diy-airconditioning waste water recovery

© 2005-2009 Dr. Ronald Stiffler All rights reserved worldwide Rel: 2.1 5.09

DIY – AIRCONDITIONING WASTE WATER RECOVERY

Ronald R. Stiffler1 1Senior Scientist, Stiffler Scientific, Humble, Texas, USA

[email protected] Abstract---This paper covers the results of a project conducted by Dr. Ronald Stiffler in which otherwise discarded water obtained from the humidity reduction process in residential air conditioning systems was diverted, captured and used in non-potable applications.

I Introduction

Because of the constantly increasing price and scarcity of water and a growing Conservation and Green awareness sweeping many parts of the globe a question arose during one of Dr. Stifflers water research projects; ‘Why is the recovered water from residential air conditioning units being discarded into sewer systems’?

Water rates in many areas of the United States have reached and in many cases equal to or exceed energy costs. This can be seen specifically in areas switching from ground to surface water sources. Along with these environmental factors is the added cost of delivery, quality, maintenance and security. Coupled with all of the above reasons it must be understood that City, State and Federal government's have found water to be a deep pocket money source, which can be continually tapped for money to fund all forms of programs and endeavors. The end user price for one thousand gallons of water in many areas of the United States is now exceeding the cost of one-kilowatt of electricity. In the area in which Dr. Stiffler conducted this project, water for the test residence cost approximately $12.60 per thousand gallons for the water, which included additional fees from Municipal Utility District (MUD), and RWA (Rural Water Authority) fees and bond payoffs, while one-kilowatt of electricity cost $0.14.

Water is essential for life as we understand it and places the consumer and provider at odds because of the delicate balance required between profit and survival.

II The Project


This research project is only applicable to areas, which require air conditioning for at least eight months of each year, and have an average Relative Humidity in excess of 45%. This project was broken up into four specific areas as listed in the following.

1) Construct and evaluate a system for capturing the normally discarded water produced by home air conditioning systems resulting from humidity reduction during the cooling cycle.

2) Determine the average number of gallons (liters) that may be removed and recovered in an average 30-day cooling period.

3) Determine the cost of an average system installation and the required payback time period at which the recovered water could be considered free.

The project worked with two air conditioning units as indicated in the following; 1ea. Trane 3 Ton, Model 2TTR2-036 1ea. Trane 2.5 Ton, Model 2TTR2-030

The total area cooled by the two air conditioning units was 3000 ft2 (679.6 m3), 3000 ft2. /5.5tons = 545.46 ft2 (123.6 m3), per air-conditioning ton.

The following pictures and text cover various configurations and results obtained from the research.

Each test A/C unit has two water output connections on the evaporator units; 1) An overflow connection, should the drain line become plugged, 2) the water output connection to the drain line. The following labeled picture shows the water connections on the project 3-ton unit. For some reason, known only to the A/C installation personnel, the project units overflow output is plugged.


Water output connections on the projects 3-ton unit

Fig: 1

It is noted that each drain line is 3/4" PVC and the two units drain lines join into a common 3/4" PVC line normally running straight to a sewer drainpipe.


Fig: 2

Not shown, but to the left in Fig: 2, is where the two A/C units 3/4" drain lines are joined into a single 3/4" drain line labeled "A/C drain source lines".

A tee and two valves were added to the existing A/C drain line; [1] Sewer drain shutoff (allowing for an easy return to the original configuration where all recovered water would drain into the sewer system), [2] Exterior feed line shutoff. The logic behind the two valve installation is based on maintaining property value should the property be sold and the 'Water Recover System' is not wanted by the new owner. In this case the valves can be configured so that the prior installation is easily returned and all external equipment can be disconnected, removed and disposed of without the removal of any piping in the attic.

The feed line from the A/C units was 3/4" PVC and a 3/4" X 3/4" X 1/2" Tee was added. A small extension 3/4" length of PVC was added to a 3/4" Ball Valve going to the sewer drain. Off of the 1/2" tap of the Tee a 1/2" Ball Valve was added between the Tee and the exterior feed line.

The ½” exterior feed ran to the edge of the roof where it joined a 90’ angle to exit the home.


Fig: 3

Once the drain line exits, various methods can be employed to handle the water, ranging from very simple gravity fed disbursement to more sophisticated storage and pumping.

For the purpose of the research project the first method employed was to store the water in a tank so that it could be measured against time. This required a tank and a measuring system as indicated in the following images.


Fig: 4

Figure (4) shows a recovery storage tank before the addition of a Ball Valve at the bottom, which allowed for controlled drainage.

The storage tank was a RubberMaid Company [3], RoughneckTM [4] 50 gallon., wheeled (wheels not shown), yard trash bin purchased at a local Wal-Mart Super Store. This storage container was selected because of capacity and cost. As seen in the photo an air vent pipe (top left) was added along with an inlet (top right) that connected to a 1/2" clear plastic hose, which in turn connected to the feed line from the A/C units.

At the bottom of the tank an outlet was fashioned from ½” PVC couplings and shown plugged with a ½” plug.

It should be noted that all pipefittings required holes in the basic tank that did not have these holes at purchase. To cut the holes a steady hand and sharp knife is all that was required. The fittings were held in place by glued sleeves (pipe couplings) on the interior side of the tank.

Fig: 5


In figure (5) you can see the measuring system that was added to the collection tank. At the bottom of the tank a Tee was added on the left side and fed a ball valve used to drain the tank, while the right side went into a 90’ which had mounted a clear plastic hose of ½” inner diameter. Fastened to this clear hose a wood yardstick graduated in both mm/cm and inches/feet.

The parts cost for the research system was $92 for materials that are easily available at most home improvement centers. The time to install the modified drain system, cut and install valves, run pipe to the building exterior and assemble the collection and measurement system took approximately 5.5 hours.

Because labor costs vary widely, project labor cost was set at $50 per hour, resulting in an installation cost of (5.5 X 50) or $275. Adding this to the cost of the pipe, valves and tank, gives a total cost of ($92 + $275) or $367.

Using a price for water of ($12.60 per 1000 gallons or 3,785 liters) the calculated payback would be ([$367 / 12.60] X 1000) or 29,130 gallons.

With Advanced Cooling Systems combined with intelligent control systems such as the Lennox SignatureStat [2], under ideal conditions can produce in excess of 285 liters (75+ gallons) per day. Using the 285 liters per day and assuming 365 days of cooling, we get (285 X 365) or 104,000 liters per year under idea conditions and daily usage. Dividing (110,300L / 104,000L) supplies the required recovery period of 1.061 years.

The Air-Conditioning Industry [2] and various experts [1] indicated a somewhat lower hourly output from that used in this paper.

Using the ideal conditions just calculated a residence would be receiving free water in the amount of 29,130 gallons a year after the first year. Of course this is ideal in that it can vary depending upon the local relative humidity, the length of the cooling period and the overall efficiency of the air-conditioning system in removing the humidity from the air being cooled, which is a function of Dew Point and evaporator temperature.


III Water Handling

Understand that the system is gravity fed, the simplest of systems would be to connect a hose to the outlet and run it into a flowerbed or other desired close location. One needs to insure that the flowerbed is large enough to absorb the water without harm to the plants from over watering.

Fig: 6


Figure (6) shows a standard garden hose connected to a matching fitting on the drainpipe and running a short distance to a flower garden. This is the simplest of all installations.

The next method is the storage of collected water, which would allow dispensing when desired or needed. The following images show some of the storage methods used throughout the continuation of the project.

The first method used to store the water is seen in Fig: 4 and was primarily used to allow collection and measurement. A problem was found with the converted RubberMaid [3] Trash Container [4] in that it is not designed for the weight that is present when filled with water, which exceeds 400 pounds. The container should not be considered for a working system because of this fact.

Fig: 7

Figure (7) shows a small storage system that was constructed from 4” PVC pipe. At the bottom a tee was used to couple to a short 4” section that contained a 12 volt submersible water pump. Two sensor electrodes were placed in the vertical holding tank to detect and turn the pump on when the tank contained approximately 7-8 liters of water.

Although this tank and method appears to be less intrusive when property restrictions may apply, it suffered from a number of problems.


