DSH 310 Components
http://decisions.iecee.org/icons/ecblank.gifDSH 310
Components
14
61010-1(ed.1);am1;am2
Standard:
IEC 61010-
1:1990+A1:1992+A2:1995
Sub clause:
14
Sheet n. 310
Page 1(1)
Subject:
Components
Key words:
- Transient
- Suppressor
- Mains
Decision taken by
ETF3 and confirmed
by CTL at its 38th
meeting, in Toronto
Question:
Is the use of transient suppressor devices such as varistors accepted in equipment and, if so,
under what conditions
Decision:
Varistors are accepted in the following conditions:
1 Between Live and neutral conductors after the mains fuse.
No component approval demanded.
2 Between Live and neutral conductors, before the mains fuse.
Only accepted if the component is approved to an international standard (IEC 61051 or
CECC 42200)
3 Between Live and Earth conductors (before or after the mains fuse)
a) pluggable equipment
devices are not accepted
b) permanently installed equipment
devices are accepted as in 1 and 2 above.
Note: Components shall be physically mounted in such a way that no hazard can arise in the
event of the device failing catastrophically.
Explanation:
Varistors are semi-conductor devices and therefore, cannot be treated as high integrity
devices and must therefore, always have additional protection.
Varistors in the equipment or installation coupled with safe construction and approvals meet
these requirements except where the disconnection of earth is possible as a single fault. In
this case, the slow deterioration of the device with time, allowing an increase in earth
leakage current, is not acceptable and the devices are, therefore, not allowed.
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