I have a 50-amp breaker on a circuit previously used for a double oven.
The new oven draws 3400 watts on 4000 watts at 240 volts, depending on
whether you believe a plate on the oven or the manual. I think that's
either 14.2 amps16.7 amps.

The question is whether I need to change the breaker, and, if so,
whether I need to also change the wire in the wall and ceiling, which
is 6-gauge aluminum. One person said a 50-amp breaker is too big
because the oven internal wiring could burn out before tripping the
breaker. I understand that logic, but if it's a legitimate concern then
why wouldn't this call for a 20-amp breaker? Nobody, I think, would use
a 20-amp breaker on an oven circuit -- always 30 or more.

What would you do, and why?

"BobH" wrote in message
ps.com...
I have a 50-amp breaker on a circuit previously used for a double oven.
The new oven draws 3400 watts on 4000 watts at 240 volts, depending on
whether you believe a plate on the oven or the manual. I think that's
either 14.2 amps16.7 amps.

The question is whether I need to change the breaker, and, if so,
whether I need to also change the wire in the wall and ceiling, which
is 6-gauge aluminum. One person said a 50-amp breaker is too big
because the oven internal wiring could burn out before tripping the
breaker. I understand that logic, but if it's a legitimate concern then
why wouldn't this call for a 20-amp breaker? Nobody, I think, would use
a 20-amp breaker on an oven circuit -- always 30 or more.

What would you do, and why?


Are the wattage ratings for all 4 burners on high, and the oven in preheat
mode? Or...other?

On 3 Nov 2006 09:35:36 -0800, "BobH" wrote:

I have a 50-amp breaker on a circuit previously used for a double oven.
The new oven draws 3400 watts on 4000 watts at 240 volts, depending on
whether you believe a plate on the oven or the manual. I think that's
either 14.2 amps16.7 amps.

The question is whether I need to change the breaker, and, if so,
whether I need to also change the wire in the wall and ceiling, which
is 6-gauge aluminum. One person said a 50-amp breaker is too big
because the oven internal wiring could burn out before tripping the
breaker. I understand that logic, but if it's a legitimate concern then
why wouldn't this call for a 20-amp breaker? Nobody, I think, would use
a 20-amp breaker on an oven circuit -- always 30 or more.

What would you do, and why?

imho:

Check your 'cut sheet' for breaker requirements. Tyically the breaker
is designed for protecting the wires, but some manufactures want a
specific size breaker for their products.

later,

tom @ www.NoCostAds.com

I would size the wire and breaker per the manufacturers specs.

The breaker is there for over current protection on the WIRE. Not your
equipment.
It is there for short circuit protection as well.

If you have over sized wire on a breaker you are putting the circuit
as a SYSTEM out of whack.

Most typical breakers operate on heating at the terminations of the
breaker. And of course amp draw. Both of these are all enginneered in
the breaker.

A #6 wont heat up as much on a 45 amp load that a #10 will.



On 3 Nov 2006 09:35:36 -0800, "BobH" wrote:

I have a 50-amp breaker on a circuit previously used for a double oven.
The new oven draws 3400 watts on 4000 watts at 240 volts, depending on
whether you believe a plate on the oven or the manual. I think that's
either 14.2 amps16.7 amps.

The question is whether I need to change the breaker, and, if so,
whether I need to also change the wire in the wall and ceiling, which
is 6-gauge aluminum. One person said a 50-amp breaker is too big
because the oven internal wiring could burn out before tripping the
breaker. I understand that logic, but if it's a legitimate concern then
why wouldn't this call for a 20-amp breaker? Nobody, I think, would use
a 20-amp breaker on an oven circuit -- always 30 or more.

What would you do, and why?

BobH wrote:
One person said a 50-amp breaker is too big
because the oven internal wiring could burn out before tripping the
breaker.

BH:

Who?

watts=current(amps) x voltage
current = watts / voltage so.........
current = 4000 / 240volts or 16.77777 amps

so you would need (two) 20 amp breakers at the panel .......one per
120volt line.

As long as you are going from a larger breaker to a smaller one, no
worry is needed for the wiring part. If you were increasing the
amps.....then the wiring would have to be a concern. A minimum of 12
gauge should be sufficient in your case at 4000 watts.

