This is easy to check. With the UPS off and nothing connected to the input
or the output, measure the resistance from the neutral terminal on the
duplex output to the ground terminal on the duplex output. If it shows
basically zero ohms then one can presume the neutral is connected to the
ground on the output. Then measure from neutral on the output to the
neutral on the input and again neutral on the output to the ground on the
input. If indeed neutral on the output is isolated then there should be no
connectivity to the input. Only the ground on the output to the ground on
the input should / must show connectivity.
73
Bob,. K4TAX
----- Original Message -----
From: "denton sprague" <denton@oregontrail.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Tuesday, September 02, 2014 8:06 PM
Subject: Re: [TenTec] TT 940 Power Supply
My big Cyberpower is still under warranty…they don't even want you running
an extension cord out of the socket!
When I was testing it, I noticed rf hash in spots throughout 80 and 40
meters….and I ordered it new specifying for telecommunications use!
Will keep in mind what you typed below when I pull the case apart for twice
annual dust bunny removal next winter.
On Sep 2, 2014, at 12:31 PM, "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
wrote:
You raise a point regarding "industrial grade sine wave ups". I have one
of those and in my chasing a noise issue, I opened the case to find the
output receptacles each have the neutral terminal {white wire} and the 3rd
pin ground terminal {green wire}connected by a solid strap. This then
says the neutral is connected to 3rd pin ground at several points, both on
the input and output. I seem to recall this is not correct according to
NEC.
Anyway, I removed the straps and my noise went away. Now, this does leave
the 3rd pin AC ground terminal on the LOAD side of the UPS connected to
the 3rd pin ground on the INPUT side of the UPS. The neutral however is
not connected from the LOAD side to the INPUT side, thus there is
significant isolation between input and output of the UPS. As it should
be in my thinking.
Is there some UL requirement, say UL1499, or other international standard
that I'm not aware that mandates the load neutral and 3rd pin AC must be
bonded? It has been too many years since I worked in this part of the
safety discipline.
Comments anyone?
73
Bob, K4TAX
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