Talking of Air Conditioning

[Jim]

I saw DerbyBorn's post on air con for his car and it got me to thinking about my portable air con unit that is for the home and getting that regassed (sorry don't even know if that is a word or not).

Anyway I have 2 portable air con units both about 8000BTU but they seem to work in a different way, both have pipes leading out to outside to push out the hot air but one has a tank that over time fills up with water and needs to be emptied now and then (once a day on average) and the other has NO water tank of any kind it was sold as an air con unit but it is not air good as the one with the water tank so i guess it's more of a room cooler just IMO you understand, what i need to know is how often should i re-gas the first unit (the one that collects water) and any idea what the cost would be, or should i just bin it when it dies and buy another one which seems a huge waste of money IMO

TIA

Jim

[Mr Pounder Esquire]

[Graham.]

I would like to know why air con units need regasing at all? Vehicle aircons seem to need regasing almost as a matter of routine, but fridges and freezers generally don't. Why?

[Scott M]

Air con units are like fridges and shouldn't need regassing as the motor is sealed in with the freon. Car systems have the drive force external to the pump which requires seals around the shaft that can allow leakage.

[charles]

probably because the seals are subject to vibration and a much wider range of temperatures than found in fridge. Also, seals dry out if the system isn't used for significnt lengths of time which, judging by many of the posts, is quite common. My last car, which I kept for 11 years, never needed regasing - but then I keep the aircon switched on.

[Andrew Gabriel]

Some of them evaporate all the water on the condensor (hot element), and thus blow it out as vapour up the elephant trunk to the outside. I have a large portable one which works that way. Although it has a tiny tank, normally nothing makes it into the tank as it's all been evaporated on the condensor. This actually makes the condensor more efficient too.

I don't actually use this anymore as I installed a proper split system

10+ years ago. Portable ones which have only an external outlet and not an external inlet are not efficient, as they are forcing outside air to be drawn into the house at the same rate they blow air out of the elephant trunk, so the unit will be half fighting with itself.

Regassing - I don't know. Last time I asked, it was just over £100 to get one regassed at this time of year (and much more in the summer, although it's often impossible to get anyone out as the weather starts warming because they all get much more lucrative work with businesses whose aircon didn't work when switched on for the first time that year). Much of that was the call-out charge and the time spent standing around with a vacuum pump on the system to dry it out. You might be able to do better if you can take it to the company to be done, and they can leave it on a vacuum pump whilst doing something else. They're not supposed to regass without finding and fixing the leak first. If they really can't find a leak, they are supposed to add a fluorescent dye so the leak can be found next time.

[harry]

The reason is that domestic fridges have hermetic compressors and are totally sealed. Car compressors have a shaft emerging which is driven off the engine. (Called semi-hermetic) There is invariable a tiny gas leak on shaft seal. As the system ages, cracks appear in various flexible pipes associated with the system also.

Non-automotive compressors of this type have a refrigerant gas reservoir which offsets this problem somewhat until the reservoir is depleted.

[Adrian]

Because fridges and freezers are in use all day, every day, so the seals don't dry out and shrink.

[DerbyBorn]

Adrian wrote in news:n6t909$bf5$ [e-mail]:

There are no seals in the same way that a car has a seal. The motor is welded into the the pressurised system.

[NY]

Whenever my car aircon has needed regassing, it's due to minor leaks in the pipes and the compression fittings to the heat exchanger etc, not because of leaks in the compressor. The last time I had it done, I needed a new heat exchanger (a wiggly pipe with fins, like the normal radiator) which had corroded because on this car it never got washed clean of winter road salt.

But two regassings (and a new heat exchanger) in 8 years is probably not too bad. At least the place where I get it done uses a UV-visible dye in the gas which allows them to trace leaks very easily. They also charge the system with air (plus dye) first of all, so I'm not paying for new freon until they know that the system is free of leaks.

[Andrew Gabriel]

They're not sealed as well as a fridge, due to the need for assembling them on a production line, the need for flexible hose couplings, etc.

Magnetic shaft couplings for things like water pumps have existed for very many decades, to avoid the need for shaft seals. I was surprised to hear that car compressors didn't use them, although maybe they'd be too big for the shaft power required.

It can be pierced by stones through the radiator grill when driving at speed - that's a common failure.

There is a requirement to fix all leaks before refilling with many of the refrigerant gasses used.

[Dave Plowman (News)]

Generally because fridge etc units have the motor integral with the compressor, so nowhere to leak.

Car compressors tend to be belt driven, and it's that shaft seal which leaks. And of course the flexible pipes to the heat exchangers because the engine moves around. Again in a fridge it is usually one rigid unit.

[Harry Bloomfield]

Graham. explained on 09/01/2016 :

Fridges and freezers are sealed, house, office and car a/c's having externally driven moving parts using seals. The seals leak, you loose the gas.

[Johnny B Good]

Still "No Cigar". More accurately, a fridge or freezer avoids the need for rotary seals around drive shafts. Only static seals being required to allow the driving energy to be transferred to the compressor (electricity).

Also, the joint seals in the heat exchanger circuits aren't subjected to the much higher vibration levels found in a vehicle's AC system so can use more reliable brazed joints, eliminating the inherent weakness of flexible joints typically required in a vehicle's AC system.

Compared to AC (car or home/office) fridges and freezers have extremely modest heat pumping demands and are (relatively) over-engineered to avoid the need for regassing as a routine maintenance procedure throughout their service life.

The temperature controlled environment of a fridge or freezer is extremely well insulated to reduce running costs, unlike the controlled environments typical of AC systems (energy leaky homes, offices and car interiors containing energy emitting sources - people and equipment).

[Harry Bloomfield]

Which is pretty much what I said !