Here is a link that will help you..........

http://muextension.missouri.edu/expl...gin/g01409.htm

Tazz wrote:
I would size the wire and breaker per the manufacturers specs.

The breaker is there for over current protection on the WIRE. Not your
equipment.
It is there for short circuit protection as well.

If you have over sized wire on a breaker you are putting the circuit
as a SYSTEM out of whack.

Most typical breakers operate on heating at the terminations of the
breaker. And of course amp draw. Both of these are all enginneered in
the breaker.

A #6 wont heat up as much on a 45 amp load that a #10 will.

Tazz:
A #6 *wire* won't heat up as much as a #10 *wire* will, given the same
load.
But both will heat up the internal element of a 50 amp circuit breaker
the
same amount. In fact, the #6 circuit will have less voltage drop.
With more
voltage available at the oven, if something internally shorts out, more
current
will flow, tripping the breaker more quickly. You don't have to
consider house
wiring as a system with the breaker like that. We are not making a
resonant
RLC circuit here. Hook up a 15A breaker to a #14 circuit and another
15A
breaker to a 500 MCM circuit, and both will be protected at 15A for
house-
wiring purposes, though the 500 MCM will be grotesquely overdoing
things
and certainly difficult to wrap around those device screws.

Cordially yours:
G P.

If the unit draws 4kw, the NEC requires you to use minimum #10 copper, with
30 amp breaker. The #6al is fine, but I'd reduce the breaker size


"BobH" wrote in message
ps.com...
I have a 50-amp breaker on a circuit previously used for a double oven.
The new oven draws 3400 watts on 4000 watts at 240 volts, depending on
whether you believe a plate on the oven or the manual. I think that's
either 14.2 amps16.7 amps.

The question is whether I need to change the breaker, and, if so,
whether I need to also change the wire in the wall and ceiling, which
is 6-gauge aluminum. One person said a 50-amp breaker is too big
because the oven internal wiring could burn out before tripping the
breaker. I understand that logic, but if it's a legitimate concern then
why wouldn't this call for a 20-amp breaker? Nobody, I think, would use
a 20-amp breaker on an oven circuit -- always 30 or more.

What would you do, and why?

According to BobH :
I have a 50-amp breaker on a circuit previously used for a double oven.
The new oven draws 3400 watts on 4000 watts at 240 volts, depending on
whether you believe a plate on the oven or the manual. I think that's
either 14.2 amps16.7 amps.

You don't need to change the wire, as long as it's larger than
the minimu.

If you do need to change the breaker, and assume that the 16.7A
is correct, by the 80% rule you'd have to use a 30A dual breaker.
[NOT two individual breakers]

But, before you do that. Do you have a cooktop too?

By NEC and CEC rules, a wall oven and cooktop are permitted to be
on the same breaker, with ampacity determined by the total of
the two rated current requirements. [In fact, at least with the CEC,
under certain restrictions, the wire to the oven only has to be
large enough for the oven draw, not the full breaker current.
Eg: you'd might run #8 or #6 on a 40 or 50A circuit to a splitter
box, which splits to two 10ga cables to the oven and cooktop.]

In your case, it's already #6Al, but is the 50A circuit shared
with a cooktop? If so, you have to factor that in too in your
breaker size calculation.

I'm a little suspicious of a 50A circuit ONLY feeding an oven,
but the risks (burnout of oven wiring itself) are fairly low.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

In article . com, "avid_hiker" wrote:

watts=current(amps) x voltage
current = watts / voltage so.........
current = 4000 / 240volts or 16.77777 amps

so you would need (two) 20 amp breakers at the panel .......one per
120volt line.

No, and no.

First, should be 30 amps. An electric stove meets the Code definition of a
"continuous load", and thus the circuit is limited to 80% of the breaker
rating. 80% of 20 amps is 16.0 amps. A 17-amp continous load requires the next
size up breaker, which is 30 amps.

