No manufacturer could ever sell something that ran load current on the
ground wire. They would create a massively unsafe condition, and in the
event that the worst happened, they would be sued out of existence. This is
aside from the fact that this has never been permitted by the electric
codes. That would be insane.
Some 240/220 volt (in fact most) have 3 wire cords indeed, but they do not
return load current on the ground wire, ever.
----- Original Message -----
From: "Ken Brown" <ken.d.brown@hawaiiantel.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, January 05, 2008 4:45 AM
Subject: Re: [TenTec] Centaur Power Cord
> Hi Chuck,
>
> > I have yet to see a commercially built 120/240 VAC Ham amplifier with a
step
> > down transformer to run the 120 VAC fan and probably the filament
> > transformer as well...
> >
> Most ham amplifiers have dual primaries on their single power
> transformer, which can be connected in series for 240 VAC operation, or
> in parallel for 120 VAC. Since they can be wired for either 240 VAC or
> 120 VAC, the fan must be able to run on 120 VAC. I would venture to
> guess that any amplifier which uses a separate filament transformer or a
> separate transformer for things other than the plate supply (not a lot
> of ham amplifiers do have separate transformers), and has dual primaries
> on the HV transformer, also has dual primaries on the other
> transformers. I suspect that some use the primaries in series (when set
> up for 240 V) as an autotransformer to power small 120 V loads.
>
> My Titan 425 uses a separate winding on the transformer to power the fan.
>
> The 9420 power supply for the Hercules II has five transformers, and
> they all have dual primaries. The Hercules II fan runs on 12 VDC, so
> there is nothing in that system that needs to run on 120 VAC when the
> 9420 is wired for 240 VAC.
>
> I challenge you to name a commercially built ham amplifier that uses a
> three wire power cord and connects any 120 VAC powered component between
> one of the hot leads and the ground lead. (other than RF bypass
> capacitors between the power leads and ground)
> > Some may exist, but I have yet to encounter one. Not to say that
wouldn't be
> > good engineering practice, but then there is the real world. I have seen
> > some commercial single phase Broadcast equipment where it wasn't done
> > either.
> Commercial broadcast transmitters are a good example of separate
> transformers used for just about every system in the transmitter.
> There are many commercial broadcast transmitters that run on single
> phase 240 VAC, probably very few that can run on 120 VAC. The ones that
> run on 240 VAC single phase likely use fans or blowers that run directly
> on 240 VAC. If it does not have to work on either 120 or 240 (like ham
> amplifiers) there is no reason to use a 120 VAC fan.
> > Looks like lots of manufactors have gone astray! You can pretty
> > much run down the list of the Ham Amp builders, and they are all
guilty!!!
> > Anyway I believe the rule is it is OK to Ground the Neutral, but NOT OK
to
> > tie the Neutral the Ground.
> You have lost me here. How can you ground the neutral, without tying the
> neutral to ground?
> > .Unless your are the Power Company, then guess
> > what they do to the Neutral at the entrance to your house and all along
the
> > system.
> They do that all along THEIR system. They do not do it all along the
> system in your house. Nor does an electrician. Only at one place.
> > ...According to the NEC code as adopted in 1996 it is OK and
> > considered safe, when necessary, to supply both 120 and 240 volt loads
in an
> > appliance that uses a 3 wire 220/240 VAC cord!
> Can you say what section of NEC states that? I'd like to look it up
> myself. I know it is fine to run a 120 volt load between a hot lead and
> neutral in a 240/120 VAC powered device that has a four wire cord with
> separate ground and neutral wires in it.
> > My statement was not
> > intended to say that ground and neutral are the same, what I said was in
> > that case they were the same, meaning the only neutral available is the
> > ground wire.
> No, the ground wire is not available to be used as a neutral. Unless you
> can tell me an NEC paragraph that says otherwise I am sticking to that
> statement.
> > Your staement, that it is NEVER, EVER, ACCEPTABLE to operate a
> > 110/120 volt load between 120 line and ground is simply inaccurate,
keeping
> > in mind that I am talking about when the load is contained within an
> > appliance that has a primary source from a 3 wire 220/240 VAC cord! If
it
> > were not, there would be thousands of electric clothes dryers in this
> > country operating improperly.
> Are there electric clothes dryers that can be wired for either 120 VAC
> or 240 VAC, and use only a three wire cord when wired for 240 VAC? I
> know there are plenty that will only run only on 240 VAC, and use a
> three wire cord. In that case everything in the dryer runs on 240 VAC
> and there is nothing running on 120 VAC that is connected between a hot
> lead and ground.
> > And yes I know the new ones come with 4 wire
> > cords.But there are still thousands and thousands of the 3 wire ones out
> > there. And then there are probably some 220 volt Air Conditioners...
> I am sure that every 220 volt air conditioner that uses a three wire
> power cord has a 220 volt compressor and a 220 volt fan, and has no need
> to connect any load between one of the hot leads and ground.
> > and what
> > else might we find???
> >
> Should be interesting to see.
>
> DE N6KB
>
>
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>
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