Isolation Barrier

by Mr Choo Wei Seng, ShowerTec Industries Sdn Bhd

Comparison of water heater with Isolation Barrier and without Isolation Barrier.

Without Isolation Barrier

In Malaysia, whenever there is a current leakage at home and, the Earthing and Residual Current Circuit Breaker (RCCB) are not functioning properly, the Earth wire will be Electrified, and lead to a HIGH CHANCE of fatality caused by the device which is, the Storage/Solar Water Heater.

Reason:

• The Storage/Solar Water Heater’s tank is made of metal (conductive), and it is connected to stainless steel hose, which is exposed to users.
• The earthing system in the entire house is inter-connected. Instead of being life-saving, it can become the root cause of electrocution simply due to the electro-mechanical failure of the RCCB (residual current circuit breaker) which is supposed to disconnect the circuit if electric current is not balanced between the live conductor and the neutral conductor.
• Refer to the picture without isolation barrier, the 14A is the load current of water heater = 3300/240=13.75 approx. = 14A. The maximum leakage current should reach 240V/500 Ohm (average body resistance under wet conditions) = 0.48Amp. (Assume a total short). The key fact in electrical shock is that, any shock current is more than 0.01 Amp(10 mil Amp) can kill a person.

With Isolation Barrier

Water is conductive but it is not a good current conductor. Therefore, an isolation barrier is added to elongate the water pathway and turn it into a “non-conductive” pathway. Studies have shown that a 1.0 metre long pathway will reduce the electric current to less than 0.005 Amp (In compliance with IEC standard). It has also been studied and confirmed that if water is travelling through a 1.0 metre (3.3 feet) long pathway and in a 10 mm inner diameter hose, the electric current will not kill a person even if the person is standing barefoot on a wet floor. Therefore, when a user touches the stainless steel hose, it is still safe.