Adding - Smart Advanced Weather Compensation to Heat Pump that's already installed

[Brendan_w]

Hi Everyone,

 

Has anyone any experience of adding a smarter controller e.g. Homely or Rasberry PI to enable advanced weather compensation to a heat pump to an existing system with a linear Weather Compensation curve? Any advice would be much appreciated.

 

In particular I'm interested in how you handled controlling multi-zones?  Also has anyone had success writing updated output weather temperatures on the modbus of a Grant/Chofu heat pump? I see this website successfully reads data from the heat pump.  https://github.com/aerona-chofu-ashp/modbus/blob/main/input-register-readonly.tsv

 

Many thanks,

Brendan

 

[JohnMo]

Grant will now work with Homely, they also list smart control also, but sure if it's the same thing.

 

What do you mean by advanced WC?

 

UFH or radiators?

Edited January 7 by JohnMo

[Beelbeebub]

24 minutes ago, Brendan_w said:

Hi Everyone,

 

Has anyone any experience of adding a smarter controller e.g. Homely or Rasberry PI to enable advanced weather compensation to a heat pump to an existing system with a linear Weather Compensation curve? Any advice would be much appreciated.

 

In particular I'm interested in how you handled controlling multi-zones?  Also has anyone had success writing updated output weather temperatures on the modbus of a Grant/Chofu heat pump? I see this website successfully reads data from the heat pump.  https://github.com/aerona-chofu-ashp/modbus/blob/main/input-register-readonly.tsv

 

Many thanks,

Brendan

 

Apparently you can write values to the Grant heatpump  Via modbus.

 

See https://github.com/aerona-chofu-ashp/modbus

 

So theoretically you could use a Raspberry pi or Arduino to calculate the optimum flow temp at any given moment using whatever scheme you want and command the HP to use that set point. 

Edited January 7 by Beelbeebub

[ReedRichards]

I'm afraid I have no idea how you would do this but if your heat pump already offers you a linear weather compensation curve then you will never be that far wrong.  So I wonder if the cost of "improving" the weather compensation would justify the benefit?  

[JohnMo]

7 hours ago, Brendan_w said:

enable advanced weather compensation

Does your heat pump accept a 0-10v input. An aircon type thermostat can output a 0-10v output, this up to reduce flow temp as required. May not work with UFH due to reaction time, but ok for radiators.

 

This is a screenshot from my manual for a different heat pump

 

[HughF]

Good luck getting a heat pump to respond to changes to flow temp that quickly - you’d want to integrate the changes over a time period otherwise it will be hunting all over the place. The compressor response curves/finer points of the PID  might not be adjustable in the Chofu. 

[JohnMo]

Double post 

Edited January 7 by JohnMo

[JohnMo]

3 minutes ago, HughF said:

Good luck getting a heat pump to respond to changes to flow temp that quickly

Those at the bottom are graphs referring to operation of circulation pump on-off cycles

 

Just section 6.2 applied, not section 7.

[HughF]

Just now, JohnMo said:

Those at the bottom are graphs referring to operation of circulation pump on-off cycles

 

Just section 6.2 applied, not section 7.

Sorry, my post was targeted to the OP.

[Dan F]

9 hours ago, JohnMo said:

What do you mean by advanced WC?

 

WC that considers more than just outide temperature to determine flow temperature. e.g.

- Temperature in coming days and not just current temperature.

- Amount of sun and impled solar gain.

 

At least this is what homely guy talked about in the discussion with heatgeek. 

[ReedRichards]

I think Heat Geek have a lot to answer for in raising aspirations that can be very difficult to achieve.  But if you are trying to anticipate the weather (and solar gain) tomorrow or the day after then surely you can do that manually once a day.  My heat pump lets you shift the weather compensation curve up and down by 1 degree increments up to 5 degrees either way and I think this is quite a common heat pump feature.  Surely that is as good as any automated system could achieve, particularly where I live where the weather forecasts are unreliable. 

[Dan F]

1 minute ago, ReedRichards said:

I think Heat Geek have a lot to answer for in raising aspirations that can be very difficult to achieve.  But if you are trying to anticipate the weather (and solar gain) tomorrow or the day after then surely you can do that manually once a day.  My heat pump lets you shift the weather compensation curve up and down by 1 degree increments up to 5 degrees either way and I think this is quite a common heat pump feature.  Surely that is as good as any automated system could achieve, particularly where I live where the weather forecasts are unreliable. 

