Split Air con

[reef]

@DampCat We've had three indoor units (two 2.5kW and a 5kW) from an 8kW outdoor unit all Mitsubishi and they've been excellent since we got them in 2022. They tick along at around 700w energy use each and the outdoor unit is silent.

 

[Terminal_Boy]

I've got it in one room, don't expect it to work miracles but it definitely helps

The stuff I got off was €12 a roll and it dropped the ambient temp in the south facing rooms we used it on by 2-3°C.

We used 5 rolls, and while it’s not the most relaxing thing to fit (think giant phone screen protectors), our is still giving that 2-3°C temp reduction 4 years later being having been exposed to 40°C summers.

As always, I would recommend shutters or an awning if those are possible as stopping the sunlight from reaching the window/doors is always the most efficient way to stop windows heating up.

 

[Grim5]

Our kitchen unit is smelling a bit when it first comes on.

Will try these cleaners:

https://amzn.eu/d/9vk7MjJ

https://amzn.eu/d/4Bqb21X

That's mould

It's because you are not drying out the system, everytime you run it in summer condensation builds up inside the heat exchanger and if you don't dry it, it causes mould

Either leave the system on 24/7, or if you insist on turning it on and off constantly, in summer after using it, let it dry out before turning it off

 

[Grim5]

I’m glad I got a split unit put in my office space last year as it’s usable both for heating and cooling if necessary.

Only downside is it’s too bloody efficient and can feel too cold.
Even when I set it to 21c it feels like a fridge.

Depends how far away you sit from it. I find the further away you are from an aircon the better. Because the temp you set is a target temp for the room, not the temp of the air coming out of the unit, and you sit too close you get hit with cold air.

I tested this by setting my air con to 18c then used a thermal camera and the air coming out of the air con was 2c, and because the air is just 2c, you will feel ice cold if you sit right next to it. This is also why portable air con's make good coolers for computers, you can funnel the near freezing air straight in

 

[CaptainRAVE]

That's mould

It's because you are not drying out the system, everytime you run it in summer condensation builds up inside the heat exchanger and if you don't dry it, it causes mould

Either leave the system on 24/7, or if you insist on turning it on and off constantly, in summer after using it, let it dry out before turning it off

How does one encourage it to dry out after use?

 

[Grim5]

How does one encourage it to dry out after use?

Mine has a button on the remote for it, I just press it and it does its thing and then turns off. Alternatively if yours has a fan function, use that and just let the fan run with the motor off (not cooling) for 30-60 mins and that should be enough to dry it

 

[CaptainRAVE]

So it’s heating time of year rather than air con. Usually I’d expect lots of water to be dripping out of the drain pipe from the outdoor unit, but it looks like it’s blocked (at the exit of the unit rather than the pipe itself). Took off one of the plastic caps elsewhere on the base of the unit and the water poured out. I may connect a pipe up to it, but for now it can just drip onto the path.

 

[SoliD]

Looking to add another unit to one room and had a quote for another 5kw wall unit to go in our ex conservatory (proper roof + lantern). Gone back to Subcool who have given me a quote of £2.3k for the mitsubishi electric, but wondering if anyone else has any recommendations for south coast installers?

 

[Richeh]

Just an FYI on a previous post I made.

Had a small installer set us up with 3x Fujitsu units, £4k. The units do what they are supposed to but don't do some things that my previous 'All In One AC from ElectriQ' did - the downside of this cheap unit is, if one thing breaks it all breaks.

Things it doesn't do that with the cost, it should. Turn off all lights on the AC unit - The most used AC unit is in my bedroom but it has a constant green light that could be turned off on the cheap model but not here.

Constant flow - My old AC would keep the fan on even if the desired temp was reached. The new AC unit turns on at whatever force you set it but once it hits the temp required it turns off. You can set it to just 'fan' mode which always stays on but it doesn't do any temp control so could just be pushing warm air around.

Pro's are - they get temp down much quicker than the cheap unit with much more energy efficiency.

Completley replaceable at each stage, the unit, the pipes, the gas etc

Basically, cheap units vs expensive install. If you can afford to replace a 'cheap £500' unit every 2-5 years and don't care about the energy bill. Go for it, they work, and as long as you know within a few years something will break and the whole thing needs to be replaced for £500.

Pay more for the 'proper' install but make sure you know what units you are going for, what they do and don't do etc - This will cost you on average £5k for 3 units. But they will have the base warranty, the installer warranty (and if you go for a smaller company they will care a lot more about feedback than a big box company). If you get the right units, the right installer, the right price - this is a much better long term (10+ years) solution. But it will be a lot more expensive initially.

 

[ultim]

ive been quoted

Daikin Perfera system

• 1 × Daikin Outdoor Multi-Split Unit
• 1 × Daikin FTXM50A – 5.0 kW Indoor Unit
• 2 × Daikin FTXM25A – 2.5 kW Indoor Units

£8300 installed. Is this a good price? I've just started my air con purchase journey after getting solar panels.

