Aircon One on One, the Things You Should Know

This is yet another of my boring Instructables without any videos or lots of images showing things.
So if you expected this and don't like just reading then please move to avoid being disappointed.
But if you think there might be something useful coming up please read on - you never know what you miss.
In either case I thank you for checking it out!

If your airconditioner, fridge or freezer works just fine then maybe you don't have to read it at all ;)
But there are those of use with an older system that seems to work less efficient.
I will try to give you some simple advise and hints on how to spot problems with the performance of you cooling system and in some case a clue on the causes.
In some cases a service will be required, but even then you would at least know why and can check if the guy is not ripping you off.

Most airconditioners or even fridges and freezers these days run on R134a as the refrigerant as it is considered to be "Ozone friendly".
Older systems often use R22 and some might still use R12.

As R12 and R22 are no longer available in most countries due to their Ozone killing capabilities these system can give you grieve when it comes to getting them serviced.
R134a systems are fine in this regard as this refrigerant is still widely used.
Some people might now think that they can just switch to R134a and be done with it but that is a no go.
R134a runs on much lower pressures and requires a different metering system for the control for starters.
Seals and compressor oils can be an inssue too in some cases.
But more on that in a bit....

If you made it here than I guess this is one of your questions.
The simple answer is a loss of gas in many cases.
For cars it is often a dirty and blocked evaporator or condeser - can you remember the last time you cleaned yours? ;)
Sometimes it is as simple as blocked filters or a faulty thermostat.
But if season after season the air coming out is less cold then you can be almost certain to have a leak somewhere.
You might have or know someone with a fridge that is older than you remember.
The funny thing is they often still cool perfectly despite missing seals and rust everywhere.
So why do they keep going until the compressor fails while your aircon does not?
What makes a system easy to install and easy to service is usually what makes them fail as well.
Where a fridge or freezer has everything fully sealed and brazed your aircon almost always has one or more mechanical pipe connections.
Split systems usually come pre-charged and with quick connectors these days, older ones have screw connections with service ports.
Even your car has the service ports.
As you might know a mechanical connection has a higher chance of failure than a brazed one, especially with constant temperature and pressure changes inside the system.
Actual cracks in evaporators or condensers are quite rare unless there was physical violence of some sort involved.

Unless you are trained service technician you can't, at least not quick and simple and without the right tools.
But there are some things that will give you a clue.

1. Is the air coming out of the hot side of your system unusally hot?
That could well mean the system is low on gas if the cold air coming out is not really cold too.

2. Is the cold pipe coming from the compressor or going to the evaporator badly frozen?
Especially on a humid day this line can freeze over but excessive ice build up is certainly a sign of refrigerant loss.

3. Is you evaporator freezing over and the hot air coming from the condeser very hot?
If the metering device is not failing then the best guess is a system low on gas, especially if 3 years or older.

4. You see oil spots under a connection or a connection that feels greasy?
Compressor oil always mixes to some extend with the refrigerant.
A slow leak can cause oil to be passed out with the refrigerant.
Unlike the refrigerant the oil will stay where it is or drop down if too much.
So this is certainly an idication for a leak.

5. The system suddenly lost most or all cooling but the compressor still runs fine.
Apart from the rare sudden decompression from a blown seal there is only the metering device and the compressor itself left.
If you can confirm the compressor kicks in as usual but apart from that no cooling happens check for temperature differences.
The cold air coming out the cold side is the same or only marginal lower temp as the air being sucked in.
The air coming out of the hot side is same or only marginal warmer than the ouside temp.
If those two are correct you can assume a fault with the compressor valves or the metering device.
It means the coolant flow is too low to have any real effect.
The same however can be true for a system that has next to refrigerant left, so a service is required either way to confirm the problem.

6. On my split system the piping to the outside is getting really hot but it still cools fine.
Many split systems use a reservoir for the refrigerant to allow for a higher fill rate at the factory and to have longer intervals before a refill would be due.
But even without it a split system has a higher gas volume in the additional pipes than a window unit.
If the level gets low the compressor might be still be able to cool the inside at (almost) suffient levels but at the expense of overheating the refrigerant as the lower volume still needs to transport the same amout of heat energy.

