Posted by: @jeegnesh

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Think I figured something out for once.  Adaptive heat curve was on, I believe this was adjusting my heat curve automagically, turned it off see if it behaves any better

Im not surprised, two differnt heat curves will likely confuse it.  I have only 1 and have turned off all autoadaption or room temp compensation and everything works much better.  I may reinstate once its basically set up but for now I want to get the basics right.

I am not sure this is an option for me at all, if my heat curve is low the downstairs will be fine but upstairs and kitchen will be cold, if I set it high then warm everywhere but the majority of the downstairs will be roasting plus I fear I will be running around 3.5kw per hour constantly.  This house does not seem to suit a single setting is my feel, could be wrong too.

Turning adaptive off has definitely left me in control of the curves now, so I keep the low and slow on as much as possible and the upstairs thermostat if it breaches just calls for a higher heat curve.  I guess its just eating more kw than I had hoped

Posted by: @jeegnesh

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This house does not seem to suit a single setting is my feel, could be wrong too.

You could be right.  What do you know of the design/history of the heating system (not the heat pump, the emitter system).  Its quite bizarre that the two zones have (apparently) been designed so differently, no boiler or heat pump that I know of can supply two temperatures simultaneously!  Was it originally designed so that the downstairs was 'mixed down' in temp and the whole system run to suit the upstairs?

Is it possible that something somewhere is restricting the flow of the upstairs/kitchen?  Are the LSVs on the rads open and the TRVs if any removed or set at max?

Also, since you are only running upstairs part time at the higher FT, what percentage of the time is this and is this being reduced by the upstairs thermostat - what happens if you turn the upstairs thermostat to max and run the upstairs at the upstairs FT 24*7.

Oh, one more question, are upstairs and downstairs on the same pump?

Its entirely possible that you would be better off running upstairs and downstairs simultaneously for a longer period.  This will allow you to reduce the upstairs FT and you can then wind back the temp downstairs by restricting the flow (or possibly arranging some mixing if there is a mixing valve.  This may (but may not) work out cheaper and will likely be more comfortable. 

Let me try answer what I know.

Yes it's the same pump, and original design and install had the whole system as 1 the only limit was on the control unit with a max flow of 45c -- with this design I was running into the issue of the downstairs getting too hot to get the upstairs to a comfort level and if I ran it with downstairs at a comfort level then the upstairs was too cold. The concept was to run pure weather comp and the one sensocomfort I had was just a controller.

I spoke to my installers, who then added a second sensocomfort and a bunch of other things (valves that can shutoff UFH and a second controller), so that I could control shutting off the downstairs from getting to warm, but I would need to run in extended mode and use the stats as top limiters.

You are right it cannot supply two temperatures simultaneously, it basically takes the call of the higher of the two, if the upstairs is calling for heat it will always use the higher curve, if both are calling it still uses higher curve, if upstairs calls only it uses the upstairs curve but closes the downstairs UFH, if downstairs only calls it uses lower curve but it also feeds this upstairs+kitchen which is fine as it does nothing much, perhaps with the heat going up and the tiny heat being emitted it almost maintains.

The LSV's were balanced and TRV's are all set to max except 1 which is second in line (should I max this one?)

If I turned the upstairs thermostat to max, then the whole system would run at the higher flow temp forever till house blew up or I had no money left, whichever comes first 🤣 

Upstairs I've basically just put a high setback of 19c in the coldest bedroom, so it comes on when it needs too which is actually not that much, usually in the night and perhaps once in the daytime for an hour or two and this is in the colder weather.  This was done to allow me to have a comfortable house temp and allow me to run a lower target temp most of the time.

The low target temp I am running not far off 24/7:-

3:30am to 10am
10am to 11am -- hot water boost after the morning showers
1:00pm to 9:30pm

Most of the time like 80/90% it will run on the low flow temp, do you suggest any changes to the running time?

Its a complex system, probably over complex to be sensible and certainly too complex to work out what might happen with any certainty if you change operating modes.

My gut feel however, is that you at least try going back to first principles and operating it as most people with mixed rads/UFH appear to operate.  If we consider the upstairs (the one with the radiators) on its own for a moment - if this were the whole house you would not be even thinking about operating it part time at a high flow temp and part time at a low flow temp, instead you would be operating it full time at the lowest temp possible.

So, as an experiment, thats where I would go.   This would start with operating the upstairs 24*7 with the external thermostat maxed, TRVs open and then turning the flow temperature down until the upstairs is only just warm enough.  That will determine the FT that the upstairs should be operated at, which will be a lot lower than the 'boost FT' you currently apply.  It may  take 24 hrs for it to settle down each time you change the FT so reckon on several days to get it correctly adjusted.  if you have any recording capability that would of course help, there is some crude capability in the MyVaillant app.

Once you have done that (or as you go along) you could either throttle the downstairs so it runs simultaneously and doesn't get too hot, or run it part time but at the temperature of the upstairs.  Just make sure that the second sensocomfort (why on earth....) isnt disturbing the settings.