 

Not HeatGeek raising aspiration, this was an interview with founder of Homely explaining how the product come about.  See: https://www.youtube.com/watch?v=RjOCzbvSaws

 

Yes, you can do your own DIY "advanced WC", but a product that has come out of research and have already worked out how to tweak things (based on forcast, sun etc.) and tested this is going to do a better job for the majority of people.  The big caveat is that Homely only works with a subset of heat pumps.

 

[joth]

11 hours ago, Dan F said:

 

WC that considers more than just outide temperature to determine flow temperature. e.g.

- Temperature in coming days and not just current temperature.

- Amount of sun and impled solar gain.

 

At least this is what homely guy talked about in the discussion with heatgeek. 

These tweaks, especially future weather, really only work in highly insulated buildings. Typical UK homes lose heat so fast that trying to do anything in advance to get ahead of a cold snap the next day is pissing in the wind.  So it's interesting Homely are focusing on marginal gains for already low energy users. 

In my mind chasing and nailing time of use shifting would be really powerful and only really possible automated. At the very least to avoid heating during short price surges. Only running heating during a short cheap rate window (E7 et al) is again marketing to the rare well built lower bill households.

 

[ReedRichards]

10 hours ago, Dan F said:

Yes, you can do your own DIY "advanced WC", but a product that has come out of research and have already worked out how to tweak things (based on forcast, sun etc.) and tested this is going to do a better job for the majority of people. 

 

I find it very hard to believe that any piece of AI situated in my house can get better information on the weather than I can.  Yesterday as I was going out my phone was telling me that there would be rain in 10 minutes.  We went for a short walk, had a coffee, went for another walk and watched the sunset and it started to rain as we were driving home at least 2 hours later; and the rain was actually a short shower.  I think the smartest thing a Homely (or similar) could do in my house would be to see how often the house got a bit too cold or a bit too hot because it got the weather predictions wrong and decide to give up trying.

[JohnMo]

24 minutes ago, ReedRichards said:

 

I find it very hard to believe that any piece of AI situated in my house can get better information on the weather than I can

 

I have just looked at 2 weather apps for my house location. One says it's currently -4 and fog, the other -2 and sun. Both have it part correct. Actually -4 and bright blue sky and sun.

 

Yesterday similar experience, said sleet between 08:00 and 10:00, it was sunny. Then 0% of rain for the rest of the day, but it rained all afternoon and evening.

[joth]

10 hours ago, Dan F said:

 

Not HeatGeek raising aspiration, this was an interview with founder of Homely explaining how the product come about.  See: https://www.youtube.com/watch?v=RjOCzbvSaws

..

 

 

Got to bless YouTube, trying to watch this, it thrust an ad for this snakeoil at me https://evoheat.co/

 

 

2 hours ago, ReedRichards said:

I find it very hard to believe that any piece of AI situated in my house can get better information on the weather than I can. 

Don't make perfect the enemy of good enough.

 

The point is not to have perfect weather forecasting, as that doesn't exist. The point is to actually have it do it. Someone might go in tweak +1 your WC one day, forget to put it back the next, or totally fail to do it the week after. For me, I get annoyed switching my ASHP between cooling and heating, a twice per year job. Fiddling with it every day is never going to happen even if I'm there - and obviously not on days I'm not there.

 

[Dan F]

3 hours ago, joth said:

These tweaks, especially future weather, really only work in highly insulated buildings. Typical UK homes lose heat so fast that trying to do anything in advance to get ahead of a cold snap the next day is pissing in the wind.  So it's interesting Homely are focusing on marginal gains for already low energy users. 

In my mind chasing and nailing time of use shifting would be really powerful and only really possible automated. At the very least to avoid heating during short price surges. Only running heating during a short cheap rate window (E7 et al) is again marketing to the rare well built lower bill households.

 

 

Agree that fair amount what Homely does has less value is a poorly insulated house.  I guess they are assuming that their target market will gradually grow though.  Homely does use TOU rates and try to optimize to use these, don't know the details though.

[Brendan_w]

Thanks everyone for their contributions.  I have a well insulated house and also a varying tariff. Even gauranteeing that I could move my Domestic Hot Water to off-peak; high external temperature times could offer significant savings.

 

I agree with folks that using a Homely would be ideal as this is well established. Has anyone installed a Homely to a Chofu heat pump? Alternatively if anyone has tried this and a Homely is not viable; I'd be quite happy to try and go the modbus route.

 

 

[JohnMo]

42 minutes ago, Brendan_w said:

high external temperature times could offer significant savings

Does the Chofu unit have a double set point? Could you just enable that via a smart relay?

