I bought a Heat Pump

Cardew

Reed_Richards said:

For me, and perhaps for anyone else considering an ASHP, the moral of this technical discussion with @shinytop is that ASHP heating controls are not very sophisticated.  In particular they tend to lack a feature called 'Load Compensation' so they don't know how hard they should work to maintain a constant room temperature.  Because of this they don't modulate to achieve the output flow temperature necessary to maintain the room temperature.  I live with this, whilst @shinytop works around it by just using Weather Compensation to maintain a constant room temperature (24/7) without using a room thermostat. 

By contrast, gas boilers generally can do Load Compensation (with the right controller) in fact I bought one in 1998 that had this feature.       

Agreed.

One of the points made in the conclusions of both Energy Saving Trust trials of a large number of heat pump installations was that the operating instructions were 'above the pay grade' of the majority of users of the  system.

This is illustrated by the above interesting discussions between two posters with a keen technical interest unsure of the most economical settings for their respective systems. What chance for Mr and Mrs Average brought up on on automatic CH systems?

Reed_Richards

Cardew said:

This is illustrated by the above interesting discussions between two posters with a keen technical interest unsure of the most economical settings for their respective systems. What chance for Mr and Mrs Average brought up on on automatic CH systems?

There's no problem at all for Mr & Mrs Average.  I use my heat pump exactly in the same way that I used the oil boiler that preceded it; Mr & Mrs average should do just the same. 

If you have a smart controller, tell it that it is controlling a Heat Pump, or an Oil Boiler if Heat Pump is not an option.  That prevents the controller from trying to run very short on/off cycles which neither a Heat Pump nor an Oil Boiler would like.  The fact that I don't have Load Compensation probably means that I don't get the best possible economy of operation.  But that's probably also true of very many gas boilers where the option is not there or there but not supported by the controller.  And (domestic) oil boilers don't modulate so they are only ever full-on or off.     

Magnitio

There are some smart thermostats that take into account the weather and the electricity rate if you are on a variable tarrif to ensure the most efficient and/or cheapest way of heating your home. One example is https://www.homelyenergy.com/

QrizB

Reed_Richards said:

... ASHP heating controls are not very sophisticated.  In particular they tend to lack a feature called 'Load Compensation' so they don't know how hard they should work to maintain a constant room temperature.

That's a bit of a surprise, since (if I'm understanding this correctly) it's the simplest sort of compensation to apply and could be entirely internal to the boiler. It needs a couple of flow temp sensors plus a tiny bit of logic. I suspect I could build my own from scratch for £20 or so, subject to the ASHP or boiler having some sort of external input that lets it modulate the power (which it clearly can do if it has weather comp).

Reed_Richards

QrizB said:

Reed_Richards said:

... ASHP heating controls are not very sophisticated.  In particular they tend to lack a feature called 'Load Compensation' so they don't know how hard they should work to maintain a constant room temperature.

That's a bit of a surprise, since (if I'm understanding this correctly) it's the simplest sort of compensation to apply and could be entirely internal to the boiler. 

That's not my understanding of Load Compensation.  The boiler needs to know how far the actual room temperature is from the set temperature.  So you need data transmission between the controller and the boiler, not just on/off switching.  For gas boilers there is a standard called Opentherm that does this and the controller I have is compatible with this - but not the heat pump.

Weather Compensation, on the other hand, is easy because the heat pump sits outside so does not need a remote thermostat to measure the outside temperature.  

Reed_Richards

Magnitio said:

There are some smart thermostats that take into account the weather and the electricity rate if you are on a variable tarrif to ensure the most efficient and/or cheapest way of heating your home. One example is https://www.homelyenergy.com/

What I need is something that can interface with the heat pump and control its output water flow temperature according to both the outside temperature and how far the set temperature in the room differs from the actual temperature.  Your only hope of getting that is to use the manufacturer's dedicated controller.  I've read that the Vaillant dedicated controller can do this but that's the only make I've heard of that can.  No third party controller will be able to do this until different manufacturers build their heat pumps to a common control standard.   

shinytop

Reed_Richards said:

Magnitio said:

There are some smart thermostats that take into account the weather and the electricity rate if you are on a variable tarrif to ensure the most efficient and/or cheapest way of heating your home. One example is https://www.homelyenergy.com/

What I need is something that can interface with the heat pump and control its output water flow temperature according to both the outside temperature and how far the set temperature in the room differs from the actual temperature.  Your only hope of getting that is to use the manufacturer's dedicated controller.  I've read that the Vaillant dedicated controller can do this but that's the only make I've heard of that can.  No third party controller will be able to do this until different manufacturers build their heat pumps to a common control standard.   

