KBAC-27D VFD on GFCI (and other questions)?

PIndelicato

PIndelicato

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Sep 16, 2002
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I just received my new KMG with KBAC-27DVFD, and one of the first things I'm reading in the VFD manual (and it's mentioned numerous times) is that it's not recommended to be used on a GFCI circuit, and that 'special software is required.' Guess what kind of circuit is in my garage!?! I'm just wondering how big of an issue this may or may not be and/or what might happen using this as is?

Also, it recommends 'fusing each AC line conductor that is not at ground potential.' Will this requirement be satisfied by my main panel circuit breaker, or do I need actual fuses on the wires supplying incoming power from the wall outlet? As a follow up question, my garage breaker is 15 Amps, where in the KBAC manual a 25 Amp fuse or breaker is recommended for 110V usage. Will my 15 Amp breaker cause me problems being under the recommended limit for the VFD?

Lastly, while I'm on the subject, I purchased an Outdoor (orange) 12/3 extension cord which I had planned to cut off the female plug at the appropriate length and access the internal wires for connection to the VFD to supply incoming power from the wall. If anyone sees any issues with this approach, please let me know.

Thanks in advance for any help!
 
GFI's are very very sensitive . As far as electrical codes go , they are only needed in wet areas in case you decide to throw a radio or something in the bath tub . All wiring needs to be correct , no reverse polarity or any shared circuits not on the same main power run for them to function properly .
 
I think that these days GFI is required in new construction garages and shops to meet code.

You will likely need a larger circuit to handle the motor, you may draw more than the 15A at startup. Since your wiring won't be rated for more than 15A anyhow, you could run a new non-GFI circuit for your VFD. You could also run a 220V circuit, which I don't think requires GFI by code in a garage.
 
Hello Paul

VFD's can put all kinds of high frequency currents into the ground wire, causing the GFI to trip repeatedly. Many of the VFD manuals have a similar warning. You might get lucky and not have any such problems or your GFI might trip as soon as you VFD to "RUN".

What kind of fuse are they recommending? A fast-blow or a slow-blow? In industrial applications, it is common to use a fast-blow input fuse rated at just over 1.25 X the VFD's rated current. This is meant to save the VFD if something bad happens to the motor or inside the VFD. They are much faster than circuit breakers.

You are best to use 220V, if at all possible. You would then use two input fuses.

If you set the acceleration time to something like a few seconds, you should not have the current surge that AcridSaint is referring to.

Phil
 
Crap, crap, crap, this is not sounding good at all! I went with this 1.5 HP 115V setup because the estimate I got for running 220V to my garage was $500-750, which I can't afford to do on top of buying the grinder, and because Rob said this package would plug in to standard, run of the mill garage wall outlet supplies and that there weren't any special electrical requirements for it.

I'm not seeing in the manual what type of fuse is specified. It says that when configured for 115V, the Maximum Current is 22 Amps, and the recommended Fuse or Circuit Breaker is 25 Amps. Is this requirement a function of the motor or the VFD itself? The motor is a 208-230V, 3 Ph Leeson 1.5 HP 110444.00. Looking at the motor specs, it's not clear to me the current requirements for it.

Thanks for the help so far and anything additional you guys can offer. I guess I need to call Rob and ask him about it too.
 
The max reccomended draw for a breaker is 80%
I have a fixed speed 3400 RPm 1 HP motor at 110 V as the max I can connect to a standard 15 amp outlet (drawing 12 amps) ( no VFD)


The manual is likely quite a reliable source of info.
If they reccomend a 25 amp breaker at 110, you cannot almost double the connected load on the existing 15 amp breakers wire and outlets.

Using that 1.5 HP motor, with either 110, or 220; you will still need to install
New breakers
new wire
New outlets & plugs (specific plugs and outlets depending on voltage and load)

220v will be cheaper than 110 v since it allows you to use smaller diameter wire.
wire diameter depends upon connected load AND length

Your options:
1. smaller motor
2. pay the electrician (and have him do the entire installation.)
 
a 1.5hp motor will run fine on a standard 20 amp circuit, older wiring, and some stuff when people are cutting corners/ costs are 15 amp circuits, which can still run a 1.5hp motor, but will risk tripping your breaker frequently. Motors are something that you can get away with running on a smaller than recommended circuit, if you don't really /lean into/ and bog down the motor. They draw the most current when they're under heavy load, and when they first start up (aka like the lights dimming in the kitchen when the fridge starts)

the GFI outlet could be a problem with the VFD causing it to trip, but really... it's cheap to go to the hardware store and buy a new outlet and swap out the GFI outlet. A GFI outlet trips when it finds an unequal load between the hot and neutral, which is assumed to mean that power is flowing somewhere it's not supposed to (aka a short to ground elsewhere) Some GFI outlets are better than others and may not pose any problems at all. That said ONLY do your own electrical work if you know EXACTLY what you're doing, how to make a circuit safe to work on, etc. Household AC power is plenty sufficient to kill someone or seriously injure them.
 
