Sealing of Openings for Window Unit Air Conditioner

22 November 2013

Introduction 

Some high rise apartments in Singapore, especially those older types, are in-built with openings for installation of window type air conditioning unit.   With the advent of inverter split air conditioning unit that can save energy,  many apartment owners have converted from the windows unit  to split air conditioner unit.  The AC installer will simply seal up the window unit openings and walk away,  leaving the owners having to face all sort of maintenance problems.  This article will describe how best to seal these openings.

What’re the maintenance problems?

The AC installer will usually seal the opening with a nice painted 3 mm plywood board,  nailed on the timber frames from inside the apartment.  This board will rot in time and allow rain water to sip onto the carpets or parquet floorings during heavy rains.  A small ledge left outside will attract not only birds to nest but also small plants to grow;  also,  the thin plywood board offers no security as they can be easily kicked open. 

What're needed? 

1. A piece of 20 mm thick plywood to cover up the hole;
2. One lots of about 30 numbers of 30 - 35 mm self-taping screws;
3. 4 number of 100 mm self taping screws
4. Few  lengths of 25x25 timber strips
5. Weather sealing strips
6. Necessary tools such as power drills,  drills,  screw drivers etc..

What precautionary measures?

Assuming that one would have to fix the heavy 20 mm board from inside the apartment to cover the opening from outside the apartment,  one necessary measure is to ensure that the board would not accidentally drop and hit some passerby beneath the openings.   This can be done by fixing ring hooks onto the board and tie strings to hold the board throughout the installation.

Installation steps 

1. Cut the 20 mm plywood to a size slightly larger than the hole;
2. Fix the ring hooks and strings,  then put board to the hole and mark up the size of the hole on the board;  alternatively, one can measure the hole and mark the board;

1. Remove the board and cut 4 number of the 25x25 timber strip to  place them exactly in the inner dimension of the opening and screw the timber strip to the board;
2. Protect the board by painting water proofing paints or seal it up with weather board or otherwise to prevent water coming into contact with the plywood;
3. Place weather sealing strip around the 4 sides of the board;
4. Prepare 4 numbers tensioner and install them onto the timber frame as shown,  making sure that the 100 mm screw is free to move and can be screw onto the 25x25 timber strips;
5. Fix the board in place and screw the 100 mm until the board is pulled in and sit tightly fitted to the timber frame with the weather sealing strip fully compressed to form the water seal;
6. Fix the 25x25 timber strip to the timber frame and remove the tensioners if necessary.

The Completed Work 

Makita Cordless Power Drill DC7100

20 November 2013

The Makita Cordless Power Drill is a handy tool.  Its power unit consists of a 7.2 volt battery pack and a fast battery charger.   This article describes how to replace the battery and repair the battery charger.

 What’s Needed

1)     For replacement of battery 

a)     Soldering iron,  solders and some connecting wires

b)     4 Nos  of 18650 Li-ion batteries.  Can also use some of the good batteries in Laptop for this purpose

 

c)     Remove the end cap of the battery pack and withdraw the batteries

d)     Solder the 18650 batteries,  2 in parallel then put them in series to make up a total voltage of 7.4 volts.  Pay particular attention to positive and negative battery terminal and make sure there are correctly wired;  also pay attention to how the resistor is connected. 

e)     Once soldering is completed, wrap the batteries with shrinkable plastic and re-assembled the batteries to the battery pack casing.

2)     For repair of the power charger 

In addition to the soldering iron,   one will need a multimeter that can measure the workings of the A1015 transistor and the 2P4M SCR thyristor.  These 2 components are likely to be at fault.  .  One would need knowledge of electronic repairs for this task.  Use the attached circuit diagram to troubleshoot.

2P4M Thyristor