Temperature checks....
A good indicator for the health of a cooling system is to measure the temperatures involved.
As a rule of thumb you can estimate that a healthy system will cool the incoming air by 10 to 15°C.
This depends on the system size, refrigerant volume and outside temperature to some extend.
On a very hot day when your inside temps match the outside temps the system will struggle to provide enough temperature difference and operates on its limit.
The best way to check is if temperatures are "moderate" in the range between 25 and 28°C or below.
The humidy should not be too high either as it greatly affects performance, if it above 75% wait for a better day ;)
So we assume the outcoming air on the cold side is between 10-15°C below what is coming in for this example.
If your system does not make 10° difference on a 25° day something is wrong and you should check for low refrigerant levels first.
If your outcoming air is coming out below 4°C you have a problem with the metering device that needs to be rectified.
A faulty metering device can cause freezing on your evaporator and with this damage the cooling pipes.

Ok, good to go? Then what do you need to measure the temps?
If you have a clamp on thermometer you have the best option, but then you would not be readin this as you might be a qualified service technician anyway...
Next best option is a tiny thermocouple on a fast acting digital thermometer or multimeter with temp reading feature.
A small sensor will be able to react very fast to minute temperature changes.
Last option would be normal in-outdoor thermometer as they are slow and not anywhere near being calibrated for their full temperature range.

What and where to measure and what to expect....
First let the damn thing run for about 15 minutes so it can reach optimum operation conditions.
Also make sure the cooling is set to max, same for the fans - you don't want the compressor to shut off while you gather your data ;)
If the performance on a hot day is bad but on a normal one you still get the 10 - 15° lower temp then it is time to check, same if you just want to satiy your curiosity in regard to your quite old system.
Depending on the refrigerant in use the temperature of the air coming out of the condenser should be like this:
Temp difference you get on the cold side is added to the outside temperature.
Now you add another 20°C to this number for cooling the compressor and overall losses.
On a 25°C day and with the air coming out inside 10° cooler this would give us 55°C as the upper limit.
Anything higher than this is a quite good indication of low system pressure and refrigerant levels.
If your temp is 45° or even lower you can be almost certain that everything is just fine.
Ok, these temps look good but I really want to be sure....
Being on the low side can mean on a good day the system performs well but above 30°C outside the cooling on the cold side won't get to the 10° difference anymore.
Here a more direct approach can help.
The coldest part of the system should be where the compressed gas goes to the evaporator.
So have to find a spot where you can measure between the compressor and the evaporator on the cold line.
Once the system is operating at peak performance this part of the system should not get below freezing.
On a good working system it should be between 4° on the lowest and 7° on the highest for good performance.
Higher or lower levels can indicate a loss of refrigerant or a problem with the metering device.
On the hot side it can be beneficial to measure as close as possible to the condeser, especially for split systems.
Some manufacturers use the longer lines on split systems for the cooling of the refrigerant if a lot of it is outside.
But no matter if you measure near the compressor where it should be cooler or the condenser input it should not be over 65° as the maximum.
If it is hotter you might be low on refrigerant.

How to measure properly and with more accuracy.
All temp readings should be as direct as possible, so in case you wondered why I did not mention IR thermometers - they are not direct and not really accurate on small and wet copper pipes.
Everything you measure should only measure the target!
So for the pipes this means insulating the sensor with foam or a piece of pipe insulation is a must, toilet paper or similar is not a good choice...
The only exception here is the incoming and outgoing air temp on the cold side of the system.
Here a so called "wet bulb" is prefered.
You use some cotton or toilet paper that you wet, not soak, in water.
The evaporation of the water in the airstream allows for a more accurate temperature reading reflecting the temps at the condenser itself - like a compensation for not being able to measure the gas temp inside.
If you have a mechanical connection, like a service port or just a connector, you should always measure on the incoming side of this connection as the brass acts like a buffer for quick temperature changes.
Of course you should use something that a good accuracy ;)
It really does make a big difference between reading just 4, 5, or 6° compared to 4.3, 5.1 or 6.8° !
Having another decimal degree won't help that much unless it is a good quality device as this usually falls withing the measuring tolerances and errors anyway.

Of course you can check much more with the right equippment but only to a certain degree and I will tell you why:
Whenever you want to use gauges on a refrigeration system to check for pressure levels you also loose a small amout of coolant.
The small the system the worse the effect of this loss.
Only way to prevent this is to have the correct refrigerant at hand and to flush the pipes and and show glass first.
You can still do checks by just connecting the gauge set as quick as possible but air compresses differently than refrigerent plus you really don't want to allow air to to get into the system.
If you do measure without flushing make sure to keep the connection as short as possible and to triple check that all vaves are closed!
Unused hoses should be scrwed onto the blind ports on the guage set to prevent any chance of a leaking valve bleeding refrigerant out!

