Multi split advice UK

[Alex34]

Hi All,

What an amazing forum you have here, I hope you don't mind a non-engineer posting but as i seemed to have lucked out and found the worlds biggest repository of aircon knowledge it would seem silly not to ask:

Does anyone have someone they would recommend to advise about and supply and fit a multi split system (primarily for heating) in a flat in the North devon area.

Also does anyone have answers/opinions/best guesses given limited information to the following?

In the UK we seem much more inclined to run air to water or ground to water systems. Is this just because we are so used to wet central heating systems, or does a wet system have strong advantages?

Will an air to air system be suitable for a victorian flat/ maisonette with a loft conversion, provided there is reasonable insulation- the sash windows can be a bit draughty and i don't know how much i will be able to do about that-but after the renovation there will be plenty of floor and ceiling insulation. I ask because I have read different opinions on whether air to air is good for buildings with a high thermal mass and my exterior walls are over 2ft thick.

What kind of price-finger in the wind stuff I know- should I expect to pay. I used a rule of thumb that was mentioned in another thread of 100w/m2 which gives me a rough guesstimate of needing about 8kw to feed 4 wall units. rooms are 24m2, 15m2, 8m2, and 32m2 with between 5m and 10m between the outdoor unit and each indoor.

Thanks in advance for any replies.

P.S If anyone is in the area there is a great pub just about a minutes walk from the flat, where they brew their own beer and I shall gladly furnish anyone who wants to pop around and offer their opinion with a few jars.

[back2space]

Hey Alex

Welcome to the forum... I actually live in a victoria flat in Leeds area.

Its a converted house and I occupy the ground floor area.

I have a multisplit system by LG, however if you was to go down this route I would reccomend a multisplit system from someone else such as mitsubishi electric, daikin, MHI, fujitsu etc as these are the market leaders.

LG is good for 1 on 1 unit but not when you are running more than one unit off the outdoor unit... as I have found out the hard way! I have had problems with the LG control strategy etc, but this is something that wouldnt be an issue on the manufacturers listed below.

You will find the air to air system is great for what you want plus in the summer you have cooling, great if you have a loft conversion like you say.

I have 3 indoor units feeding off of one outdoor unit, all three can be run together and I can control each room at a different temperature via the remote control. I can turn units on and off as I please but they must all operate in the same mode either heating or cooling, not in different modes.

The only downside to this is you may require cooling on a side of the house that has sunlight beaming through (large bay windows with glass) and heating on the other side of the house where the sun isnt shining... this however is only a problem during the beginning of spring when the sun is higher in the sky but mornings are still chilly.

Heating is fantastic, much faster to respond than a wet system whereas a air to water system using underfloor heating the temperature is achieved much slower and you tend to leave them running 24/7 over the winter.

As an air/water system uses underfloor heating you get very even temperature distribution in the room as you heat from the floor upwards.

With an air to air system you also get good heat distribution if the system is designed properly plus you have the advantage of being able to warm the room up quickly because you are heating the air directly rather than heating the floor.

Air to water systems are supposed to be more efficient as you use lower water flow temperatures than say a gas boiler would.

Cheaper install is going to be an air to air system whereas air to water system utilising underfloor heating you obviously have the disruption of installing the underfloor loops etc.

I oversized my indoor units so that I could run my fan speed at lower speeds and receive the required duty without having to suffer noise from fans being used on high speed. They are very quiet on low speed.

Manufacturers for example will size a unit based on the unit being run in high fan speed. EG 3.5kw heat output is based on the unit running in high fan speed and at low speed it may output 2.0kw however they dont show you this in sales literature.

Me for example only needs 2.5kws of heating in my lounge, if I was to put a 2.5kw unit in, it would be perfectly sized but I would have to run it in high fan speed majority of time to get that duty = more noise. This would also mean that in extremes of temperature like the winter we have just had I would only have 2.5kws of heat and no more, when really I could do with a bit more cos its so cold.

I therefore put in a 3.9kw unit so that I can run it in low fan speed all the time, I get about 2.5kws of heat output on low fan speed, however if its very cold or I have just come home from work I can put the unit onto high fan speed and I have another 2kws of heat to assist in getting the temp up, after which I return the fan speed to low.

