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Joe 90
Guest

Wed Oct 01, 2003 8:43 am

After making the original changes 2 years ago, I had the results verified by
a local electrician and he was satisfied that there were no potential
problems.

However I just recently looked at the wirirng diagrams again and there are
two points that I don't understand. I have always understood voltage as
being a potential difference. Current flows from a high potential to a low
potential. This means that the input to a device has to be at a higher
potential relative to the output, typically connected to Neutral or Ground.
This would be the case even when using ac current.

Yet when one looks at the power supply in the USA you have a common Neutral
and two 120V single phase hot lines. The typical heating element in a dryer
in the USA is connected across the two 120V lines (making a 240V supply).

Now my first point is surely if both lines are in phase at 120V then there
is no potential difference and so how can the current flow? Or is the
current only really oscillating left and right along the wires in sync. with
the phase variance, in which case why bother with the neutral (except as a
safety ground) in many ac appliances.

120V ------------------------------------- a
Neutral ----------------------------------- b
120V ------------------------------------- c

Vab =Vbc = 120V, Vac = 240V - dryer heating element is across Vac.

My second point concerns the wiring ampacity. The dryer is rated at max
30A, so one would expect the heater wires to be AWG 10 (NEC guidelines), but
in fact they are AWG 12 (max 20A). Is this because in fact the heater is
being fed by two 120V circuits? And does this mean that if I connect a
European 240V setup as follows:

N --------------------------------------- d
240V ----------------------------------- e
Dryer heater element is across Vde

that these AWG 12 wires are being stressed beyond NEC recommendations?

Thanks in advance for any responses.

"John Woodgate" <jmw_at_jmwa.demon.contraspam.yuk> wrote in message news:h0rdLp
AAtme\$EwyT_at_jmwa.demon.co.uk...
Quote:
I read in sci.engr.electrical.compliance that Joe 90

I just knew I would get asked about the supply problem!!! I live in
Switzerland now. The heavier wiring is simply not available in the DIY
shops here - its probably a safety precaution by the authorities, also
Switzerland supplies approx. 380V/220V to each dwelling so large gauge
wires are not really essential.

All the advice you were given applies, AIUI, to installations in US. In
Switzerland, the rules are quite different. What you are doing may even
be illegal there. Switzerland controls what is connected to the
electricity supply VERY tightly.

You won't get #10 wire in Europe because European cables are described
by the conductor area in square millimetres. I don't have a conversion
chart from AWG to square mm; for 30 A you probably need 6 mm^2 cable,
but it depends on exactly what sort of cable and how it is installed.
--
Regards, John Woodgate, OOO - Own Opinions Only.
http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go
to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

Isaac
Guest

Wed Oct 01, 2003 10:40 am

On Wed, 1 Oct 2003 10:43:11 +0200, Joe 90 <donot_at_usethisaddress.com> wrote:
Quote:
After making the original changes 2 years ago, I had the results verified by
a local electrician and he was satisfied that there were no potential
problems.

However I just recently looked at the wirirng diagrams again and there are
two points that I don't understand. I have always understood voltage as
being a potential difference. Current flows from a high potential to a low
potential. This means that the input to a device has to be at a higher
potential relative to the output, typically connected to Neutral or Ground.
This would be the case even when using ac current.

You should not be connecting to ground as a means of providing power flow
to anything. Don't confuse neutral (the grounded supply conductor) with
Ground (the groundING conductor).

Quote:
Yet when one looks at the power supply in the USA you have a common Neutral
and two 120V single phase hot lines. The typical heating element in a dryer
in the USA is connected across the two 120V lines (making a 240V supply).

Now my first point is surely if both lines are in phase at 120V then there
is no potential difference and so how can the current flow? Or is the
current only really oscillating left and right along the wires in sync. with
the phase variance, in which case why bother with the neutral (except as a
safety ground) in many ac appliances.

120V ------------------------------------- a
Neutral ----------------------------------- b
120V ------------------------------------- c

The current in one 120 phase is at opposite polarity (with respect to
the neutral) as the other 120v phase. The neutral is there so you
can get 120 volts too. You don't want to dry clothes in the dark do
you?

Isaac

s
Guest

Wed Oct 01, 2003 12:13 pm

it isnt two phase!i know that and im a british sparky living and working in
the uk!!it IS single phase,fed from either end of a centre tapped
transfomer,in exactly the same way as our 110 volt transformers we use for
site tools.120v----0v(neutral)----120v.240v end to end,120 end to middle.if
you need to know how this works,think of a sine wave with the centre line
being the centre tap on our transformer!!(rant over).
"John Woodgate" <jmw_at_jmwa.demon.contraspam.yuk> wrote in message
news:HtKEdNDFyve\$EwGN_at_jmwa.demon.co.uk...
Quote:
I read in sci.engr.electrical.compliance that Joe 90
about '30A wiring advice - a complication?', on Wed, 1 Oct 2003:

The confusion
stems from page 23, of Wiring Simplified 39th edition based on NEC 1999
by Richter and Schwan. It implies that supplies in USA are in single
phase whereas I would have expected a 180deg phase differential which
has indeed been confirmed by a few posters.