 

Homely doesn't want you having multi zones. It basically a WC system, with some "smart" features.

 

You cannot install Homely without being an approved installer. It is approved to be installed on the Grant unit, so assume it just connects to the modbus.

[Beelbeebub]

1 hour ago, JohnMo said:

Does the Chofu unit have a double set point? Could you just enable that via a smart relay?

 

Homely doesn't want you having multi zones. It basically a WC system, with some "smart" features.

 

You cannot install Homely without being an approved installer. It is approved to be installed on the Grant unit, so assume it just connects to the modbus.

I think there are two zone set points in the chofu manual and a configuration where you can switch between them via relay.

[JoeBano]

1 hour ago, JohnMo said:

Does the Chofu unit have a double set point? Could you just enable that via a smart relay?

 

Homely doesn't want you having multi zones. It basically a WC system, with some "smart" features.

 

You cannot install Homely without being an approved installer. It is approved to be installed on the Grant unit, so assume it just connects to the modbus.

Yes it does just a volt free terminal 

just been trying to find a switch that works with the IFTTT automation app that links to octopus agile. 
it’s just fitted a heatmiser heat and cool thermostat that does the switching for me. 

[SteamyTea]

@TerryE designed his heating system to incorporate the following days weather.

Maybe he will join us here and explain what he has actually done.  I understand it (as he is using a resistance heating system) that he calculates the expected energy for the next day, from the MET Office forecast, then adjusts the time he heats up his slab.  After some time, his program looks back at the past data and adjusts for fine tuning.

 

With an ASHP based system it is really a matter of juggling the main variables of optimal CoP and run time.  Run time is pretty easy, but optimal CoP is the hard one.  If the RH does up, that can cause the defrost cycle to kick in, possibly taking energy back out the system.

The probability of frosting should be able to be calculated statistical, as could the SCoP.  That may be worth looking at first to see if there are any meaningful gains to be had.

A while back @Ed Davies and myself looked into the probability of one sunny day following another, we got negative results, which is a result in itself (I can't remember the P Value now).  I do seem to remember that the best fit to sunshine was wind direction, but we have so little northerly winds (where I am) that it was statistically insignificant.

 

Apart from the technical challenge, which is fun, more energy could be saved by driving a very economical car.

[Gary68]

I trialed Homely a couple of years ago when they were trying to get going, then it was working with the Octopus Agile tariff but simply increased heating during lower price periods.  It did use weather forecast and learnt how fast your house heated up but it didn't work well in my average 2006 built house, with different temp requirements upstairs and down.  I only tried it as they were giving it away and there was no subscription fees.  Now its expensive and there is an additional subscription for the 'smart' features

 

I think its improved since I was using it, as its now adjusting WC but its really a system for people who have no interest in tweaking their WC, fit it and it will work out of the box at a cost, with limitations others have said as really needs a well insulated house that is all one zone.

 

I see a better application for it as an installer tool.  You leave it running for a few months over autumn/winter, it determines your WC curve, your installer comes back programs it for you and removes the device.

[TerryE]

4 hours ago, SteamyTea said:

@TerryE designed his heating system to incorporate the following days weather.

I have a passive class house which make things a lot simpler.  Once a day my CH system calculates the heating required using a couple of 1st order linear functions: one heat required as a function of forecast external temp, and a feedback adjustment on the delta between the average internal temperature over the last 24 hrs and a target set point.  This comes up with a total amount of heating energy required.  This if the external temp is below a threshold, this is split 80:20 between the slab UFH and an oil-filled rad on the 1st floor landing.  Because I use Octopus Agile, it then allocates the heating to the cheapest half-hour slots, so if I need 6 hrs of slab heating, say, then the scheduling will pick the cheapest 12 half-hour slots.  These are usually (but not always) sometime between 11PM and 6AM  UTC.

 

This is all easy because my heaters have a known heat O/P and my house has such a high thermal mass that it only makes a tiny difference to the heat ripple throughout the day.  Doing this would be a lot harder when using an ASHP where the actual heat output is hard to predict or measure and also in a more traditional house where the heating time constant is measured hours rather than days.

[sharpener]

On 09/01/2024 at 10:39, Gary68 said:

You leave it running for a few months over autumn/winter, it determines your WC curve, your installer comes back programs it for you and removes the device.

 

That's the ideal from the customer PoV but why would the installer bother? It's more hassle and if he leaves it installed I imagine he will get an ongoing commission from the renewal subscription fees to Homely, that's how these things often work.