built-in ELCB
Safety for Electric Shower water heater tripping breaker installation
To cite this article: A P Purnomoadi et al 2021 IOP Conf. Ser.: Mater. Sci. Eng. 1098 042047
A P Purnomoadi*, N W Priambodo, A S Surya, H B Tambunan, D R Jintaka, K M Tofani and M Ridwan
PLN Research Institute, Jakarta, Indonesia
Abstract. Death casualties due to electrocution when showering using electric shower water heater (ESWH) have been reported. The cases included the use of either water heater with storage system or the instantaneous water heater. There are three factors that may contribute to the event, namely, the improper installation including the grounding and wiring systems, the equipment factor, and the human error. The first two factors are the most dominant. This paper presents scenarios when one may experience an electrocution during showering, the current safety regulations in Indonesia regarding the installation of the electric shower water heater, and the mitigations to avoid casualties. The additional of ELCB (Earth Leakage Circuit Breaker) water heater tripping breaker may increase the safety factor as it protects the user from an electrical shock in shorter duration than the common Main Circuit Breaker (MCB). A successful ELCB depends also on the correct installation of protection earth wiring and grounding.
1. Introduction
Electric Shower Water Heater (ESWH) is one of the everyday house appliances in modern living. In the past, the price was high, and it required high electricity consumption that could only be afforded by the high-class people. However, nowadays, ESWHs at lower rates are available that could operate at only 350 - 400 Watts.
There are two general types of ESWH, namely, the one with the storage/ tank system and the instantaneous type. The basic principle for both is similar, i.e., bypassing the cold water into a heating element to produce hot water at the outlet. The process is known as "Joule's Heating." Figure 1 shows both types of ESWH.
Water heater with tank system consumes less power in comparison with the instantaneous one. The tank collects the water, and then, the system heats it regularly based on the reading of a thermostat sensor. The tank capacity varies from 15 to 100 liters, depends on the size of the ESWH system. Bigger capacity consumes more power.
In the instant water heater, the heating process runs faster. Consequently, it requires higher watts in comparison with the tank system. In Indonesia, the market generally sells instant ESWH with power ranges from 800 to 2400 Watts. Meanwhile, in developed countries, instant ESWHs with power above 5000 Watts are available. Higher watts mean faster heating process.
Figure 1. (a) ESWH with tank system, (b) instantaneous ESWH.
Both types ESWH provide earth-leak circuit breaker (ELCB)(water heater tripping breaker) for user safety. However, death casualties have been reported during showering [1-7]. Further investigations, found there are factors that contribute to the accidents, namely:
- The improper installation including the grounding and wiring systems, for example: thecable ampacity is below the current rates, bad grounding systems, the unavailability of
- Theequipment factor, such as, substandard design (not comply to the IEC [8] standard), wiring insulation
- Human error as this may happen when the ESWH is used by kids or people with handicap.As has been reported in [9].
2. Electrocution when showering
Electrocution happens when an electric current is passing the human body. This may occur with two possibilities:
- The body touches the live and the ground parts at the same
- The body touches two points with different voltage levels at the same
Electrocution with house appliances mostly occurs through the first. The severity level depends on the amplitude and duration of the current. The IEC 60479-1 provides a curve that relates the maximum duration vs. current amplitude that human body could stand for (see Figure-2) [9]. Table 1 explains the definition of zoning as provided by Figure 2.
According to table 1 and figure 2, ventricular fibrillation could be avoided if the duration of electrocution is less than 200 ms and the maximum current is 30 mA. Based on this recommendation, the IEC recommends the safety protection of (Earth Leakage Circuit Breaker) ELCB operates in 0.1 second (=100 ms) [10].
In Indonesia most of the housing grounding system is with TN C-S configuration, while in small case the TT system can also be found. Different scenarios could lead into electrocution; an example is given below (see figure 3); others could be found in [7]:
Equipment status:
- Hot wire has been deteriorated, the outer case becomes live and expose a safety
- ELCB malfunction, or even the ESWH is not equipped with
- The ESWH is
Installation status:
- The grounding system is TNC-S
- Main Circuit Breaker (MCB) is the only protection
In this scenario, the ELCB is neither installed nor properly works. An insulation breakdown produces a fault current to the earth. At the TN C-S grounding system, majority of fault current will flow through the ESWH casing (because of its low impedance), passing through the grounding system and back to the source. As a consequence, the fault current could be high up to 1000 A [11]. The MCB will trip after
0.4 seconds (400ms) [12]. A small part of fault current could flow to the user, Iv, with the amplitude
IOP Conf. Series: Materials Science and Engineering 1098 (2021) 042047
doi:10.1088/1757-899X/1098/4/042047
depends on the body’s impedance and the resistivity of the grounding system. This small current may be lethal as seen in Figure 2.
Figure 3. An electrocution due to insulation deterioration on phase cable on TN C-S grounding system.
3. Current safety regulations for ESWH Installations in Indonesia
Household electricity appliances in Indonesia should comply with the national standard SNI 7859:2013 [13]. The national standard adapts the IEC 60335-1: 2010 [14]. Furthermore, the SNI IEC 60335-2- 21:2010 regulates the ESWH with tank system, while the SNI IEC 60335-2-35:2010 regulates the instantaneous type. Table 2 summarizes important clauses from the standards.
IOP Conf. Series: Materials Science and Engineering
Related ELCB for water heater link:
ELCB Factory website: www.traner-elec.com
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