Do you have any other sensors connected to the heating system, or is it only the two Sensocomfort units?   

many thanks,

Drew

@drew-pa Just the two sensoComfort units (main controller in downstairs zone, remote unit in upstairs zone), plus the external sensor for weather compensation.

Same control setup as us now then. Are both of the sensors connected to the system okay?  I can’t remember off hand if you can make changes on both of the sensocomfort units, or only the master.  Does this make a difference?  

many thanks

Drew

@drew-pa Yes, they seem to be. The downstairs master unit can make any changes (including the installer settings). The upstairs remote unit can only do the basic settings/scheduling for the upstairs zone. Whichever unit is used, the changes appear to sync fine across both units and app, with no difference to the results. So at the surface level, everything looks great. And at the base level, the HP control unit/HP/plumbing appears to implement what it is told to. But there's something in the mid-level (if there is one) or comms which seems to be where the issue lies. If there's a way to force a firmware refresh (ideally without resorting to the full system factory reset that loses all the config settings) that might be the obvious next step...?

In case it is helpful for this conversation, here is a summary that I've tried to submit to Vaillant via their app feedback form (which they have previously responded to quickly) - though in classic sensoAPP style, I have no idea whether it has sent or not...

====================

1. Installer has checked over the system and agrees it is not system design, capacity or heat curve issue. There is plenty of capacity in the system, it just isn't following the chosen setback temps/times overnight.
2. Installer then performed a full factory reset. Initially we tried leaving it on manual, which worked okay for one night (8th-9th Nov). I then set the setback settings as described above, and it has reverted to the behaviour described above.
3. Setback is set to Normal mode in both zones.
4. Other settings work fine, including DHW boosts, and even setting different time periods.
5. The wall units and sensoAPP are all (after several minutes to sync) in agreement with each other. Since the factory reset I have made changes only by via the wall system control unit (as my installer suggested avoiding the app to knock out one potential source of conflict), but same result.
6. Was up at 3am with one of the kids, was colder (~17°C) than setback settings. Set quick-veto to start warming back up. Didn't do anything. From consumption charts, appeared to start warming at 6am (not the set 5am). Throughout, the wall units were reporting appropriate target temps for my schedule, the target flow temps looked plausible, as did the valve settings. But HP wasn't operating.

@drew-pa

On a side note: do you know what the button on the radio receiver box (with the "two rotating arrows" symbol) does? I can find no mention of this in the documentation I have.

This evening I am allowing myself a smug/wry smile, as after 3 weeks, 2 installer visits and various attempts to describe the problem to Valiant, I believe I've managed to get to the bottom of the issue!

Given the limited info accessible via the control panel/app, I'm rather proud of this piece of reverse engineering:

1. I noticed now and then that the circulation pump in the garage was running at times when I expected everything to be off. From tracing the pipework and system schematics, this is the heating circulation. Initially shrugged this off as just something it did.

2. I also noticed that the DHW scheduler has a separate circulation pump schedule. I didn’t think the DHW had a separate circulation pump, so that was intriguing. Even more intriguing, the default schedule looks like this (in other words, a suspicious match for our problem time-windows):

3. Tested it yesterday evening, and sure enough, editing the DHW circulation pump schedule causes the heating circulation pump to come on/off.  A look at the schematics and a quick peek inside the controller junction box appears to confirm this.

Pretty sure that explains all of the weird symptoms. At night the circulation pump is switching off, leaving the heat pump to top up the buffer tank only (rather than the house) when the return flow temp dropped. So the controller reported everything was okay, as the house cooled off every night.

TBF, the schematics are very ambiguous, with several components having different names on different sheets. If it was me doing the wiring, I’d have been perfectly comfortable connecting the secondary circulation pump to the output labelled “sec. circ.”. But no, where’s the fun in that?

Slightly sheepish-sounding installer coming tomorrow to rewire it.  In the meantime, setting the circulation pump schedule to just run 24/7 will give us back that missing control overnight.

Well done,

sounds like a productive bit of fault tracing.  We had two pumps internal to the house, one for circulation and the other for UFH circulation.   After discussion with the OG installer these have bothe been taken out now, only the pump internal to the machine is left.  System is working an absolute treat now.  

well done.

Drew

Well, it seems to be fixed. The controls are making proper sense for the first time. Maybe now I can have another go at those heat curve and setback experiments...

(Interestingly, the installer's schematics are somewhat different from the ones I downloaded from here (p9-11 for our system). Same drg.no, but his was older with no rev. no. Mine was Rev C and had lots of subtle differences. His seemed more accurate and made more sense. It seems Vaillant may have some document control issues...)