and this evening there was none left after washing up, which is not usual. The programmer has an 'Ext'(end) function which I set to +1 hour just to get some hot water available again, but nothing happened. Well, the HW light illuminated on the programmer, but there was no 'click' and the boiler didn't kick in. I tried unseating the cylinder stat and turning it right up, but that made no difference. The diverter was positioned at H because the heating had been on earlier. I wondered if it might be stuck, but if I cut the power, it goes back to W. On the programmer, I moved the HW slider between On, Once, Timed and Off, and this made no difference. However, when I moved the CH slider to Off and then back to On, the boiler kicked in to heat the water (no demand from room stat and diverter moved to W).

One other thing I noticed yesterday was that if I tried to get the CH and HW on simultaneously by turning up the room and cylinder stats, it seemed to satisfy or the other demand, but not both. E.g. if it was heating the water and I turned up the room stat, the latter showed a flame (heating demand) on the screen but nothing seemed to happen, and then it eventually seemed to give up (flame disappeared). I'm fairly sure the converse also applied - i.e. when CH was active, trying to get HW didn't work. I have yet to see the diverter at position M.

Does anyone have a feel for what the problem is here? The diverter valve seems able to switch position, but could it still be at fault, or is it more likely to be the programmer (which is a bit ancient after all, and the switches have felt a bit iffy for a while)?

Any help much appreciated, as waking up to no hot water in deepest February is not a fun game. :(
 

centralheatking

Esteemed
Plumber
My heating has developed a new and unwelcome quirk just recently, which is that it's sporadically failing to provide hot water. This is something that happened a few weeks back, but it seemed to go back to normal, but in the past couple of days it has happened again each day. We have a conventional setup with the following components:

Boiler: Vaillant Ecotec Plus 815
Programmer: Potterton EP2002 (pre-dates boiler)
Room stat: Danfoss Randall TP7001 (programmable)
Cylinder stat: Honeywell L641A
Diverter: Drayton Mid-Position Actuator MA1

The programmer has CH set to 'On' so that the room stat can take care of timings. The HW is set to 'Timed' and is on for something like 40 or 50 minutes in the morning and again in the afternoon, which is normally enough for our needs.

We've now had a couple of mornings where no hot water was available, and this evening there was none left after washing up, which is not usual. The programmer has an 'Ext'(end) function which I set to +1 hour just to get some hot water available again, but nothing happened. Well, the HW light illuminated on the programmer, but there was no 'click' and the boiler didn't kick in. I tried unseating the cylinder stat and turning it right up, but that made no difference. The diverter was positioned at H because the heating had been on earlier. I wondered if it might be stuck, but if I cut the power, it goes back to W. On the programmer, I moved the HW slider between On, Once, Timed and Off, and this made no difference. However, when I moved the CH slider to Off and then back to On, the boiler kicked in to heat the water (no demand from room stat and diverter moved to W).

One other thing I noticed yesterday was that if I tried to get the CH and HW on simultaneously by turning up the room and cylinder stats, it seemed to satisfy or the other demand, but not both. E.g. if it was heating the water and I turned up the room stat, the latter showed a flame (heating demand) on the screen but nothing seemed to happen, and then it eventually seemed to give up (flame disappeared). I'm fairly sure the converse also applied - i.e. when CH was active, trying to get HW didn't work. I have yet to see the diverter at position M.

Does anyone have a feel for what the problem is here? The diverter valve seems able to switch position, but could it still be at fault, or is it more likely to be the programmer (which is a bit ancient after all, and the switches have felt a bit iffy for a while)?

Any help much appreciated, as waking up to no hot water in deepest February is not a fun game. :(
The drayton might have a manual over ride lever have a play at least you might learn more Centralheatking
 
This requires a multimetre and someone who knows how to use one. I'd be starting at the programmer when calling for HW and go from there.
 
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Thanks both. Sounds like it might be time to call in the pros... just wanted to be sure I wasn't missing anything obvious that I might be able to check or fix myself.
 
Hmm, haven't been able to get someone in yet, but noticed things are a bit different today. Seems the HW failed to come on again this morning as we have only lukewarm water (presumably from yesterday), but today when I pressed the 'Ext' button to get an extra hour's HW heating, it clicked in fine even though the CH was also 'On' (but inactive) at the time. I wondered if this would prevent the CH demanding heat but as soon as I upped the room thermostat, the heating kicked in and the diverter moved to M. So the plot thickens... symptoms seem inconsistent/sporadic (worst kind of problem in a way!).
 
In case anyone's interested, I'm reasonably sure now that this is a programmer issue, and it seems quite consistent now:
  • HW is set to 'Timed' and comes on at 4pm
  • CH is set to 'On' as our programmable thermostat takes care of the schedule
  • At 4pm, the HW light on the programmer comes on, but nothing else happens
  • If I then go and move the CH slider (not HW!) from 'On' to 'Off', there is a click from the programmer, and the HW immediately kicks in at that point (even though the light was on already)
  • I can then slide the CH back to 'On', and the CH and HW work as required until the HW turns off at the set time
  • Basically everything then works fine until the next time the HW is due to come on, when the above cycle begins again.
So whilst I'm no expert by any means, this would seem to point to some kind of malfunction within the programmer which is preventing the HW from clicking in until the CH is 'reset' - I'm kind of intrigued as to what sort of fault (worn relay or something?) could have that effect.

Anyway, for now I'm handling this manually as I happen to be around most of the time to do it, but will want it fixing soon. I had been considering getting Hive installed anyway, so perhaps that would kill 2 birds. Otherwise I'd probably end up paying for someone to come and do some diagnosis and tell me my programmer is knackered, and then paying again for the darned thing to be replaced. Just wish I'd gone for the Hive on Black Friday when they were about £60 cheaper than they are now (but decided against the expense at the time... aah hindsight)!
 

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