Evaporator Coils

Click on EVAPORATOR to see a picture of an A frame evaporator coil.  Not all coils are like this but this is one version.

My last blog on air conditioning dealt with the metering device.  In the evaporator coil refrigerant goes through the coil and as it does the fan blows warm air from the house over it.  Usually the temperature of the refrigerant in an evaporator coil could be in the 30’s, 40’s, or 50’s.  It just depends on the temperature in the house and outside.  If your air conditioning stops working on a 100 degree day, then it might be higher if the house is really warm, but for our sake, let’s just say the temperature of the evaporator coil is around 40 degrees f.  If the temperature in your house is around 78 degree then that warm air will go over the evaporator coil where it will cause the liquid refrigerant to turn into a vapor.  Evaporator coils create a lot of water, about 10-25 gallons a day, because they are removing the moisture from the air.  This is why it is very important to have a drain switch so if the drain line gets clogged up the drain switch will turn the system off so the water doesn’t overflow and cause damage (you can put bleach in the primary drain line but don’t want to put that in the secondary drain.  I would only do this when the system will be running a lot like from May to August.  One cup of bleach once a month should be ok.)  We do not want liquid refrigerant entering the compressor because once it does it will cause damage to the compressor.  What we do is we superheat the vapor refrigerant.  Superheat means we just add more heat to the vapor so it doesn’t turn back into a liquid.  If we have 40 degrees of refrigerant in the evaporator then we want a minimum of 5 degrees superheat, which is measured at the condenser.  If you have a piston metering device the superheat will change depending on outside temperatures and inside temperatures.  TXV metering devices will be less than 35 degrees superheat.

Published in: on May 8, 2010 at 4:55 pm  Leave a Comment  

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