Go Home! Workshop Air Conditioning See All Photos
   

You might ask WHY?

I've been interested in air conditioning for a long time. I suspect part of that interest stems from magazines and the web telling you that anything to do with air conditioning or refrigeration should be left to a 'grown up' (professional).

A few years ago, I built air con for my Land Rover based on parts salvaged from a junk yard. It worked pretty well, but, all the parts were designed to use an old refrigerant gas called R12. More modern (more environmentally friendly) gasses like R134a, have smaller molecules which can escape through seals and even through the walls of plastic pipes designed for R12. While it stayed charged up, it was pretty good. It could make the inside of the windscreen ice up in the middle of summer!

I incorporated a valve which let me reverse the flow through the system. This extracts a large amount of low grade heat from the environment. The system concentrates the heat and delivers a smaller amount of high grade (high temperature) heat on the inside. The normal heater in diesel Land Rovers is pretty useless and takes a-g-e-s to heat up. This on the other hand provided heat as soon as the engine started - immediately de-misting the windscreen and making the vehicle habitable.

My workshop although well insulated, has a large area of south facing roof and gets pretty hot in the summer (30 degrees C yesterday!). It has no gas supply so any heating in the winter has to be electric. My experience with the Land Rover pointed to a reversible heat pump air conditioning system being the answer.

When it is acting as a heater, because it is just transferring heat from the outside, concentrating it along the way, it will spit out more heat than the amount of electricity you are putting into the compressor (which moves the refrigerant and hence the heat around the system).

If I were to put say 2 kW of power into the compressor, it might deliver 3 kW of heat on the inside whereas if I put 2 kW into an electric heater, I would only get 2 kW of heat output. I am therefore getting something for nothing! More efficient electric heating. Cooling in the summer is a bonus too!

I hope that my energy usage throughout the year should balance out making it no more wasteful than just providing heating in the winter.



Rather than just go & buy ready made air conditioning - most of the bits came from my favorite junk yard (Millers in Roffey, Horsham) with the rest (things like the reversing valve and copper tube) from NRS Climate Canter in Crawley. The chaps at NRS were very friendly and helped me out when I knew what I wanted, but didn't know what it was called!

I also need to thank my friend Bob King who is refrigeration 'grown up' for advice, kit and charging it up!

 
    This is my 'Rabbit Hutch'! It contains one of the condenser / evaporators, the compressor and reversing valve.

You can just about see the motor which drives a compressor from a Range rover via a belt at the front.
    This is the internal view of the hutch. The motor is on the left, the compressor in the middle, the mass of plumbing on the right is the reversing valve and receiver/dryer (more later) and at the back is the radiator (also out of a Range Rover).

The receiver dryer provides a reservoir of refrigerant and contains chemical stuff which removes moisture from the gas. Moisture is not the friend of refrigeration! It reacts with the gas to form something acidic which eats all your seals!
    It is not visible, but there is a sight glass which has another chemical thing in it which changes colour in the presence of moisture to give a warning of potential trouble down the line.  
    This photo shows the radiator which lives on the inside. It is another Range Rover part. You can see two pipes which go into the radiator. The lower of the two contains the 'orifice' and a bypass valve in parallel.

The orifice is just a constriction in the tube. Pressure on one side of the constriction keeps the refrigerant liquid, but the pressure on the other side is lower, allowing it to evaporate. It is this evaporation which actually does the cooling.
   
When the system is cooling the workshop, gas comes from the compressor through the lower tube and through the orifice. When it is heating, gas comes from the compressor through the top tube, through the radiator where it cools down. (It is hot because it has been compressed) and then through the bypass valve allowing it to go straight to the radiator outside. The one on the outside also has an orifice and bypass valve so when the gas is flowing in one direction it goes through the orifice and provides cooling.

The combination of two identical radiators, orifices and bypass valves allow the two to exchange roles depending on the direction of the gas flow.
    Here is a wider view of the internal radiator.

You can see underneath the rad is a length of guttering. When the rad is cooling, moisture condenses out of the air on the radiator fins. This needs to be caught and carried outside to a drain otherwise it would permanently rain on my work bench - not good.
    All in, it doesn't work too badly. The total build cost was about £150 plus charging up.

Millers, the Junk yard very often gets complete AC systems which have been scrapped (usually through being upgraded). It would probably be simpler & cheaper to buy one of these & plumb it in yourself. Then you can guarantee the matching of all the components capacities.

Mail me if you have any questions!