ASHP as aircon unit for bedroom

mmmmikey

Hi, appreciate there's a thread about ASHP with solar but my questions here are a bit different so please bear with me.


Health issues and medication have made the last couple of summers a real ordeal due to high night time temperatures, but I've shied away from getting aircon as it has seemed a bit of an extragance in the UK. I've realised now it's daft to suffer so have decided to do something before it gets hot and everyone sells out of cooling products.



My first thought was to buy a portable aircon unit, which is still an option, but I'm now thinking an ASHP to be used for heating as well might be a better solution. The room currently has a night storage heater and my thought is I could replace that with a low-wall ASHP.



Advantages of this would be (1) no need to find somewhere the portable aircon (PAC) and wheel it in and out as needed (2) the convenience of always having it available without being in the way (3) I could use the storage heater elsewhere to save buying one. These reasons are enough in themselves for me to be happy to spend £1000 or so on a low-wall ASHP rather than £300-£400 on a PAC, so the capital cost is not an issue, I'm mainly focused on the heating costs.



I'm not too concerned about the aircon running costs either as I'd only be using it for a few weeks every year, and I'd only be using when it's hot, which means sunshine and solar energy (obviously not at night but I could keep the room temperature down during the day and have some spare battery power to reduce night time costs).


The things I'd be interested to hear views on are, in relation to heating:


1. Noise levels. Do these units switch themselves on and off like fan heaters, or do they regulate the fan speed as needed (which presumably would make them quieter and more suited to bedroom use)? If you have one of these, would you consider having one in a bedroom, or far too noisy?


2. High-wall ASHPs look to be more widely available than low-wall units, but the size and layout of the room really make a low-wall unit a much better option. I can imagine why high-wall would be better for aircon (cold air sinking) and as such would anticipate the converse is true for heating. Does this work in practice? Is there a reason why high-wall units seem to be more common? What type have you got and why?


3. Running costs. What sort of real-world efficiency (COP?) could I expect to get running one of these units in the winter months? I'm on E7 and the heating requirement is overnight so most of the time I'd be running it at off-peak rates. But if I need to run it at peak rate for say an hour before bedtime, the costs could mount up quickly, given that I pay nearly 4 times as much for peak rate electricity. I could probably bank on up to 1kWh of battery power per day, but how much heat does that translate into in the winter months? It's a small room so I'd be surprised if I need more than 2kWh heat outside E7 times. I would anticpate making a saving in the shoulder months which would offset any additional heating costs in winter - what kind of efficiency are you getting this time of year? I realise this is all a bit vague and I'm lacking in data specific to the bedroom, so all I'm really wanting to know is whether you're reading this thinking "yes that all sounds reasonable, shouldn't end up costing much more than E7, or you might even save" or your thinking "no. no, no - you haven't thought about 'x' which is going to kill this for you"


Any comments gratefully received, in the meantime will start doing some more research on low-wall ASHPs sizes and price.

JKenH

I cannot comment on 2 and 3 but my ASHP running on ultra low setting which we use most of the time is whisper quiet (19db) so I would have no hesitation in using it in a bedroom. I find the ASHP warms a room up in minutes so I doubt you would need to run it for as long as an hour before using the room.

All my comments above relate to heating mode as I haven’t had the units long enough to need cooling. The figures on the spec sheets are, though, similar for both modes.

mmmmikey

JKenH wrote: »

I cannot comment on 2 and 3 but my ASHP running on ultra low setting which we use most of the time is whisper quiet (19db) so I would have no hesitation in using it in a bedroom. I find the ASHP warms a room up in minutes so I doubt you would need to run it for as long as an hour before using the room..

Thanks, much appreciated - what make/model do you have - I can use it as a baseline for comparison...

Martyn1981

Most of the noise is the outside unit, which itself isn't loud. Our indoor unit noise depends entirely on the fan setting. It goes to 6, and 4-6 is noticeable, whilst 1-3 is very quiet. If pre-heating a room it wouldn't matter, but for sleep, just choose a low fan setting.

Running costs were a big factor for me, till I got one and thought, 'who cares'. Your 2kWh scenario might cost you 10p, but for comfort 'who cares', and if it means less heating elsewhere, possibly cheaper, and v's the space heater, already ahead.

Not sure about height levels, it may simply be to better distribute the heat/cold.

Mine regulates based on room temp v's temp setting, with the fan remaining on the chosen speed. Perhaps others vary but it seems like a logical standard.

For excess PV heating, you'd simply put the temp high, and leave the door open, so it spreads into more of the house. I have mine running at around 23C or 24C in the conservatory, with a window to the kitchen open, and the door to the living room open. Once the living room is about 20-21C I leave that door wide open to spread more heat through the house.

When heating on import, I just have the door between conservatory and living room open.

1961Nick

Our ASHP will heat a large conservatory from zero to 20C in 10 - 15 minutes. A small bedroom would take half that & most of that will be spent waiting for it to rearrange it's gas & defrost the outdoor unit.

Most units I've encountered abroad have a nighttime running mode which is ultra quiet & shouldn't bother most people.

The temperature is controlled by fan speed variation rather than on/off cycling.

mmmmikey

Thanks everyone - enough to convince me I'm not about to do something stupid (wouldn't be the first time )

michaels

Do any of these systems combine with mhrv or include a hepa filter?

1961Nick

mmmmikey wrote: »

Thanks everyone - enough to convince me I'm not about to do something stupid (wouldn't be the first time )

Just one last word of advice, don't be tempted to oversize the unit in relation to the bedroom size. The thermostatic control on these units tends to be a bit laggy & you could find it overshooting the target temperature by a long way before it slows down.

If you come across a unit with a smart thermostat that slows it down as it approaches target that may be worth considering. I don't know if the remote thermostats that connect to ASHPs are better than the built in ones & that may be worth some research.

mmmmikey

1961Nick wrote: »

don't be tempted to oversize the unit in relation to the bedroom size

ah - thanks, hadn't thought of that, which is going to make it more of a challenge as the low wall units I've seen tend to be larger outputs, I'll have another look later.

JKenH

mmmmikey wrote: »

Thanks, much appreciated - what make/model do you have - I can use it as a baseline for comparison...

It's all in the signature

1961Nick

mmmmikey wrote: »

ah - thanks, hadn't thought of that, which is going to make it more of a challenge as the low wall units I've seen tend to be larger outputs, I'll have another look later.

The larger output would be fine with a smart thermostat that works properly.