VAX 780 on eBay

Grant Taylor cctalk at
Sun Jan 2 00:20:23 CST 2022

On 1/1/22 2:00 PM, Chris Zach via cctalk wrote:
> This is wise, but 240v is quite nice for computer equipment. I had an 
> electrician run a 240v 30a (10g wire) circuit out to my work shed, where 
> a subpanel is installed with 120v 15a and 240v 15a circuits for the 
> equipment.

I had two 120v 20A circuits, one on each leg of the 120v/240v 
residential feed, run to my computer equipment in the house I sold a few 
years ago.  I'd like to have the same again once I finally set things up 
the way that I want to.

I'd really like 3ɸ at home for a number of different things.  That would 
allow me to run computer equipment at 208v which, as I understand it, is 
more efficient than 120v.  I don't think anything I do would actually 
/need/ 240v.  I'd also like 3ɸ for other things in the house, namely 
wood working tools.

> 240 just allows you to get twice the power to the device using the same 
> size wire (14g for 15a for example).

Ya.  One might wonder why higher voltage means that you can get twice 
the power (wattage) to something.  But that's where the fact that most 
wire used for 120v circuits is rated for up to 250v which means that the 
same wire can safely carry 240v.  Hence how you can get twice the power 
by doubling the voltage.

> But modern switching computer supplies are more efficient at 240v 
> than 120v so you waste less power.
Do you have something that you can point to as reference?

Where does 208v compare to 240v / 120v?

> 120 is good for like light bulbs and stuff. Drawing over say 10a 
> continuous at 120 will pretty much burn up sockets and such in short order.

It depends on the quality of the socket.  My understanding is that a 
NEMA 5-15 is rated to sustain 15A at 120V indefinitely.  Then there are 
NEMA 5-20s which are rated for 20A.  So ... over 10A continuous seems 
quite possible if not expected with some installations.

Grant. . . .
unix || die

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