Posted by: @stuartornum

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We do a lot of talking about this stuff in this industry, yet I do not see much empirical evidence... anywhere. I would love access to this!

Thats definitely true.  There is a good reason however, its very difficult to do meaningful experiments and/or draw sound conclusions from the experiments we can do because the outside conditions keep changing (if there is any doubt about this then I would observe that we cant even determine how much heat a house loses at a specific temperature with any certainty, a figure which is crucial to design.)  The effects we are looking for often affect energy consumption by 10% or less, whereas the scatter in consumption, even at supposedly constant OAT, well exceeds this because of effects like wind, solar gain, and the fact that houses take more than a day fully to respond to changed conditions.

Thus we are, to a large extent, reliant on the theory to point us in the right direction unless we are prepared to set up experiments over many weeks/months in order that we can compensate for the variations that we cant exclude.

Fortunately the theory is fairly robust, but there are always cases where 'engineering' reality intervenes, further complicated by the fact that the 'problem' isn't necessarily well defined because it involves our sensations of warmth, which are not well calibrated.

Posted by: @stuartornum

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 I would love access to this!

Wouldn't we all!.  

As I've stated before a good add on controller, working with IAT and adjusting flow temp, will cover nearly all the problems we have encountered.

Also getting better design / Installers going forward

Posted by: @uk_pete_2000

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As I've stated before a good add on controller, working with IAT and adjusting flow temp, will cover nearly all the problems we have encountered.

Also getting better design / Installers going forward

Agreed, but it needs to be specific to heat pumps and learning of course.  Homely goes half way to this (for the heat pumps it supports) but doesn't adjust the LSVs and thus balance the emitters.  To solve this we need a controller which does the equivalent of radiator balancing, as well as adjusting the flow temperature.  SOFAIK only Adia are covering this portion at present, but in a way which involves a lot of extra hardware. Unfortunately there isnt a standard interface protocol so at present any controller has to be specific in at least some respect to the heat pump make.   

I fear we may be a few years off getting the holy grail of an affordable add on control system system that automatically sets itself up without any manual intervention although Homely seems at least to do the flow temperature part, which is more than half the battle.

@jamespa 

I don't think any system, without lots of hardware will be able to balance emmitters. That will always be done by hand etc.

Yes Homely can do it, but it's flaw May be that it needs Internet connection. Which is good as you can now group a number of options togeather and start working things out, but means it might not work independently (not fully investigated its working)

I dont think there will ever be a standard for HP, they have been around for years and still nothing. Would be good if there was, but as with our current situation there will be plenty of HP not covered.

It might be better to have a good controller, with inbuilt thermostat, that just needs a connection to whatever HP you have (modbus, zigbee, etc etc).

This way it can be offered as a fully fledge controller, just like the current HP manufacturers offers different types of controllers.

@uk_pete_2000 any thoughts on the ideal halo air controller?

Posted by: @uk_pete_2000

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Yes Homely can do it, but it's flaw May be that it needs Internet connection. Which is good as you can now group a number of options togeather and start working things out, but means it might not work independently (not fully investigated its working)

Agree with the internet connection comment, although I think (but may be wrong) it relies on this only for the more advanced features like tariff optimisation, which is OK IMHO so long as the fallback behaviour is sensible

Posted by: @uk_pete_2000

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I dont think there will ever be a standard for HP, they have been around for years and still nothing. Would be good if there was, but as with our current situation there will be plenty of HP not covered.

It might be better to have a good controller, with inbuilt thermostat, that just needs a connection to whatever HP you have (modbus, zigbee, etc etc).

This way it can be offered as a fully fledge controller, just like the current HP manufacturers offers different types of controllers.

unfortunately I think you are right with the first comment, unless its mandated by law. 

I think the problem is not just at the physical layer.  Even HPs that use eg modbus have different registers etc. (I understand).  So just because you support modbus doesnt mean you support a specific HP that also has modbus.  Any controller is going to need to read and write flow temperature and outdoor temperature as a minimum, but also likely several other parameters.  Its also going to need to know when to 'back off' and let the HP do its job unless it includes all advanced features that some manufacturers build in, defrost, anti freezing etc.

