Split Inverter Air Conditioning

[SimonH2]

Whats the maximum wattage and amperage a 1.5mm2 cable can handle?

Wattage is never quoted.

Amperage is determined by the type of protection (eg cartridge or rewirable fuse or circuit breaker), the conductor material (there are materials other than copper), insulation material (standard PVC is rated up to 70˚C, other materials can go higher), installation method (a cable buried in insulation will heat up more, and thus carry less current safely, than one buried in plaster), and grouping (if you put several cables together then you have to derate them).
But for example, a 1.5mm² thermoplastic, non-armoured, copper cable, 2 core, single phase AC, ambient 30˚C, conductor 70˚C, is stated as 20A for reference method C (clipped direct or directly buried in masonry) or 17.5A for reference method B (enclosed in conduit or trunking). The volt drop is 29 mV/A/m. Even after applying a correction factor for the type of fuse (which doesn't seem to be given for "13A" fuses), that's plenty of headroom for something running at around 7.5A max.

The cable capacity tables in BS7671 (aka "the regs") run to nearly 50 pages !

The voltage capacity of the cable is determined by the type and thickness of the insulation.

Wattage is then the product of multiplying rated current by operating voltage - though you may also have to factor in power factor if it's significantly different from 1.

If a 1.5mm cable is rated at 14A, then technically it's way higher than the 13A fuse that would be inside the plug anyway, so the fuse will blow before the wire has any issues.

Correct

But does a 1.5mm cable rated at 14A get any hotter drawing 13A than a 2.5mm cable drawing 13A?

Yes it will, it's got only 60% of the copper and thus will have higher resistance, thus more power created by the current flowing through that resistance. But, it's well within the rating of the cable and generally you can ignore the difference.

 

[john2k]

The spec sheet for the AC system says: Power input (Min-Max) W: 100-1580W

However, the sticker on the outdoor unit says:

Power Source: 220-240V ~ 50Hz, 1Ph
Rated Current: 10A
Rated Input: 2200W

Seems a bit confusing because according to the spec sheet instead of 2200W it's suposed to be 1580W, I am assuming the sticker on the unit is referring to the MAX the unit can possibly draw but the spec sheets figures of 100-1580W is referring to typical current draw which should not really go to 2200W. Either way, it seems that even with the MAX rating of 2200W, a 13A fuse on flexible cable should be fine.


Also, does anyone know how much kw/h energy typically leaving the system on lets say 12 to 14hrs a day will actually draw? The system has a A++ SEER energy rating and on the energy rating label it says: kWh/annum 201, anyone know what this 201 figure means? I know it refers to cooling efficiency. Below is a picture of the energy rating label, can anyone kindly explain what the 201 for SEER and what the SCOP rating means:

 

[john2k]

Also, is it necessary to use the cable rated for outdoor use like the Arctic ones? I'm planning to run it inside a plastic conduit anyway too.

 

[SimonH2]

SEER and SCOP are standardised measured of efficiency for cooling and heating.
http://www.daikin.co.uk/seasonal-efficiency/ seems to have a decent description if you look at the factsheet there.

In short, "efficiency" for heat pump units is expressed in terms of Coefficient of Performance since saying 300% efficiency doesn't really make sense. Under ideal conditions, pumping from a reasonably warm environment to a cool one, modern units will generally "move" around 3 units of heat for each unit of electricity input. This means that in cooling mode you'll get 3 units of cooling, or in heating mode, 4 units of heat, for each unit of lecky going in. That's in good conditions - so cooling when the room is warm and outside cold, or heating when the outside is warm and the room cold.

Once conditions depart from that ideal, performance drops. So for example, when heating a room when it's cold outside, performance can drop below unity - ie the electricity going into driving the compressor is more than the amount of heat it can pump into the room ! That's why many air-source heat pumps include an electric heater that is used instead of the heat pump when it gets down to around freezing outside.

It looks like SEER and SCOP are an attempt to define a "standard" season and conditions - so manufacturers can state how the unit performs under a common set of conditions. What it does NOT do is say what it'll cost you to run, since (just like with car MPG figures) conditions are not very likely to match with those standardised ones. But what it does do, is give you a means of comparing different units. But if the season (and your usage) met the standardised conditions, the unit would use the number of kWh (ie units) of electricity stated on the label.

And yes, you should use a cable suitable for outside use.

 

[ban-all-sheds]

it says: kWh/annum 201, anyone know what this 201 figure means?

201kWh/year?

 

[EFLImpudence]

.

 

[WhydidIstart]

I've got the correct trunking. Just a quick electrical question. If the system's spec sheet says: Power input (Min-Max) W: 100-1580W Does that mean the maximum power draw the system attempt to draw will be 1580W? If that is the case then it is way within 13A which means technically I should be able to run it off a 2.5mm flex cable wired to a 13 heavy duty plug?

