Aluminum wiring and induction cooktop

twitter007July 28, 2012

Hi,

I'm planning to replace a electric radiant heat cooktop with an induction unit. Existing wiring is aluminum romex with a 40A breaker. I measured the thickness of wire using a wire gauge and it's 3/16". So it's either a #4 or #6 cable. The new unit is rated at 10.8 KW and requires a 50A circuit.

I read somewhere that a household cooking appliance of up to 12KW can work with a 40A circuit. Can I just connect the cooktop to existing circuit?

Thank you for reporting this comment. Undo
llaatt22

Google: appliance hardwired to house aluminum wiring

The link is given in the second item listed.

There is also a Garden Web item further down. "220 etc "

Here is a link that might be useful: AMP Splicing system

    Bookmark   July 29, 2012 at 2:44AM
Thank you for reporting this comment. Undo
petey_racer

"I read somewhere that a household cooking appliance of up to 12KW can work with a 40A circuit. Can I just connect the cooktop to existing circuit?"

Yes, you are correct.

    Bookmark   July 29, 2012 at 8:11AM
Thank you for reporting this comment. Undo
brickeyee

Just as importat as the NEC circuit limits are the instalation instructions for the equipment.

If the instructions for the unit say a 50 A circuit is required you must then instal a 50 amp circuit.

The NEC determines what wire gauge are allowed for the circuit.

    Bookmark   July 29, 2012 at 8:56AM
Thank you for reporting this comment. Undo
twitter007

I talked to two electricians and got different opinions (just like brickeyee and petey_racer).
First one said (talked to him on phone) it's okay to use the existing wiring since the cooktop will draw more than 10KW only if all 5 burners are turned on at max power which is extremely unlikely. He suggested to not change the breaker so if we ever turned all burners, breaker will trip.

Second one came by and said I can keep existing wiring if it's #4 otherwise it needs to be replaced. Cost would be approx 1400 including 12 hours of labor, 80ft of #6 cu wire and 50A breaker.

If replacing the wiring cost few hundred dollars, I would do it in a heartbeat but need to research more before spending 1500 dollars on it.

To further compound the matter, my panel is Federal Pacific stab-lock.

decisions... decisions...

    Bookmark   July 30, 2012 at 1:51PM
Thank you for reporting this comment. Undo
brickeyee

"The new unit is rated at 10.8 KW and requires a 50A circuit."

If the installation instructions say "requires a 50A circuit" you do not have a choice.

You need to run conductors large enough for a 50 amp circuit protected by a 50 amp breaker.

The NEC requires manufacturer's installation instructions to be followed.
They supersede any NEC rules in this case.

The NEC still controls the wire size required, but you need a 50 amp circuit.

The NEC does allow for diversity for multiple stoves, but you only have one device.

    Bookmark   July 31, 2012 at 10:23AM
Thank you for reporting this comment. Undo
dkenny

here's something to think about..
voltage drop..while this will not cause the cooktop to draw more current like a motor. but it will reduce the heat output.this could lead to turning up the burners..hum..
maybe there is another reason besides CODE to use the proper wire size..or LARGER! but use a 50amp breaker(say 4ga copper instead of 6ga).. at 80ft at 50amp is #6 large enough? just asking I don't know the numbers off the top of my head..the NEC and other wire gauge tables exist. look them up.

other dumb question..what's the voltage? 240V or 380v?

-dkenny

    Bookmark   August 4, 2012 at 9:54PM
Thank you for reporting this comment. Undo
brickeyee

"I'm planning to replace a electric radiant heat cooktop with an induction unit. " OP

"voltage drop..while this will not cause the cooktop to draw more current like a motor. but it will reduce the heat output.this could lead to turning up the burners..hum.. "

Not necessarily true for an induction cook-top.

One of the first things most do with the the incoming power is turn into DC, to then be chopped to high frequency AC (many thousands of cycles per second) to produce the fast varying magnetic field for induction heating.

Depending on the power supply design chosen the current may increase when voltage declines.

    Bookmark   August 5, 2012 at 10:41AM
Thank you for reporting this comment. Undo
steve_fl

To further compound the matter, my panel is Federal Pacific stab-lock.

decisions... decisions...

The FIRST decision to make is to REPLACE the Federal Pacific panel!

Then start from there!

    Bookmark   August 5, 2012 at 1:31PM
Thank you for reporting this comment. Undo
ionized_gw

Grouped of induction hobs are typically are not capable of putting out equal to the additive total power of the hobs. If you turn then all on to their highest setting, the power will be chopped to some or all of them.

Just an example to make it clear. If you want to boil a large volume of water in two pots on a 4-hob cooktop, you need to know which pairs of hobs are on the same power supply and choose the hobs accordingly. Typically the hobs are paired on two power supplies. If you choose two on the same supply, you might only get 70-80% of the rated power. Probably, it will be in the manual for the appliance.

If your power supply to the cooktop is not optimal, you may get less than you can from the appliance. Few people will notice any difference, but if you are a heavy-duty cook, you might.

    Bookmark   August 5, 2012 at 8:22PM
Thank you for reporting this comment. Undo
brickeyee

Get rid of the F-P panel.

While old ones did not have problems, as the brand name was bought and sold defective breakers ended up being made and installed.

The worst offenders are 240 V double pole breakers that fail to open, or only open one side in an overload.

The overall connection of the individual breakers to the bus in the panel also left much to be desired, especially for heavy loads.

If the manufacturer's installation instructions require a circuit size, you do not get to adjust that downward based on the nameplate load of the equipment.

The electric code requires you to follow the manufacturer's instructions.

    Bookmark   August 6, 2012 at 11:36AM
Thank you for reporting this comment. Undo
dkenny

"voltage drop..while this will not cause the cooktop to draw more current like a motor. but it will reduce the heat output.this could lead to turning up the burners..hum.. "

Not necessarily true for an induction cook-top.

um..yes..its true..
the cooktop controls the strength of the magnetic field..it doesn't output more if 2 pans are placed on the same burner. the equivalent of loading a motor for no-load to full load..at least that's my thinking..

-dkenny

    Bookmark   August 6, 2012 at 9:34PM
Thank you for reporting this comment. Undo
brickeyee

"um..yes..its true.. "

It depends on how the DC supplies in the unit are designed.

MANY DC supply designs will pull more current under low voltage condition to meet their output load.

And you are wrong about many motors.

Universal motors (the ones with brushes) will just slow down, and voltage control can be used to adjust their speed.

Newer stepper motors have a DC supply and may not speed control with voltage unless designed that way.

Induction motors will draw increased current to meet the load they are driving under low suplly voltage conditions.

This can lead to overheating of the stator windings and the motor shutting down from overheat.

A lightly loaded induction motor (single or even 3-phase) CAN have the voltage trimmed back until the current starts to rise to save power.

It is a risky thing since if the motor load increases the motor will pull more current until the voltage is adjusted back up.

    Bookmark   August 7, 2012 at 10:57AM
Sign Up to comment
More Discussions
ARGH! no boxes
Went over to my daughter's house to help them change...
Ron Natalie
Looking for Ideas For Lighting at base of 300' long driveway
Sorry for the "picture through the screen"...
dixieman
Multiple Fluorescent Ballasts in one light fixture
Hello GardenWeb. I'm not new here, but couldn't log...
MikeM21
Wiring Ceiling fan
I have a new ceiling fan with a light. The fan has...
jjp2121
Too much load for circuit?
I have 200 amp service to the main panel (which has...
zver11
© 2015 Houzz Inc. Houzz® The new way to design your home™