3 single split units or one multi split - consumer advice needed

[kok]

Hi

I`m installing a new air conditioning sistem in my house. I`m going to be using it throughout the year for cooling and heating of three separate rooms (40-50 m2 each). Would you advise me to install three single split units or would a multisplit unit do the job just as well? I`m also deciding between Toshiba and Sanyo - which would you recommend?

[nike123]

If aesthetic is no problem then 3 separate units. It is cheaper and when one fails, other works.
I recommend one which has better customer support there where you live.

[Greengrocer]

Hi

I`m installing a new air conditioning sistem in my house. I`m going to be using it throughout the year for cooling and heating of three separate rooms (40-50 m2 each). Would you advise me to install three single split units or would a multisplit unit do the job just as well? I`m also deciding between Toshiba and Sanyo - which would you recommend?

40 to 50m2 per room equates to approx 4-5kW per room (based on 100w/m2). For a multi you would need a 12 or 15kW outdoor unit. They're aren't many manufacturers that make multis that big. 9kW is about the largest multi available from most. What models / capacities are you considering from Toshiba / Sanyo?
I would agree with Nike 3 separate systems is more flexible and will keep the pipe runs shorter. Also if needed you can run each room in a different mode which cannot be done with a multi.

[chemi-cool]

I also recommend 3 separate units.

Thats what I have in my house, never get short of cool / hot air, easier to maintain

[kok]

40 to 50m2 per room equates to approx 4-5kW per room (based on 100w/m2). For a multi you would need a 12 or 15kW outdoor unit. They're aren't many manufacturers that make multis that big. 9kW is about the largest multi available from most. What models / capacities are you considering from Toshiba / Sanyo?
I would agree with Nike 3 separate systems is more flexible and will keep the pipe runs shorter. Also if needed you can run each room in a different mode which cannot be done with a multi.

I thought that 3,5 kW units would be enough. I was looking at the top of the range models Super Daiseikai or even Nordic daiseikai (is the heater in the outdoor unit worth an extra 70€ per unit) from Toshiba and Shiki sai kan from Sanyo. Of course the guy selling Toshiba is telling me that Sanyo is crap and the guy selling Sanyo tells me it is the best thing since sliced bread(the only air con that is actually made in Japan, totaly different technology...). If they were evenly priced I`d go with Sanyo in a heartbeat, but since Sanyo is quite a bit more expensive I`m still undecided.

[Greengrocer]

I thought that 3,5 kW units would be enough. I was looking at the top of the range models Super Daiseikai or even Nordic daiseikai (is the heater in the outdoor unit worth an extra 70€ per unit) from Toshiba and Shiki sai kan from Sanyo. Of course the guy selling Toshiba is telling me that Sanyo is crap and the guy selling Sanyo tells me it is the best thing since sliced bread(the only air con that is actually made in Japan, totaly different technology...). If they were evenly priced I`d go with Sanyo in a heartbeat, but since Sanyo is quite a bit more expensive I`m still undecided.

The required cooling / heating capacity should be calculated for your summer / winter conditions. My suggestion of 4-5kW per room is based on an approx "rule of thumb" I use for UK residential applications. I suspect your summers are warmer and winters colder than we get so you may need even more capacity. Get supplier / installer to do a proper heat load calculation for your area and house construction.

As for the different manufactures the 3.5kW Toshiba Super Daiseikai looks like it's a bit more efficient than the Sanyo. Both are "A" rated but the Tosh has an EER of 4.12 vs the Sanyo's 4. COP's in heating are 4.42 & 4.21 respectively so there's not much in it.
The Toshiba looks like it has better air filtration system with Plasma.
The Sanyo system senses the room temp at the remote wireless controller so will cool / heat according to where the controller is located. The Toshiba system uses the more convensional return air method. There's pros & cons with both method.
Based on the info I have the Sanyo indoor units look to be a bit quieter which may be important if the rooms are bedrooms.
Overall there's probably not much between them technically.
I'm not familiar with the Tosh Nordic Daiseikai - not sold in the UK. However, I suspect it may have better heating performace at a lower outdoor temperature. As standard both systems can operate in heating down to -15c. The Nordic version may offer heating to -20c or lower. What's your design winter ambient temperature in Slovenia?
What warranties are being offered and how much for annual maintenance? These also should be considered for a proper comparrison.

