EN 50491-3-2009 pdf download.General requirements for Home and Building Electronic Systems (HBES)
and Building Automation and Control Systems (BACS) -Part 3: Electrical safety requirements.
Compliance with the required electrical separation between the device circuit and the HBES/BACS network circuit shall be tested in accordance with the test requirements in the specific product standard with the appropriate test levels specified in the Table 2 under the following conditions:
— if the electrical separation (simple and protective separation) has a creepage distance then the voltage specified by the letter A shall be used for dimension of the creepage distance. However this creepage distance shall not be less than the clearance for the electrical separation;
— if the electrical separation (simple and protective separation) has a clearance and/or a solid insulation then the voltage specified by the letters 8 and either C or 0 shall be used for dimension of the clearance and/ar the solid insulation.
— if the product standard has no test requirements for the impulse voltage test the requirement specified Table 2 shall be used;
— the test voltage related to the rated impulse voltage, when used for testing the clearances, shall be corrected according to corresponding test altitudes according to EN 60664-1.
— As an alternative to the impulse voltage test of EN 60664-1(6.1.2.2.1). the dielectric test with ac. voltage (6.1.2.2.2.2) or the dielectric test with d.c. voltage (6.1.2.2.2.3) may be used.
5.3.3 Protection from touch current
NOTE Products complying vth EN 60950-1 or EN 60065 fultd the requirements.
If the nominal voltage exceeds 25 V a.c. or 60 V d.c. or if the equipment is immersed, basic protection shall be provided for SELV and PELV circuits by insulation or barriers or enclosures.
Basic protection is generally unnecessary in normal dry conditions for:
— SELV circuits where the nominal voltage does not exceed 25 V a.c. or 60 V d.c.;
— PELV circuits where the nominal voltage does not exceed 25 V ac. or 60 V d.c. and exposed-conductive-parts and/or the live parts are connected by a protective conductor to the main earthing terminal.
In all other cases, basic protection is not required if the nominal voltage of the SELV or PELV system does not exceed 12 V a.c. or 30 V d.c.
Compliance is checked by measurement of the voltage and, if relevant, by testing the basic protection according to the product standard.
if no product standard exist, the test voltage for basic protection shall be 500 V.
5.3.3.1 HBES!BACS products connected to a telecommunication network
For HBESIBACS products connected to a telecommunication network, as classified in 4.1. the appropriate requirements in EN 41003 apply in addition to the product standard.
5.3.3.2 Limitation of the touch current from the device to the dedicated HBESIBACS network
The touch current from devices supplied from the mains supply to the HBES/BACS network shall be limited to 0,25 mA r.m.s. according to IEC 62151. 5.4.
Compliance is checked by measurement according to the test circuits in Figures 5 and 6 in IEC 62151 (based on EN 60990).
This test does not apply to devices where the circuit to be connected to the HBESIBACS network is connected to the protective or functional earthing terminal in the device. In this case the touch current from the device to the network is considered to be zero.
5.3.3.3 Summation of touch current
A device that provides a HBESIBACS network connection for connection of multiple items of other
HBES/BACS equipment, shall not create a hazard due to summation of touch current.
NOTE The background to these requirements is explained in EN 60950-1 (informative Annex W).
In these requirements, abbreviations have the following meanings:
— l is the touch current received from other equipment via a network at a port of the device;
Touch current tests. if necessary, are made using the relevant measuring instrument described in EN 60990 or any other instrument gMng the same results. A capacitive coupled a.c. source of the same line frequency and phase as the ac. mains supply is applied to each communication port such that 0,25 mA, or the actual current from other devices if known to be lower, is available to flow into that communication port. The current flowing in the earthing conductor is then measured.
5.3.3.3.2 Devices whose network ports have no reference to protective earth
If the network ports on the device do not have a common connection, each communication port shall comply with the requirements for touch current in EN 41003.
If all communication ports or any groups of such ports have a common connection including a network segment, the total touch current from each common connection shall not exceed 3,5 mA.
Compliance is checked by inspection and if necessary by the tests of EN 41003 o if there are common connection points, by the following test:
A capacitive coupled a.c. source of the same frequency and phase as the a.c. mains supply is applied to each communication port such that 0,25 mA, or the actual current from the other if known to be lower, is available to flow into that communication port. Common connection points are tested whether or not the points are accessible.
5.3.4 Protection of the communication wiring from overheating
In addition to the control function, the network may provide a power supply function. To make sure, that the communication cable is protected from overheating, the power supply shall have a short circuit andlor overload current limitation. The current-carrying capacity for the communication wires shall be at least equal to the total current limitation for the connected power supplies
The temperature limits and current-carrying capacities for the communication wires specified in HD 384.5523 shall not be exceeded.
Compliance is checked by inspection and measurement.
5.4 Installation
Installation of a home and building automation and control system shall comply with HD 60364-441.
NOTE Additional national requirements may apply.EN 50491-3-2009 pdf download.

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