Many people look at the installation of a home air conditioning unit as being beyond the possibilities for a do-it-yourselfer. Oh, putting in a window air isn’t all that bad, but putting in central air is way too much for the average person to handle. In actuality, anyone with a pretty good mechanical aptitude can do 90% of a central air conditioning installation in about 6 to 8 hours. The only part that requires the services of a certified technician are the leak checking and installation of the Freon.
If you are replacing an existing unit in an old house, you will also need to hire a certified technician for the recovery of your old Freon. Not only does the building code require that you be certified for this, but the equipment necessary to evacuate Freon and recycle it is very expensive.
Before You Begin:
Locating your condenser unit is important. You obviously don’t want to put it in front of your house, where everyone who comes to visit you can see it. But, there are a few other things you should keep in mind:
- Put your ac unit close to your circuit breaker panel. This will save you time and money for wiring the unit.
- You’ll want your ac unit as close as practically possible to your air handling unit inside. The longer your Freon lines are, the more cost for the lines and the more Freon you’ll have to pay for.
- The condenser unit needs clear ventilation all around. That means putting it at least 10 inches from the outer wall of your home, and making sure that there are no plants or brush that can touch it. Trim them back if necessary.
- Condenser units work more efficiently when in the shade.
- Your condenser unit will need to sit on level ground.
Most HVAC professions recommend a 15 tier ac unit. While there are more energy efficient units available on the market, the additional cost is so high that you don’t recoup the cost over the reasonable expected life of the unit.
How to Install it:
Start by preparing a place to place your condenser. You’ll need a pad for it to sit on, that is slightly larger than the condenser unit. You can either pour a small cement pad, or use a prefabricated one; these are usually made out of injection molded plastic. You do not want a metal one, as it can rust; or to use paving stones, as the various pavers may settle unevenly. Make sure that your pad sits level for best operation of your condenser.
Place your condenser unit in the center of the pad and insure that it sits level.
You’ll need to cut a hole in the side of your home, close to the bottom of the wall, for the pipes and electrical wires. Find something visible from both the inside and outside, such as a window, that you can use for a reference to measure from. You’ll need about a 2” diameter hole all the way through the wall.
Run the suction line from the condenser to the air handling unit. The suction line is the larger, insulated copper pipe. It’s usually easier to run this line from the inside of your home, as there will be more of it there. This line is flexible, so you can pretty much run it as you need to. However, try and straighten it as much as possible, and install it level. You’ll need to peel off a couple of feet of insulation, specifically the distance from your exterior wall to the connection on your condenser unit. Save this peeled off insulation, so that you can reinstall it on the line from outside. Be sure to attach your line to your home’s structure with plumbing clamps.
These copper lines are somewhat flexible, but cannot be bent to make sharp corners. Be careful to avoid kinking your lines when bending. Depending upon the location of your condenser unit and the hole you’ve cut in the wall, you may need to add a 45o or 90o copper plumbing elbow to make your tubing reach the condenser unit.
Run the liquid line, which is the smaller copper line, alongside your suction line, and through the same clamps, with one end at the condenser unit and the other at your air handling unit. Because of its smaller diameter, this line is more flexible than the suction line. Always cut off your lines a little long, so that you can make a final cut to the exact length. It’s very difficult to gauge the proper location for your cut, when you have a bunch of excess material. Both of these copper tubes can me cut with a tubing cutter.
Installing the Electrical Disconnect Box:
Building code requires the installation of an electrical disconnect box at all air conditioning condenser units. This box will either have a switch for turning off power to the unit, or a removable jumper, which is pulled out to turn off power.
The box needs to be mounted to the exterior of your house, somewhere near your condenser unit. You can easily mount the box with screws, through the back wall of the box.
You will need to run power from your electrical panel to the disconnect box, and from the disconnect box to your air conditioning condenser. Check the manufacturer’s instructions which came with the unit for the wire size required, it will probably be 8 or 10 gauge. This will depend upon the size of your condenser. Please note that this is 220 VAC power, not 120 VAC. Most of your connections in your breaker box are 120 VAC, but there are a few connections for 220 power.
Flexible conduit is typically used for air conditioning installations. You can buy flexible conduit for this purpose, with the wires already run through it. Since this is an external electrical installation, you will need to use waterproof strain reliefs for the conduit entering your disconnect box.
To attach your wires inside the disconnect box you will need to remove the switch. There are three pairs of two connections. One, mounted to the back of the box, is not attached to the switch; this is for your (green) ground wire. Strip off about 1/2” of insulation on both ground wires and connect them here.
You will now have two black wires and two red wires to connect. It really doesn’t matter which pair of lugs is used for the black and which for the red; just that both black wires are going to one pair of lugs (close together) and both red wires are going to the other. Make sure you get a solid connection with the copper wire and tighten the lug down securely.
Re-install your switch and make sure it is turned off.
Open the electrical panel on the condenser unit, and run the end of your flexible conduit/wires into it. You will need to use a waterproof strain relief at this point as well.
The ground wire attaches at this end the same way it did at the disconnect box.
The red and black wires will need to have crimp on spade lugs attached to them for connection to the contactor (relay) inside the electrical panel. Be sure to line up red with red and black with black.
Installing Control Wires:
You will need to run a two-conductor, 18 gauge control wire from your air handling unit to the condenser unit. This wire can be run alongside the Freon lines and attached with wire ties. At the condenser end, these wires need to connect to the control wire contacts on the contactor (relay). Use wire nuts to connect the wires.
What You Need to Know About the Building Code:
The law requires that final testing and installation of Freon be conducted by a trained and licensed technician. You can’t even buy Freon without a license.
Depending upon your municipality, you may need to have a certified electrician make the final electrical connection to your breaker box.
All exterior wiring must be sealed against water.
Your big money saver is going to be doing the labor yourself. A contractor will typically charge between $1,000 to $1,500 for the installation of a central air unit.