Wiring power to VFD

J

Jason Fry

Joined
Jun 5, 2008
Messages
3,231
About the time my KBAC 27 died, I also moved shops. I've got an opportunity therefore to relatively start over with my power configuration.

I had a plug to the wall, a switch in the power line, and the on/off switch on the VFD.

Would it be OK to hard wire the power from the wall, keeping the inline switch plus the VFD switch?

FWIW, I'm not sure what killed the VFD after four years, but the repair tech says the board has gone bad. I lived rural, and we had power outages nearly once a month. New place is in town, should be more power stability.
 
I make it a habit to make sure VFD is off when done for the day. prevents damage if power goes f*bar during the nite
 
You can hardwire the VFD if you have a dedicated junction box for it, proper end clamps/fittings, and a double pole power switch in the line. In the long run, a plug and socket is simpler and allows other tools to be plugged in to use the socket. It also allows a complete disconnect if there is a concern, like a big lightning storm.

I would suggest you run a 25 amp 220V line ( 10/3 with ground) to the bench from the breaker box ( 25 amp dual breaker), and put a duplex box there. That will allow two 220V tools to be plugged in at the same time.

3Ph motors are often cheap. Some are free or available for the scrap price. 1/2HP and 3/4HP are great for low power tools ( drill press, bench tools). 1HP is good for many tools ( band saw larger quill drill press, milling machines). 2HP and 3HP are more than enough for any grinder.

Things to convert to 220VAC 3H motors with VFD:
Drill press
grinder
disc sander
band saw ( wood and metal saws)
6X36" or 6X48" belt sander ( great for cleaning up handle blocks and flattening scales)
Lathe ( wood and metal)
Large diameter grinding wheels
Shop ventilation fan
Shop press

Now, if someone is setting up a permanent shop, it is a real gain to install a 3PH converter and wire the shop for both single phase and three phase power. This allows you to use 3Ph in - 3Ph out VFDs. These are really low cost on the sales sites. The phase converters are not all that expensive, and can run lots of equipment at one time. This will allow you to buy surplus 3Ph things like heaters, welders, etc. These can be found for a fraction of the price of a single phase unit ... and usually have more power. They are also usually industrial grade and made like tanks.
 
This is only a 12x16 shop, in a house I don't intend to live in for more than a few years. I did run the 10/3 wire on a dedicated circuit, and also did the same for my welder plug. I have the double pole switch wired in on the machine already. I only went with the plug last time because I had the plug in the wall already. I think I'll hardwire this time.

FWIW, after nearly 10 years of knifemaking, and in keeping with the usual advice from this forum, in my 12x16 shop, I put two circuits of 220 (grinder, welder), and 9 regular outlets on five circuits. I ran a 50 amp service with #8 wire, and still have three slots left in the box. I still have to add more lighting, but so far, so good. Wish I had more space, but I'm going to make good use of what I have.
 
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