Ductless Air Conditioning vs Updating Central Heating?

Jaffa0range · 4 September 2017 at 8:08PM

We're just in the early process of moving house, moving to the 'technical forever home' a detached 3 bed bungalow with a concrete floor. On viewing we noticed that it has a single line central heating system installed, with pipework that's been in the concrete ground since early '80's and the system by design won't win any efficiency awards considering it has 11 rooms and some 15 odd radiators. The boiler although we've been told is decent (Floor mounted Worcester High Flow 400 combi unit) we've no idea how old or what condition it's in.

The house in general needs a fair amount of renovation so the plan was to put in a dual line system and new radiators before anything else. This is obviously a fair amount of work ripping up concrete floors and putting new pipework back in with access points at pipe joins/manifolds etc. Having the pipework on show is definite no-no. Still mindful that the boiler still feeds the showers/taps on the other side of the house but there is no concern for any deteriorating/leaking pipework at present so it can be left be.

With the amount of work involved, I thought I'd look at other options, and stumbled across ductless AC systems, specifically the LG system looks very smart. They have the ability to heat & cool and control the house per zone/individual room (up to 9 zones), potentially being much more efficient overall because of the individual control. The internal units are much less invasive than radiators and seeing as it's the 'forever home' I can see it being beneficial over the years with regards to the cooling ability and future proofing the house. It will be a self install and although still a lot of work, it' not chasing out miles of concrete floor, as most of the AC install will run through the loft.

With an 8 zone 50k BTU external unit coupled with with 7-8 internal units, pipework/sundries and a firm to come out and vac, leak check and gas I think it'll come in around 5-6k? The pipework in the floor probably 1-2k and more disruption/time.

Anyone using this system? Something similar? Worth it? How efficient is it over conventional central heating, will it pay for itself over 5-10 years? Should I just stick with the old fashioned central heating and get on with the inevitable?

Any other thoughts appreciated, thanks.

matelodave · 5 September 2017 at 12:17PM

It looks like a good idea if you can put up with the internal units.

Depending on the layout of your house you might be able to run the refrigerant pipework around the outside of the house or in the loft rather than digging up concrete.

I'm guessing that you should be able to get a COP of around 2.5-3 for heating but it will cost during the summer if you use it for cooling, so it's worth bearing in mind that it will have a year round operating cost unlike a normal heating system.

Air-to-air systems don't qualify for the Renewable Heat Incentive so you wont get any benefit like Air to Water systems do.

I'd investigate it a bit more and get some quotes as I reckon your £5-6k might be a bit on the light side although I have no experience of a split system.

We've got an Air-water heatpump with an overlay underfloor heating system - saved pulling up all the floor as it lays on top)

To be honest I'd see how well the existing system copes and cost to run as it will take an awfully long time to get a return on say £8-10k for a heatpump system.

Gas is still cheaper (assuming that's what you've got) and I'm sure that a new gas system would cost a lot less to install.

It could be worth looking at an overlay system off a gas boiler. You have the benefit of no rads but you do need to plan it carefully and get the manifolds in the right place.

It wasn't everso cheap when we put ours in seven years ago but we do like the fact that our bungalow is warm all over and we dont have to think about where to put the furniture etc as we dont have any radiators to get in the way. It's also very easy to zone control. Each of our rooms has it's own zone.

It runs at a lower temperature than a radiator system so can work out cheaper to run but it's not as responsive with a heat pump as we can run the temperatures very low. It would be a bit different with a gas boiler

I've got more info on what we did if you want to PM me

Jaffa0range · 5 September 2017 at 3:25PM

Thanks Mateldave.

Combi boiler is Gas powered.

5-6k was priced up via a few online sites for equipment and on the basis of a self install. Have you sent you a PM regarding the underfloor heating, sounds like possibly a good option if it voids having to re pipe the the house!

Cardew · 6 September 2017 at 5:14PM

Very few people would suggest a heat pump if mains gas was available.