It just means my units are not running flat out all the time and I have a "buffer" zone of heat should it be very cold or I require a quick warm up time.

I got a good deal on the system price, and install cost about £600, that was for 2 indoor units, I have just added a further unit onto my spare room as this room can drop as low as 10C during the day in winter, it has helped really well and maintains room temp at 21-22C.

If I was to do it again, I would invest in Mitsi or MHI without a doubt, they have some very nice floor console units, that blow heat out the bottom warming your feet, which again is great in winter as the floor is usually cold in any heating system unless its underfloor heating.

Hope this helps, any thing else you would like to know just ask.

[lomb]

Air to air has better COPs than air to water at +7 degrees and is more economical. The accepted theory is that ground to water is better at zero and sub zero air temperatures as the ground retains some heat at night. It is only really suitable for underfloor heating or massive radiators so if these are out then its a no go. Air to water also needs underfloor or massive radiators. Both are not instant heat and one has to leave the heating on for many hours to get a response. This may or may not be suitable depending on ones lifestyle. If retired or work from home great if not then financially crippling potentially. Gas heating is probably better +cheaper than these options.
Air to air on the other hand offers rapid warm up on demand, advantage that it can cool also and modern systems are cheap to run. This can easily supplement a gas system.
Multisplits have their disadvantages, they are dearer to run than single units, dont offer great controllability, there is no redundancy,can be leak prone and if it breaks down you are at the mercy of the manufacturer/service. Also if a compressor fails the junk can get in the pipework and contaminate everything.How does 2 or 3 grand sound for a replacement circuit board and compressor? Id stick to single units if at all possible.

[lomb]

Also in many cases the multisplits are DEARER to install than singles. Generally installers prefer to install multis as its easier for them but the efficency figures vary wildly depending on whether one inner unit is on or say the other 3 if its a 4 split system. The latter could give one a COP of 4.5 say the former possibly 1.5 or 2. Modern singles should give you 4.5 -5.5 on their own. Thats 5.5 kw for every kw of electric used. However electric is more than 3 times dearer per kilowatt so it isnt as good as it seems. Hope that helps

[freezetech]

there are many multi splits on the market i would definatly go down this route there are units that have one outdoor unit and multiple indoor units that you control independantly. these units also come with very good cop and don t forget they dehumidify as well

[lomb]

there are many multi splits on the market i would definatly go down this route there are units that have one outdoor unit and multiple indoor units that you control independantly. these units also come with very good cop and don t forget they dehumidify as well

Unless a 3 pipe VRF system(expensive to own and fix) then the system cannot heat and cool in seperate rooms. Also i havent seen any multi that has better efficiency than singles and that with ALL units on . Daikin and Hitatchi publish COP figures and even their A rated multis can be D or E rated if only one or two inner units are on and the system is a 4 split say. The only advantage of a multi is less outer units.
Even Daikins VRF systems have lower efficiency than single splits!!

[back2space]

Yes my multi system is more efficient if I have all of them turned on at the same time, this is because the unit is designed to drive 4 indoor units so if only one is used, there is a limit to what it can ramp down to so if your going to be using all your indoor units at the same time go down multi route if not then get single splits.

[freezetech]

i agree singles are always better than multi s but going on where he lives i think has limited space for seperate outdoor units so multi split would be better disadvantage is if it breaks down he eiter freezes or roasts

[back2space]

i agree singles are always better than multi s but going on where he lives i think has limited space for seperate outdoor units so multi split would be better disadvantage is if it breaks down he eiter freezes or roasts

I also was short on space for outdoor unit hence the multi,

The way I see it is if you had a gas boiler if it breaks down you suffer the same as if a multi broke down.

[Alex34]

Wow, thanks everyone for great info.

[back2space]

Has it helped? Can you give us any more info and we might be able to be more specific?

[Alex34]

back2space, I'm really glad there's someone who has a similar set up to what I'm thinking, really encouraging to hear that it can work.

Can you tell me how your install looks? what have you done with the refrigerant pipes? chased into wall or in trunking? how was the install? one supplier I spoke to said that they tended not to do air to air in domestic situations because of the pipe work being quite large once its lagged, and so it makes it hard to put under floors into studs etc.

regarding oversizing, did you oversize your outdoor unit to match or do you just never use all your indoor units at full- or is this not possible

Thanks to everyone else for the advice on multis, I think due to space I won't be able to go with singles.
Does anyone have info on the systems best able to ramp down?
what is the best way to use the system. i. use it like a central heating system, or just spot heat rooms as and when, or another method.