Yes, well, you and me both. I have had scorn and derision heaped by US
citizens for describing their system as 'two-phase'. But it IS! (
--
Regards, John Woodgate, OOO - Own Opinions Only.
http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go
to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

C What I Mean
Guest

Wed Oct 01, 2003 12:28 pm

"Joe 90" <donot_at_usethisaddress.com> wrote in message
news:3f79f827\$1_4_at_news.bluewin.ch...
Quote:
I am making some changes to an electrical dryer. Where I live, I cannot
get
hold of 10 gauge wire for the 30A circuit - I know, don't ask why, pls.
Can
I use two 12 gauge wires connected in parallel? Based on my electrical
knowledge, this would split the max current between the two wires allowing
the wires to run cooler and well below max capacity.

First of all, it is most likely not up to code where you might be. With
that said, #12 is actually rated for 25 amps under certain conditions. NEC
(USA) just requires a 20 circuit protection on it in construction. In
panels, we can use the full rating of the wire but must allow for #10 field
wiring if between 20 and 30 amps..

Second of all, most likely your load my not be a full 30 amps. If you have
a way to do it, test it.

Next, the wires in parallel will have no problem with 30 amps from a
technical stand point. Yours is a code issue, which may be a safety issue.

I don't recommend you do it, but there is an answer.

John Woodgate
Guest

Wed Oct 01, 2003 12:42 pm

I read in sci.engr.electrical.compliance that Joe 90
'30A wiring advice - a complication?', on Wed, 1 Oct 2003:

Quote:
However I just recently looked at the wirirng diagrams again and there
are two points that I don't understand. I have always understood
voltage as being a potential difference. Current flows from a high
potential to a low potential. This means that the input to a device has
to be at a higher potential relative to the output, typically connected
to Neutral or Ground. This would be the case even when using ac current.

NOT TO GROUND! That would be deadly dangerous!
Quote:

Yet when one looks at the power supply in the USA you have a common
Neutral and two 120V single phase hot lines. The typical heating
element in a dryer in the USA is connected across the two 120V lines
(making a 240V supply).

Now my first point is surely if both lines are in phase at 120V then
there is no potential difference and so how can the current flow?

They ARE NOT in phase. The fat that you have to ask this question
indicates that you are in out of your depth. There is no blame for not
knowing, but there IS for dealing with things that you don't know about.

Simple logic would tell you that your assumptions are wrong, because the
US system works, whereas you 'proved' it couldn't.

Quote:
Or is
the current only really oscillating left and right along the wires in
sync. with the phase variance, in which case why bother with the neutral
(except as a safety ground) in many ac appliances.

The neutral is very definitely not a safety ground and must not ever be
used as one.
Quote:

120V ------------------------------------- a
Neutral ----------------------------------- b
120V ------------------------------------- c

Vab =Vbc = 120V, Vac = 240V - dryer heating element is across Vac.

My second point concerns the wiring ampacity. The dryer is rated at max
30A, so one would expect the heater wires to be AWG 10 (NEC guidelines),
but in fact they are AWG 12 (max 20A).

Are these wires internal to the dryer? If so, the NEC ampacity tables
don't apply, because the installation conditions are different.

Quote:
Is this because in fact the
heater is being fed by two 120V circuits?

No.

Quote:
And does this mean that if I
connect a European 240V setup as follows:

N --------------------------------------- d
240V ----------------------------------- e
Dryer heater element is across Vde

that these AWG 12 wires are being stressed beyond NEC recommendations?

No, not if the dryer was designed correctly in the first place. Does it
have a UL sticker?
Quote:

AWG10 has an area of 0.008155 sq. in., which is 5.26 sq. mm. AWG 12 has

0.005129 sq. in., which is 3.3 sq. mm. As multicore building
installation cables, these would, if they were standard sizes, be rated
at roughly 30A and 20 A respectively in Europe. But as single-conductor
cables, inside an appliance, the current ratings might be MUCH higher
(around 43 A and 35 A), depending on the insulating material and the
local ambient temperature.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

Joe 90
Guest

Wed Oct 01, 2003 1:01 pm

Quote:
They ARE NOT in phase. The fact that you have to ask this question
indicates that you are in out of your depth. There is no blame for not
knowing, but there IS for dealing with things that you don't know about.

