Tandem Breakers

[Chuck B]

I have a 200-amp Square D QO panel in my cottage and wonder if 15 and 20 amp tandem breakers are usually acceptable relative to the IRC code. I'm in Michigan.
Wiring cottage kitchen and wondered if following circuit plans are correct in terms of correct amperage and whether each item needs to be on a dedicated circuit per my preliminary plans. Please also suggest GFCI protection if advisable on circuits where I have not indicated a GFCI:

DISHWASHER: Dedicated 15-amp
DISPOSAL: Dedicated 15-amp
RECEPTACLES: 20-amp GFCI protected. Two separate circuits.
OVER RANGE MICROWAVE: Dedicated 20-amp.
30" ELECTRIC SLIDE IN RANGE: 50-amp, 4-wire, dedicated line. 8-gauge wire.
LIGHTING: Over sink (1 recessed), ceiling (4 recessed), Celing Fan (1), Under cabinet accent lighting, all on (1) 15-amp dedicated circuit. Need 2 circuits?
Any light switches controlling above sink recessed light, and 3-way switch for 4 ceiling cans in close proximity to sink need GFCI?
Thanks guys.

 

[ActionDave]

QO panel will have slots in the bar where the back of the breaker clips on if it is meant to accept tandems. There will also be something in the paperwork glued on the inside of the panel but I always find it a pain in the neck to read.

Your GFCI's are good unless you are are NEC 2014 code. GFCI is not required for lights switches.

 

[Sponsor]

 

[Chuck B]

QO panel will have slots in the bar where the back of the breaker clips on if it is meant to accept tandems. There will also be something in the paperwork glued on the inside of the panel but I always find it a pain in the neck to read.

Your GFCI's are good unless you are are NEC 2014 code. GFCI is not required for lights switches.

Thanks Dave!

 

[JerryR]

Is the 50a 4-wire OK with #8 or should it be #6?

 

[Onokai]

50 amp is #6
40 amp #8
30 amp#10
20 amp #12
15 amp#14

NFPA 70 of the National Electrical Code, #8 TW copper is good for 40 amps, and #6 TW copper is good for 50 amps. You could get away with using #8, and probably not have any issues in the near future. The problem is that TW wire, which is what you would be using in a house, is rated for 75*c,; over time the wire will be heated and cooled many times, and so the insulation will become brittle and crack and fall off. #8 will become hotter than #6 under the same load. So 20 years from now you might have a fire because you chose #8 today.
The wire coating matters and if if this is all Greek to you use #6 and be safe.
Mark

 

[JerryR]

Is the 50a 4-wire OK with #8 or should it be #6?

Reason I asked this question is I recently redid our kitchen. It had #8 NM cable with 50 amp range circuit. I had electrician run a new #6 4-wire NM cable. He told me that some inspectors would allow #8 but I was not comfortable with that. Looking at the charts #6 NM should ge good for 55 amps and #8 for 40 amps.

 

[Jadnashua]

A stove that calls for a 50A breaker may only pull 40A to allow for the 80% rule (not sure it applies to a stove, but personally, I think it should). A breaker is designed to protect the wiring, not the device(s) connected to it, so regardless, you need the 6g wire if you have a 50A breaker. Now, in places like England, the plug has a fuse in it that is designed to protect the device. Some devices sold here may have internal overcurrent protection, but it is not required.