[Amps] 220V wiring: Was Question about safety ground connection

Gary Schafer garyschafer at comcast.net
Thu Nov 17 20:46:15 EST 2005

> -----Original Message-----
> From: Bill Turner [mailto:dezrat1242 at ispwest.com]
> Sent: Thursday, November 17, 2005 9:47 AM
> To: Gary Schafer; amps at contesting.com
> Subject: RE: [Amps] 220V wiring: Was Question about safety ground
> connection
> At 09:15 PM 11/16/2005, Gary Schafer wrote:
> >You are trying to make it complicated when it is not.
> >
> >Suppose your neutral does open with a four wire circuit, your 120 volt
> fan
> >just stops running.
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> I'm afraid it actually is more complicated than you think.
> First of all, if your fan stops running that itself is a safety
> hazard, but the complications go beyond that.
> Consider the case of a 120 volt blower connected from neutral to one
> hot, and a 120 volt relay connected from neutral to the other hot.
> Perfectly legal, right? What happens if the neutral opens? You then
> have 240 volts across the series string of blower and relay. The
> blower is almost certainly a lower impedance than the relay, so it
> will most likely slow way down or stop completely, while the relay
> will become seriously overheated. Both are a safety hazard. It would
> be far better to have both items be 240 volt to begin with, and
> connected from hot to hot.
> I still maintain the existing NEC code allowing use of a neutral is
> an attempt to placate some powerful special interests in the
> electrical industry. It is NOT the safest approach to the issue.
> 73, Bill W6WRT

How about if the blower itself burns open and stops?
If you are concerned about the blower not moving air then install an air
flow sensor switch in the air path. Of course I suppose that switch could
fail too and leave you out in the cold (or heat as it may be).

It is poor practice to split the 240 and run some things from each side for
the 120 volt circuits in an amplifier. Choose one side and stick with it.
Eliminates all kinds of problems.

Then how about all those 120 volt appliances in your house? I would get rid
of them too. If you have an open neutral going to the house you will have
all sorts of items in series across 240 volts to worry about. I have had
this happen and survived! So did all the appliances!

You could move to the UK where there is only 240 volts. But if you choose to
stay in the U.S. and suffer with our power system then you are stuck with
the design of the power system in place and must work around it.  :>)

Gary  K4FMX

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