[kok]

The required cooling / heating capacity should be calculated for your summer / winter conditions. My suggestion of 4-5kW per room is based on an approx "rule of thumb" I use for UK residential applications. I suspect your summers are warmer and winters colder than we get so you may need even more capacity. Get supplier / installer to do a proper heat load calculation for your area and house construction.

As for the different manufactures the 3.5kW Toshiba Super Daiseikai looks like it's a bit more efficient than the Sanyo. Both are "A" rated but the Tosh has an EER of 4.12 vs the Sanyo's 4. COP's in heating are 4.42 & 4.21 respectively so there's not much in it.
The Toshiba looks like it has better air filtration system with Plasma.
The Sanyo system senses the room temp at the remote wireless controller so will cool / heat according to where the controller is located. The Toshiba system uses the more convensional return air method. There's pros & cons with both method.
Based on the info I have the Sanyo indoor units look to be a bit quieter which may be important if the rooms are bedrooms.
Overall there's probably not much between them technically.
I'm not familiar with the Tosh Nordic Daiseikai - not sold in the UK. However, I suspect it may have better heating performace at a lower outdoor temperature. As standard both systems can operate in heating down to -15c. The Nordic version may offer heating to -20c or lower. What's your design winter ambient temperature in Slovenia?
What warranties are being offered and how much for annual maintenance? These also should be considered for a proper comparrison.

I believe that we have a little higher insulation standards here in Slovenia, which is probably the reason why the local installers have all recomended me the 3,5kw units. But i`ll look into it again, so thanks for the advice.
Nordic Daiseikai has exactly the same specs as Super Daiseikai - the only difference is that it has an electric wire(heater) under the propeler in the outdoor unit, which prevents condens from freezing. Taht is also where Sanyo really shines on paper with a totaly new technology which eliminates the need for reverse cycle defrost it utilises hot gas injection defrosting, for non-stop heating operation. Sanyo also has 0,6 kW higher heating capacity and looks sexier. Both manufacturers have the same basic 2 year warranty. Average temperature in Junuary is -1C, with peaks of -1oC to - 15C.

[Greengrocer]

I believe that we have a little higher insulation standards here in Slovenia, which is probably the reason why the local installers have all recomended me the 3,5kw units. But i`ll look into it again, so thanks for the advice.
Nordic Daiseikai has exactly the same specs as Super Daiseikai - the only difference is that it has an electric wire(heater) under the propeler in the outdoor unit, which prevents condens from freezing. Taht is also where Sanyo really shines on paper with a totaly new technology which eliminates the need for reverse cycle defrost it utilises hot gas injection defrosting, for non-stop heating operation. Sanyo also has 0,6 kW higher heating capacity and looks sexier. Both manufacturers have the same basic 2 year warranty. Average temperature in Junuary is -1C, with peaks of -1oC to - 15C.

Sounds like you've made your mind up. A 2 year warranty sounds a bit light though. Normally both these manufacturers offer a 3 years parts warranty (at least in UK). Labour is down to the installer which should be at least 12months.
You might find the systems will struggle to produce enough heat in ambients of -10/-15c. I don't have a tech manual for these but I suspect they will struggle to produce 1.5kW at these lower ambients. If they are the only form of heating in the rooms you may want to consider some additional / supplimental heating just in case.

[kok]

I guess we have a slightly lower warranty standards over here.

Anyway thank you all for your advice - I`m definitely going with 3 single split units now.

[kok]

Oh, one more question: When do the manufactures usually launch new models?

[Debonair Spain]

Oh, one more question: When do the manufactures usually launch new models?


