quote""" Anyone ever do something like this or has my inner engineer run amok? """quote

Yes you can but you'd find it inefficient.
To make a homemade swamp cooler you'd need to place it over a well of water like a plastic kiddie pool, have a pump to draw it up, and a perforated pipe to dispense it over the fins on the condensing coils. The problem with the coils are that they're typically a single small diameter tube so you won't get a lot of water through the tube.
As for heating I'd don't think you'd get any rise in temp, it would most likely stay the same with no fan and drop slightly in temp when you ran the fan.
I actually drew up a sketch years ago on a superheating unit based off working with the absorbed heat from the refrigerant on it's way back from the evap to the condensing unit. I found a mfg who offered different sizes of refrigerant cooling tubes that circulated water on the outside of that and within another tube to shed the heat. The application of these are for shedding refrigerant heat and also raising water temps to heat coils which preheat water before entering a large commercial water heater. Note, the water being heated by the dual tube was only used to absorb and shed the heat. I thought that by introducing pool water in there and sending it back to the pool I'd be capturing free swimming pool heat from the process of grabbing it before it made its way to the condensing coils. In SE Texas our AC's are running way before the pool temps rise naturally. I hate paying for the additional electricity for my heaters or my chillers to heat/cool my pool water. I love to tinker and will take any free bonus on something like this.

One of my best bud's, a commercial HVAC contractor laughed at me, but said he'd help engineer the system, then the water got warm on it's own and I blew it off.

See ya,
Kelly

Kelly,

You have valid point about the tube size, it is far too small to pass the full flow of the pump which will limit th effectiveness of it. On the other hand, the smaller the tube the more efficient it is at heat transfer (better surface area to volume ratio) I don't really agree with your estimation that it would have no heating and minimal cooling - from what i'm been able to dig up online (which is not conclusive by any stretch) the condensor is designed to operate about about a 25F temperature differential. In early spring we can often get that kind of air-water difference, and since this is a 5-ton (60,000 BTU) unit, that's a lot of heating/cooling even with reduced efficiency. Under 10 degrees you're probably right, the effectiveness would be pretty poor, but even so the only energy it's using is a fan which beats the hell out of a gas heater. (Without the fan it'd do nothing whatsoever) I'm not expecting miracles, but it might help a little.

On the other hand, my primary concern is not the effectiveness - it either works or it doesn't, and it will only cost me a few PVC and copper fittings. (and it'd be fun to find out, I think!) My chief issue is what effect having such a considerable amount of copper tubing in the pool circulation would have. I've heard it can stain the pool black at high concentrations but I don't know if it's a concern (Freon is chlorine based, so it should be well "cured" if that's even possible) and what I can do to counteract any effects it might have.

Any ideas?

First thing I'm curious about is what part of the country are you in?

My assumptions are based on SE Texas.
I just don't see a fan pulling air across the coils in normal everyday heat to add a lot of heat to the water.
My guess would be that the initial water would absorb some heat and that once the tube cooled off after shedding the heat that the tube would remain at or near the temp of the water passing through, I may be way wrong though!!!
Your correct in the energy consumption, most fans in condensing units are like 1/5 of a horsepower so they draw very little juice.
I do see the unit doing so-so as a chiller with water running down the fins while the air is pulled across it.
I went to college in west Texas where the humidity is nill and our AC was based on a swamp cooler, as the air was drawn over the damp fins on the coils it chilled the air and added a little moisture to it increasing the humidity indoors slightly.
I wouldn't worry a bit about copper piping, it is THE BEST of all pipe materials. Just keep your PH and ALK neutral, and test for the metal once a month, pool heaters have always used copper tubes with fins as the backbone of temp transfer for their heat exchanger.
The funny thing is I'm back to thinking about the dual tubed piping again, we had a wicked cold winter last year and I, once again, kicked on the heaters to bring on an earlier swim season for me and the kids. I hadn't had passing thoughts about this in years until I read your thread. I have a very large pool with a whole bunch of water and will take ANY FREEBIE that I can lay my hands on. Like yourself, I thought about just how cheap solder, flux, and random fittings would be when compared against the cost of the additional electricity and propane I use when running my gas fired heaters and my heat pumps.
Another thought I had then was placing a 3 or 4 core radiator over the fan shroud with big zipties holding it to the grill surface and letting water circulate through it. If a heavy duty radiator can shed the heat of hot water from the engine surely it could absorb heat from the air passing out of the unit and pass it to the cool pool water circulating within it, but I thought that tapping into the heat from the refrigerant was a better idea.

I guess we all enjoy a little "inner engineer" in us.

See ya,
Kelly

1) A 3/8" copper tube won't allow much water. The main flow will need to be bypassed. There will be erosion if too much is pushed.

2) The copper would need to be thoroughly cleaned. The coolant it had before was also mixed with oil.

3) The ph, alk and calcium levels in the pool must be kept in normal limits or the copper will form scale deposits or break down and stain the pool.

4) The air won't heat the tubing enough to be worth the effort. A 3/8" flow into a 2" flow won't add a whole lot of heat calories to the 2" flow, even if it's 5 degrees warmer.

5) 60K BTUs isn't enough. The pool will loose that faster than you can put it in.

Scott

Well... poo. It does not look too good. I just did some preliminary calcs on pressure losses of the 1/4" tubing in the condensor and at best I could force maybe 2 GPM through it. (and even that'd probably need to use a booster pump - each circuit loop is nearly 100' long) While I still think those 2 GPM would in fact be very well heated or cooled (very close to whatever ambient is) that's a drop in the bucket for a 19,000 GPM body of water. So much for that idea.

But now if I could somehow flatten this thing out... it'd make a HELLUVA solar collector... anyone know how to bend (unbend) a radiator?

Kelly - Yes, I'm in Sugar Land to be exact. My pool is alway naturally high alkaline so pH wouldn't be a problem at all.
Scott - agree with everything but point 5 - The concept would have only accelerated natural heating and cooling, not work in opposition to it, so the BTU's would not be lost, at least not right away.

I didn't mean to imply it would work against it, just be very inadequate.

Scott