ASHP Modulation ratio

[SteamyTea]

7 minutes ago, JamesPa said:

Let's all hope our politicians have the staying power and conviction to lose votes by introducing unpopular policies

People vote on prejudice of the opposition, not on the lying, cheating, and now, porn watching, policies of the current government.

Or just give a compulsory 1 hour lecture, repeated everyday, on energy and climate change.

Just today I had to explain to a builder, yet again, that it does not matter if it is a fan heater or an oil filled heater, 1 kWh of electricity can only be converters to 1 kWh of thermal energy at best. Oil in the radiator does not cause magic to happen.

[ReedRichards]

12 hours ago, HughF said:

.... I'm impressed by the offering from LG to be honest - how do you find the controller? 

 

I find it rather primitive compared to a standard central heating controller.  For example there is no Holiday Mode so in order to turn off the hot water heating when away I had to remove all timed programming of the hot water.  Otherwise when I tried to turn it off it would only stay off for the duration of the current timed period.   

[HughF]

2 minutes ago, ReedRichards said:

 

I find it rather primitive compared to a standard central heating controller.  For example there is no Holiday Mode so in order to turn off the hot water heating when away I had to remove all timed programming of the hot water.  Otherwise when I tried to turn it off it would only stay off for the duration of the current timed period.   

Ok, that wouldn’t be an issue for me as the property is never unoccupied. How do you find the ease of use with the ai mode (weather comp)?

[JamesPa]

So given the challenges with the politics we probably do need ashps with a high turndown ratio so they can manage without a buffer tank, self learning controllers so that relatively untrained installers can fit and forget and the controller will sort itself out with sensible weather compensation etc. without the (untrained) customer having to intervene.  Plus a solution to the dhw problem which doesn't involve the major disruption of retro-fitting a uvc caused by the tundish/drain arrangement.  If these problems can be cracked an ashp becomes no more difficult to fit than a gas boiler at which point (if we can also get the price right) we don't need politicians to make unpopular decisions for change to happen.

 

The good news is that none of that seems technologically difficult, but the industry seems to innovate at a snails pace so sadly it could be a long time unless a disruptor emerges.

Edited April 29, 2022 by JamesPa

[ReedRichards]

11 hours ago, HughF said:

Ok, that wouldn’t be an issue for me as the property is never unoccupied. How do you find the ease of use with the ai mode (weather comp)?

 

The weather compensation is linear and the four parameters are set in the installer settings.  Thereafter you can vary the target leaving water temperature by + or - 5 C but I have never needed to do that.  The controller might also be capable of Load Compensation, but it's not a documented feature.

[HughF]

1 hour ago, ReedRichards said:

 

The weather compensation is linear and the four parameters are set in the installer settings.  Thereafter you can vary the target leaving water temperature by + or - 5 C but I have never needed to do that.  The controller might also be capable of Load Compensation, but it's not a documented feature.

It was my guess from reading the installation blurb that when you set the 'temperature sensor' setting to air+water then it uses the internal air temperature (measured by the controller) as part of the control strategy, implying load compensation. But it's hard to find any concrete data on that.

 

Interesting that you don't find the requirement to nudge the weather comp up or down. Do you have your curve matching the house losses and just leave the heating on 24/7/365, or do you use a timer + room stat.

 

I'm trying to figure out the best/most appropriate control strategy for an ashp retrofit on an property I'm renovating and I'm looking at the options available from various manufacturers. Some have a impressive controller (LG, samsung), others (cool energy for example) seem to just use a buffer sensor and a 'call for heat' input from a programmer, relying on any room stats (if fitted) to drive the zone valves and pumps downstream of the buffer. The weather comp just varies the buffer target temp, irrespective of any room stats calling for heat.

 

Not sure what's the best strategy to be honest and I'd welcome a discussion on that, I will probably start a separate thread.