Second, it must not be two separate breakers, but rather one double-pole
breaker.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

avid_hiker wrote:
watts=current(amps) x voltage
current = watts / voltage so.........
current = 4000 / 240volts or 16.77777 amps

only for straight resistance devices

now most heating elements change in resistance as they change in
tempature, so the wattage listed might not for max, but for power
output while at temp.

also, the stovetop burners *might* be 120V (2 burners for each side of
the 240)

my advice, find the nameplate, contact the manufacturer, and find out
what wiring and breaker to use. they know the right answer, as telling
the wrong one sets them up for a lawsuit

On Sat, 04 Nov 2006 13:59:50 GMT, (Doug Miller)
wrote:

In article . com, "avid_hiker" wrote:

watts=current(amps) x voltage
current = watts / voltage so.........
current = 4000 / 240volts or 16.77777 amps

so you would need (two) 20 amp breakers at the panel .......one per
120volt line.

No, and no.

First, should be 30 amps. An electric stove meets the Code definition of a
"continuous load", and thus the circuit is limited to 80% of the breaker
rating. 80% of 20 amps is 16.0 amps. A 17-amp continous load requires the next
size up breaker, which is 30 amps.

Second, it must not be two separate breakers, but rather one double-pole
breaker.

Any new breaker for a 240V circuit needs to be double-pole, but is it
important enough to replace older ones that aren't double-pole?
--
51 days until the winter solstice celebration

Mark Lloyd
http://notstupid.laughingsquid.com

"Unlike biological evolution. 'intelligent design' is
not a genuine scientific theory and, therefore, has
no place in the curriculum of our nation's public
school classes." -- Ted Kennedy

BobH wrote:
I have a 50-amp breaker on a circuit previously used for a double oven.
The new oven draws 3400 watts on 4000 watts at 240 volts, depending on
whether you believe a plate on the oven or the manual. I think that's
either 14.2 amps16.7 amps.

what does the oven manual say for a breaker?

is 6-gauge aluminum. One person said a 50-amp breaker is too big
because the oven internal wiring could burn out before tripping the
breaker. I understand that logic, but if it's a legitimate concern then

which should you believe, the person or the company that made the oven?
who would be responsible is something goes wrong?

In article , Mark Lloyd wrote:
On Sat, 04 Nov 2006 13:59:50 GMT, (Doug Miller)
wrote:

In article . com,
"avid_hiker" wrote:

watts=current(amps) x voltage
current = watts / voltage so.........
current = 4000 / 240volts or 16.77777 amps

so you would need (two) 20 amp breakers at the panel .......one per
120volt line.

No, and no.

First, should be 30 amps. An electric stove meets the Code definition of a
"continuous load", and thus the circuit is limited to 80% of the breaker
rating. 80% of 20 amps is 16.0 amps. A 17-amp continous load requires the next

size up breaker, which is 30 amps.

Second, it must not be two separate breakers, but rather one double-pole
breaker.

Any new breaker for a 240V circuit needs to be double-pole, but is it
important enough to replace older ones that aren't double-pole?

Yes -- it's a Code violation, and a safety hazard, to use two separate 120V
breakers for a 240V circuit unless the handles are tied together to as to
produce a *single* disconnect for *both* hot conductors.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Two clarifications:

1. The suggestion that two electricians gave me is to use a 20-amp or
30-amp double-pole breaker, so there's no need to discuss one vs. two
breakers here.

2. This is a wall oven only on a dedicated circuit. There is a separate
circuit for a cooktop elsewhere in the kitchen.

A rant:

The manufacturer, Frigidaire/Electrolux, is almost useless. Like a lot
of big companies, it has a customer-service organization apparently
designed to block consumers from getting in touch with any
knowledgeable person. The manual and the customer service people just
say conform to your local codes, ask your own electrician, etc., when
presented with a problem such as how to connect the oven's small
16-gauge copper wire to 6-gauge aluminum in the wall, for which nobody
makes a connector.

A conclusion:

As for the circuit rating, I quote from the multiple-model manual:

"The fuse size must not exceed the circuit rating of the appliance
specified on the nameplate."

There is no "circuit rating" on the nameplate. There is only the
wattage, which is 3.4 kw at 240 volts and a similar number for 208
volts, which I guess is for Canada.