I run my disc grinder and horizontal grinder vfd on a gfi circuit so far no issues but the motor is just 1 hp.
 
This is officially starting to suck now!

Unfortunately I did not have the opportunity to call Rob today to discuss with him as it was a little hectic around here, but from the rest of the input above it seems things are not looking good at all. I specifically went with this particular setup because I wanted the most powerful variable speed setup possible without having to modify the electrical in my garage. Had I known modifications would have been required in this case, I would have either gone with a smaller motor and/or step pulleys or a larger, more powerful motor (if I was going to upgrade to 220V.) Now it appears I have a setup that is not as powerful as it could be on 220V and more powerful than it should be for my current wiring. Highly frustrating to say the least...

Also, I assume the GFCI is in place because it is local code, and I certainly wouldn't want to give my insurance company any reason to deny any claim that could arise in the future (also why I would never attempt doing this work myself.)

Thanks again to everyone who provided their opinions and expertise.
 
Hello Paul

Where is your nearest 220V outlet, relative to your garage? It will be either the stove in your kitchen or the clothes dryer. If you don't want to modify the electrical system in your house, you can run a long 220V power cord from where your stove or dryer plugs in to your grinder. It should not cost anywhere near the cost of an electrician to make such a power cord. It is not a lot more difficult than connecting the 110V extension cord that you had already purchased. You should be able to purchase the required plug and cable from the big box home improvement stores in your area. You should then have ample current capacity to run a 1.5hp motor.

If you must run from 110V, you will have to find the documentation showing how to rewire your motor for 110V and follow those instructions. You will also have to read the VFD manual to make sure it allows operation at 110V. Many will trip on undervoltage. Your typical 15A 110V circuit has just about enough capacity to allow a 1.5hp motor to run. Unfortunately, induction motors have starting surges that are typically 6 to 8 times the running current. This starting surge will likely cause your breaker to trip. You can use the VFD to ramp the motor speed up from zero to 100% over several seconds to eliminate this starting surge. Eliminating the starting surge is one of the main reasons industrial users buy VFD's. Again, you will have to read the VFD manual to find out how to set the acceleration time. I believe that Rob's website has a page titled "Suggested set up notes" with relevant information.

Regards,

Phil So
 
Phil,

Thanks for your additional input and suggestions. This VFD can operate on either 110 or 220 via a jumper change, and I'm told that it will output and drive a 220 motor with either input voltage...hence the 208-230 motor (this one can't operate on 110). I was previously under the impression that a VFD could not convert voltage (only phase) but according to Rob that is what this device will do (ie, drive a 220 motor from a 110 input.)

My dryer outlet would not be ideal but at this point it may be worth considering. It would require about a 30 ft. +/- extension cord, which my impression is that that's not a good idea but I'm obviously not an expert in things electrical. Also, I just checked the dryer breaker, and it's 30 amps...the KBAC recommends a max of 20 amps when set for 220V operation, so that seems to be yet another problem with that scenario.

I'm trying to stay calm and not get too frustrated or upset until I can talk to Rob about all of this next week, but it's getting hard at this point. I'm really anxious to get this thing hooked up and running (Phoenix summer is approaching fast!) and I spent a lot of money and (I thought) did my due diligence and asked the right questions before buying in an effort to avoid running into these sorts of issues that now appear to be in my way of moving forward.

Thanks again for everyone's input!
 
Hi Paul, No need to worry yet.

This VFD is a heavy and rugged piece of industrial equipment. Hence the hi current rating. It is rated for 22A max....this doesn't mean that you have to run it on a 25A circuit. Most of us run it on your regular ol 15A residential outlets. That's what I use here in the shop on a daily basis (not GFI). Your breaker is smaller than the rating on the drive...and thats not a bad thing. Your breaker is designed to protect the electrical system from overloads...and if you should overload it...it will trip. With this in mind, your breaker will trip at 15A...which gives you a large safety margin from damaging your 22A VFD.

There are many, many success stories of the same system running in a 110V 15A shop. So, if I may suggest....give it a try before making any drastic changes. Go ahead and set it up to run on 110V...then plug it into your GFI outlet and flip the switch.

My first thought is that when you do this, you'll be a happy grinding mad man :D

...but if you have troubles...then let's address them.

The extension cord is a good choice. Once again, on the down stream side of the electrical breaker, you want the components rated equal to, or greater than the breaker rating...and NEVER less. This way, by design, the breaker is the weak link in the electrical chain....and will trip should there be an overload.

On the other hand.....if this machinery proves to be the wrong choice for you....or if you have any regrets...just let me know and we'll take it all back for full refund.

Hang in there and let me know if I can help.

Sincerely,
Rob
 
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rfrink said:
Hi Phil, No need to worry yet.