[MikeSharp01]

On 26/04/2022 at 15:27, JamesPa said:

Yes its true that buffers are a kludge largely to make up for short fall in modulation albeit all they can do is extend the on/off times not change the on/off ratio.  But buffer tanks are lossy, take up lots of space and cost money thereby contributing to reasons not to have ASHP.  Most on here are probably in an 'early adopter' mindset, but if ASHP is to solve the massive retrofit problem we have then they need to be easy to use!  I am personally an early adopter but really don't want a buffer tank if I can possibly avoid it precisely for the reasons above and because it is a kludge.

man after my own heart Recently the more I fiddle with numbers around ASHPs (Despite an innovator / early adopter mindset) the closer I come to just following in the footsteps of @TerryE and using a Willis heater - the only thing it cannot do is cool on the few days a year our PHPP outcome says we might find cooling useful!

[MikeSharp01]

31 minutes ago, HughF said:

Not sure what's the best strategy to be honest and I'd welcome a discussion on that, I will probably start a separate thread.

This is another cruncher because the strategy is just one strategy when actually you probably need more than one - I guess that weather compensation was put in to allow a more flexible strategy but it seems a very crude scheme from those that I have looked at and the push up / down idea is something that needs also to be dynamic but relies on humans to adjust it. Its feels like we need some sort of heuristic system (not human) that learns from the responses to the various stimuli and so tunes the scheme to the users and the building.

[HughF]

47 minutes ago, MikeSharp01 said:

This is another cruncher because the strategy is just one strategy when actually you probably need more than one - I guess that weather compensation was put in to allow a more flexible strategy but it seems a very crude scheme from those that I have looked at and the push up / down idea is something that needs also to be dynamic but relies on humans to adjust it. Its feels like we need some sort of heuristic system (not human) that learns from the responses to the various stimuli and so tunes the scheme to the users and the building.

Rs485 based flow temp setting, from home assistant, based on time of day and who is home (with each family member preferring a certain house temperature)?

[ReedRichards]

7 hours ago, HughF said:

It was my guess from reading the installation blurb that when you set the 'temperature sensor' setting to air+water then it uses the internal air temperature (measured by the controller) as part of the control strategy, implying load compensation. But it's hard to find any concrete data on that.

 

Interesting that you don't find the requirement to nudge the weather comp up or down. Do you have your curve matching the house losses and just leave the heating on 24/7/365, or do you use a timer + room stat.

 

 

I looked at my MCS certificate and that specifies the outside temperature for the heat loss calculation so I used that outside temperature and the specified flow temperature as the lower limits of weather compensation.  Then I assumed the heat loss from my house depended linearly on the difference between my room temperature and the outside temperature and calculated the required radiator temperatures to match the heat loss, then made a linear approximation to that curve.  That  gave me the upper limits.  Written like this it sounds complicated but actually it's very easy.  Possibly this is still giving me warmer leaving water than I need - but I'll look at that next winter.

 

I have a room stat which I set back a few degrees at night then ramp up the set temperature as the day progresses.  My house actually has two zones which makes things more complicated.

 

My installer says "air + water" gives you load compensation but I haven't yet tried to verify this.  It's not documented, that  I can find.

[MikeSharp01]

16 hours ago, HughF said:

Rs485 based flow temp setting, from home assistant, based on time of day and who is home (with each family member preferring a certain house temperature)?

That is a start but maybe, like weather compensation, you need to get ahead of the activity and the people. So predicting who will be home and what sorts of things they will be upto so you can prepare the best case for the combination. Although that also implies that none of them will be happy if they all prefer it slightly different. 

[JamesPa]

"Rs485 based flow temp setting, from home assistant, based on time of day and who is home (with each family member preferring a certain house temperature)?"

 

HughF - have you actually implemented that or is it just an idea.   If somehow the controller (or aspects of the controller) and the hardware could be separated, then at least some of the limitations of current combinations could be overcome more elegantly (and more to the point more efficiently) than using other, totally disconnected, bolt-ons.