GE GFK-0825F user manual B

GFK-0825F B-1
Installing Additional Suppression
This appendix describes some precautions that can be taken in an installation to help assure proper
operation.
It is possible some insta llations might exceed the s ur ge immunity capabilities specified in chapter
1. This is most likely in outd oor installa t i ons or where th e power source i s from another bu ilding or
ground system . It is pruden t to provide local transient pr otection.
Note
MOVs do a good job of absorbing transients on communications, control, and
power lines, provided th e total energy of those trans i ents does not exceed the
rating of the device.
However, if the energy of th e transient exceeds the rat ing of the device, the MOV
may be either damaged or destroyed. This failure may not be visibly or
electrically evident . MOVs should be regularly inspected for signs of damage to
assure continued protection against transients. For some applications, periodic
replacement of critical MOVs is recommended, even if they do not show signs of
damage.
Suppression at the Power Lines
Protection can be provided by connecting higher-energy MOVs across the power lines (for
instance, between Hot and Neutral) and from line to frame ground (safety ground). This triangular
configuration requires three MOVs for each long power feed. If the total power feed len gth is about
100 feet or less, one set of MOVs should be enough for any number of devices. The axial-leaded
LA series of MOVs from Harris is often used. The 14mm size, model V130LA10 rated at 38
joules is usually sufficient. The MOVs used should be able to handle most line transients.
Measurement of actual transients may be required in extreme cases to decide what MOVs to use.
B
Appendix