As has already been said, this looks like an inverter system from the variable power and also the high efficiency rating, however you really should make sure it is inverter as the start-up currents of the non-inverter systems can be massive. I.e. in the 3 - 8 times full load range, also the power factor of a stalled motor is usually not good, so assuming PF of 0.5 this effectively doubles the already high starting current (assuming we calculated that from 3 – 8 times the wattage).

Fuses will protect the cable, but these massive start-up currents can cause problems when the cables are too thin as the voltage drop will be high in this start condition which may mean the compressor motor won't start up quickly - or worse won't start at all. This usually happens after cycling off and on when the compressor has to start against an already partially pressurised system.

For the above reasons the installation instructions usually say somewhere what size protective device is required and from that you can determine the cable size.

I know not relevant for your install, but regarding the 'quick connect' refrigerant lines that were being discussed, it's not a good idea to reopen the self-sealing ones unless you absolutely have to. This is because usually after several months of operation they will stick and you will lose all your refrigerant if you try to disconnect them.

 

[john2k]

As has already been said, this looks like an inverter system from the variable power and also the high efficiency rating, however you really should make sure it is inverter as the start-up currents of the non-inverter systems can be massive. I.e. in the 3 - 8 times full load range, also the power factor of a stalled motor is usually not good, so assuming PF of 0.5 this effectively doubles the already high starting current (assuming we calculated that from 3 – 8 times the wattage).

Fuses will protect the cable, but these massive start-up currents can cause problems when the cables are too thin as the voltage drop will be high in this start condition which may mean the compressor motor won't start up quickly - or worse won't start at all. This usually happens after cycling off and on when the compressor has to start against an already partially pressurised system.

100℅ a inverter system. Supplier also mentioned that any models made 2014 onwards have to be inverter systems.

 

[john2k]

Seeing as 1.5mm2 cable should be sufficient, I am thinking to go with this cable: http://www.screwfix.com/p/time-arctic-flexible-cable-3183yag-3-core-1-5mm-x-10m-blue/95612

Any thoughts?

 

[john2k]

Just had my system installed. A F Gas engineer installed it.

They used the pipes and did the flaring and cut pipe exactly to length. In total the length of pipe is probably around 3.5meters long. Once they made all the connections, they release the refrigerant using the allen-key. They coupled the copper pipe but instead of using couplers they use some tool to create a flare and kind of weld the pipes together rather than using solder.

The system has been working fine. Today I went outside to look at the unit. And there is a sticker on it that says the following:

1. Ensure to evacuate the air inside the indoor unit and pipes with vacuum pump.
2. Make sure the additional amount of refrigerant to be charged is based on the pipe size and length please refer to INSTALLATION INSTRUCTIONS for details.
3. Incorrect installation due to ignoring of the instruction will cause serious problem to the machine.

The second step I am assuming isnt needed because the amount of refrigerant inside the system is enough for the 3.5m length that my pipes run. But the first step says something about evacuating air from indoor unit. They didn't use any vacuum pump or do any air evacuation indoors. I did ask if the system needed to be bled but they said that is usually needed for very long runs. So basically all they did was connected the pipework and the wiring and released the refrigerant. Reading this sticker has made me a little paranoid lol.

 

[SimonH2]

They coupled the copper pipe but instead of using couplers they use some tool to create a flare and kind of weld the pipes together rather than using solder.

The connections at the ends are typically a flared end - the end of the pipe is flared out into a acone, and then this is clamped firmly between the conical point of the fitting and the internal cone of the nut. Some internal units just have a pair of pipes sticking out to braze the connections to.
The connections are brazed, typically using a propane torch and no flux - the reducing properties of having the flame set right (and the right technique) stop the copper oxidising before the braze wets it.

The system has been working fine. Today I went outside to look at the unit. And there is a sticker on it that says the following:

1. Ensure to evacuate the air inside the indoor unit and pipes with vacuum pump.
2. Make sure the additional amount of refrigerant to be charged is based on the pipe size and length please refer to INSTALLATION INSTRUCTIONS for details.
3. Incorrect installation due to ignoring of the instruction will cause serious problem to the machine.

That sounds about right.

The second step I am assuming isnt needed because the amount of refrigerant inside the system is enough for the 3.5m length that my pipes run.

Yes, the systems come pre-loaded, and for short pipes the additional amount isn't critical.

But the first step says something about evacuating air from indoor unit. They didn't use any vacuum pump or do any air evacuation indoors. I did ask if the system needed to be bled but they said that is usually needed for very long runs. So basically all they did was connected the pipework and the wiring and released the refrigerant. Reading this sticker has made me a little paranoid lol.