Posted by: @uk_pete_2000

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I don't think any system, without lots of hardware will be able to balance emitters. That will always be done by hand etc.

 

Adia Thermal evidently think that a system with (essentially) an electrically driven TRV on each rad can do the job.  Is that lost of hardware?  Arguably yes but I cant see how it can ever be done without this as an absolute minimum (although maybe they could be fit, leave for a few weeks, remove, sort of rented).  They add a central controller and some hydronics.  The hydronics seems unnecessary in principle since its basically measuring flow and deltaT which heat pumps know.  The central controller is presumably necessary (a) to coordinate the flow setting valves and (b) deal with flow temp from the heat pump.

Posted by: @ajbevster

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@uk_pete_2000 any thoughts on the ideal halo air controller?

Nice looking controller, follows much the same as other ones. Would need to see some documentation about advanced mode, as ideal could be setting up to high in WC to stop complaints.

If its in relationship to comment about controllers, then yes this could be a good starting point as it has a zigbee connection to the HP.

How was the chat with Ideal ?

Posted by: @jamespa

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Its also going to need to know when to 'back off' and let the HP do its job unless it includes all advanced features that some manufacturers build in, defrost, anti freezing etc.

Agreed, but as we are looking at something that's set to run 24/7 then the other featured don't need to be changed / looked at. So if does decide to turn off HP then HP controls will take over antifreeze duties.

Posted by: @jamespa

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an electrically driven TRV on each rad can do the job.  Is that lost of hardware?  Arguably yes but I cant see how it can ever be done without this as an absolute minimum

Okay, those kind of controllers can be added, but you are now getting into the roll of Home Assistant (others are available) and taking the HP as the centre of the house building it outwards to control more and more of the heating and even expaned to monitor things like flow,  buffers, dhw etc. Just add sensors as required. But basic system will control HP with just connection and thermostate.

All can be done and once programmed into HA it can be locked down and left to run system.

A nice NUC box would work, then a nice looking remote thermostate.

User can then use mobile for interface and setting temp / schedule etc.

Posted by: @jamespa

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Posted by: @jamespa

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Its also going to need to know when to 'back off' and let the HP do its job unless it includes all advanced features that some manufacturers build in, defrost, anti freezing etc.

 

 

Agreed, but as we are looking at something that's set to run 24/7 then the other featured don't need to be changed / looked at. So if does decide to turn off HP then HP controls will take over antifreeze duties.

Thats fair.  Essentially all the controller needs to do is adjust target flow temperature (or possibly the WC curve so that the heat pump is left to adjust flow temperature to reasch the target in the most efficient way for that heat pump) 

Posted by: @uk_pete_2000

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Okay, those kind of controllers can be added, but you are now getting into the roll of Home Assistant (others are available) and taking the HP as the centre of the house building it outwards to control more and more of the heating and even expaned to monitor things like flow,  buffers, dhw etc. Just add sensors as required. But basic system will control HP with just connection and thermostate.

I wasnt thinking that the adjustment of individual flow rate to emitters would be dynamic, Im literally thinking it would perform the same function as an LSV.  Without this we dont have balanced radiators unless either the installer stays a long time and returns, or householder does the job, so we end up falling back to on/off pseudo balancing by TRVs.  Perhaps we should just restore the knob that, decades ago before TRVs, used to be on the top of every LSV.  Householder would then naturally do the adjustment themselves and, because they are lazy, once they find a happy medium will leave it there.  Actually the more I think about this the better the idea is!

Someone will of course then sell an automated knob interface.  

@uk_pete_2000 I am now totally confused how your minimum output 6kW heat pump is coping with <3kW load without serious cycling, but never mind.

Regarding defrost cycle, according to openenergymonitor.org a heat pump of your size uses about 1kWh of energy for defrost. They indicate that their data shows that most people don´t need a volumizer for defrost either. For a thermal store with 25kWh charge this is not significant unless you need 10 defrosts during your off-cycle.

Anyway, you could take another approach if your heat pump can manage all these situations somehow without too much cycling. Your heat pump needs minimum 16 l/min flow. Therefore you can add a 10-30 l/min flow meter in the main flow to emitters, set the pumps to constant pressure and then adjust all flow valves proportionally according to their relative outputs so that the cumulative flow is slightly more than 16 l/min. Then reposition the buffer tank where it needs to be. In the bin. Connect HP directly to emitters and let it loose. By my calculation you have around 300l water in your system so you should not need a volumizer. Just a stupid thought.

