SIZING A GAS WATER HEATER
Hot Water Demand
All taps in your home when opened deliver a flow rate of water which if we are to measure will be amount of water (in litres) it can deliver over a period of time (in minutes). As an example a basin tap may deliver 10 litres of water per minute when being used. Gas geysers are generally sized according to amount of hot water (litres) it can deliver over a period of time (minute). So a gas geyser should be sized to cater for the peak hot water demand of the house hold at any particular point in time. For example if one is using a shower with hot water demand of 15 litres per minute, and a hot water tap at the basin (10 litres per minute) at the same time the peak hot water demand would be 25 litres per minute. If the basin tap is closed the hot water demand will be showers demand of 15 litres per minute. Most South African homes are accustomed to staggering hot water usage, so it is not typical to find a home where multiple hot water taps/appliances are used at the same time. Once the peak hot water demand of the home is determine then one selects the respective gas geyser.
Bosch residential gas geysers models: 11, 14, 18, 24 or 27 litres per minute.
Incoming water temperature is a critical consideration, which varies by region and season.
Unlike a geyser which stores and maintains the water at a set temperature, a gas geyser heats the incoming cold water instantaneously. Depending on the desired settings of the gas geyser, the gas geyser would raises the incoming water temperature between 25°C and 50°C*.
* Bosch Models