If this were my house that is what I would do.  Obviously Id be wanting to collect OAT data at lease simultaneously so I have some chance of comparing the operating modes (given that the weather wont stay the same).

No guarantee that this will be better but I repeat that, if the upstairs were the whole house, you wouldn't be operating it in this split-temperature mode.

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PS - has the house been turned upside down relative to when the heating was designed.  One common arrangement in a very well insulated house is UFH downstairs where there are living rooms, and little or nothing upstairs where there are bedrooms.  This relies on heat rising and the fact that you typically want bedrooms colder than living rooms.  

The house has not been turned upside down, bedrooms are all upstairs.

So the way you would start and sorry to keep going on - would be that you set a static FT and just let the system run? Or you would pick a heat curve suited for upstairs as you are saying max out the stats would it not make more sense to just make them inactive (dumb)? I guess what I am not getting with my gas boiler mindset is how does it not get too hot if its constantly running?

By the way the so called boost for upstairs its not any kind of mega FT, its prob like 40c

I guess thats the other thing when that boost runs its consumes around 3.5kw, so in the always on mode am I talking close to 24 * 3.5kw = 84kw  (minus a couple of hours when hot water runs) as thats a pretty mega bill surely, or have I got something wrong here?

Posted by: @jeegnesh

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So the way you would start and sorry to keep going on - would be that you set a static FT and just let the system run? Or you would pick a heat curve suited for upstairs as you are saying max out the stats would it not make more sense to just make them inactive (dumb)? I guess what I am not getting with my gas boiler mindset is how does it not get too hot if its constantly running?

I was saying The latter not the former - pick a heat curve suited for upstairs, but see my final comment below before and please respond you do anything as it seems I may not fully understand your config.

Max out the stats or as you say make them dumb .... but maxing them out just involves turning a dial so thats what Id do first!

"I guess what I am not getting with my gas boiler mindset is how does it not get too hot if its constantly running? "- You adjust the WC curve down until that doesn't happen, then you leave it.  WC should hopefully more or less take care.  Some tweaking possible bus basically you run it on WC as low as it can go.

Posted by: @jeegnesh

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I guess thats the other thing when that boost runs its consumes around 3.5kw, so in the always on mode am I talking close to 24 * 3.5kw = 84kw  (minus a couple of hours when hot water runs) as thats a pretty mega bill surely, or have I got something wrong here?

It shouldn't consume 3.5kW because its constantly on, so the house will warm up and it wont need to dump so much energy in. 

The thing to remember is that you have to put in exactly the same amount of energy as the house loses, and the house doesn't stop losing energy because you have turned the heating off.  In fact it continues to lose almost exactly the same amount of energy, decreasing a bit as the house cools down.  What that means is that when you turn it back on it has to work much harder.   If it doesn't cool down much then the 'saving' in energy lost is small and can easily be outweighed by the greater efficiency in drip feeding energy in.  Slow and low drip feeds energy at the same rate as you are losing it. 

Posted by: @jeegnesh

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The house has not been turned upside down, bedrooms are all upstairs.

 

OK thats the surprise.  So I am getting that upstairs you have bedrooms plus kitchen, downstairs you have living rooms - is this correct.  If you run at the temps suited to downstairs is it only the kitchen thats too cold or are the bedrooms also too cold.  That may affect the best way to proceed.  Perhaps you could answer this and I might revise my suggestions.

You will love this, regards the house config, different improvements have happened at different times, hence the mix-mash, at one point we had 2 gas boilers, one combo and one system but we won't even go there.

Downstairs = Living Room, Dining Room, Study, Hallways and the Kitchen (all UFH, Kitchen is in screed rather a massive lump and very large space 9m x 5m with alot of glass too) rest of the downstairs is new Wunda insulation board with pipes and then the tiles (hence quick heat)

Upstairs = Bedrooms and Bathroom

The reason the Upstairs and the Kitchen got tied together as a potential circuit is because those are the places where the heating can be 2c lower (also the kitchen radiator is still in place too due to the heat demand needed)

@jeegnesh wow

. exactly which rooms are too cold if you run at the 'downstairs' flow temperature.

The Kitchen and pretty much all the rooms upstairs except my daughters bedroom for some reason maybe as hers is south facing.

@jeegnesh 

Thanks.  One last question then I'll do some back of the envelope calculations tomorrow.

Please confirm what times of day you are running at curve 0.3 and what times at curve 0.9 (is it timed or by thermostat).  If you can't give me times, roughly how many hours per day at 0.3 and how many hours per day at 0.9?

I’ll have to go with hours as the 0.9 is not timed but triggered by low temperature breach via thermostat. But I can estimate hours on each from the past cold spell. 

0.9 - 5 hours 

0.3 - 10

0.9 tends to kick in early am hours then afternoon and possibly late evening. For me it’s like a threshold for the upstairs not to go below