View Full Version : Do A/C Units Run Out Of Freon?
09-11-2007, 12:36 AM
A friend and I got talking about replacing his a/c unit and I mentioned I thought I needed to recharge mine as it didn't seem as cold as it used to. He said that they don't "run out" of freon like cars, that it must have a leak. The unit is about four years old. Is there any truth to what he said that it doesn't use up the freon? I consider myself a relatively intelligent individual and an avid DIY'er and my thinking tells me it has to eventually use up the freon.
09-11-2007, 03:31 AM
Think of refrigerators that seem to last forever. Freon is not consumed by the system. If recharging is needed, a leak would be the cause.
Aside from a leak, a significant change in cooling output could be caused by an obstruction (dirt/dust/lint/etc.) of air flow either at the evaporator core inside the furnace (air handler) or the condensor unit outside.
09-11-2007, 04:02 AM
That's why I'm here, learn something new everyday. Guess I'll check it for leaks. Thanks for the info :)
Freon in A/C units goes from a liquid to a gas and back again by way of the compressor and during this whole process changes temperature.
The original purpose of A/C developement in the beginning was to remove moisture from the air.
The cooling was just an unplanned additional benifit derrived from the process.
Car units "use up" Freon, or any other refrigerant, because their pump has an external power source which requires shaft seals. These can leak. A home system has a sealed unit which can only lose refrigerant if there is a leak. Unless you have the proper equipment you will not find the leak, especially since it can be very small or the loss would happen very quickly. An A/C technician should be able to find the leak, although it may not be easy to do so. He also may not be permitted to recharge the unit until he does find the leak.
09-11-2007, 07:11 AM
As usual, hj is right on it. The shaft seal on any pump is the most difficult component. Think auto water pump shaft seals. Most moderate size air conditioning sytems in homes and applicances are "hermetically sealed" meaning the entire pump is completely contained within that sealed cannister. The only connections to the outside world are the inlet and outlet pipes, usually brazed.
Back in the day, GE was designing the reactor main coolant pumps for Hyman Rickover. Any leak from the shaft seal was going to be contaminated water, so that is a problem, even though the reacor compartment iteslf is completely contained and not occupied by humans. GE said they needed a leak spec to design to. Hyman said "zero". They said, "you can't design to zero". Hyman said "OK>> 1 drop in 20 years. deal with it." And they did.
09-11-2007, 08:23 PM
Another source of refrigerant loss in an automobile is through the flexible hoses that connect the compressor to the evaporator. These are required since the motor moves in relation to the dash where the evaporator is. A refrigerator can often work fine for 20+ years, a central a/c unit can as well. A car unit won't, it will need a recharge and maybe new hoses or compressor.
09-11-2007, 09:23 PM
All kinds of good info. I'll see how it goes once the attic is fully insulated again. It's partly done now due to our remodel, but even before I tore the house apart it just didn't seem as if it was getting as cold as it used to. It also helped that the temps in Indy went from 90 to 70 in 48hrs. and looks like it will stay cool now. Have any of guys dealt with radiant barriers in the attic? I've been researching and the results are definitely hit and miss from what I've read but it does look like it would work for our house that was built in the 60's which isn't so "tight" like new homes. I would be using the sheets on the rafters. Is it worth it?
09-12-2007, 06:07 AM
A radiant barrier in my condo lowered the attic temp in the order of 20-degrees in the summer and even with around R40 in the attic, prior to this, the ceiling got hot by the end of the day. Since, the ceiling is the same temp as an interior wall. Go for it.
09-12-2007, 09:07 AM
Good deal, thanks for the info.
09-13-2007, 08:21 AM
After 4 years your A-coil could use a good cleaning. That is a common cause of reduced cooling output.
09-19-2007, 11:14 PM
Any seal...your car's engine main seal, or its compressor seal for the ac needs a small amout of weepage to lubricate it. Otherwise, friction and heat would destroy the seal! Thats why you have to get your cars ac recharged every 5-6 years! Your home unit...motor and compressor...both are sealed in a welded can. No seal needed. If the freon drops, then there is a leak. Stop the leakage in your car, and the seal for the belt driven compressor would probably die within days of truning on that ac.