VFD Wiring?

C

comet_sharp

Joined
Aug 22, 2016
Messages
256
Hey guys,
Just got my Northridge tool grinder in today with a Leeson 2hp motor wired to 110V. I do everything on my workbench in my garage. On the side of the wall that my workbench is on there is a standard grounded outlet and on the wall on the opposite side of the garage there is a GFI outlet. I set up the grinder (super easy), mounted the VFD and motor, got the drive wheel on and wanted to hear my baby speak. I turned it on and it blew my breaker. I reset the breaker and the outlet was still "dead" until I hit the button on the GFI outlet on the opposite wall. I'm assuming the grounded outlet on my workbench side of the wall is wired to the GFI on the opposite side and I just need to call an electrician and get it re-wired to it's own breaker? Any advice on this would be great, I'm ready to use this thing.
Thanks,
Trey/Comet
 
I've heard of GFI's not liking VFD's. There can be some feedback from them, the sensitivity of a GFI can make it trip. Your grinder outlet is then wired into the same circuit as the GFI outlet...
By the way, are you sure that the breaker is rated for your maximum startup amp draw with that motor/vfd? Could be that simple. Do you have any other outlets you could try plugging the grinder into, on a different circuit?
I don't know how confident/competent you are electrically. If amperage seemed unlikely to be the problem, I'd check the motor/VFD wiring for any faults. Then what I'd do to make sure is maybe first shut off the breaker, test the circuit to make sure it's dead, and get into the GFI outlet box, bypass it temporarily with wirenuts, then breaker on and try the grinder again to see if it was indeed the GFI.
 
A GFI reads any variation in the lines and shuts off the current flow instantly. Things like intercoms will place an audio signal on the lines and trip the GFI. Things that cause fluctuations, like some electronic circuits .... including VFDs .... may cause the same type signals and trip the GFI.

You should either move the wires going from the GFI to the second socket to the feed side of the GFI in order to send a direct line to the outlet, or replace the GFI with a standard outlet. The code requires the garage to have GFI, so make sure to replace/reverse things when you move or sell the place. If any of t hat sounds like Greek to you, get someone else to do it for you.

If you are handy with power circuits, you can put a by-pass switch to send the power past the GFI socket and to the other outlet.
 
I would use this as an opportunity to run a dedicated line/outlet to your grinder. If you only have 14/2 wire on 15 amp breakers going to multiple outlets, your grinder is going to soak up a lot of that and anything else with a minor draw on that circuit will trip your breaker.

And if you're going to go to that trouble, you may as well run it in 220 as it's really not much more expense.

If you don't do that and you just replace the GFCI outlet with a standard one, then you should look into your VFDs programming for accel, decel, type options and reprogram for softer starts and stops.

However I think it's possible you have a deeper issue if you tripped both the GFCI and the breaker, possible a wiring mistake in the VFD to motor, although most VFDs will simply error out in that case, and throw a code.
 
I agree, the best case would be to run a dedicated 220V circuit for the grinder. There will be more power!
 
Thanks for the advice guys. I think it just tripped the gfci and not the breaker. I tried the breaker first because I didnt realize it was tied to the gfci. Im replacing the gfci when I get off work and will look into re-wiring. I'll do some research on it first and grind some in the mean time. Hell just knowing I can go to 220 makes me want to rewire though.
 
Assuming a 15amp circuit, 2hp. All on its own is max to run on 15 amp.
Add start up loads & efficiency loss of your VFD & are on the edge of an adequate circuit.

Firstly, I would plug into a non-GFCI circuit & see what happens.

Some GFCIs will trip if their power is removed. Also as mentioned, Some GFCIs dont like fast electronic switched loads.

Lastly, its always a good idea to run 240v to these machines.
 
i think the GFCI just happened to trip first. you didn't say what brand VFD you have. I checked the manual for my Leeson and their 1.5Hp VFD draws 21 amps when running off 120VAC.
scott
 
Its a Nema4 kbac vfd with a leeson 2hp motor wired for 110v. I remived the gfci on the opposite wall and replaced it with a normal heavy duty outlet and my grinder is running smooth! Time to jbweld my glass platen liner on and to it!
 
Things aren't adding up mathematically. Please take a picture of nameplate and post it or list motor specs off of nameplate. Also, is it on a 20 amp or 15 amp ciricuit?
 
Last edited:
Sorry forgot the title
Reading on my phone after thirteen hours work.
Saw 2hp and 110v - forgot this was a VFD thread. Your good.
 
That helps. If there is easy access to the panel (close to the work area) its always nice to have motor loads on dedicated circuits.
 
The panel is in the garage which is my "shop" but aside from putting pcs together and changing out a receptacle im not really sure what im doing when it comes to wiring. Only thing on the circuit that is running at the same time as the grinder is 1 or 2 work lights and my wifes little deel freezer.
 
I have also read that VFD's do not work well on a GFI protected outlet. If you can afford to have an electrician come out then ask for a 220 outlet and set up your vfd for 220. If you can't do that then turn off your breaker and remove the GFI and put in a standard outlet. I had this problem and cured it by removing the GFI but a year later I had 220 installed for 2 grinders with 2 hp motors anyway. No more problems since. Just my opinion. Larry
 
It does require a dedicated 20 amp circuit that freezer on the same line is not a good idea, if you were doing some hard grinding and the compressor on the freezer starts up it very well could overload it, we had a guy who was running a few shop lights and a window air conditioner on the same circuit and smoked his vfd we gave him a new one but learned a lesson about the fragility of vfds, you should check the wire gage the longer the wire run the larger it needs to be, and make sure its a true 20 amp outlet they have a horizontal blade slot, we also did some amp clamp testing and at startup they pull alot more amps than stated on the motor plate.
 
You must log in or register to reply here.
Back
Top