Does anyone know of a multi split that can be controlled from one central location?

thanks again for your time

[Alex34]

blimey didn't think anyone else would be up this late...

back2space what extra info would you need

[eggs]

I have a Daikin 4MX in my house.

Only thing I can offer is DON'T LET THE WIFE OR KIDS GET ANYWHERE NEAR THE CONTROLS.

Quite often I get home from work and the central heating is on full tilt, with the A/C set to max cooling and all the windows in the house open........and every light on.:confused:

Energy efficiency??.....My ar$e.

Eggs

[back2space]

back2space, I'm really glad there's someone who has a similar set up to what I'm thinking, really encouraging to hear that it can work.

Can you tell me how your install looks? what have you done with the refrigerant pipes? chased into wall or in trunking? how was the install? one supplier I spoke to said that they tended not to do air to air in domestic situations because of the pipe work being quite large once its lagged, and so it makes it hard to put under floors into studs etc.

regarding oversizing, did you oversize your outdoor unit to match or do you just never use all your indoor units at full- or is this not possible

Thanks to everyone else for the advice on multis, I think due to space I won't be able to go with singles.
Does anyone have info on the systems best able to ramp down?
what is the best way to use the system. i. use it like a central heating system, or just spot heat rooms as and when, or another method.

Does anyone know of a multi split that can be controlled from one central location?

thanks again for your time

My install looks very neat on the inside, no refrigerant pipes on show at all... the pipes go out the back of the unit through the hole in the wall.

There is piping running along the outside of the house to the outdoor unit, this could be contained within trunking but as I rent a flat that the landlord doesnt keep upto the maintainance of the outside I didnt bother with trunking.

Whatever the guys are telling you its rubbish, pipework is not obtrusive at all and trunking can cover it in and also be painted and well hidden.

Originally it was only intended that I would have 2 indoor units despite the outdoor being capable of having 4 units.

2 units to my outdoor unit means when 2 indoors are running the outdoor unit will deliver full duty to the indoors (3.9kw per unit). My outdoor is 8.4kws output in heating. Now I have a 3rd unit attached if all three are running then I get about 2.81kws per indoor unit, so technically the outdoor then becomes undersized. The heat load of the room at 5C outdoor temp is only about 2.5kws per room so I can run all three in low fan speed and still maintain room temps just as well.

When it is very cold outside below 0C it is usually best to switch one of the indoor units off, perhaps my bedroom until the other rooms have caught up then I switch it back on. This is only for an hour or so, my bedroom is only maintained at 19C whereas the other two rooms are 22C. So my setup works fine for me.

Best systems as stated previously are mitsubishi electric, daikin, mitsubishi heavy industries, fujitsu.

Your best systems with the best control strategy are Mitsi Electric... very good, if I was doing it again it would be mitsi.

They can ramp down to next to nothing so they never switch off but can output as little as 500watts of heat if need be! Fantastic really.. as the lg can only go as low as 1200 watts which is not as good.

Use it as you would any other heating system, get the wall mounted controllers and then you can set up 7 day timer schedules with different temperatures for different periods in the day, this is on mitsi, fantastic really. Best to get separate controllers for each unit otherwise you would have the same temperature in each room. You could have the controllers mounted in a cupboard though so kids cant play with them. I tend to leave mine on during the night sometimes with the set point lowered as its so cheap to heat with them... of course not as cheap as turning them off but I would rather have that comfort of the house always being cosy.

If you fancy chatting on msn, then feel free to add me

richard.clarke@live.co.uk

[lomb]

I also was short on space for outdoor unit hence the multi,

The way I see it is if you had a gas boiler if it breaks down you suffer the same as if a multi broke down.


Not quite... parts for ac units can take upto 3 or 4 weeks to arrive from abroad. There are posts about parts for daikin units taking that long.
Parts for something like a worcester gas boiler are all available next day or sooner.

I suppose if there is no room for seperate outdoor units there isnt a choice but personally i would rather make room than go the multi route. The other advantage of singles is in winter when you have full output rather than the sharing that richard talks about.