You are right to be paranoid - because the job was bodged.
The pipes must be evacuated before charging (adding refrigerant), for several reasons. First and foremost - you do not want any air or moisture in the system. Air will affect performance, moisture will freeze and cause problems.
It also allows the installer to check that there are no leaks. The typical check here is to leave the pump running for a while until the gauges show that it's not dropping in pressure any more - and then shutoff the valves on the gauge set and leave the pump running for a few more minutes. The gauge shouldn't move, and especially, it should not move at all when the valve is opened again - if it does, then air leaked into the system while the valve was closed.
There is a technique of adding refrigerant to the system, then letting it out. It mixes with the air, and when you let it out, it takes most of the air with it. But, this is illegal unless youa re using equipment to recover the gas - and if you have that to hand, then you might as well just do the job properly I have done that myself - but it was on the car, I was using propane, and it let it out into the air intake (I was running on propane anyway) so it got burnt.
I suggest you call the manufacturer and ask their advice. They may say that if it's running fine then leave it. It needs testing fully in all modes - especially cooling. The worst place to get a bit of ice is in teh expansion valve or capilliary - and that won't happen in heating mode.
But I would suspect they are more likely to say that the installer should come back, empty the system, pump it down (apply a vacuum), and re-charge with fresh refrigerant. The installer will be really pi**ed off if you make him do that - apart from his time, it'll cost him for new refrigerant, and it'll cost him to dispose of the old (contaminated) refrigerant. If he sets off to just let the gas out into the atmosphere - tell him you been told to call the police if he does that as it's a criminal offence (that should put the sh*ts up him).

 

[ajstoneservices]

They won't have used a vaccum pump indoors it is done at the outdoor unit.

 

[john2k]

You are right to be paranoid - because the job was bodged.
The pipes must be evacuated before charging (adding refrigerant), for several reasons. First and foremost - you do not want any air or moisture in the system. Air will affect performance, moisture will freeze and cause problems.
It also allows the installer to check that there are no leaks. The typical check here is to leave the pump running for a while until the gauges show that it's not dropping in pressure any more - and then shutoff the valves on the gauge set and leave the pump running for a few more minutes. The gauge shouldn't move, and especially, it should not move at all when the valve is opened again - if it does, then air leaked into the system while the valve was closed.
There is a technique of adding refrigerant to the system, then letting it out. It mixes with the air, and when you let it out, it takes most of the air with it. But, this is illegal unless youa re using equipment to recover the gas - and if you have that to hand, then you might as well just do the job properly I have done that myself - but it was on the car, I was using propane, and it let it out into the air intake (I was running on propane anyway) so it got burnt.
I suggest you call the manufacturer and ask their advice. They may say that if it's running fine then leave it. It needs testing fully in all modes - especially cooling. The worst place to get a bit of ice is in teh expansion valve or capilliary - and that won't happen in heating mode.
But I would suspect they are more likely to say that the installer should come back, empty the system, pump it down (apply a vacuum), and re-charge with fresh refrigerant. The installer will be really pi**ed off if you make him do that - apart from his time, it'll cost him for new refrigerant, and it'll cost him to dispose of the old (contaminated) refrigerant. If he sets off to just let the gas out into the atmosphere - tell him you been told to call the police if he does that as it's a criminal offence (that should put the sh*ts up him).

I emailed the installer to ask the same question and they said: vacuuming the system is only needed when you have numerous brazes across the pipe route or on systems that are longer than around 10m. They said that they pushed gas through the pipes and when they installed it, all the pipes were securely taped shut to avoid anything getting into the system. They say that there was only one braze per unit which they cleared the pipes out after with gas and re taped up the system to avoid any thing getting in the system.

Is there a way I can test to see if there is air in the system or if anything is wrong? because installer says if anything is wrong they will come out to fix it. When I put it on cooling mode, initially it blows as a fan and after a few minutes then chilled cold air comes out. And in heat mode, it takes a few minutes before it blows hot air.

 

[SimonH2]

Is there a way I can test to see if there is air in the system or if anything is wrong? because installer says if anything is wrong they will come out to fix it. When I put it on cooling mode, initially it blows as a fan and after a few minutes then chilled cold air comes out. And in heat mode, it takes a few minutes before it blows hot air.

It sounds like it's working - that's the only test you can do.
I'll still contact the manufacturer and ask their advice - the installer may have invalidated the warranty, in which case you would want them to do whatever the manufacturer requires them to do to re-instate it. What they say is correct - to a point; but it's still taking "shortcuts".

 

[davelx]

t. When I put it on cooling mode, initially it blows as a fan and after a few minutes then chilled cold air comes out. And in heat mode, it takes a few minutes before it blows hot air.

That's how mine works.