New (Earth) Ground Wire Trips Breaker

[Rob_Feature]

I've got a Westinghouse WB78 and a while back I added a new power cord since the old one was pretty scary.  I put on a 3-prong and I believe the originals just had a 2 prong (is that right?)

Anyway, I attached the (green earth) ground wire to the metal plate that the compressor sits on by just fastening it down with one of the existing bolts.  Most of the time it works fine.

But then for a while I was stumped as to why my GFCI outlet kept popping.  I messed with everything for a long time, only to find that nothing would consistently cause problems...until I unhooked my ground.  Then it never popped again.

Now, I know it's entirely possible that a GFCI won't pop as easily with no ground attached...so maybe I'm just bypassing the problem (just guessing on that part).  

What's it sound like to you?  Is there an actual issue that's causing something hot to run back to that 'ground plate' and trip the breaker?  Could it be that I don't have a good enough ground in that location by attaching it to that bolt (and if not there, where else)? Maybe too much paint/grime where I attached?

I know enough about this to avoid frying myself, otherwise learning as I go.  Thoughts?

[johnieG]

The GFCI isn’t lying, you’ve got ground leakage somewhere.

Could be your compressors deck plate isn’t bonded to the rest of the machines chassis.  
So the compressor should be bonded to the deck plate & the deck plate is normally grounded via the mounting bolts holding it in place to the floor of the chassis thus grounding the whole machine, if the GFCI keeps tripping, then check you compressor for a grounded motor winding,

Unplug the machine & measure with an ohm meter between the ground ( earth) pin & each blade of the power plug one at a time, it should read infinite or max scale of your meter, if one or the other reads at a lower range, then something’s starting to short to ground, this is often a common problem for people who power-wash the condensor fan motor / compressor area & get the electrical components wet, the water gets into tge motors insulation & cause a high resistance ground or the water simply shorts out a connector , etc

You can also unplug the compressor from the control socket on the harness & check each blade of the compressors plug to the case of the compressor itself ( you may have to sand or scrape down to bare metal to check it thoroughly)

Grounding is good & keeps you safe, don’t remove it, find the problem & fix it.

[Rob_Feature]

Just wanted to say "thanks" Johnie!  It turns out the compressor deck wasn't tightened down very well...I tightened it, fastened the ground and have had no issues since!

PS:  This is the machine where I brought you the compressor 2 years in a row.  I realized late last year that I think the second visit to you was unnecessary...I'm pretty sure the compressor was tripping off (some kind of safety being tripped) on really hot days due to poor electrical in my garage.  Moved it to the house plugs this year and we'll see how it goes!