Regarding snake oil controls, I seem to be the only heretic here. I control my system exactly as I want with 8 thermostats. I can hear the guffaws already. Firstly, my heat load at 2C is ~4kW. I chose heat pump size based on 15C OAT, not -3C, to match the minimum output to house load at that temperature and then implement WC. I have a Samsung Gen 4 Split 4kw HP with a hydronic unit incorporating a UPM3 pump with integrated speed control. The HP is directly connected to the UFH without buffer or additional pumps and enough secondary loops are open to match the minimum 5 l/min flow. The main loops I want to control (lounge, kitchen, bedroom, etc) have thermostats. The HP runs out of puff at 2C. For cold periods, I fire up the wood-burner in the 60m2 lounge and the thermostat kicks in so that the heat pump directs all heat to the rest of the house. We actually use it much more as it is enjoyable. Thermostat in the kitchen guards against overheating and I can adjust temperatures with the others, including programming heating off during peak periods. Large thermal mass is a bonus. There are some other refinements like volumizer in return leg which is rather debatable. So who needs fancy controls?

Posted by: @heatgeek

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So who needs fancy controls?

I think your argument is based on the relatively unusual case of a very low loss house with a large slab/UFH operating at a low flow temperature.  The vast majority of the UK housing stock is not very low loss and has radiators operating at 45C or more.  They are very different beasts as regards control and the effect of non-optimal settings.

That said, even in this case (and based on my personal experience as well as the extensive discussions here and elsewhere) almost nobody without a ToU tarrif needs anything at all beyond what comes natively with the heat pump and maybe a TRV or two for bedrooms and/or as a limiter for areas subject to large solar gain

However that presumes that installers set the heat pump up and balance radiators correctly, which they don't, at least in part because they cant in the time which they have available (or indeed at all if they install in the summer).

To me this is the central problem and if it could be solved most people would be happy with the way their installation works.  Thats where some control comes in.

Happy to debate this one as it seems to me that the practical question of how installers are going to set up a system in a small time at the end of a tiring week is crucial to the success of the mass roll out. 

My strong suspicion is that, in the absence of something more than we have today, installers will default to thermostats giving on off control, weather compensation set 5C or more above the optimum, and TRVs.  If the FT is only 30C the penalty wont be so great, but if its 45 or 50C then it will be significant.  

@heatgeek 

It's because of the buffer it can cope, as long as I don't run it too long. Then because I have a 2° difference across the top, extra temp builds up in the buffer, until it reaches the same as the flow temp and we cycle. Stopping the HP before 12hrs has run, stops cycling, hence we don't start the heating cycle (if required) till 04.00 hrs and run till 16.00hrs

The thermal store had two points, 1 was about having to increase the flow temp to bring the thermal store upto a decent temp ready to off load into the emmitters. My screen shot shows the defrosting which take place just by raising it 5° and its 4c OAT. Now that's not too much of a problem, I can just increase the time to 3hrs and see what temp the buffer gets too.

 The 2nd one is the stopper. As the HP will be off, while the buffer is dumped into the emmitters, it will start a antifreeze cycle and use the same water in the buffer to stop it freezing till turned back on. Once the temp is below 4c it runs all the time and i want it to run all the time.  So all the heat I put in will be wasted

which takes us back to the reason i started looking at the buffer and explaining different situations so people have options. I had already worked out that the HP and CH pumps are slightly mismatched and after taking some steps that mismatch is a lot lower.

You are forgetting one of the problems that I and other people have, the buffer is part of the  manufacture guarantee and rather than just say bin it, work with people to help sort it out. 

In our case the buffer helps us keep the system running the way it does. By providing the split between each system, and by working with it I can see how and where to make improvements and they all include using the buffer.

once again you miss the fact that if we run from HP with nothing and go direct, then yes it will work, our HP can push upto 50l/min, but it will cool the house down when it starts its antifreeze cycle and that runs for 12 hrs. So we would have to push the HP even