Put it on a set of saw horses so your not bending over. Put this perhaps on the driveway because cleaners and lots of water is involved.

Remove the plastic cover on the front to expose the fins and perhaps the filter. Using care not to damage the fins or the tiny tube that may be attached to the front of the fins itself.

The plastic cover that was removed can be scrubbed clean with any quality cleaner that will not harm plastic. Good old warm and soapy water always does the trick. A soft brush will aid in getting between the grooves in the panel.

ON the AC system itself. Tape a plastic baggie over the control section. Then simply using a soft scrub brush and water wash the unit down. Hose it off as needed. Just try not to direct the water onto the control area and directly onto the fan motor that drives the blower and outside fan part. Try to spray the foam or metal tray that the coil sits on, and be sure to spray and brush well the inside blower wheel that should be partly exposed from where the air comes out. The better you clean, the better the fan will blow cold air.

There is really nothing you can hurt as long as you attempt to keep water out of where the wires and switches are connected. Once done, tilt and move unit around to dump as much water you can out of the unit and let sit for a few hours to let it dry off in the hot sun. Just try not to turn the unit upside down. Once that is done and if the system is a 110 volt unit, plug it in and run the fan on high. This will help blow out any water that may be hidden in cavities that you cannot see plus is will dry it off better before you install it and run it.

If your home has cooling issues when its hot, I would suggest that the contractor do two things.

1. Do a manual J heat load on the house to determine if the size of the system is correct for the home. Many systems are oversized and that is costly to you and can cause discomfort in the way of excessive humidity.

2. Do a manual D duct sizing on the house. Once you are sure your current system is correctly sized then you can check the current size of the ducts to what the report findings suggest. Manual D will determine exactly what size ducts are required to deliver the correct amount of air to each and every room. If they are incorrect and sometimes they are, you may want to change a few or just one to make the system perform better.

Once both of those things are done and the proper equipment and duct sized are installed. Then you should insulate the ducts with at least 2" of foil back insulation to assure against condensation. It is very important that the outside foil vapor barrier be properly sealed to prevent condensate from forming and the possibility of mold development.

Try to limit the flex ducts as much as you can. They are impossible regardless of what duct cleaning companies tell you to properly clean. And the longer they are the worse the air flow coming out the other end. Do NOT use any duct board or interior duct lining on the system. The liners and duct board are made of fiberglass and if not done properly will result in fibers being released into the air. Not a good thing.

The furnace thermostat uses only two wires. (W)hite and (R)ed. The red wire comes from the transformer in the furnace up to the thermostat. Once the thermostat calls for heat it makes a connection to the (W)hite wire which is then connected to the gas valve and it powers it up and turns it on.

In traditional heating and cooling systems the (R)ed wire comes up to the thermostat which like before is the power from the transformer. The switch somewhere on the thermostat selects what wires will be powered up when the thermostat calls for heat or cooling. In the case of heating the same thing as above takes place, the power is connected from the (R)ed wire through the thermostat then back to the (W)hite wire and the heat runs. In the cooling mode the power goes from the (R)ed wire to the (Y)ellow wire, which in turn powers up the outside part of the cooling system. Also at the same time the (G)reen wire which is connected to the relay in the furnace is powered up in conjunction with the (Y)ellow wire control and the fan starts at the same time the AC turns on. Lastly of course the (G)reen wire is turned on by itself should you turn the switch that says fan on/auto to the on position. It is then the fan runs regardless if the heat or cooling system is running on its own.

So to recap. R is transformer, Rw is 2nd transformer should two exist. W is heat, W1, W2 is additional stages of heating should your furnace require this type of connection, Y is cooling and Y1, Y2 etc are different stages of cooling again dependent upon the type of system you have. Lastly G is the fan control. Ideally the wires are connected based upon their colors that match the screw letters. However this is not always the case, so beware, do not try to connect these colored wires to the color letter. It may not always be the same.

On some older systems the AC system contained its own transformer. When that was the case, the power that comes from the AC system is connected to the RC post and the (Y)ellow wire is connected to the Y post as before. IN your case even if its not age related, if you have a 2nd independent AC system perhaps located in the attic and the furnace or boiler is located elsewhere. Get a pro to do this wiring. It can be done, but its tricky assuring your wires are connected to the correct side of each transformer as this makes a big difference depending upon how each system is wired.

As A1tec service stated, I would suggest that you hire a pro to do this wiring for you. Let them purchase the correct thermostat that has the features you want in conjunction with the proper sub-base needed to wire the system(s) you have.