Dont listen to an installer that tells you there isnt room for piping, the widest pipe likely to be used is 12mm and there is 26 mm of insulation around that so thats 38mm, well under the average stud thickness. Installers generally just want easy profitable numbers(human nature same as us all) so take their advice with the above in mind. I have heard all kinds of nonsense with regards to efficiency of multis,vrfs and singles, read the manufacturers brochure and look at the real numbers.

[back2space]

Not quite... parts for ac units can take upto 3 or 4 weeks to arrive from abroad. There are posts about parts for daikin units taking that long.
Parts for something like a worcester gas boiler are all available next day or sooner.

I suppose if there is no room for seperate outdoor units there isnt a choice but personally i would rather make room than go the multi route. The other advantage of singles is in winter when you have full output rather than the sharing that richard talks about.

Dont listen to an installer that tells you there isnt room for piping, the widest pipe likely to be used is 12mm and there is 26 mm of insulation around that so thats 38mm, well under the average stud thickness. Installers generally just want easy profitable numbers(human nature same as us all) so take their advice with the above in mind. I have heard all kinds of nonsense with regards to efficiency of multis,vrfs and singles, read the manufacturers brochure and look at the real numbers.

I only lose about 1kw of heat if all three indoors are running at same time, but even then the indoors are running more with in designed size, as the heat load for the rooms is about 2.3kws and they are still getting more than that (2.89kw).

The way to resolve that if you want full output is to get the next size up outdoor unit, that is capable of powering all 3 at full out put all the time if all indoors are run at the same time... you can get away without it though if you have oversized in the first place. It only starts affectng it if the shared duty of the outdoor across the indoors is less than the actual required heat load of the room.

I agree on the parts thing but I think this is the same for all manufacturers, our worcester bosch boiler had the fan module break down and it took them 7 days to get it back in stock.

I had thermisters replaced on my lg system they were received the next day from LG comfort cooling who keep good stock of parts.

[Alex34]

Hi again,

Back2Space I was just reading your post on the mse heat pump thread also very helpful and informative.

you posted a link to steve heads install.
.youtube.com/watch?v=79UAP...eature=related

(i'm not allowed to post links so anyone who wants to see it will have to add the www in themselves)

the kind of trunking he has in is house is exactly what would send the missus into a blue fit.

Also his downstairs unit is very close to the ceiling.
I thought this caused short cycling- if it doesn't then that's great because i would ideally put my units in the space above the door frames.

Also
STILL LOOKING FOR RECOMENDATIONS FOR AN INSTALLER IN NORTH DEVON- BARNSTAPLE AREA

[back2space]

Hi again,

Back2Space I was just reading your post on the mse heat pump thread also very helpful and informative.

you posted a link to steve heads install.
.youtube.com/watch?v=79UAP...eature=related

(i'm not allowed to post links so anyone who wants to see it will have to add the www in themselves)

the kind of trunking he has in is house is exactly what would send the missus into a blue fit.

Also his downstairs unit is very close to the ceiling.
I thought this caused short cycling- if it doesn't then that's great because i would ideally put my units in the space above the door frames.

Also
STILL LOOKING FOR RECOMENDATIONS FOR AN INSTALLER IN NORTH DEVON- BARNSTAPLE AREA

They are designed to be mounted at that level, it would cause short cycling if they were mounted close to the floor as they force hot air towards the floor in heating and cooling they throw air across from the unit blanketing the room with cool air.

The only thing that would make them short cycle is if someone thing in front of the unit eg a wall too close or a cupboard or something like that under the unit.

The trunking, you could mount the unit on the external wall so that the pipes go straight out the back of the unit to the outside, to minimise trunking on the outside you could mount the unit back to back.

Otherwise you could just leave the pipes uncovered on the outside, they have black lagging over them and will probably stand out just as much as the trunking.

Other people I know have trailed the pipes through black guttering downpipe.

[Brian_UK]

^Alex^ Sorry, can't complete your youtube link for you as it is incorrect.

[back2space]

^Alex^ Sorry, can't complete your youtube link for you as it is incorrect.

This is the correct one

http://www.youtube.com/watch?v=oCehY4KKE74