[A/S] Air Conditioning

[Jack Canavera <jackcanavera@xxxxxxxxx>]

I received this information from Dometic regarding the
diagnosis of potential problems with my Duo-Therm air
conditioner.  I thought you might find it interesting.

Jack


Air Conditioner Freeze-Up
Causes:
1, dirty coils and air filters
2. re-circulation of cold air into the return side of
the air conditioner
3. using  automatic or low fan speeds in higher
humidity and ambient temperatures 
4. restricted ducting or restriction in air flow
5. air-conditioner empty or low on charge
6. freeze control defective or improperly placed
   ****(standard air conditioner, not heat pumps
except when used with 5 button CCC)

Testing procedure:
**Required**- Ambient temperature must be at 70F
degrees or higher to perform these checks.
                          ******** Evaporator coil
must not be frozen up********

Start by turning the air conditioner on to HIGH cool
and let run for 15-20 minutes.

TAKE THE FOLLOWING AIR TEMPERATURE READINGS-
Outside ambient temperature
Approximate humidity (high or low)
Inside coach temperature
Return air temperature
Discharge (supply) air temperature

*Once you have taken theses temperatures, use an Amp
meter to measure the Amp draw on the COMPRESSOR COMMON
LEAD (run) wire of the compressor. Refer to the model
specific Installation and Operating manual for the
rated compressor run amp draw.
Note** This amp reading is accurate at 95f degrees
ambient temperature, 80f degrees coach temperature, 50
% relative humidity. *TIP- For every 10f degrees under
95 degrees subtract 1 amp. For every 10f degrees above
95 degrees add 1 amp.  

EXAMPLE: model 57915.531 air conditioner. Rated amp
draw 12.1 amps @ 95f degrees.
Field  condition-  Ambient temperature is 80 degrees. 
How to figure-   95 - 80 = 15,      15 / 10 = 1.5,    
12.1 - 1.5 = 11.4
Actual approximate amp draw at field conditions=  10 -
11.5 amps

If compressor amp reading is less than the calculated
figure, and the temperature split between the return
air and discharge air is not approximately 18 - 20
degrees the air conditioner has a refrigerant leak or
is low on charge.

If the amp reading higher than the calculated figure,
and the temperature split is not between 18 - 20 deg
the air conditioner has restriction in air flow on the
condenser coil. Check number(s) 1, 3, 4 

There should be a difference of approximately 18-20
degrees between the return air temperature and the
discharge air temperature. If not check  number(s) 1,
2, 3, 4, 5, take amp draw on compressor run wire.

There should be little or no difference in temperature
between the return air temperature and coach
temperature. Check number(s) 2


=====
Jack Canavera
STL. Mo.
'01 Safari 27'