Still wanna continue? Ok...
You have the service ports and the tool to connect to get pressure readings - is that enough?
Yes and no, no because I am too lazy to cater for all possible options in regards to service ports, high pressure side and low pressure side.
So if you don't know where to connect the gauges and hoses on your system check Youtube, there are a lot of tutorials and show offs available to give you the info you need to find the correct port and what to look out for.
I just say that in general the port that feels cold when operating is on the low side and goes onto the blue gauge, the warm one goes on the red gauge.
The next thing you should have is a so called PT Chart.
They are available through a simple Google search for any type of refrigerant out there.
A PT Chart gives information about the temperature at which a refrigerant starts to boil at a given pressure - or the other way around for that matter.
Some videos you might have watched before finding this might have stated that you only need to be within a certain pressure range for the low and high side of a system to have it operating properly.
The problem that this is as flase as it is true.
If the author was correct he would given you the corresponding temperature readings during his test and stated why this pressure is considered to be ok.
But I found a lot videos that just said a R22 system should be between 60 and 75PSI on the low side when running.
What they did not tell was the temperatures or the amount coolant required for the system, let alone the actual room size it was meant to cool at max performance.
For big split systems like used in commercial buildings this might be fine and good, but a window unit or even portable system might alreay be starting to damage the compressor above 65PSI....
So what to do?
Just to make myself clear: If your previous temperature checks already confirmed the system is low on refrigerant there is little point in wasting more of it unless you are willing to find the leak and have refrigerant at hand to fill up if required.
I assume you are ready on all accounts at your end but won't go into the details of actually filling a systems so it is back to specs - this comes soon in another Instructable for those who dare and then even with pics ;)
Make sure all valves on the gauge set are closed and connect the blue and red lines to the correct port on your system, the yellow line should be looped to the blind connector.
Quick work helps to keep the refrigerant loss at a minimum.
Both gauges should now show about the same pressure unless the system was running before.
Once the compressor starts the low pressure side will go down and the high pressure side will go up.
Depending on system size and temperatures it can take 10-20 minutes until the readings stabilise.
During that time you can connect your temperature probes to the high and low side on the coldest and hottest points in the system.
Once all is stable check the pressure gauges - they will give you the actual pressure and on an inner ring the corresponding temperature for several refrigerants at this pressure.
Here is where the PT Charts comes into play.
I am trying to keep it as simple as possible so I won't go into too much detail as big problems mean you need to fill up and that is another Instructable.
As an example we use R22 and a inside temp of 25°, outside temp 30°C.
The low side on the gauge reads around 58PSI and the inner ring tells us a temp of around minus 3°C.
This means at this pressure the R22 would start to boil at around minus 3°C.
If we now make our imaginary temperaure measurment on the cold side and read minus 3° or even below we can be almost certain the system is low on gas.
Firstly we want to be above freezing to prevent condensation and freezing on the lines, secondly if this freezing climbs into the evaporator during long uses we might see real damage.
So double check if the temp at the inlet of the evaporator is still below 4°C.
If a wet bulb on the air outlet show below this temp you also know the refrigerant is low.
Ok, you want to check the high side...
On the highside we should expect a a temperature below 65°C unless you are in a hot climate and outside temps are around 40 or higher.
But our assumed system gives us a pressure of 125PSI and a temp of around 23°C.
We already know the outside temp is 30°C and for that simple reason the air coming out there could not be colder than that.
So there is out first clue of low refrigerant levels.
If we know check the actual temperature on the hot side we might see 62°C.
Let's use out fancy PT Chart here to show it's usefulness.
If we check the chart we notice two things:
a) the temperature where our R22 would boil at 125PSI is around 22°C.
b) the pressure at which R22 would boil at our imaginary 62° is around 350PSI - this would be above safety limits if true.
We can assume certain losses to make the real temperature higher than it should or the real pressure lower for that matter.
But if the PT Chart states 22° at our measured pressure it simply means the refrigerant is taking in much more heat than what it can handle.
Assuming the hardware is ok it would indicated a very low level of refrigerant.
For the cold side it is opposite, a much colder system shows low levels.
Here you want the actual temperature at least 5-7°C higher than what the PT Chart states for the given pressure.
Simple reason is that a much colder temperature can allow liquid gas to get into the compressor which would result in sudden death syndrome ;)
This should only be possible on an overfilled system though as low system has the undercooling happening way before reaching the compressor.
You often see parts of the evaporator frosting over.