Quoting further from the manual:

"The single wall oven can consume up to 4000W at 240 Vac; use a circuit
breaker of 30 Amp with wire gauge #8 AWG."

This figure of 4000 watts disagrees with the 3.4 kw on the nameplate.
So that leaves us with either 14.2 or 16.7 amps.

Thanks for the information about the 80 percent rule. I had not heard
of that. Does that mean that, even on a circuit for a single appliance,
the breaker size should be 1/.8 (1.25) times the maximum expected load
on the circuit?

If I am interpreting that correctly, then a 20-amp double-pole breaker
would handle a load of 14.2 amps multiplied by 1.25, but a 16.7-amp
load multiplied by 1.25 would call for a 20.9-amp breaker, so I'd go up
to 30 amps. In light of the ambiguity of the manufacturer's
information, 30 amps seems best.

Does that make sense? Any other thoughts?

The manufacturer isn't being ambiguous. Voltages vary and wattages will vary
with the voltage differences. The manufacturer says to use a 30 amp breaker
with #8 copper. What don't you understand?


"BobH" wrote in message
oups.com...
Two clarifications:

1. The suggestion that two electricians gave me is to use a 20-amp or
30-amp double-pole breaker, so there's no need to discuss one vs. two
breakers here.

2. This is a wall oven only on a dedicated circuit. There is a separate
circuit for a cooktop elsewhere in the kitchen.

A rant:

The manufacturer, Frigidaire/Electrolux, is almost useless. Like a lot
of big companies, it has a customer-service organization apparently
designed to block consumers from getting in touch with any
knowledgeable person. The manual and the customer service people just
say conform to your local codes, ask your own electrician, etc., when
presented with a problem such as how to connect the oven's small
16-gauge copper wire to 6-gauge aluminum in the wall, for which nobody
makes a connector.

A conclusion:

As for the circuit rating, I quote from the multiple-model manual:

"The fuse size must not exceed the circuit rating of the appliance
specified on the nameplate."

There is no "circuit rating" on the nameplate. There is only the
wattage, which is 3.4 kw at 240 volts and a similar number for 208
volts, which I guess is for Canada.

Quoting further from the manual:

"The single wall oven can consume up to 4000W at 240 Vac; use a circuit
breaker of 30 Amp with wire gauge #8 AWG."

This figure of 4000 watts disagrees with the 3.4 kw on the nameplate.
So that leaves us with either 14.2 or 16.7 amps.

Thanks for the information about the 80 percent rule. I had not heard
of that. Does that mean that, even on a circuit for a single appliance,
the breaker size should be 1/.8 (1.25) times the maximum expected load
on the circuit?

If I am interpreting that correctly, then a 20-amp double-pole breaker
would handle a load of 14.2 amps multiplied by 1.25, but a 16.7-amp
load multiplied by 1.25 would call for a 20.9-amp breaker, so I'd go up
to 30 amps. In light of the ambiguity of the manufacturer's
information, 30 amps seems best.

Does that make sense? Any other thoughts?

Point taken,
And I stand corrected.

Typically the OCP protects only the conductors.
Is it ok to oversize the conductors on any application?

I have heard of oversizing grounds and neutrals on computer and
lighting loads for harmonic issues. But have never heard using larger
conductors on the line voltatge.. Of course the OP has this as an
existing situation and not a new install. I suppose this is why the
code addresses minimums and not maximums. makes sense.

I would agree that getting a 500kcmil around a screw on an outlet will
be somewhat hard. But dont you know someone will try to engineer it at
some point and time. LOL

respectfully

Tazz.




Tazz:
A #6 *wire* won't heat up as much as a #10 *wire* will, given the same
load.
But both will heat up the internal element of a 50 amp circuit breaker
the
same amount. In fact, the #6 circuit will have less voltage drop.
With more
voltage available at the oven, if something internally shorts out, more
current
will flow, tripping the breaker more quickly. You don't have to
consider house
wiring as a system with the breaker like that. We are not making a
resonant
RLC circuit here. Hook up a 15A breaker to a #14 circuit and another
15A
breaker to a 500 MCM circuit, and both will be protected at 15A for
house-
wiring purposes, though the 500 MCM will be grotesquely overdoing
things
and certainly difficult to wrap around those device screws.

