@cathoderay ok, just when I think I’m getting there…..

I want to have a bath and temperature of the water is at 36°

I thought the DHW would kick in if the temperature fell 5°? Or is it 15°? Feel like I’m losing it 🤯

Posted by: @cathyem1

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I thought the DHW would kick in if the temperature fell 5°? Or is it 15°?

It took me a while to get my head round how it works - at least, how I think it works.

The default drop in temperature from the set DHW temperature that triggers DHW heating is 5 degrees. If your set DHW is 45 degrees, then a reheat will be triggered when the tank actual temp drops to 40 degrees (or maybe 39 - ie setting the drop to 5 degrees actually means 'when the drop is more than 5 degrees' - I say this based on my own observations of when my system will trigger a reheat).

If you have DHW heating on a timer, as you do, then a reheat triggered by a 5 or more degree drop in actual DHW temperature will only happen when the DHW is timed to be on. For example, if the DHW is timed to come on between 1300 and 1400 (as mine is, as I don't have a time of use tariff), and I have a set DHE temp of 50 degrees, and a drop trigger of 10 degrees (as I do), then if the DHW is say 38 degrees at 1200 nothing will happen (DHW is OFF), however, come 1300 the DHW will come on, and the tank will reheat. If however the tank was at 42 degrees at 1300, a reheat won't happen, because the drop isn't large enough, even though the DHW heating is nominally ON.

Now occasionally I might need to manually trigger a reheat eg I want to have a bath, but the tank actual temp is too cool. Let's say I want a bath at 0900 and the tank is at 32 degrees. This I think is the situation you were in, DHW too cool and outside the timed DHW reheat period. To get the DHW heating to come on, you have to turn it on manually on the wired controller home page: Unlock > right arrow to DHW temp (which will change from showing the actual to the set temp) > toggle on (top right hand button) and then finally OK. The small right hand panel tap icon should get squiggles by it, and the 'compressor' icon should move to the right hand panel, and a tap should appear in the middle panel - all indications that DHW heating is ON, and you should see the actual DHW temp start to rise to your set temp. You can if you want turn it off (same steps as above, only this time toggle off rather than on) when it is warm enough, which I typically do when it has got to 45 degrees, which is warm enough for a bath; no need to get to 50 degrees. 

[This paragraph is of secondary importance, it covers a rare event, the preceding paragraph cover the much more common situation. Very occasionally, the above scenario happens, tank actual temp is a bit cool for a bath, but the actual DHW isn't cool enough to trigger a reheat. Let's say, on my settings (set DHW temp 50 degrees, drop trigger 10 degrees), the tank happens to be at 41 degrees and I want to have a bath. If I run a bath with it at 41 degrees, it will run cool before the bath has filled, so I need to get the water a little warmer, but the above manual routine won't work, because the DHW tank temperature drop isn't large enough. To get round that, I have to set the set DHW high enough (ie more than 10 degrees above the current actual temp - in this scenario I might set it to 55 degrees) to trigger a reheat, and then do the manual DHW turn as described in the preceding paragraph. Most importantly, if you do ever have to do this, watch the DHW temp as it rises, and turn the DHW heating off when it is warm enough, and reset the set DHW temp to your normal setting.]     

@cathoderay Of course! Thank you so much for your wisdom. I’m printing out your advice so i don’t forget. I have ADHD so a printed copy always helps.

While I’m here, do you have any issues with the clock on the wired controller? My clock keeps gaining time very quickly.

Posted by: @cathyem1

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While I’m here, do you have any issues with the clock on the wired controller? My clock keeps gaining time very quickly.

Not that I am aware of. Perhaps your wired controller is in a tardis? 

Seriously though, of course it shouldn't gain time. I can't think of anything in the controller that would alter time keeping, which is after all a very basic and at the same time fundamental activity. Maybe take some readings to show how fast it is gaining time and then ask your supplier about it?  

@cathoderay He’s going to love me 😉

I’ve just checked and it has gained 8 minutes since last night!

Posted by: @cathyem1

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He’s going to love me 😉

I’ve just checked and it has gained 8 minutes since last night!

I know, and these things are always awkward, but that doesn't mean you should have to put up with something that is clearly malfunctioning. If it can't keep time, what else is it getting wrong, either because the time keeping is out, or coincidentally?

Posted by: @cathyem1

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I’ve just checked and it has gained 8 minutes since last night!

Hmm. That could just be down to relativity.

What orbit are you in?

@transparent Oh! The Einstein effect!😉 Toodles

@cathyem1 Many digital time-clocks have two sources of data in order to retain some level of synchronisation during a power-cut.

They can pick up time from a master source, such as the internet, which uses Coordinated Universalised Time (UTC)
and there's also a date/time clock chip within them, powered by a lithium disulphide cell which has about 10-years life.

Whether or not your heat-pump system was ever intended to be synchronised to UTC,
the symptom you describe suggests that it's actually operating from an internal chip.

Posted by: @cathoderay

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If it can't keep time, what else is it getting wrong,

There's unlikely to be any other fault as a direct consequence.

The date/time clock chip uses a quartz crystal oscillator and is separate from the electronics which is running the programming software.

The software itself doesn't malfunction just because it's being fed an 'incorrect time'.
It has no frame of reference to 'know' what is correct.

Posted by: @transparent

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There's unlikely to be any other fault as a direct consequence.

I was aware at the time I was writing very concisely, perhaps too concisely.

What I was getting at was the possibility of:

(a) a direct consequence of the timer being out, eg something timed to happen at hh:mm will happen at hh:mm +/- the current error

and, quite separately

(b) if the timer is out of whack, might other things as yet unknown also be out of whack? Basically when one find error I can't help but wonder what other errors there might be.  

Posted by: @transparent

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The software itself doesn't malfunction just because it's being fed an 'incorrect time'.

Likely not, but it will give the wrong answer.  But it, and very likely we unless there is an obvious error, just don't know it is giving the wrong answer. It becomes GIGO. That's why it is so important to cross check independent sources of data whenever possible. 

@cathoderay The supplier has agreed our control panel is defective and has agreed to seek a replacement from Baxi. He’ll swap it when he comes to add the glycol etc to the solar thermal water heating and add some extra insulation to the pipes in the airing cupboard 🥰

Posted by: @cathyem1

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The supplier has agreed our control panel is defective and has agreed to seek a replacement from Baxi.

Sounds like good progress!