Idiots guiide to best use of ASHP please!

downshifter

Morning. I live in social housing and earlier this year had an air source heat pump installed which is great and works well.  However I'm sure I'm not using it in the best or most economical way 

When it was installed they handed me the thermostat thingie and said control it with this.  Which obviously works fine but may not be the best.  Ive read the manual, read all sorts of things on line, watched youtube videos and am completely blinded by science, graphs, charts, keep it on all the time (what does that even mean), turn it off when not at home and so on and so forth.    Much contradictory guidance - I really need a simpler explanation  Can anyone point me in the right direction?  I'm sure it's also dependent on my lifestyle so I recognise I need to adapt any advice to that too.

Thank you so much.

Mstty

These are our top lessons after 15 months with ASHP

1) set the system to run on the weather compensation curve. Set it as low as you can to maintain heat in the house (our comfort level is 18oC plus

2) if you can set the hot water to heat when the sun hits your ASHP.

3) make sure any auxillary electric heaters are turned off (normally in engineer menus)

4) you can't run an ASHP efficiently if you use it like a gas boiler. Low heat on over a longer period of time.

Astria

Mstty said:

These are our top lessons after 15 months with ASHP

1) set the system to run on the weather compensation curve. Set it as low as you can to maintain heat in the house (our comfort level is 18oC plus

All good points, this one specially important. Some installers actively disable WC as it causes people to ring up and complain when the system isn't like their old gas boiler - it's not supposed to be.

ASHP can be poor to bring up a house to a higher temperature - they are much better at keeping the house at an ideal temperature, i.e. producing enough head to combat the heat loss of your property, so maintaining the temperature. This is why some people say leave it on 24/7. Also they are more efficient the warmer it is outside, so try and not increase temperature (and thus demand) at night when temperatures are low and there's no sun.

shinytop

It's hard to be general because the controls and the way they are installed and set up is different. All good points so far but maybe if you could answer a few questions folks may have some specific advice.

1. Make and model of ASHP, size and age of house
2. Radiators or underfloor heating
3. Is the thermostat the same make as the ASHP or is it a 3rd party one?
4. ASHPs normally run in either (1) fixed flow temperature mode (radiators are always the same temperature), (2) weather compenansated mode (colder outside = hotter radiators) or (3) something clever based on your target room temperature and the outside temperature.  Do you know which yours is?  It probably won't be (3) if your thermostat is a different brand to your ASHP.

downshifter

Thank you for these hints and tips.  It is an Ecodan r32 with radiators. House is old (thick walls) open plan - one room with single glazed door to outside downstairs, 2 bedrooms and bathroom upstairs.  Thermostat is also Mitsubishi.  I remember checking the weather compensation when I first got it and read the manual with great enthusiasm but little understanding and it is activated.

As it's social housing I doubt there's anything 'clever' involved as in my experience any work done is good (and I'm hugely grateful) but basic.  I'm not sure I really want it hotter just because the outside temp is colder as it's more about how I feel rather than how it is outside.  The door is always being left open esp first thing in the morning to let pets out and in, or I'll go to the bin, fill bird feeders etc. and first thing I'm always warm even if there's snow on the ground so I don't have heating  on - or rather the thermostat is set at about 7 degrees as it is overnight.  I also open several windows till mid morning as I'm warm from bed or shower still or have been out walking dog - always hot work!

It's really from after lunch through till evening that I need it on more but I gather that moving the thermostat from 7 or so up till say 15 or 16 is a nono as it causes the pump to go into boost mode which is expensive.  So I try to increase by a couple of degrees and bit by bit get it up to being warm enough to sit and watch telly in the evening.  I turn it right back down at about 9 and go to bed at 10.30 and def don't need it on overnight, esp as the bedroom window is always open.

Maybe I'll just have to leave things as they are and take the hit with the bill as I am several hundreds in credit at the moment.  Getting rid of the 'always on' immersion heater has made a big difference financially.

Thanks for any more hints and tips.

DS

macman

Even the most economic heating system around is not going to be economic if you are in the habit of leaving doors and windows open for extended periods! Just turn the rads down rather than opening the windows. Obviously you need to ventilate, but not permanently in winter.

Gerry1

Not sure that weather compensation is supposed to make it hotter.

More likely that it will advance or retard the start time so that it will start later if it's warm outside and vice versa, so that the property will always reach the set temperature at just the right moment.

Mstty

If setting you thermostat to 15/16oc sends your ASHP  into boost mode. (I presume you mean it turns on the auxillary electrify heater(s) let's call them immersion for simplicity) then the system is not setup properly and you are not running the weather compensation curve and have probably been left with a system setup with a high temperature by the installers to stop you calling them back as it doesn't replicate a gas central heating system.

