AC Troubleshooting Chart
This AC troubleshooting chart is like a cheat sheet. By following
all the symptoms of your AC system, you can pinpoint exactly what's
wrong. Troubleshooting chart is by Heat Controller.
You can find that chart
here.
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Troubleshooting with Superheat
These four temperature differentials are the critical measurements
used to determine all refrigerant related problems. Often a manifold
gauge set is not even necessary.
- Superheat is a temperature differential.
- Subcooling is a temperature differential.
- Evaporator entering air versus leaving air temperature is a
differential.
- Condenser entering air versus leaving air temperature is a
differential.
Critical Temperature Differentials
- Air temperature drop over the evaporator should not exceed 20
degrees F.
- Air temperature rise over the condenser should not exceed 30
degrees F.
- The low side superheat should be between 20 and 30 degrees.
- The condenser subcooling should not exceed 15 degrees.
- An air temperature drop over the evaporator greater than 20 degrees
indicates low evaporator airflow.
- An air temperature rise over the condenser greater than 30 degrees
indicates low condenser airflow.
- A low side superheat less than 20 degrees indicates too much liquid
refrigerant is in the low side.
- A low side superheat greater than 30 degrees indicates too little
refrigerant is in the low side.
- A condenser subcooling exceeding 15 degrees indicates too much
liquid refrigerant is in the high side.
Comparing these readings will lead to an understanding of what is
wrong with the system. For example, assuming adequate airflow over both
the evaporator and condenser the following is true.
- High superheat with high condenser subcooling indicates a
restriction. Too much liquid is in the high side and too little in the
low side.
- Low superheat with high subcooling indicates an overcharge. Too much
liquid on both sides.
- High superheat with low condenser subcooling indicates an
undercharge. Not enough liquid on either side.
- Low side superheat and condenser subcooling simply tell us where the
refrigerant is located.
- Too much refrigerant on the high side and too little on the low side
indicates a restriction.
- Too much on both sides indicates an overcharge and not enough on
either side indicates an undercharge.
Carlyle O6D, O6E and O6CC Video
Troubleshooting Carrier Carlyle O6D, O6E and O6CC video.
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Sizing a Air Conditioning System
A few basics sizing your cooling system. I am not going into the science
of sizing the system. I am going to keep it simple, and use a sizing system
that has worked since dinosaurs needed A/C.
400 Square feet per ton!
THATS IT!
If your house is 800 square feet, you need 2 tons of A/C.
If your house is 1200 square feet, you need 3 tons of A/C.
Starting to make sense?? A/C systems are sold in 1/2 ton
increments, and residentially the systems go up to 5 tons.
Sizing a system
for commercial applications will be different. Because, we will have to deal
with computers, copy machines, lighting, people etc. All these extra
elements release heat which will have to be included in your calculations. Over sizing a system in a commercial application will not
hurt. I suggest using the basic sizing plus adding tonnage for all the
elements. How much tonnage to add? That I cannot tell you, without doing a
heat calculation. I will try to find some charts and get that posted here.
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Air Ductwork Sizing
If you need help designing and sizing your ductwork,
Perfect-Home-Hvac-Design.com provides Manual J
calculations and Manual D calculations duct design for your
home.
- 10 ft x 10 ft room requires 6" duct supply
- 12 ft x 12 ft room requires 7" duct supply
- 14 ft x 14 ft room requires 8" duct supply
Rooms Larger than 200 SF should have 2 Duct supplies
- 200
square foot requires 2 6" duct supplies
- 300 square foot requires 2 7" duct supplies
- 400 square foot requires 2 8" duct supplies
These are only estimations of duct sizing. Sometimes you have to
consider the length of the duct run and if the room is in the sun
most of the day. Over sizing the ductwork won't hurt since you can
always adjust the air flow using the damper in the collar.
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