Or that I am thinking things through very logically. The confusion stems
from page 23, of Wiring Simplified 39th edition based on NEC 1999 by Richter
and Schwan. It implies that supplies in USA are in single phase whereas I
would have expected a 180deg phase differential which has indeed been
confirmed by a few posters.

Also just to underline, when dealing with any such DIY projects I do get a
qualified electrician in to validate the work before switching on. As far
as I am aware I have not broken any Swiss regs.

Dr John Stockton
Guest

Wed Oct 01, 2003 1:26 pm

JRS: In article <3f79f827\$1_4_at_news.bluewin.ch>, seen in news:sci.engr.e
lectrical.compliance, Joe 90 <donot_at_usethisaddress.com> posted at Tue,
30 Sep 2003 23:39:45 :-

Quote:
I am making some changes to an electrical dryer. Where I live, I cannot get
hold of 10 gauge wire for the 30A circuit - I know, don't ask why, pls. Can
I use two 12 gauge wires connected in parallel? Based on my electrical
knowledge, this would split the max current between the two wires allowing
the wires to run cooler and well below max capacity.

Your location, Switzerland, is reasonably obvious to those who consider
Those who do not do so are generally assumed to be Americans - and thus
generally non-conversant with international standards.

Perhaps, personally, you are American - no born-and-bred European should
expect to find "gauge" size wire available retail within the EU - and CH
is within, though not of, the EU.

There must be a professional need for wire rated at well over 30A;
consult a friendly professional, or your local equivalent of RS
Components

--
Web <URL:http://www.merlyn.demon.co.uk/> - FAQish topics, acronyms, & links.
Correct <= 4-line sig. separator as above, a line precisely "-- " (SoRFC1036)
Do not Mail News to me. Before a reply, quote with ">" or "> " (SoRFC1036)

s
Guest

Wed Oct 01, 2003 1:31 pm

im sorry to disagree but i dont consider this to be a true two phase
system,as only one phase is entering the transformer,one leaving.the centre
tap being there for safety/alternate voltage.if this were a true two
phase,then it could be fed straight into a squirrel cage motor without the
need of a starting capacitor to phase shift the feild,or am i missing
something quite fundamental here??
"John Woodgate" <jmw_at_jmwa.demon.contraspam.yuk> wrote in message
news:+odasYAY+6e\$EwRJ_at_jmwa.demon.co.uk...
Quote:
I read in sci.engr.electrical.compliance that s <sim.mich_at_cwcom.net
wiring advice - a complication?', on Wed, 1 Oct 2003:

it isnt two phase!i know that and im a british sparky living and working
in the uk!!it IS single phase,fed from either end of a centre tapped
transfomer,in exactly the same way as our 110 volt transformers we use
for site tools.120v----0v(neutral)----120v.240v end to end,120 end to
middle.if you need to know how this works,think of a sine wave with the
centre line being the centre tap on our transformer!!(rant over). :-P

Well, I'm a Chartered Electrical Engineer, living and working in UK, and
although your detailed explanation is correct, that IS the description
of a two-phase system.

Just as the phase angles between the conductors of a 3-phase system are
120 degrees, so that the three angles add to 360 degrees, the angles
between the phases of a 2-phase system are 180 degrees, adding up to 360
degrees.
--
Regards, John Woodgate, OOO - Own Opinions Only.
http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go
to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

John Woodgate
Guest

Wed Oct 01, 2003 4:10 pm

I read in sci.engr.electrical.compliance that Joe 90
about '30A wiring advice - a complication?', on Wed, 1 Oct 2003:

Quote:
The confusion
stems from page 23, of Wiring Simplified 39th edition based on NEC 1999
by Richter and Schwan. It implies that supplies in USA are in single
phase whereas I would have expected a 180deg phase differential which
has indeed been confirmed by a few posters.

Yes, well, you and me both. I have had scorn and derision heaped by US
citizens for describing their system as 'two-phase'. But it IS! (
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

obsidian
Guest

Wed Oct 01, 2003 6:13 pm

3 phase....
380 phase to phase gives you more or less 220
phase to neutral

--
obsidian

wrote in message
news:w2teb.4366\$1m2.3354_at_news02.roc.ny...
Quote:

message
news:3f7a16db\$1_1_at_news.bluewin.ch...
problem!!! I live in
Switzerland now. The heavier wiring is simply
not available in the DIY
shops
here - its probably a safety precaution by the
authorities, also
Switzerland
supplies approx. 380V/220V to each dwelling so
large gauge wires are not
really essential.

