This should stir up some discussion

We had a solenoid fail on the grain dryer tonight. There are no manuals or drawings, but that is not the point of this discussion.

The dryer has 240VAC hooked to the incoming power lugs, but there is only a ground lug. I had assumed that all was 240VAC in it, but there are a lot of 120VAC control components. That means the chassis of the dryer is carrying voltage.

I am thinking about lifting the 120VAC neutral from the chassis and hooking a neutral back to the main disconnect, I have the conductors unused now.

Are you SURE there's not a 240-120 Volt control transformer in the control panel somewhere? That would not be at all unusual for a grain dryer.

I looked for it tonight, did not see it, but was distracted fixing issue.

For years electric stoves had 3 wires for service. Internally the (stupid never used but sometimes buzzed till all knobs were twisted pulled and pushed) clock timer was 120v. The neutral was considered ground. It was decided in modern times that it was a bad idea, but there was insulation between the chassis and the feed to the clock (both hot from one branch, and a wire to the neutral buss. Jim

As an example, the dryer in the middle of the post linked below is 2-phase, with no neutral, and a control transformer to power the small relays and timers at 120 Volts, which in turn operate 240 Volt coils in the motor contractors.
SuperB

That is the big brother, where did you find the transformer?

There is a control transformer in there someplace, worked on many grain driers over the years, can't remember any that didn't have a control transformer hiding someplace, just pray you don't have to mess with the capacitor networks some have on the blower motors, spend one fall filling my days dealing with that, gutted a few and started over from scratch, amazing what you can do with relays and a PLC nowadays, and some analog I.O. Cards.

David, not being there nor having any schematics I have no idea if it contains any 240/120 transformers or what, so I cant speak as to how its wired. (Don't know how anyone can not seeing it??)

For years past stoves or dryers etc. that had BOTH 120 and 240 loads were fed with ONLY 3 wires, two Hots L1 & L2 (240 volts) and a bare/green Equipment Grounding Conductor. Of course that meant the bare/green was used to carry live return current. If that bare green was bonded to the appliances outer conductive metal case while a 120 volt load was in use and you touched it, there can potentially be a parallel current flow through your body YIKES. Im sure you wouldn't open an electrical box and strip away the insulation off the white Neutral and tell your grandkids to go ahead and touch that wire little Johnny!!! Well, if the case/frame is bonded to a wire that's carrying current YOURE DOING THE SAME THING. Ever wonder why that white wire is insulated but the ground is bare and bonded to case/frame HMMMMMMMMMM

Then the NEC and perhaps UL and other knowledgeable electrical minds improved safety by requiring four wires to an appliance that had BOTH 120 and 240 volt loads. Two Hots, Neutral, Equipment Grounding Conductor. That way the equipment grounding conductor is dedicated for carrying fault current ONLY and there's no live current carrying conductor bonded to the outer metal case/frame which you touch Yayyyyyyyyyy much safer

However as I have said, just because trained professional electricians and engineers do things a certain way that agrees with the NEC's panel of expert recommendations or UL regardless if any codes have been adopted or not, yall feel free to wire and do things as you please if you know better then the experts, its you and your kids and grandkids lives you are gambling with not mine.

NO WARRANTY get it, this may be right it may be wrong, I'm NOT saying it is or it isn't, do as you please.

John T

do older 3 wire stoves that have an interior 120v lamp, and 3 wire welders with a 120v fan get away with it or?

It's in the control panel, I can't remember exactly where, but remember seeing it on the schematic and in person.

Jim I must say your description of the never used buzzing-till-all-knobs-were-twisted-pulled-and pushed clock brought back memories of home!

I'm sure I'm not the only one who knows EXACTLY what you're talking about.

I built and wired special machines for many years. The main power to the machines was usually 240v, 3 phase and we always used a separately derived( i.e. 240/120 volt single phase transformer) system for the controls for isolation from spikes, etc. I would bet there's a transformer hidden in there somewhere. We wired things somewhat differently 50 years ago, much safer now.

I think they do. I've seen a ton of those (and Im sure you have) set ups and I doubt anyone knows or cares or has raised the issue (old ones might be grandfatherd).

However, Id "guess" (haven't bought one in years) any newer stove is gonna have that new 4 wire receptacle anyway. I doubt the concern for a shop welder like a Lincoln 240 VAC Buzz Box raises the level of a stove where the kiddies are. However I don't know if those fans are 120 or 240???

If UL or the NEC or anyone was asked this they would have to weigh in on the 4 wire method Im sure.

Sorry no specific answer for you

John T

in the case of the old stoves or old welders.. i bet it's grandfathered stuff. I don't think i have seen anything 220 3 prong in a while past a dryer.. and it's been a long while., like pre 1999 easy..

David G,
Yep, there are some who will be stirred up. As for me, if it's worked that way for decades, what's the biggie? I wouldn't change it.

I have been using 3 wire clothes dryer for the past 45 years. Mine sits on a basement floor. Not dead yet. Never been shocked. They have 220v heating elements and 110v blower motor.

They still sell new ones with 3 wire. So I ask, where are all class action cases? IF IT'S SOOOOOOO DANGEROUS, WHY HAVEN'T WE SEEN DO-WEE, CHEAT-EM AND HOW advertising on TV if you or a love one has been killed call now, time is limited?????
It's time for some to get on their soap box and preach NEC codes.
George

Maybe someone can expIain why 120/240v stick weIders have onIy a 3 prong pIugin??

(reply to post at 16:58:35 11/11/14)

Click to expand...

Because if company A sells only four wire dryers. Company B will have some of the four wire market and all the three wire market
You don't think Bubba is going to call his brother-in law Bill-Bob over and have to pay for two cases of beer, a four wire receptacle and a run of 10/3 dryer wire? When Bubba can just plug the new dryer into the old three prong receptacle.
As far as Bubba is concerned. If today he doesn't feel a shock, the clothes dry and the dryer doesn't burst into a sparking ball of flames. The installation was just fine.

3 wire clothes dryers and ranges have been around
for decades, and they still are making them.
Please post where someone has been killed because
of the old 3 wire dryers, then someone has sued
the manufacture. Where are all the 3 wire
recalls? Where are all the class action
lawsuits???
Bubba and I think there is way too much to do
about NOTHING with all this grounding stuff.
Yep, go ahead and get on a soap box and tell me
to put a grounding rod next to my dryer, won't
happen. I'm not changing the wiring to my dryer,
now or ever.
George

Because the welder uses 240V. The ground is to hold the cabinet at near earth potential. To prevent developing a dangerous potential from induction, capacitance or a winding to chassis failure.

George I don't give a rats AZZ about what you believe and do. I just hope that your Darwin yourself out before you influence somebody else into a hazardous situation.

2-1 step down xformer in there for sure. I have one in my sawmill cabinet to run all the contacters etc as they are 120 v.