[GreenKeys] Grounding and GFI's

[Bob Camp]

Hi

GFI's are a significant problem when it comes to older gear. Since they 
trip out on minor current imbalances they are really designed to work 
with gear that has total isolation of the AC line to ground. The other 
thing that they depend on is a single path back to ground *through* the 
GFI. It's this second requirement that often gets messed up. Cross 
grounding gear between different GFI'd circuits is a no-no. Running a 
grounded antenna to the chassis of a GFI'd radio is also against the 
rules. If the Model 28 is on one GFI and the computer is on another GFI 
that's a problem if there is a direct ground connection between the 
28's keyboard and the frame ground on the RS-232 input on the computer.

I'm not trying to say that it's time to throw out the GFI's. They could 
save your life. They only will do that if they are being used properly. 
There are ways to break up the direct grounds that work just fine. You 
just have to take the time to build and install them.

A while back I figured out that I am one of those people who are safer 
if they am more worried about what I am doing. GFI's make me worry 
less. The choice I made was to put the garage/wood working shop on 
GFI's (no down side there). I put the computer/radio/Teletype room on 
non-GFI circuits. I simply could not figure out a way to run GFI's in 
there and have them do what they are supposed to do. I would rather 
*know* that there are no GFI's than *assume* there are working GFI's. 
My choice may not be your choice.

Of course if you are going the no GFI way you *must* do it all the old 
fashion way. Everything gets three conductor cords. All the chassis are 
checked for grounding (including that 28 ASR cabinet !!!). All the 
grounds on the wall sockets get checked with the little plug in tester. 
The antennas are grounded and surge supressed. Death by electrocution 
is not a good thing ...

Since a lot of gear has been though multiple owners it's never clear 
what the condition of it's chassis ground is. I certainly have been in 
a rush to get that new toy running. It's only human to want to try a 
new gizmo out. I wish I could say that I always check the ground before 
I fire the gear up, but no I'm far from perfect in that respect. Yes I 
have tripped a breaker that way. So don't do as I do, do as I say. 
Check the ground on that 28 or 15 *before* you plug it in. The wire is 
simply to old on a 15 to be trusted without some basic checks. GFI's 
don't respond to 125 VDC ... If you don't have a simple VOM then skip 
the burger and fries for lunch and get one. It's something the safety 
guy says you should have.

End of rant ....

	Take Care!
		
		Bob Camp
		KB8TQ