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Rotary phase converter: local ground or all the way to the panel?

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Rotary phase converter: local ground or all the way to the panel? rpseguin 02-27-2008
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Posted by on February 27, 2008, 4:10 pm
Folks:

I gotta say, when you start tossing 20HP rotary convertors and 10 hp
motors
into the pot, economy starts to shed its meaning. Best to do the job
right.
If a 10 hp motor can't pay for its own infrastructure it might as well
go to
pasture. I'd say this even goes if the motor is for recreational use
-- fun
does have value, but fun can turn bad if you cut corners. Don't skimp
on
your hot sticks when turning on your Tesla coil.

But, man, ten horses...some people have big fun, I guess.

A P



PexSupply Save 50 468x60
Posted by Ken Sterling on February 27, 2008, 9:23 pm
>Ok.
>Thanks for everybody's help in the earlier thread.
>The 20HP rotary phase converter is working, but I now need to place it
>in the garage, about 70+ feet wiring run distance from the main
>breaker panel.
>
>Given the cost of copper wire these days, my inclination is to run
>just the two hots to the panel and to put a grounding rod close up to
>the garage and run a local ground to it.
>I see no reason to run a neutral line from the panel (the machines are
>all 3 phase).
>
>I know that I could run a ground line to the panel AND run a local
>grounding rod, but is it a bad idea to just do a local ground?
>
>What gage wire for a 20HP RPC, but the main/biggest load/machine will
>be a 10HP spindle and a couple of 2HP machines, never all at the same
>time? ($ signs get much bigger with the wire gage/diameter :-)
>
>Anybody near San Jose, CA have a spool of #4 or larger gage for
>cheap? :-)
>
>Thanks in advance!
Don't know your actual installation plan, but you may be able to pick
up a coil of #4 AL triplex from the local power company - some of it
gets scrapped, either from teardown, or a leftover chunk off of a
reel.
Ken.


Posted by Jeffrey Lebowski on February 27, 2008, 9:31 pm

<Ken Sterling (Ken Sterling)> wrote in message
> >Ok.
> >Thanks for everybody's help in the earlier thread.
> >The 20HP rotary phase converter is working, but I now need to place it
> >in the garage, about 70+ feet wiring run distance from the main
> >breaker panel.
> >
> >Given the cost of copper wire these days, my inclination is to run
> >just the two hots to the panel and to put a grounding rod close up to
> >the garage and run a local ground to it.
> >I see no reason to run a neutral line from the panel (the machines are
> >all 3 phase).
> >
> >I know that I could run a ground line to the panel AND run a local
> >grounding rod, but is it a bad idea to just do a local ground?
> >
> >What gage wire for a 20HP RPC, but the main/biggest load/machine will
> >be a 10HP spindle and a couple of 2HP machines, never all at the same
> >time? ($ signs get much bigger with the wire gage/diameter :-)
> >
> >Anybody near San Jose, CA have a spool of #4 or larger gage for
> >cheap? :-)
> >
> >Thanks in advance!
> Don't know your actual installation plan, but you may be able to pick
> up a coil of #4 AL triplex from the local power company - some of it
> gets scrapped, either from teardown, or a leftover chunk off of a
> reel.
> Ken.
>

Shhh but in a pinch I've used a "strand"--twisted together from 3 individual
pieces of #12 or 14 copper.

--



Posted by rpseguin on February 28, 2008, 3:59 am
> Shhh but in a pinch I've used a "strand"--twisted together from 3 individual
> pieces of #12 or 14 copper.


:-)
I get the message. I won't cheap out. My credit card is feeling the
strain though.

Still looking around for some #2 or bigger. I've got a lead on some
#4 wire.

My plan, after all the advice is to put a single phase 100A subpanel
in the garage.
That subpanel will have a breaker for the RPC.


Main
Panel
|
| #2 wire, 70+ feet run
|
1ph
Sub-panel
|
| 60A 2 pole breaker, #2 wire, 10 foot max run
|
RPC
|
| #2 wire, 10 foot max run
|
3ph
Panel
(3ph/pole breakers for machines)


Posted by Ned Simmons on February 28, 2008, 8:56 am
On Thu, 28 Feb 2008 00:59:59 -0800 (PST), rpseguin

>> Shhh but in a pinch I've used a "strand"--twisted together from 3 individual
>> pieces of #12 or 14 copper.
>
>
>:-)
>I get the message. I won't cheap out. My credit card is feeling the
>strain though.
>
>Still looking around for some #2 or bigger. I've got a lead on some
>#4 wire.
>

As has been mentioned, you don't need a full size ground. You should
check the code, but my recollection is that a #10 is a suitable
grounding conductor for a 60A circuit.

--
Ned Simmons

Page 4 of 5       < 1 2 3 > last >>
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