VFD and GFCI

[ptonsparky]

Background:
Farmer customer called and wants a 120v recept installed at Pivot to power new equipment for chemical application at variable rates. Different portions of the field may need less product so the rate could be adjusted accordingly. Technology is now available to do this. Early stages yet and retrofitting older pivots won’t be as exact as new. Pivots are 480v

Of course my problem is how much power. Turns out 16.6 amps at 120v. The specific motor they want to use is 230 volt 3Ph only. I’ve seen a photo of the nameplate. They will be using a VFD that steps the 120v up to 230 then to the VFD that gives them the 3Ph.

My receptacle will need to be GFCId, even if we supply them with 230.
What are the chances that GFCI will hold? 0?

 

[Ingenieur]

why wouldn't it?
do you think harmonic distortion on the line side will trip it?

 

[ptonsparky]

why wouldn't it?
do you think harmonic distortion on the line side will trip it?

That and Leakage current.

 

[ptonsparky]

Two of the three VFDs I have literature for indicate >3.5 ma possible.

 

[Ingenieur]

why do you need that low of protection?
why not hardwire to an equip level gf cb ~30 mA
is there a code the requires gfci?

we use 3500 hp 4160 vfd's and 100 mA gf relays
we operate at 10-15 mA

do you links to the drives?

3.5 mA at 120 ~ <35 kOhm, seems really low

 

[ptonsparky]

why do you need that low of protection?
why not hardwire to an equip level gf cb ~30 mA
is there a code the requires gfci?

we use 3500 hp 4160 vfd's and 100 mA gf relays
we operate at 10-15 mA

do you links to the drives?

3.5 mA at 120 ~ <35 kOhm, seems really low

They want a receptacle.
NEC 210.8 (B) requires GFCI protection for personnel.

 

[kwired]

why do you need that low of protection?
why not hardwire to an equip level gf cb ~30 mA
is there a code the requires gfci?

we use 3500 hp 4160 vfd's and 100 mA gf relays
we operate at 10-15 mA

do you links to the drives?

3.5 mA at 120 ~ <35 kOhm, seems really low

Not having any familiarity with the application leaves you standing in a dark room.

I have farmers that have dozens of these units (though they are all 480 volt three phase units) that they remove when not in use, and have different sizes and types even depending on what product they are injecting into the system. So one receptacle many possible machines that could get plugged into it.

Now make that receptacle 15 or 20 amp 120 volts and since it is already outdoors - GFCI protection would be required.

As far as OP's VFD driven machine - don't know why it couldn't be made with a 480 volt input drive, and maybe they do have them but the owner thought the 120 volt sounded like the way to go for some reason - even though they probably already had 480 volt receptacles at the irrigation sites. 120 volt may have had a lower price tag, but they never consulted their electrician on what it would take to connect it. Adding transformer, and other accessories very well cost more then just going with the 480 volt drive.

 

[Ingenieur]

They want a receptacle.
NEC 210.8 (B) requires GFCI protection for personnel.

exception 2

or live with nuisance tripping

 

[ptonsparky]

exception 2

or live with nuisance tripping

:rotflmao:
I know you have seen farms, how does 2 even come close in the wildest stretch of the imagination?

 

[ptonsparky]

Not having any familiarity with the application leaves you standing in a dark room.

I have farmers that have dozens of these units (though they are all 480 volt three phase units) that they remove when not in use, and have different sizes and types even depending on what product they are injecting into the system. So one receptacle many possible machines that could get plugged into it.

Now make that receptacle 15 or 20 amp 120 volts and since it is already outdoors - GFCI protection would be required.

As far as OP's VFD driven machine - don't know why it couldn't be made with a 480 volt input drive, and maybe they do have them but the owner thought the 120 volt sounded like the way to go for some reason - even though they probably already had 480 volt receptacles at the irrigation sites. 120 volt may have had a lower price tag, but they never consulted their electrician on what it would take to connect it. Adding transformer, and other accessories very well cost more then just going with the 480 volt drive.

It is the developer wanting a simple plug and go. I’ve already suggested the 480 but they have a specific 230v motor in mind. I’ll meet with the local branch next week.

 

[kwired]

exception 2

or live with nuisance tripping

exception 2 is for electric snow-melting, deicing, or pipeline and vessel heating equipment. "Chemigation" equipment is far from any of those.

No farmer I work for is going to find a tripped GFCI acceptable reason for stopping the pesticide pump, fertilizer pump, or whatever they are applying. Not the way an electrician should approach it but is how you come to understand how they will approach it. When they come out to check things and find the injection pump stopped but the pivot has made a half circle since they last checked they don't know where the pivot was when the injection pump stopped.

Most of them currently use 1/2-3/4 HP 480 volt pump motors. You can set them up with a 1 or 2 amp fuse to (somewhat) properly provide overload protection, but is almost guaranteed they will replace them with at least 6 amp fuses the first time they blow any fuses. 6 amp typically will allow that pump to run at locked rotor current until the motor fails.

I've tried to put in manual motor overloads before that will stop the pivot and well if it trips - only to get complaints on how it shut everything down. Had one that wasn't even the owner, just the guy renting the field for that season that got pretty upset with me that my motor overload device shut down his entire system (I changed some things earlier that year when owner converted from a diesel power unit to an electric well). I came right out to see what was going on, told him his injection pump was drawing too much, but he didn't want to hear it and wanted me to put back the simple three fuses he was accustomed to - they never give any trouble unless motor is toast. So I put the fuse holder in - and it blew fuses within minutes. I had this "I told you so" feeling but couldn't say it. He finally figured out he had the wrong injector nozzle installed and it was the reason for the high loading:slaphead:

People that work in and even manage industrial plants learn to live with these inconveniences as they are constantly reminded that OSHA can come in and produce large fines for seemingly little things. These farmers aren't so used to that.

