Should the pipes from a central air unit on the outside of the house be "wrapped" with foam ??
Mine were wrapped originally but it has been falling away...I can feel the "cold" in the pipes and they sweat...this can't be good and it seems they will eventually 'rot' and have to be replaced...
I get different opinions...one AC guy said it is only 'cosmetic' but that makes no sense to me.
Some of my bigger pipes are cold and whomever did it 'tied' the 'hot' feeling smaller copper pipes up to them with what looks like 'weedeater string'.
...So, question is....should the pipes from the 'compresser of a central AC' located on the outside of the house that run 'into the wall' of the house be wrapped or not ?? Whatever the answer...someone please explain..."why" or "why not".
Thanks...

Insulated is a better term than "wrapped", and yes, they should be insulated. The reason is that the pipe is carrying refrigerant to your air-handling unit, which has been designed for refrigerant at a certain temperature. If the pipe is not insulated, the refrigerant could lose (more accurately: gain) some temperature on its way to the air-handling unit, and thus negatively affect performance. Worse yet, in extreme high temperatures, the refrigerant could change state from cold liquid to warmer vapor, and you wouldn't have any performance at all. The opposite could happen in the return pipe, though not as likely: the refrigerant, in the coolest outside temperatures, could turn from a vapor to a liquid in the pipe, which would not be good news for the compressor.

There is a product called Armaflex, which is pipe inssulation with a slit along the length, allowing it to be snapped over the pipe quite easily. It's a dark gray rubbery foam insulation.

If your talking about the refrigerant lines that run from the outside condensing unit to the inside evaporator unit (fan) yes they should be wrapped but only the large line and it does not have to be real perfect the last few inches or so.
The reason to wrap this pipe is two fold, one reason is prevent the sweating of the large pipe which would not be good within the walls as we do not want this to occur for reasons I am sure you already know.
The 2nd and most important reason is we do not want the gas inside the pipe to condense to a liquid if it cools down. To understand this you need to know a bit about the cycle the liquid and gas in the pipe goes.

The outside unit is called a condenser. It takes the gas which is returning from the inside evaporator and compresses it. This is done with, the compressor inside the big outside box. Once it does this it pushes the high temp gas into the outside coils that surround the compressor and it gives off the heat. That is why the heat blows out of the fan. This cools the gas down to a liquid. Because the liquid takes up less room then the gas version of itself. It can use a smaller pipe. This is the small one that is warm or hot to the touch. This liquid goes up the unit in the house and through some devices in which it changes back into a gas again. As it changes to a gas it picks up the heat from the house. This heat is sort of hidden in the gas but the feeling on the pipe is that of cold. This is why the pipe sweats. This now cold feeling (Large) pipe which should be insulated with the black foam brings this gas back to the outside where it starts the cycle all over again. If the large pipe was not properly insulated it would begin to act like the outside unit and cool the gas down. As it would do this the gas would begin to change back over to a liquid. Because we cannot compress a liquid it would break the compressor. So having this insulation over the pipe would help prevent this.

So after this long winded answer. You should keep the pipe insulation around the pipe as much as possible. At least up to the valves or cabinet of the outside unit. If a foot or so was damaged by a week eater I would not worry too much, but this can be easily fixed by going to one of the big box stores and purchase a length of this stuff in the plumbing isle for about five dollars. And place it around the pipe yourself. Using a little electrical tape or duct tape to protect this may help. Be careful not to damage the small wires that are along the side of the pipes as these are the control wires from the thermostat and tell the system when to turn on and off.

One more bit of info. If the outside large pipe is sweating, this is good. This is a sign that the system is running properly. If it was warm, too little gas in system the house would not cool. If it was frozen again to little gas which happens before the pipe gets warm is a sign that you are loosing gas and need to get it fixed.

as was stated above, the large, vapor/suction line needs to be insulated, the Armaflex is better then the lighter plumbing foam tubes (both are black in colour) the Armaflex is more dense. there is a special adhiesive that is used to secure the armaflex, very much like contact cement and does a good job. electrical tape is a good second to secure it. I have seen ceilings damaged from the vapor line (large one) having condensation dripping off of the line on to the attic flooring or even rotting the floor out of the closet the inside unit is placed in. having a catch pan under the unit is also a good idea, have seen too many units with out an overflow pan. have also seen a trough (rain troughs) under the line set up to actually drain out of the same access where the line or the condensate drain exits.

I have also seen where the liquid line (small line) also being insulated where the line is accessable where children might be able grab hold of it (being it is hot and can be very very hot).

mike