MODULE V - Electrical engineering

MODULE V Electrical engineering - Basics Page 40

6.2.3 Safety measures against overload and short-circuit

Fuses
Most fuses function as follows: A thin wire within the fuse is melting when a certain nominal current is exceeded and interrupts the current flow either for a whole electric circuit (= conductor protection fuse) or within an individual electric device (= device protection fuse). Fuses should not be bridged under any circumstances or replaced by fuses with a higher nominal current.
Conductor protection switches
These switches possess two separate release mechanisms and are so called "current limiting automatic releasers". If an overcurrent is occurring because of an overload, a bimetal releaser (thermal releaser) releases the switch and disconnects the electric circuit from the power supply.
If a short-circuit occurs, the electric circuit is being interrupted immediately by an electromagnetic instantaneous switch releaser. The switch can only be operated again by hand after the cause of the error has been eliminated.
Motor protection switches
Motor protection switches which are normally used in larger installations and systems function similarly as conductor protection switches. If a too high current occurs a bimetal switch, making use of the heat/thermal effect of electric current, is disconnecting the electricity mains of the installation. The switch can only be operated again after the bimetal has cooled down.

6.3 Safety areas

Sanitary and heating installations and maintenance works are often carried out in areas where the installed devices come directly or indirectly in contact with water. In these rooms or areas (e.g. bath rooms, shower rooms, sauna, etc...) special area divisions and area regulations have to be considered. DIN 0100 defines these areas. DIN 0100 also specifies that in such areas only particularly protected electric devices can be installed. The necessary safety type is indicated on the corresponding device by the letters IP (IP = International protection) followed by two consecutive numbers:

Electric devices - safety types
# 1	Contact and foreign element protection	# 2	Water protection
0	no protection	0	no protection
1	large foreign elements, d > 50mm	1	vertically dropping water
2	medium sized foreign bodies, d > 12mm	2	diagonally dropping water
3	small foreign bodies, d > 2,5mm	3	spray water
4	very small foreign bodies, d > 1mm	4	splash water
5	dust protected	5	jet water
6	dust proof	6	strong water jet
		7	dive in
		8	submerge
If after the two letters IP there is only a single number indicated for the safety type, an X is set for the not necessary safety type (e.g.: IP X4, IP 3X)

Diagram 53: Area division for rooms with a bathing and/or showering tub and potential equalisation

Area B 0: It includes the inside of the bathing or showering tub
Area B 1: Limitation through vertical areas around the bathing or showering tub
Area B 2: It includes a spraying range of 0,6m around area B 1
Area B 3: Next area behind B2 with a width of 2,4m e

English translation of technical terms and sentences of the diagram above:

Durchflusserwärmer	=	Continuous flow water heater
Spiegelbeleuchtung	=	Mirror lights
Sprechanlage	=	Intercom
Wasserleitung	=	Water pipe
Speicheranschluss	=	Storage connection
Grenze des Sprühbereichs	=	Limit of the spraying area
Anschlussösen an Wanne und Abflussstutzen	=	Connection loop of the bathing tub and connecting piece of the drain
Cu-Leitung zusätzlicher Potentialausgleich mit 4mm2	=	Copper pipe, additional potential equalisation of 4mm2
zur PA-Schiene	=	to the PA-bar