Remove VFD from compressor possible?

[davehall]

This might sound dumb, I'm old school. I have a 40hp air compressor that is set up with VFD controls. I've never been able to get it to work. I don't need or want the VFD. Can I make it work like a non-VFD compressor and if so, how? THanks

 

[davehall]

Some additional info: this is a brand new USAir compressor 40hp, 480v. connecting to a 100 amp disco.

A couple of compressed air techs I have talked to don't wan't to mess with it because they don't know the brand and want to sell me their own brand of compressor.

 

[zbang]

If nothing else-
Is it still under any warranty?
What does the manufacturer say?
"I can't get it to work" could mean a lot, -what- doesn't work?? Could be that the motor is faulty and removing the VFD won't help.
Find some better air techs.
Removing the VFD means fitting the correct motor starter and pressure switch. That might also void any UL/etc listing it has.

(Are you an electrician or motor tech?)

 

[ptonsparky]

Call in an electrician. Typically not the residential one down the street.
Who hooked it up in the first place?

 

[tortuga]

Some additional info: this is a brand new USAir compressor 40hp, 480v. connecting to a 100 amp disco.

A couple of compressed air techs I have talked to don't wan't to mess with it because they don't know the brand and want to sell me their own brand of compressor.

Thats pretty common with techs. I second the others call around and get a local sparky to give you a consultation on the VFD. Also if you post the link to the make / model of the unit on here you might get some help on here if its just a programing issue and not a DIY wiring issue.

 

[zbang]

I did a little research on USAir compressors. These are rotary screw compressors with a 10 year warranty and electronic controls (and even bluetooth monitoring and "call home" functions!). You do not want to be messing around with the insides unless you really know what's going on, especially if it's new!!! (And then say Bye-bye to the warranty and UL listing.)

Read the operations manual and then call the factory for technical support. If the incoming power is not correct, get an electrician to fix that.

 

[retirede]

The VFD is part of the capacity control system. Don’t remove it.

 

[Jraef]

Just from experience;

Unless the VFD is roughly 3x the size of the motor, it will not be able to start a compressor if the unload valve is not open to atmosphere. Even though it is new, there may be an issue with the unload solenoid that means it is not engaging. The same could be true of a mechanical unloader. If they don’t unload for startup, the VFD just goes into current limit to protect itself until it shuts down on stalled motor.

 

[retirede]

Just from experience;

Unless the VFD is roughly 3x the size of the motor, it will not be able to start a compressor if the unload valve is not open to atmosphere. Even though it is new, there may be an issue with the unload solenoid that means it is not engaging. The same could be true of a mechanical unloader. If they don’t unload for startup, the VFD just goes into current limit to protect itself until it shuts down on stalled motor.

If this is a brand new compressor, the initial start is always unloaded. No pressure in the internals = no load.

 

[hbiss]

Some additional info: this is a brand new USAir compressor 40hp, 480v. connecting to a 100 amp disco.

If it's brand new why are you here and not talking to the company you bought it from??

-Hal

 

[Besoeker3]

This might sound dumb, I'm old school. I have a 40hp air compressor that is set up with VFD controls. I've never been able to get it to work. I don't need or want the VFD. Can I make it work like a non-VFD compressor and if so, how? THanks

Are you possibly in the wrong forum? Most here have some experience of VFDs - they have been around for decades.

 

[hbiss]

... talking to the company you bought it from- to make it work.

You still haven't told us what the problem is.

-Hal

 

[tom baker]

Will the ac rep help with startup?

 

[davehall]

OK. I hear ya. I'm pretty sure he told me 1 yr warranty but I could be wrong. I tried to call cust service many times and never got through so then I had a couple of a/ c techs I know come over to look at it and they did not want anything to do with it.

I'm going to try again calling them. I thought I got screwed because it was about half price compared to Kaeser and others here locally.

Thanks much for your research and info.

... talking to the company you bought it from- to make it work.

You still haven't told us what the problem is.

-Hal

Sorry, still here. extremely busy. wearing a lot of hats right now.

Here is the story. I found this machine on Ebay. My 25 HP screw Kaeser unit was not keeping up so I had them quote me on a 40hp one. Way too high for me, so the one I found on Ebay seemed almost too good to be true. When I connected to power and tried to turn on just to check rotation, nothing happened. I assumed it was a setting on the VFD that was off so I tried to call them and could not get through.

I'm not an electrician but somewhat familiar with electrical code, can look up branch circuit size, wire size, etc. Built a couple of vacuum form machines with 3ph heat zones, PLC controllers etc. But I'm old school and don't know a damn thing about VFD.

Anyway, I disconnected the USAir unit and got a used Kaeser 50hp. I also need to replace all the air lines (3/4" pipe) and many other issues.

I am trying to get hold of USAir customer service now. Thanks to the responses I have received on this forum, I am not making any mods to this machine. I just wish there was an expert in my area that would come out and help me deal with this company.

Thanks to all who replied to me on here!

 

[tom baker]

You are most welcome.

 

[Jraef]

VFDs don't just "turn on" out of the box, they need programming and methods to tell them to turn on and off, what speed to run etc. etc. If you bought a cheap machine from FleaBay and it was not properly set up, the seller should be helping you. If you can't get that help, the lesson learned here might be "you get what you pay for"...

 

[retirede]

VFDs don't just "turn on" out of the box, they need programming and methods to tell them to turn on and off, what speed to run etc. etc. If you bought a cheap machine from FleaBay and it was not properly set up, the seller should be helping you. If you can't get that help, the lesson learned here might be "you get what you pay for"...

Yeah, the VFD would have been setup properly by the manufacturer, but there’s no telling what the reseller did to muck it up.

 

[Jraef]

Yeah, the VFD would have been setup properly by the manufacturer, …

One would hope….

My next door neighbor just bought a cheap little Chineseum mini wood lathe off of Fleabay, brand new. It has a VFD on it, but wouldn’t work. He asked me to look at it, it was at factory defaults so would only work from the keypad even though they had a control station on the front of the lathe wired to the VFD control terminals. Reading the manual was like trying to read something written by a first grader where every third word was misspelled and context meant nothing. He bought me a pizza and a beer, he still owes me…

 

[hbiss]

I found this machine on Ebay. My 25 HP screw Kaeser unit was not keeping up so I had them quote me on a 40hp one. Way too high for me, so the one I found on Ebay seemed almost too good to be true. When I connected to power and tried to turn on just to check rotation, nothing happened. I assumed it was a setting on the VFD that was off so I tried to call them and could not get through.

So, you need us to tell you what the problem is?
You bought it off Ebay.
No dealer is going to touch it even if it was brand new.
There is no warranty.
Moral of the story is "you get what you pay for".

-Hal

 

[ptonsparky]

'Almost too good to be true' usually is.