How dumb is this?

To paraphrase your question...
'How can I do something without actually doing anything...?'

My answer to thread title...?

'Very'

Del, Del, Del - silly kitty! I think the question was a very good one, and per several of the replies, so did several others. It's "very" to NOT be thinking of things like this, and you, you solar hot water advocate, of all felines, should 'fess up to it! 'Tain't a-tall dumb to want to save energy/money...

I installed several water pre-heaters years ago that were simple versions of a heat/energy recovery systems, they were even funded by the power company on new construction to help balance their load. I'm sure all this technology has come a long way since then and that different regions and climates employ different methods.

Back then the discharge line on the condenser (just after the compressor) was routed to an external wall mount heat exchanger that pre heated the water heater supply line. This greatly improved the A/C efficiency for cooling and a thermostat holds it out below approx. 50F on heat pumps during the winter.

I'm actually surprised this isn't more common.

This is an interesting subject, recovering heat from airconditioning.

This is called "superheat" recovery. About 5 to 10% of the heat lost in condenser can be recovered as low grade heat. I am trying to do this at my work place to heat boiler water. Sofar the AC machine supplier is not agreeable to this but I am still trying.

In your case, you will have to add an addtional condenser in series with the present condenser so that part of the heat can be recovered. But this means lot of plumbing as well as addition of condenser in gas circuit.

This is a great answer, rsalaskar. One can actually build a pre-condenser using copper tubing coils in a tank about the size of a 20 gal. water hearer tank, well insulated, and the compressed refrigerant could be used to heat water in the tank to a relatively warm temperature. This warmed (preheated) water, in turn, can be can be fed directly to your current Water heater or could be directed to a secondary solar water heater on the roof of your dwelling and then to the water heater. Care is needed, however, to not let the water reach the boiling point unless the system is designed and certified to be safe for the heat/pressure of the steam produced. Keep in mind, too, that steam can be used to drive a heat engine that would drive an electric generator. In my time working in refineries, I spent much of my time designing retrofitted heat recovery systems to improve the refinery's energy efficiency. Most homes actually through away or waste well over half of the energy they purchase. This not only includes the heat from air conditioners but the scrapes of food preparation, clippings, old newspapers, plastic containers, human wastes, etc. All this waste is in reality energy. If we could find ways to harness this energy, then we could easily reduce dependence on fossil fuels, conserve this limited but valuable resource, and reduce the huge greenhouse gas emissions each of us produce each day. Plus one more incentive; to convert our wastes can not only save us a lot of money, it can even produce an added income. Please that the time to look at one effort toward this by another fine Indian Engineer. Look at the CR4 blog for APIX.

no cutting or splicing, ding, you lose

Nice link, thanks, this is my favourite subject.

In India, biogas plant based on cowdung can be seen in villages, the goverment subsidies the small plants for family cooking requirements. The plants work because the feed is in the form of slurry that flows through system. But when it comes to agrowaste, you need to breakdown the feed to convert into slurry, a difficult proposition. At my work place and at my home, we convert the vegitable waste/canteen waste in to composte to use as fertiliser for garden though no energy is recovered.

Please do share such interesting information and links.

how about some type of temp foam board tunnel to direct the heat off the unit to the underside of the hot tub if the tub is in a frame like most are. The water could be warm and ready all the time. But it might breed alge over time.

You actually made 2 great comments!

(1) I had difficulty to find an AC guy to do the modification. Most of them don't know very much and are very afraid to modify anything. They only plug leaks and change parts until the system works... I was not impressed by their trade.

(2) I am also surprised that it is not mandatory for air conditioners to have a water heating connection. So much energy is lost... It would only cost one or two hundred dollars for the manufacturer to do it.

I was an A/C serviceman for about a year and due to lack of training I regrettably did a lot more parts changing than real trouble shooting.There are good service techs and designers but they are too-far-and-few-between. It's just a get rich scheme for the owners.

As for the amount of wasted energy in residential cooling! Geothermal and heat recovery such as you did should be law!

yOU KNOW COULD HAVE SNAKED SOME SMALL COPPER TUBE AROUND THE LINE FEEDING YOUR OUTSIDE UNIT. Then install a solar powered pump to circulate water by tapping you lines around the Hot tub and the heat picked up from the feeder line would have heated the water. I do not know exactly how it would affect your cooling inside the home if any but that line carries a lot of heat.

If you used real small line warpping it around the feeder then used a larger line at the hottub a solar pump would move the water to the circulation system.

I seem to remember a design using a one way valves with a very small copper lines wrapped around a line with hot material flowing thru it that when the water is heated to a certain point it may create a low volume continous flow as the water expands and begins to press forward the forward movement created a enough pull to bring more water into the line.

I wish I could remember where I saw that setup.

"I wish I could remember where I saw that setup".

Your coffee maker probably has one.

Two ideas.

Most of the residential condensers use a top mounted fan to pull cool air through the condenser coils to remove heat and send the heat out the top. Grab a large radiator, or two smaller ones and fabricate ducting to force the hot air from the condenser to blow through the radiator. Keep it large to keep airflow up. Then run water lines into and out of radiator,and back to hot tub. You can then fabricate a water to water heat transfer unit by building an inner pipe inside an outer pipe. 1.5" pvc inside 4" pvc. No corrosion if pvc. Isolated heat transfer fluid. Run a small water pump from the same power supply as the condenser fan.

A more efficient system could be fabricated using a liquid to liquid cooler, but that would require installing it into the refrigerant lines as stated before.