Swipe · 6 September 2017 at 9:32PM

Cardew wrote: »

Very few people would suggest a heat pump if mains gas was available.

I have aircon split units in my home which perform superbly for most of the seasons. However, I find they really have to work overtime on the coldest winter days. If we get sleet, wet snow or freezing fog I may as well forget it and bring out the fan heaters due to the constant defrost cycling. Luckily we don't get too many of these days over winter.

I agree with Cardew and would swap my aircon units tomorrow for a mains gas heating system if I we had a gas supply in my village.

Jaffa0range · 7 September 2017 at 10:53AM

Swipe wrote: »

I have aircon split units in my home which perform superbly for most of the seasons. However, I find they really have to work overtime on the coldest winter days. If we get sleet, wet snow or freezing fog I may as well forget it and bring out the fan heaters due to the constant defrost cycling. Luckily we don't get too many of these days over winter.

I agree with Cardew and would swap my aircon units tomorrow for a mains gas heating system if I we had a gas supply in my village.

Interesting to hear his. I lived with a ducted AC system for 4 odd years when we lived in the US when I was much younger (too young to care about these things) where the climate was much hotter in summer and 4 foot of snow freezing come winter and the AC always kept the house perfectly comfortable.

What system are you using? How do you find living with AC in general? Is it efficient to run during winter?

Ultimately as many pros as I can see to fitting a Multi split system, the most important job will be it's ability to warm the house come winter. All the other pros are just bonus points.

zeupater · 7 September 2017 at 1:44PM

Jaffa0range wrote: »

... Anyone using this system? Something similar? Worth it? How efficient is it over conventional central heating, will it pay for itself over 5-10 years? Should I just stick with the old fashioned central heating and get on with the inevitable?

Any other thoughts appreciated, thanks.

Hi

Any other thoughts ? ..... Make yourself a big mug of coffee & pop across to the G&E forum to have a look at this thread ....

zeupater wrote: »

Hi All

The combination of a small ASHP(Air/Air) with Solar pv seems to be a valid pairing of complementary technologies which has been raised a number of times on this forum.

The idea of this thread is to encourage discussion of this combination in order to validate what an appropriate equipment specification would look like in order to maximise performance benefits in a typical domestic environment.

Obviously, it is well understood that a typical domestic-scale solar pv system will not generate sufficient energy to provide winter heating, but should be considered as being a 'shoulder' months supplementary heat source for well insulated properties ... it is therefore best to concentrate on Spring & Autumn as being the target periods for heat provision, with an additional benefit of provision of cooling in heat-wave conditions such as we've been experiencing recently.

HTH
Z

HTH
Z

Swipe · 7 September 2017 at 6:06PM

Jaffa0range wrote: »

What system are you using? How do you find living with AC in general? Is it efficient to run during winter?

I have a couple of 3.5KW Daikin heat pumps. They are very cheap to run. I don't think my rural bungalow is a very good test case as it loses heat very fast via the uninsulated suspended wooden floors throughout. As a result of this, I'm mostly heating a house when I get home in an evening from an internal temperature of around 10C in the depths of winter. Unless it's really cold I can get the rooms that the units are in to a comfortable temperature in less than 30 minutes. In a reasonably insulated house my pumps would have to work less harder once up to temp. I was tempted to oversize them but I'm glad I didn't as I would have found they'd be constantly cycling on and off during the shoulder seasons which is not good for the compressors apparently.

They are pretty much maintenance free apart from checking the outside units are free from leaves and debris and I hoover the internal dust filters every few weeks. The internal fans can be quite noisy when they ramp up but quieten down to barely noticeable background noise once the room is up to temp. As much as I like them, I'd much prefer gas central heating if it were an option.

richardc1983 · 7 September 2017 at 9:04PM

My input here is if there is gas it's still cheaper to heat with gas as it's cheaper than electric per unit but the LG system will be more efficient at producing heat plus you'll have air con in summer. Air to air heating is quick as well but you generally do need set poInts higher than with central heating as there is no residual heat emitted like there is from radiators when rooms reach thermostat off. Given the choice though At a new build it would be LG air to air or air to water (utilising fan coils so I get cooling also and low temp rads for bathrooms etc.