 

[devil84]

Hi. Just had a multi split installed

MHI 8Kw outdoor multi split

5kw
2.5kw
2.0kw

Premium range.

How efficient are these AC to keep a room warm? How much would the 5kw cost at 28p per kw. Is it 4 times efficient so does that mean in effect 7p per kw?

It is better to keep it running for a few hours or only turning it in and off when the needed

 

[andy_mk3]

Yes that's how it works. With a COP of 4, 1kwh of energy = 4kwh of heat. You will likely find that the COP isn't quite that high in the cold, but it'll still be very efficient. Leavning it running should work out better than turning it on and off.

 

[CaptainRAVE]

Hi. Just had a multi split installed

MHI 8Kw outdoor multi split

5kw
2.5kw
2.0kw

Premium range.

How efficient are these AC to keep a room warm? How much would the 5kw cost at 28p per kw. Is it 4 times efficient so does that mean in effect 7p per kw?

It is better to keep it running for a few hours or only turning it in and off when the needed

A few hours a day in the rooms we want to heat seems cheaper than running the gas boiler. I usually give the house a good blast just before the night tariff ends too. Our house is well insulated, so the heat holds well.

 

[b0rn2sk8]

Don't forget when doing your sums, your gas boiler is probably only 85% effcient in reality.

When running the AC, it's modulation is usually tied to fan speed so low fanspeed is the lowest modulation and the most effcient. As above, its more effcient to run it for longer on low fan speed than it is to try to heat the room up quickly with high fan speed.

 

[devil84]

Don't forget when doing your sums, your gas boiler is probably only 85% effcient in reality.

When running the AC, it's modulation is usually tied to fan speed so low fanspeed is the lowest modulation and the most effcient. As above, its more effcient to run it for longer on low fan speed than it is to try to heat the room up quickly with high fan speed.

Thank you. So once i have matintained a temperature and run it at lowest fan speed (and say 19c) it is working at 4x COP efficiency ?

 

[b0rn2sk8]

It will be running at whatever the maximum COP it can achieve in the current circumstances. COP varies with outside temperature so its not as clear cut as low = 4 COP.

There should be some tables somewhere for your unit.

 

[DarkBahamut]

Generally speaking on A2A COPs are a bit higher than A2W (because you have one less heat exchanger to go through and refrigerant tempatures can be lower too), and they are a little less temperature sensitive.

On my Daikin units, the data sheet list the COP as 4.2 @ -5 C OAT (21 C inside target). That's at max output too, at minimum modulation the COP is 4.75 @ -5 C. There's some caveats because they don't count defrosts in that so real world is lower, but we achieved about a ~4.1 COP is the recent very cold weather. Coldest day with a low of -7 had 22.5 kWh input power, compared to about 110 kWh on our gas boiler.

There's some other multi split catches too, because on some units efficiency drops significantly if you only have one unit running. On my Daikin 4 port unit, if you have one unit running compared to all 4, then COP drops from ~5.3 to ~3.2. You generally want to avoid this on affected units. That would bring me to:

MHI 8Kw outdoor multi split

I don't know the exact model of outdoor unit you have, but the MHI 8 kW (SCM80ZM) unit I found as an example at minimum modulation, running 1 5 kW indoor unit, has a minimum heat output of 1.1 kW, with a minimum input power of 390 W. Thats a COP of 2.82. Pretty bad. The same outdoor unit running 3 indoor units (A 5 kW, 2.5 kW and 2.0 kW) all at the same time has a minimum heat output of 1.6 kW, and a minimum input power of 370 W, now with a COP of 4.32. AKA it got 50% more efficient. (Source: https://www.mhi.com/group/maco/products/downloads/pdf/sr_series_2022.pdf / Page 57)

Obviously if you only need heat in one room then you're pretty stuck, but it is worth bearing in mind that it's usually a serious COP hit to do that so best avoided if possible. Better to heat all of them together and turn it off once they all get up to temp. A2A has much, much lower cycling losses than A2W does because there isn't 100+ kg of water mass to deal with.

 

[devil84]

Generally speaking on A2A COPs are a bit higher than A2W (because you have one less heat exchanger to go through and refrigerant tempatures can be lower too), and they are a little less temperature sensitive.

On my Daikin units, the data sheet list the COP as 4.2 @ -5 C OAT (21 C inside target). That's at max output too, at minimum modulation the COP is 4.75 @ -5 C. There's some caveats because they don't count defrosts in that so real world is lower, but we achieved about a ~4.1 COP is the recent very cold weather. Coldest day with a low of -7 had 22.5 kWh input power, compared to about 110 kWh on our gas boiler.