Usually beginning of year or at major air conditioning shows.

[chemi-cool]

I have one Sanyo Ergo split in one of the bedrooms, 12 years without any problem, excellent machine.

[back2space]

One thing when I have looked into this is that if you have 3 separate systems, and perhaps you may only have 1 system running at any time for instance in heating you may only have bedroom set at 18 and lounge at 22 and other unit set at 18C. The lounge unit may only be running providing the heat while the other units are thermo off. Theres no point having a big outdoor unit running one unit at any one time. I checked mitsubishis multisplits, the outdoor unit can ramp down to 1.5kw of cooling output at its lowest, using about 400watts electricity.

Whereas having separate splits systems you have perfectly sized outdoor unit to match the indoor that unit can ramp down to 900watts of cooling output using about 250 watts of electricity.

So the main reason is efficiency, how often are all 3 units going to be running demanding heating/cooling?

[Greengrocer]

One thing when I have looked into this is that if you have 3 separate systems, and perhaps you may only have 1 system running at any time for instance in heating you may only have bedroom set at 18 and lounge at 22 and other unit set at 18C. The lounge unit may only be running providing the heat while the other units are thermo off. Theres no point having a big outdoor unit running one unit at any one time. I checked mitsubishis multisplits, the outdoor unit can ramp down to 1.5kw of cooling output at its lowest, using about 400watts electricity.

Whereas having separate splits systems you have perfectly sized outdoor unit to match the indoor that unit can ramp down to 900watts of cooling output using about 250 watts of electricity.

So the main reason is efficiency, how often are all 3 units going to be running demanding heating/cooling?

The main reason for going down the Multi route (1 outdoor 2,3,4,5 indoor units) is normally due to restricted external space for multiple outdoor units &/or a limited power supply – 1 power supply for multi system whereas 3 are needed for 3 separate splits + space to locate 3 outdoor units.
A multi system can only cool or heat at any one time so to reduce the chance of simultaneous cooling & heating demands the indoor units should serve similar sized rooms or types of rooms e.g. all bedrooms or rooms facing the same aspect (N,S,E or West). If you mix room types (e.g. ground floor Lounge & 1st floor bedroom) or different aspects (North & South facing) on the same outdoor unit you increase the chance for simultaneous cooling / heating demands. Another factor is lifestyle diversity e.g. when are the rooms used and are they used at the same time? For a residential house the bedrooms are not normally occupied at the same time as the lounge. In a commercial building all areas are generally occupied at the same time so this type of diversity does not exist so much.
However, lifestyle diversity in a residential home can be used to reduce the size of the outdoor unit if the rooms served are not all occupied at the same time.
E.g. Theoretical residential system.
2 rooms - 1 x upstairs bedroom & 1 x downstairs lounge. Bedroom cooling/heating load =2kW (at night), lounge cooling / heating load =5kW (during day or evenings only).
Two separate split systems would require a 2kW & 5kW system for a total of 7kW installed. On a multi system it is feasible to install a 2kW & 5kW indoor unit but only install a 5kW outdoor unit. When occupied the outdoor unit has ample capacity for each room. However, if both rooms were occupied at the same time and both required cooling or heating at the same time then the 5kW outdoor would be undersized. The situation for heating would be similar since the occupants can only be in one room at a time - theoretically.
On most multi systems you can determine which indoor unit is the master (or at least on Daikin you can). This unit will control the operational mode of the outdoor unit. If the other indoor units want the same mode as the master then all well & good. If not then they have to wait until the master (& any other indoor units) have been satisfied. Once satisfied the master unit will then allow the opposite mode of operation if required by any other indoor unit.
So to answer your question “how often do simultaneous demands for heating and cooling occur”. The answer depends on how you design the system and what temperatures you set in each room.
Of course you could also mix 1:1 splits and Multi’s on the same building. Done this many times. 1:1 Splits downstairs for larger capacity lounge / conservatory and multi system upstairs for the bedrooms.
As the old saying goes “there’s more than one way to skin a cat”.;)

[back2space]

Very informative post Greengrocer, what are your thoughts on the issue of efficiences across multisplits and the outdoor unit not being able to ramp down as low as say a perfectly sized 1:1 installation?