Before you jump the gun a word about under the roof systems...
If you want to measure temperatures on the hot side of the system it means measuring what is around the thing and not what temperature you might have in your backyard under a shady tree...
The other thing is that these systems are often designed to work on the limits in terms of hot side temperatures.
For most refrigerants this limit is around 70°C.
If it is far hotter than this under your roof you might want to consider to use a duct system to at least get the hot exhaust air to the outside instead of further heating the roof cavity.
The best option is to combine this with an insulated box around the unit that has the air inlets where the air enters the unit.
This way you not only remove the hot air from the system but also force cooler air into the roof cavity.
Efficiency can be be improoved by 20% or more in hot and sunny areas.

Back in the day we only had power hungry airconditioners and we just had to check for the power consumption to know how much the next power bill will sting.
Now we not only have inverter technology but also statements like maximum room size or certain "BTU" amounts.
No matter what technology is used (as long as there is a compressor involved) you can be quite certain that you need corresponding power levels to outside temperatures, room size and desired cold temperatures.
Especially portable units often fail to satisfy the expectation of the buyer who trusted the seller.
Regular outside temperatures above 30°C require a systems designed for this purpose as standard units are often designed with these temperatures as their limit.
Sometimes you can spot the difference when two units with quite similar power requirements have big differences in conderser sizes.
A bigger condenser can handle higher temps much better but requires a bit more refrigerant.
On units dedicated for hot and humid climates you often see that the condenser is much bigger than the evaporator.
The one thing that all have in common is that they won't give you less than 4°C on the cold output side.
In general you can say an inverter system uses less than the max power if not operating under full capacity.
And higher BTU values should indicate greate cooling performance.
So if one 10000BTU unit has a max rating of 4.6kW and the other 10000BTU unit has 5.4kW than the first would be considered to be more efficient.
An inverter system makes sense where you have quite big temperature changes from day to night or where you might want a system that is in high use with enough reserve for extra hot days.
Here a slightly overpowered unit would be the best choice as it will be operating below capacity most of the time and use less power than a system on the limits of capacity - for the same othe factors and conditions.

If you are in the Arizona desert and a seller tries to tell you a 2kW portable system that will cool your 75 square meter bungalow build in the 60's then you are in for a nasty surprise when the summer goens in.
Most people think only the compressor is doing the hard work and has the responsibilty for the power consumption.
The fact is that most systems use quite power hungry fans as well.
And I guess you agree that a 50W motor would not be able to move the air aorund in a ducted cooling system for your house....
So you really have to check the details before buying if you want to avoid paying more for electricity than you would have to.
Most window and portable systems these day are in the range of 3.5 t 5kW.
The majority of systems that a buyer can install himself is usually in the max range of what a normal wall outlet can handle.
When you select a new airconditioner you want a system that not only suits your cooling needs but also your comfort.
After all you don't want an airconditioner that is so noisy that you need to crank the TV up until your neighbour complains about both....

If budget is a must then do your homework!
Avoid fancy extras and let the seller know what to expect in terms of inside and ouside temperatures - plus possible problems with the sun shining on it...
If you only need to cool a single room for 8 hours or so for sleeping it is best to go with an inverter system as they are far less noisy.

Portable systems....
Here we have very few split systems still avlailable as the manufactoring costs and profits for the all in one designs with a hot air ehaust are better.
No matter what you try they are the noisiest of the lot.
Compressor and often two additional fans work in the same housing.
Proper noise insulation costs more, same for a proper way of getting rif of the condesating water....
A good system can often be spotted if it already offers a double walled and insulated hot air outlet with a properly designed adapter system to fit your window type.
Split systems here stand out if they offer a very flexible connection hose that is at least 2.5m long - anything under this only makes the installation a problem if you need to got through a window.
They can also offer lower noise levels, especially if you find the rare one with the compressor in the outside part.
Best performance is for smaller rooms up to around 20 square meters, above that you would need something with a 20amp plug.

Window units....
A window or wall unit is only as good as the airflow can reach - a fact most people irgnore these days.
If your outlet is right above the TV so you can enjoy footy with a cold beer and your bedroom is 15m down the hallway and around the corner you can't expect much.
Even less if the evening sun is heating it up.
For medium sized homes or those with bad insulation ratings it is best to have two units.
One in the general living area and one in the main bedroom - if you have kids consder them too ;)
To cool a normal sized home with a single window unit means at least 5kW and that only if airflow and layout allow for it.
So using two let's say 3.5kW units that are actuall able to cool the area down so they can shut off for a moment or two use less than a 5kW+ unit running continously without being able to cool the area down.
Some inverter units are out there but most are the standard "on-off" type.
The noise level is usually acceptable unless you are really close an it is on full power.