A few hours/days spent of your time learning about your heat pump will save you a fortune going forward.

chris_n

Weather compensation I supposed to make the water in the heating system warmer as the temperature outside drops. The idea is that the water warms to compensate for the increased heat loss due to colder temperatures, not to make the house hotter. 
The main problems with this are, people expect radiators to be hot not lukewarm. The compensation curve needs to be set to suit the heat loss of each individual building / lifestyle. Plumbers and 'heating engineers' then turn compensation off to make the system feel more like a gas boiler and the efficiency drops and costs go through the roof.

matelodave

Gerry1 said:

Not sure that weather compensation is supposed to make it hotter.

More likely that it will advance or retard the start time so that it will start later if it's warm outside and vice versa, so that the property will always reach the set temperature at just the right moment.

Weather compensation adjusts the flow temperature from the boiler or heatpump to try to balance it with the heat loss of the building. When the temperature outside is reasonably mild then the flow temp is reduced and when its colder the temp is incresaed. This ensures that the system is running at optimum efficiency and reduces boiler cycling. Running a boiler or heatpump at higher temps than necessary just wastes energy.

A heatpump is designed to run for longer periods at low temperatures rather than on/off like a conventional boiler and they are more sensitive to weather variations. Increasing the flow temp by 10 degreess can easily increase your electricity consumption by 20-25%.

The clever thing is to adjust the compensation curve to suit. 

Ceol

downshifter said:

Thank you for these hints and tips.  It is an Ecodan r32 with radiators. House is old (thick walls) open plan - one room with single glazed door to outside downstairs, 2 bedrooms and bathroom upstairs.  Thermostat is also Mitsubishi.  I remember checking the weather compensation when I first got it and read the manual with great enthusiasm but little understanding and it is activated.

As it's social housing I doubt there's anything 'clever' involved as in my experience any work done is good (and I'm hugely grateful) but basic.  I'm not sure I really want it hotter just because the outside temp is colder as it's more about how I feel rather than how it is outside.  The door is always being left open esp first thing in the morning to let pets out and in, or I'll go to the bin, fill bird feeders etc. and first thing I'm always warm even if there's snow on the ground so I don't have heating  on - or rather the thermostat is set at about 7 degrees as it is overnight.  I also open several windows till mid morning as I'm warm from bed or shower still or have been out walking dog - always hot work!

It's really from after lunch through till evening that I need it on more but I gather that moving the thermostat from 7 or so up till say 15 or 16 is a nono as it causes the pump to go into boost mode which is expensive.  So I try to increase by a couple of degrees and bit by bit get it up to being warm enough to sit and watch telly in the evening.  I turn it right back down at about 9 and go to bed at 10.30 and def don't need it on overnight, esp as the bedroom window is always open.

Maybe I'll just have to leave things as they are and take the hit with the bill as I am several hundreds in credit at the moment.  Getting rid of the 'always on' immersion heater has made a big difference financially.

Thanks for any more hints and tips.

DS

There's quite a lot to unpack here to get you to an efficient system. Obviously as one person said, try to close your doors when you take the bin out behind you or it'll never be efficient!

Secondly, although your thermostat is set to 7C, what temperature does the house actually get to? For most people, setting to 7C basically just means turning it off, which is fine for a gas boiler, but not recommended for a heat pump. You're much better keeping it on low for more of the time than turning the thermostat off several times a day. Instead of opening the windows, why don't you wear less clothing to take the dog for a walk, or stand outside for 5 mins to cool down afterwards, so that way you're not letting all that heat (and your money) out the window?

Next, on the point of turning the thermostat up slowly, this does not make any difference (unless your controller is doing something weird). If your thermostat is calling for heat, then your heat pump will fight to get the water in the system up to the expected flow temperature no matter how high you set the thermostat. You could set your thermostat to 12C, 19C or 25C and it would not make a difference to the power the heat pump is using. Therefore if you want to change the thermostat temp, just change it once to whatever you want.

Your use case is a bit unique given how much you open your windows. Generally heat pumps need warmish flow temperatures (ie the temperature of the radiators), and to be on all day, possibly with a set back temp overnight.

What might actually make a difference in your case is further hot water adjustments. To what temperature do you need the hot water? The lower the better with a heat pump really, although you'll probably want at least 45C. Then you'll need to think about how often your heat pump does a disinfection cycle when it heats the hot water cylinder up higher to kill legionella bacteria. How often does yours do this? You shouldn't need it more than weekly, and some controllers allow fortnightly.