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What does it take to install a simple central air system?

Posted on 25 April, 2017 at 22:57
Air conditioning is something most people take for granted until it's broken.

If your a new home buyer, you will be faced with replacing a component or the entire system at some point in time. It's expensive equipment.  I sell 13 and 14 SEER equipment all the time.  The higher the SEER Rating the better the equipment is built to save energy.

So why do Air conditioning tech's charge so much? If we truly love our jobs and want to help people  stay happy shouldn't it be less expensive? 

Air conditioning is complex.  It requires a lot of thought and expertise to even put a system together correctly.

Here I am preparing to Braze copper tubing to a evaporator in a basement.  Try working with a 2,000 degree torch in one hand while applying molten alloys around in a circular pipe for a while.

This is the part on the inside.

Here is a simple oxygen and acetylene torch set used to join copper pipes together or cut metal. This cost about $400 plus filling gas bottles.  You have to buy brazing rods, safety equipment and find a gas supplier to exchange your empty bottles.

It's serious business- brazing pipes. If your not careful you melt the copper and pieces of molten metal fall on the floor and you will have a hole in the pipe. Tech's are hired to work the copper tubing and fill it with refrigerant, not destroy the copper.  This would be a problem!


These gases have to be stored in a safe location.  The gas coming out of the tanks has to be mixed by the operator in just the right proportion to get the flame at the correct temperature and pressure.
It's takes some practice.

Once the copper tubes have all the right fittings, they are brazed or silver soldered together.. The technician has to use Nitrogen to pressurize the system at around 300-400 psi and look for leaks.  If I find one, I have to get the torch out again or tighten a fitting that I overlooked.  It happens if your not super careful.


The nitrogen is used for a few things other than just pressure test.  We use it while we braze to keep oxidation out of the system.  We have to keep a lot of this around.







The gauges used to check pressure inside of the system are able to withstand 500 psig!  This is a lot of pressure, but on  hot July summer day, the gases get under that much pressure if there is a problem, so we have to be prepared.

If the needle doesn't move while the technician puts in the nitrogen we can move on to the evacuation process.

If it does move, we have to find the leak and repair it.




So if the pressure holds, we release the nitrogen back into the atmosphere.  It's not a dangerous gas.

Here,  I put the evacuation pump, which a powerful tool designed to pull air out of the system to use. I have removed condensables from the complete copper tubing system.

When the air is removed it creates a vacuum.  In a vacuum, water boils at a much lower temperature.  As the evacuation process is underway, we watch steam rise out of the baffle on the pump.  Here we see the micron gauge telling me that the system is down to 231 microns per cubic inch.  This is good because refrigeration and water don't mix.  Ice crystals inside your copper tubing would be called condensables and they make trouble...the system will freeze up and I mean quickly.

At some point the system will be ready for refrigerant .  So the tech plans to release the refrigerant stored inside the condensor and start it up.  Using special allen wrenches the King valves are opened and the gas is released into the fresh copper tubing..it's in a vacuum, so it rushes through quickly!

Inside the house, wiring passes through the thermostat on the wall.  We can turn the system on cool and if the wiring has been hook up correctly the condensor fan will turn on using electronic ignition via a magnetic coil. The compressor kicks on and wallaa!

There is 24 volts to pull the contacts together.  this voltage is supplied by the furnace to or air handler.  The 220 volts required to turn the compressor is on a disconnect.  This is 220 volts AC and it is dangerous.  You have to be trained to work with high voltage or you can get shocked really easily.

Once the levels are checked with the gauges the technician  has to figure out if the pressure are correct for that given day. If the system isn't in the correct parameters the refrigerant level has to be modified.  This is a science too.  To much gas and the system bogs down and possibly damage the compressor. Too little and the evaporator will freeze up due to an incomplete cycle. Super heat or Sub cooling is the science techs learn to work with in school. There are others ways using temperature and air speed.  This requires some good math skills and some specialized tools.  I'm happy using the super heat and sub cooling methods.





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