Why does somebody feel the light electric shocks when touching the faucet combination? Let’s look at a scheme of electrical insulation bathroom equipment of old construction houses.
Fig.1. Scheme of electrical insulation without PE wire in the bathroom
Each appliance has insulated from the hull. It insulation has some resistance, ideally very large.
The hull of the appliance is connected to the Cold water pipe or Hot water pipe, Soil pipe. It stands on the Floor, which often is wet. These circuits have low resistance of insulation.
Also, devices in the bathroom stand on the floor and are connected to the pipes.
What will be, if the insulation resistance of the washing machine became worse? Voltage of everything, which was connected to the hull of washing machine, will increase.
Fig.2. Electric shock from water. The path of the leakage current in the case of poor insulation
While somebody are touching the tap, the leakage current will flow through the circuit with less resistance: phase L1 – a small resistance to the washing machine insulation – the case of the washing machine – the resistance of the pipe cold water – Cold water pipe – the resistance of the Cold water pipe to the faucet combination – tap – water – human body – crude floor. Then current will flow from the floor to all possible directions – to the Soil pipe, to Hot water pipe, to the ground, etc.
The potential equalization system will increase safety from electric shock. In fact, if everything conductive, to which a person can touch, will be connected to the PE wire, then everything will have the identical voltage even in case with a problem in the washing machine insulation. The voltage will be approximately zero volts between enclosures of all the appliances and pipes in the bathroom, and the current will not be able to flow through the human body.
Fig.3. The path of the leakage current in the circuit with PE wire and poor insulation
Leakage currents will increase and it is advisable to use the circuit-breaker with RCD
One question – is it possible to make the potential equalization system only in single apartment, but not everywhere in the apartment building? The answer is – you cannot if you do not have a project. The bad potential equalization system is very dangerous for the people of your house.
Text has been updated February 4, 2017 by the author: