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#1 goku

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Posted 17 September 2008 - 01:19 PM

here's the problem, the AC on my house leaks freon, then the radiator (inside) freezes over stopping all air flow. to the best of my thinking the unit must be over filled to prevent freezing. overfilling decreases efficientcy.

the surface area of the inside radiator is too small for the compressor.

are all AC units overfilled?

where is the logic?

#2 CraigD

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Posted 17 September 2008 - 02:57 PM

here's the problem, the AC on my house leaks freon, then the radiator (inside) freezes over stopping all air flow.

I had a similar problem in 2003.

A short term, hard to do, and not very satisfactory fix was to keep an eye on the air volume of the ducts, and when they dropped, “blip” the thermostat controls to heat for about a minute, long enough to melt the ice from the coils. This had to be repeated every few hours, and lead to an unexpected complication of some nasty green stuff growing at the drain line, which was never intended to handle so much runoff. Also, as you guessed, increasing the air flow can help a little, so when I knew I was going to have big demand (a hot day and/or a lot of people inside), removing the filter and return grill seemed to up the air flow significantly, helping some.

After marveling at these trick while at a hot summer party and eyeballing the frozen coils, a HVAC pro friend explained to me that the problem was the system’s compressor/pump, at that the only cure was to replace it. For the typical home system, it’s about a $600 part. Since everything about my system looked rusty and ratty (we guessed it was 30-45 years old) and since I’d have had to break federal law to mess with the old Freon-using system myself, I went for about $2400 more for a completely new 14SEER heater/AC. It’s about paid for itself in lower electric use since then, and is much quieter and more comfortable than the old one.

Note that this diagnosis assumes that you’re sure you have enough refrigerant (you did say you were leaking, so if that's the case, fix that! - but you're probably not), and no blockages in the ducts, such as a clogged air filter, so check the latter. Being low on refrigerant can freeze the coils too, but only over part of them. If you are low on refrigerant, and you system isn’t ancient, you’ve almost certainly got a leak that’ll have to be fixed, a sad story that can be more work than replacing the whole unit.

to the best of my thinking the unit must be over filled to prevent freezing. overfilling decreases efficientcy.

The coolant in most ACs is in a semi-gas state in most of the line, with a fluid trap (the tank with the filling valve) to allow it to have more or less coolant in gas or liquid form. As long as there’s some coolant in the trap, and the compressor is working right, it’ll maintain close to the right system pressure. An overfilled AC won’t work at all – the compressor will (I’ve been told – I’ve never had the nerve of bad sense to find out for myself) make a great racket and self-destruct if it tries to pump liquid, and the whole system will hardly pump heat at all.

Freon and similar refrigerants freeze at around -150 C, so are just not going to freeze under any natural conditions on Earth.
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#3 TaimurMubeen

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Posted 29 November 2016 - 04:21 PM

If over the pressure the compressor Trip Automatically.