[Greengrocer]

Very informative post Greengrocer, what are your thoughts on the issue of efficiences across multisplits and the outdoor unit not being able to ramp down as low as say a perfectly sized 1:1 installation?

Hi Back2space.

To a large extent the minimum turndown ratio / capacity of a Multi split will depend on the manufacturer. Some are better than others. Looking at Misubishi Electric systems their nom 5.2kW MXZ-3A54VA outdoor unit has a min / max cooling capacity of 2.9 to 6.8kW.
A similar sized Daikin 3MXS52E has a min / max range of 1.95 to 7.07kW. Both at rated at a nominal 5.2kW.

The min / max capacities are also dependant on the size of the indoor units connected. You need to inspect the manufacturers multi split combination ratings to see what the differences are for specific indoor unit combinations.
Generally speaking the smaller the system capacity the lower the minimum turndown that can be achieved e.g. a nominal 10kW Mitsi MXZ-5A100VA has a cooling range of 3.7 to 11kW.

At the end of the day the system must be selected for the max capacity required for each room. You should therefore also consider the power input differences between the 1:1 splits and multi's at their respective full load or 50% capacities since this is where they will spend most of their time. I suspect there will be greater variances at these levels.
Of course the other factor that comes into play is the energy efficiency (EER/COP) of each individual unit or system. Once again som are better than others.
For example Hitachi have just launch a 1:1 High wall split (S range). The 1.8kW model (0.5kW to 2.4kW cooling range) has an EER (cooling) of 6.0 and a COP (heating) of 6.36 which is the highest I've seen so far. Three of these splits would almost certainly beat a 3:1 A/A rated multi on power input. However, they would cost considerably more to supply / install.
It's swings and roundabouts.

[back2space]

Hi Back2space.

To a large extent the minimum turndown ratio / capacity of a Multi split will depend on the manufacturer. Some are better than others. Looking at Misubishi Electric systems their nom 5.2kW MXZ-3A54VA outdoor unit has a min / max cooling capacity of 2.9 to 6.8kW.
A similar sized Daikin 3MXS52E has a min / max range of 1.95 to 7.07kW. Both at rated at a nominal 5.2kW.

The min / max capacities are also dependant on the size of the indoor units connected. You need to inspect the manufacturers multi split combination ratings to see what the differences are for specific indoor unit combinations.
Generally speaking the smaller the system capacity the lower the minimum turndown that can be achieved e.g. a nominal 10kW Mitsi MXZ-5A100VA has a cooling range of 3.7 to 11kW.

At the end of the day the system must be selected for the max capacity required for each room. You should therefore also consider the power input differences between the 1:1 splits and multi's at their respective full load or 50% capacities since this is where they will spend most of their time. I suspect there will be greater variances at these levels.
Of course the other factor that comes into play is the energy efficiency (EER/COP) of each individual unit or system. Once again som are better than others.
For example Hitachi have just launch a 1:1 High wall split (S range). The 1.8kW model (0.5kW to 2.4kW cooling range) has an EER (cooling) of 6.0 and a COP (heating) of 6.36 which is the highest I've seen so far. Three of these splits would almost certainly beat a 3:1 A/A rated multi on power input. However, they would cost considerably more to supply / install.
It's swings and roundabouts.

Im going for 3 indoor floor mounts connected to the MXZ-80 Outdoor unit. Mitsi.

They are 3.5kw for the indoors and will be run at ultra low fan speed.

Getting LG system ripped out actually as its not working properly and replacing with Mitsi... LG = Crap!

3.5kw i understand is the output at high fan speed, so at ultra low fan speed output is prob about 2kw? Perhaps?

