How to Clean Air Conditioning Evaporator Unit Properly

20 December 2018

There are a lot of articles written about how to clean air conditioning evaporator units.   Many advised  to use chemical foam;  some preferred to use the cleaning chemicals specially blended for air conditioning washing.   There are merits and demerits depending on how each method can remove the “dirt”.  This article will describe a method that will thoroughly clean the air conditioning evaporator. 

Where is this Evaporating Coil located?

The coil is always located indoors for split unit air conditioners.  It is always hidden inside the air grille box or cover and always behind the air filter as shown

When to do Chemical Cleaning?

The air conditioning unit will tell us with the following telltale signs:-

1)  The air conditioner is no longer as cold and;

2)  The fan speed needs to be turned high before one can feel any cold air blowing,  plus

3)  The air conditioner is making a louder air splashing noise and lastly;

4)  The compressor will turn off sooner before the set room temperature is reached (only for air conditioning unit that has anti-freezing control for the evaporating coil)

Why Compressor Cuts Off Sooner?

The air conditioner that has anti-freezing control will have  a thermal sensor attached to the returning refrigeration pipe.  If the coil is dirty,  the evaporator coil temperature will get lower and will eventually freeze up unless the temperature change is picked up by this thermal sensor which will automatically cut off the compressor operation.

What are the Traditional Methods?

a)  Foam Cleaning 

One would spray foam onto the coil and wait for about 10 to 15 minutes for the foam to work its way into the coil. After that, spray washing the coil with clean water or just leave for the condensate water to "drain"  the foam into the outlet drain.   This method is fast but does not allow the fan blades to be cleaned

b)  Chemical Spraying

One would just spray the chemical onto the coil and wait for about 10 to 15 minutes for the chemical to work into the coil,  then spray washing the chemical.  This method can be used to clean the fan blades.

Both methods are fast but they are not cleaning the coil thoroughly.  For proper cleaning,  one should clean the air condition evaporator unit  using “Chemical Bathing” method which is recommended to be done at least once every 10 years.

What is Chemical Bathing Method?

It is a cleaning method that pours chemical water over the coil to clean the coil thoroughly.  This method will involve some dismantling including the draining tray if one wants to conserve the chemical water for repeated cleaning;   otherwise,  one could just let chemical water drain out into the outlet drain.     

Preparation: 

 Besides having the necessary things such as a ladder,  paint or cleaning brushes,  cleaning rags and other preparation work such as switching off power supply etc,  one should have the following

Description	Action	Remark (Double-click to enlarge)
1.   Chemical Cleaning Fluid	Available easily from Horme Store or any air conditioning hardware stores @ about SGD$15/= per 5 litres or gallon
2.  Plastic basin
3.  Plastic tumbler or mug
4.  Cotton buds
5.  Hand Gloves		To prevent hand and fingers from prolonged soaking in the chemical water

Step by Step 

using Panasonic Inverter Air Conditioner as an example

Description	Action	Remark (Double-click to enlarge)
1.   Preparation work	1.  Switch off the power as safety precaution 2.  Remove the filter if necessary 3.  To make the chemical water,  mix one cup of chemical with about 5 cups of clean water in the plastic basic
2.  Dismantling the air grille cover	1.  Remove the plastic caps that covered up the 2 screws and remove the screws as shown; 2.  Lift to open the horizontal air vane to clear the grille cover; 3.  Hold both sides of the grille cover and pull it forward toward yourself 4.  If the cover could not be dislocated and removed easily,  try releasing the 3 plastic catch that holds the top of the grille cover as shown
3.  Dismantling the draining tray	The draining tray and the air discharge grille is one complete unit. To dismantle 1.  Pull the air discharge grille downward to loosen  the tray unit from its seats 2.  Remove the drain hose that is connected to the draining tray
4.   Coil Surface Cleaning	1. Dip paint brush in chemical water and brush the fins in the same direction as and along the fins; 2.  Collect the chemical water at the bottom of the coil using the basin 3.  Repeat action until the fins are all cleaned and shining on the surface.
5.  Doing Chemical Bath	1.  Use the plastic mug to pour the chemical water from the top of the coil and collect the water at the bottom of the coil using the basin 2.  Repeat for the rest of the fin and coil;	Note:  A air or water pressure pump would be helpful to push the chemical water through the fins but it is not really necessary unless the coil is so stuck with dirt that cannot be cleaned by pouring water over the fins
6.  Water Rinsing	1.  Repeat step 5 but using clean water instead of chemical water 2.  Change the water as and when necessary for proper cleaning	The chemical water needs to be rinsed "thoroughly" so that it will not be left to “attack” the flimsy fins
7.   Fan Blade Cleaning	1.  Dip the cotton bud in chemical water and clean the blade leaf by leaf and blade by blade until all the dirt are removed Note:  One could use chemical spray to soften the dirt before removing them either using water and follow up the cleaning by using cotton buds.	Important:  Never apply any pressure to the blade as a bend in the fan blade will put the wheel off balance,  creating unnecessary noises and vibrations during operation  The alternative is to dismantle the cross flow fan by removing the screw as shown above and removing the fan bearing on the other end.  It would be necessary to dismantle the control board and also dislocate and lift up the evaporator to provide space to remove the cross flow fan.
8.  Completion and Assembly	1.  Reverse the dismantling procedure to fit all components back in place 2.  Switch on the air conditioner after placing a piece of cloth or plastic to catch the  dirt “flying” out from the fan blades.	If the coil has been properly cleaned,  one should notice that the air conditioner’s compressor will never stop operating until the set room temperature has been reached.

Result

Unfortunately,   there was no picture capturing the result of the cleaning but this picture did show up the shine of the lower part of the coil under the ceiling light.   The picture was intended to show the temporary shelve put up to ease the cleaning operation of the fan blade.