Mitsubishi Ecodan heat pumps can do this with the FTC5/6 controllers.  It's called auto adaptation.  It will work either (1) with the wired controller if it's in a suitable place to detect the room temperature (2) with a separate wired in thermistor to detect room temperature or (3) with Mitsubishis's own wireless controller.  It won't work with 3rd party thermostats which, no matter how 'smart' they are, are effectively just on/off switches to the ASHP.

shinytop

Reed_Richards said:

Cardew said:

This is illustrated by the above interesting discussions between two posters with a keen technical interest unsure of the most economical settings for their respective systems. What chance for Mr and Mrs Average brought up on on automatic CH systems?

There's no problem at all for Mr & Mrs Average.  I use my heat pump exactly in the same way that I used the oil boiler that preceded it; Mr & Mrs average should do just the same. 

If you have a smart controller, tell it that it is controlling a Heat Pump, or an Oil Boiler if Heat Pump is not an option.  That prevents the controller from trying to run very short on/off cycles which neither a Heat Pump nor an Oil Boiler would like.  The fact that I don't have Load Compensation probably means that I don't get the best possible economy of operation.  But that's probably also true of very many gas boilers where the option is not there or there but not supported by the controller.  And (domestic) oil boilers don't modulate so they are only ever full-on or off.     

I would disagree.  Using an ASHP like a boiler is unlikely to be the most efficient way of operating it.  

It's not just Mr and Mrs Average who don't know what they're doing.  It's Mr Plumber (yes I know it could be a Ms) who installs and sets up the ASHP too.  He might be a good plumber/gas fitter but he might not be a good heating engineer.  All the technology and knowledge exists now to make ASHPs work and is often just sat there being unused or not used properly.

My installer could have told me how to set up my ASHP the way I do now but they didn't. Why not? IMO partly lack of knowledge on their part and partly because it takes a little bit of extra time and effort. What they did was to set it up in a way that would be  OK for for most but optimal for nobody.  

You have to use an EV differently to an ICE vehicle and it's the same with ASHPs and boilers.         
 

Magnitio

Reed_Richards said:

Magnitio said:

There are some smart thermostats that take into account the weather and the electricity rate if you are on a variable tarrif to ensure the most efficient and/or cheapest way of heating your home. One example is https://www.homelyenergy.com/

What I need is something that can interface with the heat pump and control its output water flow temperature according to both the outside temperature and how far the set temperature in the room differs from the actual temperature.  Your only hope of getting that is to use the manufacturer's dedicated controller.  I've read that the Vaillant dedicated controller can do this but that's the only make I've heard of that can.  No third party controller will be able to do this until different manufacturers build their heat pumps to a common control standard.   

Homely is currently compatible with the following:

• Daikin
• Mitsubishi (with a FTC5 or a FTC6)
• Kensa
• Samsung
• Midea

You're right, manufacturers need to either provide common control standards and/or an easy interface for thermostat controllers to integrate with.

Cardew

Reed_Richards said:

Cardew said:

This is illustrated by the above interesting discussions between two posters with a keen technical interest unsure of the most economical settings for their respective systems. What chance for Mr and Mrs Average brought up on on automatic CH systems?

There's no problem at all for Mr & Mrs Average.  I use my heat pump exactly in the same way that I used the oil boiler that preceded it; Mr & Mrs average should do just the same. 

Really?Really? Then why all the discussion?

My post simply agreed with the EST conclusion that operating an ASHP in the most efficient manner was too complicated for ‘Mr and Mrs Average’. That conclusion was reinforced by the technical discussion between you and ‘shinytop’ where you(understandably) are still not certain of the optimum operating procedure for your respective installations.

From shinytop

It’s taken a lot of fiddling around with weather compensation curves and spreadsheets to get where I am.  I am running the system completely unlike I would a boiler.  I have my thermostats set to 30C and control the room temperature using flow temp/weather compensation only.  This keeps my house at 20-21C between (so far) -3C and 12C without any intervention.  The radiators are between 35C and 40C most of the time.  This won’t work for all houses or people but works for us.  It takes a big leap of faith to turn the thermostats up to the max and leave the heating on 24/7 but it works.  Having warm radiators instead of hot ones also takes a bit of getting used to.

From Reed_Richards

I use a nighttime set-back on my heating controller.  For the sake of simplicity we'll say it is 21 C from 07:00 to 22:30 then 18 C overnight.  If the outside temperature is near 0 C it takes about 6 hours for the temperature to cool from 21 to 18 so the heat pump is off all that time.  That leaves 2.5 hour for my controller to get the temperature back up to 21 C in time for 07:00.  It will do this automatically if I set "Comfort Mode".  But to do this it has to make the water in my radiators hotter than is necessary to maintain a constant 21 C which means it will be running less efficiently.

The truth is what I actually do is more complicated than my simple explanation.  I set back the room temperature by 3 C at 22:30 then up by 1 C in time for 07:00 and gradually up during the day until it arrives back at the base temperature (21 C) at 17:00. 

Which is better for fuel economy, @shinytop's strategy of maintaining a constant internal temperature or mine?  With a conventional boiler I should win but with a heat pump it's not so obvious. 

Doesn't the last sentence sum up the position?