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So, I'm about to move into a house with an air-source heat pump. It's a 3 bed bungalow, pretty well insulated. This will be a new experience so I've been trying to educate myself using the university of Google, but I'm left confused about how I should plan to programme my thermostat.
The house will be occupied during the day so we will need a constant temperature, but during the night, should we turn it down a lot, or is it more economical to keep it fairly warm? This seems like a daft question, and maybe it is, but it's my understanding that using the auxiliary heater to increase the house temperature from night temperature to day temperature is massively expensive and to be avoided.
Any advice from heating experts, or other people with ASHP, is very welcome - even if it's to say "you're talking absolute blx".
Separately I'm wondering if it's worth it to ask a professional to pay us a visit to advise on how to set up the ASHP and show us how it integrates with hot-water and PV solar?
Underfloor heating or radiators?
Radiators. ()They are just "2 unit" radiators and not really huge, but when we've been in the property it's felt warm and not draughty so my initial fears that it would need a lot of work are maybe unfounded.
The idea that it uses less energy to maintain a constant temperature than to let it cool down and reheat is a fallacy.
You should check whether there's a reduced rate for night use of electricity, at which point it makes sense to run it flat out during this period to get as much heat as possible into the house, and then just the occasional top-up during the day.
You might find there's a big time lag between the heating coming on and anything happening and you'll need to take this into account.
Our ASHP controller works by adjusting the temperature curve, rather than just responding to a thermostat and calling for ‘heat’. The curve takes into account both ambient air temperature and internal temperature and from most accounts you need to adjust it to find the one that suits you best. The systems is always on - we’re at home anyway. It doesn’t ‘give off’ heat like traditional CH - in fact the radiators rarely feel warm at all. The house typically is 19-20C, all-day, every day, although once the sun comes out, it does warm up more.
Ive been involved with many ASHP installations. We generally tamper proof the settings, so they cannot be changed. There is a reason for this - the general householder has no idea how it works and what the settings should be.
One we were called to had gone cold, they had by-passed the locked controller, and adjusted the temperature themselves, but set one of the temperatures for less than 20 degrees, not knowing that doing that turned down the output from the unit, but did not turn down the room temperature, which is what they were attempting to do. As they unit was set too low, it just could not supply any heat for the rooms or water.
Another one turned it off every night at the main switch, to save power, but then found, once turned back on at 8am, it would not get warm for 5 hours, as the hot water takes precedence before the heating.
Download the full installation and set up manual, read it thoroughly before adjusting anything. And thye really shoudl eb left on 24 hrs a day. Once the right temperature has been met, they will turn off.
We generally tamper proof the settings, so they cannot be changed. There is a reason for this – the general householder has no idea how it works and what the settings should be.
This looks like sound advice for my case.
What is a bit confusing is that there are (as I recall from visiting the property) three different types of controls:
1. The box related to the ASHP itself (LG ThermaV)
2. A timer (Honeywell 6400)
3. A (single) thermostat control in the hallway
I'm not at all clear how these interact. I'm guessing that I should keep my fingers well clear of the LG controls!
I read that as heart pump.
Carry on!
What Alanl and Dovebiker said.
We are also only a few months into this but actively told that the room thermostat is only to meet building regs - whack it up high so it doesn't intervene and let the heatpump controls sort things out based on outside temp and the curve plus offset. The outside is what eventually makes your house cold anyway. Rad stats only used to keep bedrooms cooler.
With a system that is most economical when responding slowly, it makes a lot of sense to work off outside air temperature. If you wait for inside to drop, it is too late to react without using the expensive direct electric heat.
Alanl - any tips on dealing with spring days and solar gain? Would you suggest subtly different curves for different times of year or just use the offset to cool things a little?
Thanks so much for the helpful responses!
I have a dumb question - what exactly do you mean by “the curve”?
Alanl – any tips on dealing with spring days and solar gain? Would you suggest subtly different curves for different times of year or just use the offset to cool things a little?
Sorry, no idea. I work as an electrician alongside the guy who fits the units and sets them up, I get called back to adjust things, but unless it is basic, I have to make the phone call to ask how to do it.
I am actually booked onto my Part L energy efficiency course next month, then the ASHP installers course in June, so will know a lot more then.
So does this mean when you go to bed at night your room will be 20deg ?
That’s not pleasant for sleeping in, or does it mean you have to set a bedroom for a constant temp which in reality may be nice for sleeping but not getting dressed etc ?
Heat geek make good videos explaining how to get the most out your heat pump, they explain in this video that it's dependent on a variety of factors. It's not one rule for all ASHP installs
It is often more cost effective to leave the heat pump on 24/7, but programme a set-back temperature that's a few degrees lower for when you're asleep or out for the day.
I have a dumb question – what exactly do you mean by “the curve”?
This is the first hit on Google: http://tech-controllers.com/blog/heating-curve---what-is-it-and-how-to-set-it
Essentially, you may have to play around with the controls to find the one that works best for you - but coming in and cranking up the heating is the least efficient way of doing it due to the large thermal lag, it takes 5-6 hours for it to ‘catch up’ by which time you’ve probably over-shot.
The idea that it uses less energy to maintain a constant temperature than to let it cool down and reheat is a fallacy.
Dependent on insulation, airtightness and heating system.
As above, really low energy homes are different from majority of homes, as are the systems that control and heat them.
This is the first hit on Google:
Aah - thanks 🙂
I wonder what controls you have on your unit to set the curve? Looking at the user manual for the one I'm getting it looks like there's just one parameter I can change - "a bit hotter or a bit colder".
General advice is to have it on 24 7 but a bit lower at night - it doesn't have the power to get back up to temperature quickly enough.
I wonder what controls you have on your unit to set the curve? Looking at the user manual for the one I’m getting it looks like there’s just one parameter I can change – “a bit hotter or a bit colder”
Mine is a NIBE heat pump + controller - it has a colour screen display with lots of menus and I can select curve settings - there’s lots of pre-sets or I can even adjust it based on external and internal temperatures. I’ve just knocked it down from 5 to 4 out of 20.
I have a heatpump as well - I think that the option is for warm bedroom -or cooler the response time is too slow to have it cooler in the evening / night and warm for the morning. It works well on the curve generally.