[GreenKeys] Ground Fault Circuit Interrupters

[COURYHOUSE at aol.com]

great  info Jeff...  also in another   article  you  mentioned  separate  
grounds  being   a no no... can   you elaborate    why  not!?
 
Ed#
 
 
 
 
In a message dated 10/2/2013 12:31:23 P.M. Mountain Standard Time,  
jdangus at att.net writes:

Ground  Fault Circuit Interrupters.

>From the Underwriters  Labs:
<http://www.ul.com/global/documents/offerings/perspectives/regulators/techni
cal/ul_GroundFaultProtectiveDevices.pdf>

>From  4 to 6 mA current imbalance to trip.

At 60 Hz and 120 VAC, this is  equal to  2000 to 3000 ohms.
For capacitive reactance in that range it  is 1.326  to 0.884 uF

However, even a 0.47 uF capacitor with wax  paper dielectric that
has aged badly over the years may have an equivalent  parallel
resistive leakage current as  high as 4 to 6  mA.

Almost ALL equipment up through the 70's tended to have  both
sides of the AC line bypassed to the chassis.

A side effect of  this, is that with a faulty or non-existent ground
this acts like a voltage  divider and puts roughly 60 vac between
the chassis and ground. (Or with a  good ground, causes leakage
current to unbalance the GFCI  equipment.)

Newer equipment has a single capacitor across the line,  THEN a
common mode choke in series with the line, and then two  bypass
capacitors to ground. Current UL rules require the use of type  X
and type Y capacitors in this configuration to keep from either  a,
shorting out or b, setting fire to themselves in the event of  a
failure.

Jeff-1.0
wa6fwi


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