This should do the trick works out cheaper if you have more than 2 indoor units to get multi split if less than 3 indoor units cheaper to get separate splits 1:1 as you call it.

What do you reckon to my configuration.

I have oversized slightly by 1.5kw as so when we have hot days or many friends or parties we can use the extra capacity in high fan speed and not have to worry about being too hot/cold.

Plus the extra heating capacity is there on the cold winters mornings/nights.

Oh and I have already put a post on about oversizing inverters.. have you seen it, not sure if im doing the right thing.

Im only oversizing 1.5kws though nothing major.

[Greengrocer]

Im going for 3 indoor floor mounts connected to the MXZ-80 Outdoor unit. Mitsi.

They are 3.5kw for the indoors and will be run at ultra low fan speed.

Getting LG system ripped out actually as its not working properly and replacing with Mitsi... LG = Crap!

3.5kw i understand is the output at high fan speed, so at ultra low fan speed output is prob about 2kw? Perhaps?

This should do the trick works out cheaper if you have more than 2 indoor units to get multi split if less than 3 indoor units cheaper to get separate splits 1:1 as you call it.

What do you reckon to my configuration.

I have oversized slightly by 1.5kw as so when we have hot days or many friends or parties we can use the extra capacity in high fan speed and not have to worry about being too hot/cold.

Plus the extra heating capacity is there on the cold winters mornings/nights.

Oh and I have already put a post on about oversizing inverters.. have you seen it, not sure if im doing the right thing.

Im only oversizing 1.5kws though nothing major.

Your combination (3 x size 35 indoors & 1 x MXZ-4A80VA outdoor) will give you this:-

2.65kW Cooling / 3.13kW Heating on each indoor unit at full load.
i.e. all units running in same mode together on design UK conditions which for Mitsi are:-
Summer 21cDb/15cWb room temp, 27c ambient.
Winter 21cDb room temp, -1cWb ambient.

These capacities will be high indoor fan speed. At lower fan speeds the indoor unit capacity will be reduced (need to look at Mitsi Tech manual for this info which I don't have to hand).
However, at milder ambient temps the capacity of the outdoor unit increases so this helps to counter balance the lower fan speed setting - to a point.
All in all your selection (not knowing the full details or how load estimate was done) looks OK. You could put larger indoor units onto this outdoor unit if you wanted. For the MFZ floor mounted the max combination is 1 x size 35 & 2 x size 50. This gives you 2.96/3.48kW cooling / heating on the 50's but reduces the 35 capacity to 2.08/2.44kW.
Also bare in mind that if one of the indoor units is turned off the remaining two can access the full capacity of the outdoor units so in your case 2 x 35's would increase from 2.65kW cooling each to nearer their full 3.5kW rating.

For residential projects I use a check / rule of thumb of 80-100watts cooling / m2 of floor area which is a pretty good check method for most situations - except conservatories. 80watts/m2 for bedrooms & 100w/m2 elsewhere. What's yours like for each room served?

Oversizing inverter systems is not normally a problem providing you don't go to OTT. If sized correctly (for max summer / winter conditions) any A/C system is oversized for other times of the year when ambient temps are milder. Inverter systems are no different. It simply ramps down to find it's balance point and sits there until something changes (ambient temp, room load, room set point etc).

Hope this helps.

[back2space]

Many thanks for that Greengrocer.

The mitsi kit sounds great, I could do with looking at a tech manual I think to see how performance is measured at low fan speeds etc.

I currenty have lg 2 x 3.5 indoor to one 7kw outdoor unit. This system is oversized now slightly although on the very cold days this yr it did struggle in bringing the temps up in the house beyond 21C. However I think this is because its LG and the control strategy is the reason its going!!

My rooms here are large victorian rooms, high ceilings, no insulation in walls, draughty double glazing and can get as low as 10C in winter inside if no heating on!

I prefer a slighty oversized design as it means that I can leave internal doors open to hallways etc and the extra cooling capacity also goes into these areas that are not air conditioned/ kitchen and bathroom and long hallway.