How do they supply 380v/220v? Presumably the
220v is single pole. Where
does the additional 160v come from?

Gary Tait
Guest

Wed Oct 01, 2003 8:33 pm

Whereas On Tue, 30 Sep 2003 20:48:43 -0400, "John McGaw"
<nowhere_at_all.xyz> scribbled:
, I thus relpy:
Quote:
Or is CH simply a convenient posting location?

CH is the TLD for Switzerland.
--
Gary J. Tait . Email is at yahoo.com ; ID:classicsat

Gary Tait
Guest

Wed Oct 01, 2003 8:35 pm

Whereas On Wed, 1 Oct 2003 01:50:42 +0200, "Joe 90"
, I thus relpy:
Quote:

The dryer works fine following some modifications I made - basically
disconnecting internal 120V circuits that only served to provide some
advanced functions which we don't miss like moisture sensor based automatic
drying. I connected the heating element across a 240V supply and the motor
(5.2A, 1/2hp) and timer across a stepped down 120V. But whilst running, the
wires do feel a litle warm (note the unit has been running fine for the last
2 years in Switzerland and continues to do so) and this bothers me.

Wade thanks for your feedback, I feel really stupid not having realized that
in the first place. I think the best solution will be to get some #8 wire
from a friend in the USA.

No, the best solution would be to hire a Swiss electrician to wire it
up., or forget it and buy a Swiss/EU approved dryer, instead of trying
to make the NA one to work.
--
Gary J. Tait . Email is at yahoo.com ; ID:classicsat

Gary Tait
Guest

Wed Oct 01, 2003 8:45 pm

Whereas On Wed, 1 Oct 2003 10:43:11 +0200, "Joe 90"
, I thus relpy:
Quote:
After making the original changes 2 years ago, I had the results verified by
a local electrician and he was satisfied that there were no potential
problems.

However I just recently looked at the wirirng diagrams again and there are
two points that I don't understand. I have always understood voltage as
being a potential difference. Current flows from a high potential to a low
potential. This means that the input to a device has to be at a higher
potential relative to the output, typically connected to Neutral or Ground.
This would be the case even when using ac current.

Yet when one looks at the power supply in the USA you have a common Neutral
and two 120V single phase hot lines. The typical heating element in a dryer
in the USA is connected across the two 120V lines (making a 240V supply).

Now my first point is surely if both lines are in phase at 120V then there
is no potential difference and so how can the current flow? Or is the
current only really oscillating left and right along the wires in sync. with
the phase variance, in which case why bother with the neutral (except as a
safety ground) in many ac appliances.

120V ------------------------------------- a
Neutral ----------------------------------- b
120V ------------------------------------- c

Vab =Vbc = 120V, Vac = 240V - dryer heating element is across Vac.

It is Vab= -Vbc=120, Vac=240V. Note the -Vbc, it is 180 degrees out of
phase of Vab.

Quote:
My second point concerns the wiring ampacity. The dryer is rated at max
30A, so one would expect the heater wires to be AWG 10 (NEC guidelines), but
in fact they are AWG 12 (max 20A). Is this because in fact the heater is
being fed by two 120V circuits? And does this mean that if I connect a
European 240V setup as follows:

N --------------------------------------- d
240V ----------------------------------- e
Dryer heater element is across Vde

Don't forget there is a motor and a timer in the dryer also, and they
need 120V.

Quote:

that these AWG 12 wires are being stressed beyond NEC recommendations?

They seem to allow it, so it is okay.

Quote:
Thanks in advance for any responses.

--
Gary J. Tait . Email is at yahoo.com ; ID:classicsat

Spehro Pefhany
Guest

Wed Oct 01, 2003 8:50 pm

On Wed, 01 Oct 2003 16:45:12 -0400, the renowned Gary Tait
<seesig_at_xxx.yyy> wrote:

Quote:

Don't forget there is a motor and a timer in the dryer also, and they
need 120V.

And generally a light bulb. Since the neutral only carries an amp or
two, it could probably be recreated with a compact 230:120 control
transformer or autotransformer, but I have no idea what getting that
intalled to code for a Swiss residence would involve.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff_at_interlog.com Info for manufacturers: http://www.trexon.com

Joe 90
Guest

Wed Oct 01, 2003 10:18 pm

Quote:
No, the best solution would be to hire a Swiss electrician to wire it
up., or forget it and buy a Swiss/EU approved dryer, instead of trying
to make the NA one to work.
--
Gary J. Tait . Email is at yahoo.com ; ID:classicsat

The unit already works (has been working fine in Switzerland for past 2
years!) and has been checked over by a Swiss electrician for safety. I
simply wanted to extend the wiring but culd not find and awg8. Thx.

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