1. Points O, M and R can be shown on the chart.
2. Point ADP can be indicated and lines drawn between these points as shown.
3. The room ratio line can be drawn.
4. Point S is then shown on the chart, on the room ratio line at 18oC.
5. A horizontal line is then drawn from point S towards the line O – ADP.
6. Point W can then be found where the horizontal line W - S intersects the line O - ADP.
From the psychrometric chart point W is at approximately 9oC dry bulb.
The heat ratio is 12 kW sensible / 22 kW total = 0.545.