This VFD is a heavy and rugged piece of industrial equipment. Hence the hi current rating. It is rated for 22A max....this doesn't mean that you have to run it on a 25A circuit. Most of us run it on your regular ol 15A residential outlets. That's what I use here in the shop on a daily basis (not GFI). Your breaker is smaller than the rating on the drive...and thats not a bad thing. Your breaker is designed to protect the electrical system from overloads...and if you should overload it...it will trip. With this in mind, your breaker will trip at 15A...which gives you a large safety margin from damaging your 22A VFD.

There are many, many success stories of the same system running in a 110V 15A shop. So, if I may suggest....give it a try before making any drastic changes. Go ahead and set it up to run on 110V...then plug it into your GFI outlet and flip the switch.

My first thought is that when you do this, you'll be a happy grinding mad man :D

...but if you have troubles...then let's address them.

The extension cord is a good choice. Once again, on the down stream side of the electrical breaker, you want the components rated equal to, or greater than the breaker rating...and NEVER less. This way, by design, the breaker is the weak link in the electrical chain....and will trip should there be an overload.

On the other hand.....if this machinery proves to be the wrong choice for you....or if you have any regrets...just let me know and we'll take it all back for full refund.

Hang in there and let me know if I can help.

Sincerely,
Rob
Click to expand...

Rob,

Thank you so much for taking the time to weigh in here (on the weekend no less!) and for easing my mind about the concerns over the GFCI and the breaker rating in my garage. It seemed like the GFCI warning was about the third sentence into the manual, and was repeated multiple times throughout so it seemed like something to take seriously. I had not wanted to move forward with anything before I had the chance to speak with you in case things needed to be returned or exchanged, but it sounds like I can go ahead and give it a try before taking that step based upon your reports of success with others with similar household circuits.

I had meant to call you yesterday afternoon, but I ran out of time with the 3 hour time difference. At about 1:00 PM I was inhaling lunch with my wife on the patio before calling when she exclaimed that one of my dogs had hold some kind of 'critter'. To make a long story short, somehow a clutch of ~6 quail chicks had made it into our yard and the dogs were going berserk over them. By the time we had wrangled the dogs and located, captured, and released 2 chicks (sadly, there were 4 casualties) to safety, it was past 5:00 PM in Ohio.

Anyway, thanks again for taking the time to address my concerns on the weekend and for giving me the reassurance to proceed with getting things setup. I'll give you a call on Monday if any questions or issues come up.
 
rfrink said:
On the other hand.....if this machinery proves to be the wrong choice for you....or if you have any regrets...just let me know and we'll take it all back for full refund.

Hang in there and let me know if I can help.

Sincerely,
Rob
Click to expand...

Damn Rob , you are a man of integrity . A wonderful thing , of course we all knew this already but it cannot hurt to say it again .
 
Paul

You should be OK as Rob states. If you are tripping with the 15A breaker, after increasing the acceleration time, you can look in the VFD manual and turn down the current limit. You should not have to reduce it by much. This will limit the maximum power that you can get out of your set up but you will be able to work without interruption.

I you are using the long power cord to the 220V plug, make sure the cable is rated for at least 30A. This means that you should use 10AWG, 3 conductor cable. The length will be more of an inconvenience to you than an electrical issue. You will get about a volt or two of voltage drop in the cable, at maximum load. If an electrician ran a new 220V circuit to your garage, there would likely be a similar length of 10AWG cable installed to get the 220V to your garage. There is also likely to be something in the order of hundreds of feet of cable between the electrical panel in your house and your distribution transformer.

Take care.

Phil
 
ONeill said:
Damn Rob , you are a man of integrity . A wonderful thing , of course we all knew this already but it cannot hurt to say it again .
Click to expand...

Thanks Jack! The KMG was designed with the idea of limitless versatility...not only is how you use it...but also how you set it up. Understandably, this can be somewhat intimidating...or just downright confusing and frustrating. After all, we just want to grind...not fiddle with a machine all day.

But most importantly...I think it's very important to have a great feeling about your tools and machinery.

For me, I do my best work with the tools and machines that I love to use.

If there are regrets and ill memories associated, they will crop up everytime to use it...and perhaps your best work may be squelch.

Love your tools, love your shop...love your work!!
 
Well, I hemmed and hawed for a while over the weekend about whether or not to paint the grinder before I set it up...finally I decided I had better set it up and test everything BEFORE painting in case anything had to be exchanged or sent back, so I got everything set up, motor wired, VFD settings made, etc. This morning I need to connect the motor to the VFD, wire the main power cord, and turn it on and see what happens. Aside from my apprehension about the GFCI issue, I love this machine already just handling it and working with it to set it up, and can't wait to start using it. It makes my Craftsman look absurd by comparison.

Hopefully I can report back in a few hours with grand success. Thanks again to all who contributed with their suggestions and expertise!
 
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