Welcome cold weather, goodbye hot water? Some instant heater owners have been calling up as they are not getting sufficient hot water during the rainy streak. Why is that?
To answer this question, let us look at the insides of an instant water heater.
Instant heaters are compact, heating systems designed to quickly raise the temperature of an incoming stream of cold water. The incoming water passes through a flow restrictor, which reduces the flow rate of water. A reduced flow rate gives the water more time to get heated as it flows around the element. Finally, the heated water gets to the end user.
A typical instant water heater system at its highest performance is designed to raise the water temperature by an average of 8°C. In Singapore, the average person showers with 38°C – 40°C of hot water.
On normal days, cold water enters the heater at 30°C:
30°C + 8°C = 38°C
On cooler days, however, cold water enters the heater at 21°C:
21°C + 8°C = 29°C
Now you can appreciate why the instant heater cannot produce hot water on a cooler day.
There is a knob on the heater which controls water temperature. Doesn’t that work?
The knob on an instant heater is the flow restrictor which we mentioned earlier on.
If you turn on the water for the shower head and turn the knob to lower temperature at the same time, you will notice that the water pressure at the shower increases as the knob is set from high to low. The higher the flow rate, the cooler the water.