Figure (8) shows the necessary electronic control that was needed to turn the pump on when the sensor electrodes detected water. The circuit was required to have a build in ‘On’ delay so that the switch and pump did not oscillate between off and on during peak water collection.

The connection from the pump to the exit hose did not include a check valve and as such would gravity drain the tank if the exit hose were not elevated above the sensor electrodes. The elevation of the exit hose also caused additional stress on the small pump because it not had to provide extra lift.

Fig: 8

Figure (8) shows the control circuit and the waterproof Sprinkler Control System Box that was used to house it.

In an attempt to simplify the operation and requirements of a pumped system the components of Fig: 7-8 were removed and the vertical tank was replaced with an 8-gallon plastic pail with a lid. The pail was outfitted with the necessary inlet connection and a 12-volt Bilge pump with Float Switch was mounted in the pail.


This configuration had one major problem and that was due to the 3-amperes of current required which required a fairly large external power supply. Although this approach could be handled with a solar panel for charging a battery to run the pump, this idea was not tested.

What was found and can serve, as a dual-purpose system is a tank designed for water retention, and is a 50-gallon Rain Barrel [6] and was purchased at Northern Tool Company [5]. This tank comes with build in hose connections, hoses and a drainage valve. The tank is designed for the weight of the water and has two overflow controls and it must be mentioned that the tank also has a build in washable filter to keep large foreign matter from entering the tank.

What is so nice about this tank is that it can double as its intended purpose (Rain Barrel) and a holding tank for the recovered A/C water. The tank is a total gravity drain system and the instructions with the tank explain how to mount the tank to allow better drainage on other than flat areas at or below the tank elevation.

Fig: 9

It may not be practical in all case to use the tank as a dual-purpose collector because of the locations of down spouts from guttering systems, nevertheless this tank was found to be ideal for the recovery system.


After about a year and one-half of operation the test system developed a problem with drainage from the air conditioner output line. As it turned out the air conditioner was serviced and a number of minor air leaks were sealed with a standard aluminum tape placed over the leaks. What resulted was that the drain could not handle large volumes of recover water, as it was unable to draw in enough air.

Placing a Tee in the outlet from the A/C water line and installing a vertical air intake line of about 18” in length solved this problem. This was done with both A/C units. The vertical pipe must be long enough to insure that it will never fill and overflow or at least insure that the pipe is mounted above the overflow pan to insure damage will never result to the structure.

IV Summary

The water recover from this type of collection system is NOT POTABLE which means it should NEVER be used for Human or Animal consumption. This water is only suitable for ALMOST all type of vegetation. Never try filtering this water for Human or Animal consumption, as it would take a qualified laboratory to determine its continued safety.

This system is still in use today and was placed in operation in 2005. The water output is sufficient to water medium sized flowerbeds, sections of a small garden and three citrus trees.

It is without doubt that this is a wasted resource and should be implemented by those qualified to do so and done in all systems where the benefit will exceed the cost and provide a payback in a year or less.


References

[1] Various air conditioning experts and equipment manufactures state that the Traditional non-variable or single speed A/C units remove on average 5.68 liters (1.5 gallons) of water vapor per hour, while variable speed systems remove 8.04 liters (2.125 gallons) per hour.

Jimmy West A/C, http://www.jimmiewest.com/sig_stat.htm

ASHRAE, http://www.ashrae.org/template/AssetDetail?assetid=20750

J.P. Timmerman Co., http://www.johnptimmermanco.com/details.php?IDnum=45

[2] Lennox Company, SignatureStatTM Control for advanced cooling systems. http://www.lennox.com/products/overview.asp?model=SIGSTAT

[3] The RubberMaid Company http://www.rubbermaid.com/rubbermaid/product/parentCategory.jhtml?pCat=HPCat100527

[4] RubberMaid 50 gallon Trash Container, http://www.rubbermaid.com/rubbermaid/product/category.jhtml?cat=HPCat280072

[5] Northern Tool Company, http://www.northerntool.com/

[6] Suncast Rain Barrel — 50-Gallon Capacity, Model# RB5010PK

diy-airconditioning waste water recovery

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