Green Tractor Talk banner

1 - 4 of 4 Posts

·
Registered
Joined
·
733 Posts
Discussion Starter #1
I can easily find InLine GFCI's for 110v, can a person use a 110v inline GFCI for 220v?
I'm no electrical expert, so I figured I'd ask first...

FWIW, The pressure washer I have doesnt have a GFCI (its a Heavy Duty/Farm Brew setup)...So I'd like to put one in line....
 

·
Premium Member
Joined
·
6,593 Posts

·
Premium Member
Joined
·
971 Posts
Here's a 240V GFI, but it's not cheap...

http://ecatalog.squared.com/fulldetail.cfm?partnumber=QO220GFI

Here's the part numbers for the 2 pole Square D breakers:

http://www.schneider-electric.us/?LinkServID=3F813F3C-215E-545B-E058584AC6A61592&showMeta=0

And finally, here's a 30 amp breaker that only cost $110:

http://www.superbreakers.net/qo230gf.html?gclid=CK2CkrfS86QCFYft7QodBBsshg

so you can get 240 GFIs.

As for using a two 120V ones, one for each leg, it won't work. Here's why. The 120V GFI breaker connects to both the hot and the neutral of the wire that runs off to the load. It also has a wire that goes to the neutral bus bar in your breaker box. The breaker basically constantly looks to see if the same current that goes out on the hot wire comes back on the neutral wire. If it's not the same, the breaker trips since that means that there is some other path (to ground) that is the return for the current on the hot wire. That "ground fault" current would be you standing in a puddle holding the black wire on the circuit :mocking:. FWIW, this can be a simple transformer wound such that the current going out on hot (wound in one direction) cancels the current coming back on the neutral (wound in the opposite direction) such that there is no resultant magnetic field. This transformer would have a sense winding on it that (typically) goes to some circuitry that amplifies and conditions the imbalance in such a way that it can trip the breaker.

Now if you had two 120V GFIs feeding a 240 circuit, and let's for now assume it's a really clean load such as a purely resistive heater coil, then all the current going out on the hot leg on one side would be coming back in on the hot leg of the other side. Neither single pole GFI would see _any_ neutral current and this would look like the grandest ground fault of all time.

Real currents are uglier than a pure resistive. You also have the effect of capacitive loads on motors and inductive loading from coils. So the phase of the current is important, and there also has to be some way to avoid false tripping from startups, ground bumps from lightning strikes, and the like. That's why there's a chip in there.

For the 250 GFI's, the breaker has basically the same task- make sure that all currents leaving either hot wire comes back on either the other hot wires or neutral. So it's a little more complex. Add to that lower volume, and that's why they are so expensive.

Hope this makes sense.... :unknown:

Pete
 

·
Administrator
Joined
·
18,298 Posts
Check your PM's Dave...
 
1 - 4 of 4 Posts
Top