I bought a Heat Pump

Reed_Richards

shinytop said:

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

 

I don't disagree with that statement but it is perfectly feasible.  As things stand there tends to be a trade-off between efficiency and convenience.   Mr and Mrs Average can run their heat pump as if it was an (oil) boiler.  They won't get the maximum efficiency but lots of conventional boilers are run too hot to achieve their maximum efficiency. 

I like to sleep in a cool bedroom but my wife likes the bedroom door open so the only compromise is to allow the house to cool at night.  I hope that does not cost us too much.      

QrizB

Reed_Richards said:

I like to sleep in a cool bedroom but my wife likes the bedroom door open so the only compromise is to allow the house to cool at night.  I hope that does not cost us too much.      

However much it costs, it's still going to be cheaper than a divorce

Meatballs

Reed_Richards said:

shinytop said:

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

 

I don't disagree with that statement but it is perfectly feasible.  As things stand there tends to be a trade-off between efficiency and convenience.   Mr and Mrs Average can run their heat pump as if it was an (oil) boiler.  They won't get the maximum efficiency but lots of conventional boilers are run too hot to achieve their maximum efficiency. 

I like to sleep in a cool bedroom but my wife likes the bedroom door open so the only compromise is to allow the house to cool at night.  I hope that does not cost us too much.      

Lots of competing issues at bedtime for heating.

Keep windows shut/curtains shut for maximum heat loss prevention? Condensation on windows, potentially promoting a bit of mould growth.

Open curtains - less/no condensation, but still potentially spiking CO2 levels and high room humidity.

Crack window open a bit - more heat loss, lower CO2, lower humidity. 

Run a dehumidifier/PIV/MVHR? 



The only real thing I can say for sure is getting an air quality sensor gives you more things to worry about  

shinytop

Reed_Richards said:

shinytop said:

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

 

I don't disagree with that statement but it is perfectly feasible.  As things stand there tends to be a trade-off between efficiency and convenience.   Mr and Mrs Average can run their heat pump as if it was an (oil) boiler.  They won't get the maximum efficiency but lots of conventional boilers are run too hot to achieve their maximum efficiency. 

I like to sleep in a cool bedroom but my wife likes the bedroom door open so the only compromise is to allow the house to cool at night.  I hope that does not cost us too much.      

I agree. Ours worked quite well in boiler mode and if electricity had remained at 11p/kWh I might have just left it as it was!!

shinytop

Cardew said:

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?

There is plenty knowledge out there on how to set up ASHPs optimally but it hasn't trickled down to most suppliers and installers. Yes of course it's too complicated for Mr and Mrs Average to work out the optimal way of running their heat pump in their house and then make the adjustments.  But they don't need to; that should be the installer's job.  If it's set up properly and Mr and Mrs Average are given the right instructions then their ASHP should be no harder than their old boiler to operate and adjust.    

Most people don't know how to run their gas boiler in the most efficient way either anyway.  There are always debates on the best way to heat a house with a boiler on MSE.  The difference is that until recently it hasn't really mattered because the fuel was so cheap.  With an ASHP you have more expensive energy and a much bigger hit on efficiency if you get it wrong. 

shinytop

Magnitio said:

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.

@Magnitio

Do you know what 'compatible' means? My wireless thermostats are definitely compatible with my ASHP because they can switch the ASHP on and off in my two zones.  I can see how Homely can work out and store how long it takes to heat your house and how it can use external factors like ambient temperature, weather forecasts, room temperature and tariffs to work out the best time to run the heat pump.  But can it integrate with the ASHP's internal controls and change things like the flow temperature and/or compressor speed?  It would be great if it could do this.  Unless it can though, it's still going to be just a slightly cleverer on/off switch for the ASHP.  

EDIT - @Magnitio, this is a real question, I'm not having a go, although having re-read it looks like I am!

Reed_Richards

Cardew said:

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?

Because manifestly @shinytop and I are both techies and would like to try and squeeze the last drop of  efficiency out of our heat source.  Mr and Mrs Average don't need to do this any more than they need to do it with their gas boiler (which, given the rise in fuel prices is perhaps something they should pay more attention to). 

There's an interesting article on gas boiler efficiency here: https://theintergasshop.co.uk/content/187-why-your-new-gas-boiler-isnt-efficient

Magnitio

@Magnitio

Do you know what 'compatible' means? My wireless thermostats are definitely compatible with my ASHP because they can switch the ASHP on and off in my two zones.  I can see how Homely can work out and store how long it takes to heat your house and how it can use external factors like ambient temperature, weather forecasts, room temperature and tariffs to work out the best time to run the heat pump.  But can it integrate with the ASHP's internal controls and change things like the flow temperature and/or compressor speed?  It would be great if it could do this.  Unless it can though, it's still going to be just a slightly cleverer on/off switch for the ASHP.  

EDIT - @Magnitio, this is a real question, I'm not having a go, although having re-read it looks like I am!

@shinytop
I don't know. I've had a look at their website and a recent video interview with them, but it is difficult to tell how integrated it is. There are comments about increasing the output when electricity is at a cheaper rate, even if it means slightly lower efficiency. This suggests more integration than a simple on-off switching. I would also have expected them to list more heat-pumps than they do if it was a simple switching process. Worth contacting them if you want to know more.

Reed_Richards

I have been simultaneously massively impressed and a little horrified by @shinytop's method of controlling their heat pump using finely-tuned weather compensation and abandoning the use of a room thermostat.  This is not something that Mr and Mrs Average would either want or need to do ( @Cardew ) but it's probably the right way to eke out every last drop of efficiency that a heat pump can provide.

It has inspired me to be more ambitious with my weather compensation settings.  I now have

Outdoor temperature:           Min 1 max 19
Leaving Water Temperature: Max 50 Min 26

50 C is the maximum LWT specified on my MCS certificate and this target temperature will be used if the outside temperature is 1 C or lower.
If the outside temperature is 19 C or higher the target LWT would be 26 C.
Otherwise there is a linear relationship so if the outside temperature is 10 C (half way between 1 & 19) then the target LWT would be 38 C (half way between 50 & 26).   So far this has proven to be sufficient to keep the house warm with the outside temperature at 8 C or below.  It means that the target Leaving Water Temperature is lower than it used to be which, in principle, should give me greater efficiency.  It's hard to be sure if this is working because the outside temperature is never constant.  But the peak power per cycle of the heat pump seems to have dropped.       
      

Meatballs

Keep dropping it slowly until it no longer meets the heat demand then pop it back up