Calculating breaker size for an electric range.

Where did he say he was going to mix wire gauges? He said that he already had #6 and didn't want to buy #8. Did some posts in this thread not show up?

It's going to be 6AWG from the panel to the plug. The breaker will be labeled RANGE.

He didn't, just drawing on experiences from my bad luck(at times), I think I have enough wire and find that at the end I'm short a few feet. Resulting in me having to run out and get more.

So applying that to his situation, it can arise that he starts with 6# for his 40amp branch, and could end up finishing up with 8# if he runs out and has to buy more, and want to save a buck.

So, just a hypathetical situation.

tom

I never do that. I measure the run and the wire. If there isn't enough I buy what I need before I start working. On the other hand, I had a 100 foot fish tape I added footage markings to so i could see how much wire I needed for hidden conduits. partial reels were run through the wire measuring machine and labeled so i could grab the closest to my needs and minimize waste. Scrap was usually just a few feet from a 1000 foot spool of wire. I did commercial sound work for three school boards, as well as their specialty work. If I ran into electrical problems I fixed them and attached a note to the work order so their electricians could inspect the work, or in a few cases have the proper agency inspect the work. I never failed an inspection.

The nastiest thing I found in a school was a dead PA system. The wire at the breaker was black, but it was pink at the outlet. Neutral was white at the panel and was yellow at the outlet. I pulled out the wires to find that they were spliced inside the conduit, and only the line had been taped. I would like to have got my hands on the idiot that pulled that stunt.

So, in other words, there's no problem with using the larger conductor. I have more than enough to run the circuit.

R. Tarin

As long as it fits the lugs and isn't too stiff to bend in the boxes.

Just wondering, sure I understand you don't want to buy smaller wire, but why not just buy the bigger breaker? I mean you are taking the time to run the larger cable, why not have the setup ready for a larger range later in place?

Hey, I know i'm prying, but this is how I learn by asking questions.

tom

I'm not the one running the wire, but you replied to my post.

As far as a larger breaker, an oversize breaker is almost as bad as having no breaker. You have to match it to the rated load. The advantage of a larger gauge wire is reduced resistance which lowers the losses.

I was always told that the distribution overcurrent protection devices (fuses and/or circuit breakers) were intended to protect the cable and other distribution components (switches, recepticles, etc.), and that if a powered device needed protection it should be marked "operate only from circuits with xx-amp overcurrent protection" or have its own input fuse/circuit breaker.

I just went through getting a building permit for a church to replace a single 3-phase kitchen range with two single-phase ranges. Not simple because the existing 120/208V was connected directly to the main 1000-amp panel with a fused disconnect and the new ranges were listed for use with 50-amp circuit breakers (marked on a label on the ranges). The main panel in this case had available fault current at 208V of 42,000 AIC. With an AIC this high one has to either use overcurrent devices rated to interrupt the 42,000AIC (expensive either as high rated breakers or a combination of fuse and circuit breaker with a published 'series' rating of at least 42,000AIC) or have a professional engineer submit calculations based on wire size, length, etc, showing that the impedance of the wire to the subpanel reduces the available fault current to an acceptable value while providing the current for the designated load.

The lesson is that selection of the circuit breaker for a range is not always simple. All new ranges in the USA and Canada will have a clear label specifying the service to be provided to the range. For homes with 120/240 200A utility service, the more standard 10,000AIC rated circuit breakers should be suitable. If you do not know enough to qualify as an electrician, get help from a licensed electrician.

Bill Kaszeta Photovoltaic Resources Int'l Tempe Arizona USA snipped-for-privacy@pvri-removethis.biz

I haven't worked with interrupting currents that high, but I have worked with 7000 VDC high current power wiring in transmitters. 30 Amp shielded 10 KV cable with special termination at the three single phase step-up transformers to the rectifier cabinet in a RCA TTU-25B TV transmitter.

If you read all of my reply you will have seen that I told him to use the breaker rated for the range.

I worked as a commercial electrician for a while and have built a commercial UHF TV station from the ground up.

Sometimes you run a heavier wire so the stove can be replaced with a larger commercial unit without running new wire by simply changing the breaker to match the new stove and oven and oven. Its just another form of "futures", like running a couple extra pieces of conduit into the ceiling when a new building is built.

I've also run into the situation where an electric stove and oven were replaced with a gas unit that needed a 20 amp circuit for the electric pilot lights and convenience outlet so the 40 amp dual circuit breaker was replaced with a single 20 amp and the outlet was changed to a standard duplex outlet so they customer could change back to the electric stove and oven if gas became unavailable again.

No, I don't have a journeyman's license, but I'm disabled and no longer able to do the work. I always had a recent copy of the NEC book in my truck and I never failed a single inspection.