Most cheap installerst offer you a system at a price you just can't resist and you might be tempted to get a split system.
Be aware that bargain price only too often equals cheap as well as surprise later on.
The one thing you want a split system for is to have the outside unit always in a cool and shady spot with enough airflow and a very quite and efficient indoor unit to cool as much as possible.
Where portable units are on the opposite end split systems can be so quite you forget they are running, especially with an inverter system.
But what makes a "good" system better than then cheap alternatives?
A proper chop will have an option to show you systems of interest in a running condition.
This is the best way to know upfront how noisy it might be in your enviroment.
If other systems are running ask for them to be turned off so you can make a proper judgement.
Even if the actual fan system is considered "quite" it does not mean it goes as far as including the air in and outlets.
See it like the difference between a luxury limosine and a 10grand cheap import.
Where you Merc for example has a lot of money spent on designing the perfect airflow with minimum noise the import just uses flexible hoses that sound like your vacuum cleaner when running on full.
You have massive hearing loss anyway or your partner snores like a sawmill?
Then it might not matter anyway but otherwsie you should always make sure you can tolerate the noise of the system you selected before buying it.
Often you can find online reviews but no name brands usually mean no feedback and a lot of noise.

A good working system should cool the incoming air by about 12-15°C.

Last but certainly not least the filters!
Every airconditioner needs filters to make sure the evaporator (and sometimes the condenser as well) will stay clean. Cheap and nasty systems only too often have ill fitting filter screens or you have to flip the front cove up before getting access and the holding clips fail. The current and sad standard for most systems these days is a simple and single layer mesh screen. Sligthly better for filtering are multi-layered ones but they return the favour when it comes to cleaning them because it is often very hard to really get them clean. For people with dust or particle related alleries this often means the only way is a highly priced top of the line aircon system or a lot of DIY work to add hepa filters. Some mid range companies now start to offer systems aimed at people with allergies. Mostly standard units with added filter compartments plus better seals on the intake side. In any case you want to stay aware from anything that looks and feels flimsy or too soft to hold its shape. Especially if you have carpet and pets you will value a filter change that is quick and easy as you will have to do it often to keep the system healthy. There have been people going as far as court to make claims their filters blocked up withing a week and also claiming they cleaned them even more often. Before you go there please consider that the filter will only catch what is in the air to start with! So if you let a lot of dust and dirt in the house, have dogs or cats and even carpet you might want to consider cleaning and dusting more often if your filter fills up too quick - no offence!!! There are also articles and videos claiming that placing a wet towel or similar in front of the cold air intake will improve the cooling to a great degree. Again: think before you do! ;) The evaporating water brings the additional cooling nothing else. And this comes at the expense of a restricted airflow and highe humidity. If the air is too dry then place the wet towel in front of the outlet but never in front of the intake and blocking it with it! If you need need to clean your filter often due to ongoing use you might wonder if you are doing it right. Common sense for screen fliters states to flush them with water from the back - that means you flush against the airflow direction. Is you do a lot of cooking while the aircon is running you might already know that the filter will be much harder to clean - same for smokers. If greasy residue from cooking or too much smoking makes you filters sticky and hard to clean then alcohol or methylated spirit will help you. Before flushing with water place the filter screen on something of no importance and cover the ground with a layer of plastic foil or cling wrap followed by a layer of kitchen paper. Place the filter on it and spray the alcohol onto it until you see the paper underneath starts to soak. Cover with another layer of paper and soak this as well - on a hot day cover the paper with something to slow the evaporation of the alcohol. Before all dries up flush with water from the backside - repeat the entire process if the screen is still sticky or feels greasy.

Water to clean and assist.... On hot days people claim using the garden hose on the hot side of the aircon will help it cooling. Well, that is true if you don't flush dirt into it and keep doing it - but whar's the point of wasting all that water and standing outside in the heat? ;) In very hot and dry climates a water mist going through the condenser will reall help with system perfromance. Spraying or even flooding from the outside is just a waste of water with little effect as the airflow will prevent any decent wtting required for evaporation. For the inside in very dry climates is it best to place a wet towel lengthwise into the outgoing airflow. Less restriction and it will dry quickly compared to blocking the outlet partially with it. Never, ever! use water anywhere near electrical connections or controls of any kind and never allow them to get wet! Window units with a dirty condenser can usually be cleaned from the outside with low to moderate water pressure - try to stay in the direction of the fins, don't force the water against them! It often helps to spray the fins first with soapy water to allow and debris to soften - and of course to do this with the unit turned off as otherwise it will be too hot. The indoor evaporator should not need any cleaning if the filter is working and kept clean. Never use a pressure washer to clean your aircon!