Oh my goodness here we go again discussing how to put a plug on a ham
amplifier.
After having worked in the past as a professional electrician not a ham
wiring his own rig I have found:
240V circuits don't have neutrals... They have each side of the line plus a
safety ground. A pair of blacks, a red and a black, or a pair of reds. The
safety ground is either bare or it is GREEN.
A 240/120 circuit to power SOME ranges, maybe dryers, ovens whatever have
both 240V components and 120V components..... Something like a 120V outlet
on the backsplash on a 240V appliance. This is a 4 wire installation. A
pair of lines, a white neutral (with a neutral buss) and a green safety
ground.
At no point in the existence of the world is NEUTRAL = GROUND. However the
two are connected together at your main service entrance panel... PERIOD.
They are not connect together at any subfeed panels.
The two are connected together BECAUSE... Your power company provides two
lines and a neutral to power your house. YOU provide the ground. This is
done at the panel with the two tied together.
NOW, if you want to build a ham rig with 240/120 power, go right ahead. If
you WANT TO DO IT TO CODE, you better hang a 4 wire cord on the damn thing
and a 4 conductor plug. You better not GROUND that neutral putting the 120V
return currents on the chassis. It requires an additional NEUTRAL BUSS...
Do it!
There isn't a ham rig in the world that to code runs 240/120 circuits.
HOWEVER... The Alpha 77DX/SX illegally ran a two wire cord plus ground and
utilized the chassis as a neutral. This rig should have been a 240/120
system. I'm surprised it went to production. It obviously wasn't UL
approved. Or somebody wasn't looking close if it was.
Just because you can do it doesn't make it right.
TOM, does know what he is talking about.
While I don't bow to him in the east every morning, I haven't found him to
be wrong on many occasions.
If I do I will make sure I let him know and I'm sure he would expect me to
do so.
BOB DD
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of jeremy-ca
Sent: Sunday, July 08, 2007 6:51 PM
To: Tom W8JI; Amps Amps
Subject: Re: [Amps] Transformer question
So then you are trying to convince us that anyone who has a 240V dryer,
range, AC, Air Compressor or similar device with the neutral tied to the
ground at the wall outlet and at the device has a safety issue.
Sorry Tom, but the NEC manual disagrees with you and Id much rather follow
what the experts say.
And I have yet to see any 240V single phase ham amplifier manufacturer
provide a 4 wire cable.
In looking thru my amp manuals going back 40+ years I see that all 240V
configurations show the neutral connected to chassis ground. This, strangely
enough, includes Ameritron and verified with the AL-1200 on the bench for
repairs.
As you state Tom, this really isn't complicated.
Carl
KM1H
----- Original Message -----
From: "Tom W8JI" <w8ji@w8ji.com>
To: "Amps Amps" <amps@contesting.com>
Sent: Sunday, July 08, 2007 3:36 PM
Subject: Re: [Amps] Transformer question
> >
>> When I completely wired my current home I followed the NEC
>> code and had no problem with any level of inspection
>> including many 240V outlets in the shop, shack, and
>> garage.
>
> This really isn't complicated.
>
> If you have the neutral connected to the safety ground or to
> the chassis of any device at any point other than the main
> panel, you have faulty wiring.
>
> If there is any connection from the chassis or other exposed
> conductive parts to the power line neutral, you have faulty
> wiring.
>
> Any return currents for 120 have to be through the neutral,
> and the ONLY point the neutral can be connected to the
> safety ground is at the main breaker box.
>
> So if we build an amplifier and tie one end of a 120V
> transformer to the chassis, it is a safety issue. It doesn't
> pass code and also presents a hazard to the user.
>
> This means if you have a PA that uses a neutral return to
> obtain 120V it has to use a four wire outlet. You just
> shouldn't wire it to a three wire plug. We should never
> ground one primary end of a blower or filament transformer
> to the chassis. The reason being if the neutral opens the
> cabinet would have 120V on it.
>
> It has been this way by regulation at least 30 years now,
> and it was good common sense long before then. So unless he
> has a double insulated cabinet or a four wire outlet, he
> cannot simply ground the filament or control primary to the
> chassis or the safety ground of the power system.
>
> 73 Tom
>
>
>
>
>
>
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