HEATING WATER WITH YOUR CENTRAL AC

[tomturbomatic]

Do any of you who live far enough South use a heat recovery loop on your AC condenser to heat much of your domestic hot water? There are places that need AC almost year round and the waste heat can keep the water heater's back up heat, electric or gas, from being needed for months.

Friends in FL had one in their house. It kept the condenser fan from operating so the water absorbed the heat. By the end of the day, they had a 50 gallon tank full of very hot water. And even though we used some in the evening, the AC ran enough during the night that the water was plenty hot in the morning. During the day, there was hot water for laundry and it would still have the tank full of hot water in the evening.

 

[DADoES]

I don't personally know anybody who has that kind of system, but I've heard of it. Certainly is a fantastic idea.

 

[sudsman]

ITs a Great idea

Would love to know more about it... Like free hot water ,Take that you big bad gas company,,,,.... LOL

 

[magic clean]

Tom, yup it is a great system. Back in the 80's I had a new construction Pulte home in Broward county FL--Ft. Lauderdale. It was an FPL "Watt-Wise" compliant home. The energy saving program they had back then. Anyway, it worked as you've described. Kept the electric bill quite reasonable. I've always wanted it since.

The system was called a Trane "heat-bank" or something like that.

 

[gansky1]

Jeff & Cal in Maryland have this in their home - seems to work beautifully and provides an abundance of heated water. I think Jeff said that it doesn't heat it to 120-140, but gets close enough that the standard water heater has to work much less to meet demand. Perhaps he'll see this and explain more about it.

I'd love to have it in my house but I have no room for the "storage" tank (extra water heater) and if I put any more plumbing in this house... But with the price of copper these days, it would be like saving for retirement!

 

[whirlcool]

Seeing how much heat an A/C unit throws off, I imagine you could make quite a bit of hot water. If you put the tank in the attic (like a lot of homes down here have) the surrounding heat in the attic could help preseve the water temperature.
I wonder how you would set up such a system. I think you would have to have some kind of heat exchanger attatched to your ourside A/C unit.

 

[DADoES]

Ummm. How weird. A couple mins ago I found out somebody in town does have a system like this on a new house. Interesting. They had planned on installing an 85-gal tank to handle their jacuzzi tub, but the door to the closet where the tank is to go is too narrow for anything but a 40-gal tank. Oooopsie.

 

[Cybrvanr]

attic hot water

Hot water right out of the attic is what happens to me! During the hottest days of summer, I don't even turn my attic-mounted water heater on...it just absorbs the heat up there! I can have a nice hot shower in the evening and not even turn on the heater!

 

[foraloysius]

Hardly anyone overhere in the Netherlands has central airconditioning, but solar water heaters are installed in a lot of the new houses. These solar water heaters are installed in the attic and are heated by a solar panel on the roof. There is a flow through/tankless water heater in the system to heat the water when there is not enough sun or if a lot of hot water is used.

 

[toggleswitch]

My friends have two central A/C units.One for their house. Another in the form of a heat-pump pool heater.

Instead of running two separate units (one dumping waste heat the into the ambient air, the other extracting it) the waste heat from the house could simply be dumped into the pool.

Worst case scenario- put the heat-pump pool heater (funcitioning as an evaporator coil) in the attic/soffit.
Should cool it tremendously and hugely lessen the burden on the home's A/C unit.

 

[tomturbomatic]

Greg, you would not need another tank. It just heats the regular domestic hot water, but you really need to live someplace where 90+ temperatures are the rule for several months of the year and fairly warm weather necessitates using the AC most of the rest of it. My friends kept their tank at the lowest setting during mild weather, but turned it to pilot only once the weather really warmed up.

Yes, there is a heat exchanger and a water pump. They drew water from the bottom of the tank, pumped it through the heat exchanger on the outside condenser and then back into the top of the tank. They could do that because of mild winters. Up here you either have to bring the Freon inside to the heat exchanger so that nothing is in danger of freezing in the winter, or have a valve to shut off water to the heat exchanger and a way to drain the outdoor loop. Unless you are like Jeff and find these things on sale, cheap, and can install them yourself, they probably would not begin to save money until quite a few years pass with our shorter cooling season. And as electric rates rise to the skies, are you going to use your central AC as much in the future as you do now?

 

[brisnat81]

We can get these in standalones

There is a few companies now in AU, that make hot water heaters with a built in Compressor.

With an input of 500w they claim to be able to maintain a 400L tank at 60deg all year round depending on the location. They are not quick recovery, but make hotwater very cheap compared to the 4.8KW element thats usually employed. They still contain the traditional element, so you can boost the temp if you have a run of very cold days.

The advantage of these over solar heating, is that they operate whenever the temperature is over 4degC, which in Australia, is most of the country all year round, and also means they work at night, when there is no sun.

We need to upgrade our tank, and have looked at getting one. However a standard 4.8KW 400L tank is about $1000, the Heatpump tank is $3800, it'd take about 5 years worth of energy savings for it to pay for itself, and at this stage we plan to sell up and move before then.

 

[compactc9]

About water heaters in attics. I would be nervous about that, what if it leaks or something? And how do you get it in the attic?

 

[spinout]

And as an added bonus...

A condensing vapor to water heat exchanger is rather compact and much more efficient than the common air cooled units and can improve the A/C systems overall performance, especially on hot days.

Note that the water outlet temperature is deliberately kept on the lower side to maintain condensor efficiency even though typical refrigerant condensing temps can be much higher.

 

[foraloysius]

Overhere most houses have concrete floors on every floor, so a small leak in the attic isn't a problem. And since most leaks with water heaters start slowly there is no problem. Most attics are accessable by regular stairs.