Not trying to create excuses, just trying to paint a real picture.

Back to OP - The VFD itself is possibly going to be an issue for many farmers, adding a not so needed GFCI because someone decided 120 volt supply was a great idea (not) just makes things worse. And we never experience any lightning damages at irrigation equipment that has the highest elevation and is also a conductive object on a 160 acre parcel of land either:happyno:

 

[Ingenieur]

:rotflmao:
I know you have seen farms, how does 2 even come close in the wildest stretch of the imagination?

a commercial farm set up for production, ie, industrial establishment
limited access
trained personnel
design not compatiible gfci


MUST be recept
MUST be gfci
vfd gnd i > trip point

there is no solution
must live with nuisance tripping

must have gfci:
bathrooms
kitchens
rooftops
outdoors
sinks
indoor wet locations, washdown, etc
locker rooms
garages for handheld portable tools, etc
none apply in your case

sounds live you've contrived an 'issue' and set false arbitrary conditions as to make it unsolvable

:ashamed:

 

[Ingenieur]

exception 2 is for electric snow-melting, deicing, or pipeline and vessel heating equipment. "Chemigation" equipment is far from any of those.

No farmer I work for is going to find a tripped GFCI acceptable reason for stopping the pesticide pump, fertilizer pump, or whatever they are applying. Not the way an electrician should approach it but is how you come to understand how they will approach it. When they come out to check things and find the injection pump stopped but the pivot has made a half circle since they last checked they don't know where the pivot was when the injection pump stopped.

Most of them currently use 1/2-3/4 HP 480 volt pump motors. You can set them up with a 1 or 2 amp fuse to (somewhat) properly provide overload protection, but is almost guaranteed they will replace them with at least 6 amp fuses the first time they blow any fuses. 6 amp typically will allow that pump to run at locked rotor current until the motor fails.

I've tried to put in manual motor overloads before that will stop the pivot and well if it trips - only to get complaints on how it shut everything down. Had one that wasn't even the owner, just the guy renting the field for that season that got pretty upset with me that my motor overload device shut down his entire system (I changed some things earlier that year when owner converted from a diesel power unit to an electric well). I came right out to see what was going on, told him his injection pump was drawing too much, but he didn't want to hear it and wanted me to put back the simple three fuses he was accustomed to - they never give any trouble unless motor is toast. So I put the fuse holder in - and it blew fuses within minutes. I had this "I told you so" feeling but couldn't say it. He finally figured out he had the wrong injector nozzle installed and it was the reason for the high loading:slaphead:

People that work in and even manage industrial plants learn to live with these inconveniences as they are constantly reminded that OSHA can come in and produce large fines for seemingly little things. These farmers aren't so used to that.

Not trying to create excuses, just trying to paint a real picture.

Back to OP - The VFD itself is possibly going to be an issue for many farmers, adding a not so needed GFCI because someone decided 120 volt supply was a great idea (not) just makes things worse. And we never experience any lightning damages at irrigation equipment that has the highest elevation and is also a conductive object on a 160 acre parcel of land either:happyno:

did not say it was one of those devices
a device incompatible with a gfci, most mfgs recommend 30 or 300 mA cb's

 

[kwired]

a commercial farm set up for production, ie, industrial establishment
limited access
trainrd personell
design not compatiible

I maybe had more rant on other things in my last post, but the first part was

"exception 2 is for electric snow-melting, deicing, or pipeline and vessel heating equipment. "Chemigation" equipment is far from any of those."

 

[Ingenieur]

most people that understand process control use adjustable rate feed pumps
not vfd's

http://www.vaawwa.org/file/Committe... Ops Chemical Pump Types and Applications.pdf

I have worked in water/wastewater, pharma, process water treatment
can't seeing a vfd
if a larger pump is required it pumps into bypass metering or a rate control valve

a vfd will vary flow
as feed tank level drops so will suction head (overall head increases) as does flow rate

 

[Ingenieur]

I maybe had more rant on other things in my last post, but the first part was

"exception 2 is for electric snow-melting, deicing, or pipeline and vessel heating equipment. "Chemigation" equipment is far from any of those."

it also states other equip that the design is NOT COMPATIBLE with gfci's, such as a vfd

 

[Ingenieur]

here's the 'other than dwelling' locations that must have gfci
at least per the code I have on hand 2011
which requires it on a vfd in an commercial farm?

bathrooms
kitchens
rooftops
outdoors
sinks
indoor wet locations, washdown, etc
locker rooms
garages for handheld portable tools, etc

 

[MyCleveland]

here's the 'other than dwelling' locations that must have gfci
at least per the code I have on hand 2011
which requires it on a vfd in an commercial farm?

bathrooms
kitchens
rooftops
outdoors
sinks
indoor wet locations, washdown, etc
locker rooms
garages for handheld portable tools, etc

210.8.....is all about RECEPTACLES.
Remove the receptacle and install disc/OCPD in place of the receptacle. NO gfci needed.

 

[Ingenieur]

210.8.....is all about RECEPTACLES.
Remove the receptacle and install disc/OCPD in place of the receptacle. NO gfci needed.

not an option

MUST be recept
MUST be gfci
0% chance of it not tripping (100% that it will) per op
can't change wiring
can't change metering method, must be vfd

even though code does not required for this application

 

[kwired]

it also states other equip that the design is NOT COMPATIBLE with gfci's, such as a vfd

Which NEC are you reading, that is not in 2014, and in 2017 exception 2 is now exception 1, but is otherwise unchanged.

Another condition if it did apply is the receptacle not be readily accessible. How does one do that at the typical center pivot irrigation site? The cord ultimately ends up at equipment that sits right on the ground regardless of where you put the receptacle.