I have an LG multi split serving 4 rooms I also have mains gas and the new gas boiler with opentherm is still cheaper to run and it's on anyway to provide the hot water. With a multi system you absolutely must oversize the outdoor unit to be larger than you need. That goes for indoor units also. There are two reasons for doing this, you won't be running the unit flat out most of the year and at those times the unit will ramp down its compressor speed and therefore provide less output. Having your indoor units oversized also means you don't have to run the fan speeds at full whack and so it's quieter unless you are just starting heating from cold the extra airflow with a larger unit helps heat the house quicker then you can revert back to low speed. With a indoor unit perfectly sized to the room you'll prob have to run it at maximum fan speed most the time in heating and that's then more noisy.

Manufacturers rate the indoor unit output on high fan speed so as an example say you fit a 2kw unit for heating/cooling. The unit will only give that output with the fan on high.... meaning more noise. At lower fan speeds the same unit will prob only give 800w cooling/heating on low. Now if you fit a 3.5kw unit and run that in high you will get 3.5kw heating/or cooling. Run it on low your output is likely to be 1.5kw which if you are clever and leave internal doors open for heat to circulate then that's more than enough.

The defrost cycle on modern units is much better, coil design on the LG systems is also designed so you don't have as much frost build up - my system hardly went into defrost last year.. because the outdoor unit is oversized it's generally never running at full tilt apart from start up or really cold. Once rooms starting cycling off at thermostat off then the compressor slows down you have this massive coil surface area collecting heat for only a few rooms and is more than enough to supply rooms as and when they come on and off. When people worry about units cycling off it's usually cos they have a 1-1 split a multi serves multiple indoors chances are you'll have at least one requiring heating and as that room reaches temp another room will prob come on also.

I would recommend you install wired controllers and use the temp sensor in those as high up sensors on the wall and with a multi unit there is always a little heat inside the unit circulating refrigerant (to allow oil to return to compressor) all whole the outdoor is operating. The sensor in the unit can pick up on this heat so the room temp can drop and if not detect it as the sensor is warm and cosy in the unit and high up. Wired remote controllers resolve this and you can also set 7 day schedules and temperature patterns etc.

With the LG unit you can also limit the maximum output in amps. So say the unit is rated at 14amp maximum amp draw then you can limit it to either 12amp down to 10amp... this saves energy as the compressor maximum speed is limited and also means that there would be less defrosts as your technically using a smaller compressor but still with the large surface area of the coil outside (that collects heat) and with the oversized indoor units you'll still maintain room conditions etc. Mines a 13amp max and I set it to 10amp and never an issue.

With a larger outdoor unit also than you need means you have a larger coil, if the unit is never ramped up fully cos it has extra capacity when you really need it the fans on the outdoor unit slow down and thus less moisture laden air is moved through the coil... defrost cycles happen none stop on undersized systems on the worst of the winter days... because the compressor is running flat out (results in the evaporating temp of the refrigerant outside being very low and thus causing moisture to freeze up) and the outdoor fan is running flat out also trying to pull as much air through the coil to collect heat. A low evaporating temp is due to a high heat demand so the condensing temp of the refrigerant indoors is higher until the heat demand is satisfied the unit will then start backing off and slow down resulting in lower condensing temp (air blowing outside not as hot) and a higher evaporating temp (refrigerant outside in the unit not having to collect as much heat so doesn't need to be as cold). Having an oversized unit means the compressor and fans can run slower which results in the evaporating temperature being higher as not as much heat is required to satisfy indoor demand.

Probably very technical above but I can explain further if there's parts you don't understand.

Ductless Air Conditioning vs Updating Central Heating?

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