There's some other multi split catches too, because on some units efficiency drops significantly if you only have one unit running. On my Daikin 4 port unit, if you have one unit running compared to all 4, then COP drops from ~5.3 to ~3.2. You generally want to avoid this on affected units. That would bring me to:



I don't know the exact model of outdoor unit you have, but the MHI 8 kW (SCM80ZM) unit I found as an example at minimum modulation, running 1 5 kW indoor unit, has a minimum heat output of 1.1 kW, with a minimum input power of 390 W. Thats a COP of 2.82. Pretty bad. The same outdoor unit running 3 indoor units (A 5 kW, 2.5 kW and 2.0 kW) all at the same time has a minimum heat output of 1.6 kW, and a minimum input power of 370 W, now with a COP of 4.32. AKA it got 50% more efficient. (Source: https://www.mhi.com/group/maco/products/downloads/pdf/sr_series_2022.pdf / Page 57)

Obviously if you only need heat in one room then you're pretty stuck, but it is worth bearing in mind that it's usually a serious COP hit to do that so best avoided if possible. Better to heat all of them together and turn it off once they all get up to temp. A2A has much, much lower cycling losses than A2W does because there isn't 100+ kg of water mass to deal with.

Wow trying to get my head round that.

Does that effectively mean I am using less power if all 3 are running at same time at low load ? Minimum input of 370w vs 390w

Trying to work out what I should do n in reality bad it’

 

[reef]

Generally speaking on A2A COPs are a bit higher than A2W (because you have one less heat exchanger to go through and refrigerant tempatures can be lower too), and they are a little less temperature sensitive.

On my Daikin units, the data sheet list the COP as 4.2 @ -5 C OAT (21 C inside target). That's at max output too, at minimum modulation the COP is 4.75 @ -5 C. There's some caveats because they don't count defrosts in that so real world is lower, but we achieved about a ~4.1 COP is the recent very cold weather. Coldest day with a low of -7 had 22.5 kWh input power, compared to about 110 kWh on our gas boiler.

There's some other multi split catches too, because on some units efficiency drops significantly if you only have one unit running. On my Daikin 4 port unit, if you have one unit running compared to all 4, then COP drops from ~5.3 to ~3.2. You generally want to avoid this on affected units. That would bring me to:



I don't know the exact model of outdoor unit you have, but the MHI 8 kW (SCM80ZM) unit I found as an example at minimum modulation, running 1 5 kW indoor unit, has a minimum heat output of 1.1 kW, with a minimum input power of 390 W. Thats a COP of 2.82. Pretty bad. The same outdoor unit running 3 indoor units (A 5 kW, 2.5 kW and 2.0 kW) all at the same time has a minimum heat output of 1.6 kW, and a minimum input power of 370 W, now with a COP of 4.32. AKA it got 50% more efficient. (Source: https://www.mhi.com/group/maco/products/downloads/pdf/sr_series_2022.pdf / Page 57)

Obviously if you only need heat in one room then you're pretty stuck, but it is worth bearing in mind that it's usually a serious COP hit to do that so best avoided if possible. Better to heat all of them together and turn it off once they all get up to temp. A2A has much, much lower cycling losses than A2W does because there isn't 100+ kg of water mass to deal with.

This is spot on. We have a MHI 8kW air to air system as well with a 5.0kW and two 2.5kW internal units and for heating it is not very efficient if using single units. For cooling it is excellent. You can run the single 5kW unit and it'll tick along at under 700w. For heating, it'll use well over 1kW usage on a single room with the 2.5kW inverter but not much more than double that with all three indoor units going.

Its worth mentioning in heating mode when its cold outside it is loud. Ours is wall mounted and its very audible inside. We tend to only use it for heating in short bursts for the living room as thats our coldest room.

 

[devil84]

This is spot on. We have a MHI 8kW air to air system as well with a 5.0kW and two 2.5kW internal units and for heating it is not very efficient if using single units. For cooling it is excellent. You can run the single 5kW unit and it'll tick along at under 700w. For heating, it'll use well over 1kW usage on a single room with the 2.5kW inverter but not much more than double that with all three indoor units going.

Its worth mentioning in heating mode when its cold outside it is loud. Ours is wall mounted and its very audible inside. We tend to only use it for heating in short bursts for the living room as thats our coldest room.

Appreciate the inisght, sounds we like we got near identical system. Here is my real life use case.

In winter, use the 5kw system to heat up my open plan kitchen/dinner. Are we saying that will be use 700watts of electricity if cooling, how about heating ? Whilst if I use the 2.5kw unit, it will use 1kw in heating mode

I only plan to use the smaller unit in summer as they are on first and second floor so it’s get really hot on south facing side.

Also I am thinking of adding a 3.5kw (outdoor unit can connect 4) to heat up my loungue in winter so in reality (in future) I will be using the 5kw and 3.5kw to heat my ground floor - which I assume will make it much more efficient now.

Would appreciate your thoughts. (Wish I had known some of this at purchase!)