Cordially yours:
G P.

On Sat, 04 Nov 2006 20:09:08 GMT, (Doug Miller)
wrote:

In article , Mark Lloyd wrote:
On Sat, 04 Nov 2006 13:59:50 GMT, (Doug Miller)
wrote:

In article . com,
"avid_hiker" wrote:

watts=current(amps) x voltage
current = watts / voltage so.........
current = 4000 / 240volts or 16.77777 amps

so you would need (two) 20 amp breakers at the panel .......one per
120volt line.

No, and no.

First, should be 30 amps. An electric stove meets the Code definition of a
"continuous load", and thus the circuit is limited to 80% of the breaker
rating. 80% of 20 amps is 16.0 amps. A 17-amp continous load requires the next

size up breaker, which is 30 amps.

Second, it must not be two separate breakers, but rather one double-pole
breaker.

Any new breaker for a 240V circuit needs to be double-pole, but is it
important enough to replace older ones that aren't double-pole?

Yes -- it's a Code violation, and a safety hazard, to use two separate 120V
breakers for a 240V circuit unless the handles are tied together to as to
produce a *single* disconnect for *both* hot conductors.


Having the breakers tied together, also prevents the dumb questions
like, I installed both breakers, but nothing happens. Each hot gives
me 120v to ground, but then to each other, I get 0. WTF?

rest head in my hand, shaking



later,

tom @ www.IRantAndRave.com

RBM (remove this) wrote:
The manufacturer isn't being ambiguous. Voltages vary and wattages will vary
with the voltage differences. The manufacturer says to use a 30 amp breaker
with #8 copper. What don't you understand?


If the manual says 4000 watts and the plate on the oven says 3.4
kilowatts, that looks ambiguous to me.

According to BobH :
A rant:

The manufacturer, Frigidaire/Electrolux, is almost useless. Like a lot
of big companies, it has a customer-service organization apparently
designed to block consumers from getting in touch with any
knowledgeable person. The manual and the customer service people just
say conform to your local codes, ask your own electrician, etc., when
presented with a problem such as how to connect the oven's small
16-gauge copper wire to 6-gauge aluminum in the wall, for which nobody
makes a connector.

This is often done with a small breaker box.

There is no "circuit rating" on the nameplate. There is only the
wattage, which is 3.4 kw at 240 volts and a similar number for 208
volts, which I guess is for Canada.

No, we're 240V just like you. 208V is when it's powered off
two hots of a 3 phase circuit. The legs are 120V referenced
to neutral, but 208V apart. You see this in industrial/commercial,
especially "warehouse-office" conversions, staff areas in
industrial buildings etc. Quite rare in straight residential,
but sometimes...

Thanks for the information about the 80 percent rule. I had not heard
of that. Does that mean that, even on a circuit for a single appliance,
the breaker size should be 1/.8 (1.25) times the maximum expected load
on the circuit?

If I am interpreting that correctly, then a 20-amp double-pole breaker
would handle a load of 14.2 amps multiplied by 1.25, but a 16.7-amp
load multiplied by 1.25 would call for a 20.9-amp breaker, so I'd go up
to 30 amps. In light of the ambiguity of the manufacturer's
information, 30 amps seems best.

Exactly.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.

According to Tazz :
Point taken,
And I stand corrected.

Typically the OCP protects only the conductors.
Is it ok to oversize the conductors on any application?

Yes. And no... ;-)

It's reasonably common to upsize the conductors a notch or two
for various reasons - eg: reduction of resistive voltage drop on
long circuits.

However, it's expensive to do, and in many cases you can run
into situations where the wire size exceeds the permissible
range on the devices you connect it to. You're going to flunk
an inspection with 0000 wire on a 15A outlet for example.

The inspector may ask, for example, "why the heck are you using
10ga on a 15A outlet?" You'd better have a good answer, or
the inspector may flunk you for workmanship.

"The circuit is so long that 10ga limits my voltage drop to 3V"
is a good answer. "I had a chunk laying around" is probably
a bad one.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.