Correct fuses for kitchen range and 50A circuit

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Hey everybody.

I was inspecting the fuses for my kitchen range, and I'm not sure about whether they are the correct fuses.

One is marked "BUSS NON 60 amp ONE-TIME FUSE". The other is "BUSS 35 AMP no. 25035 ONE-TIME FUSE"

I expected them to both be 50 amps, but I don't really know what to expect.

The house is about 50 years old. The range has a 10-50P plug, plugged into the 10-50R outlet.

Is this the right setup for using general 50A 250V power from this outlet, not just for a range?

Thanks.
 

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Norcal01

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Depends on the size of the conductors used to feed the range receptacle, if 8 AWG NM cable then should be 40A fuses, if 6 AWG NM, then 50A fuses, but the 35A fuse is not unsafe, just the smallest fuse that fits a 60A fuse clip, undersizing fuses just can lead to clearing a fuse when one least expects it.
 
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Thanks for giving me the idea to get in and measure the wires.

For now, here is a slightly different question: is there a reason that someone who knows what they are doing would choose these particular fuses, 35A and 60A, for a 50A circuit?

I find that my range is rated 10.5 kW @ 120/240V.
 

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If you REALLY used 10+ kw, the 35 amp one would have blown.
And if you add the power ratings of the individual components, it comes to almost 13,000 W: 2x1500 + 2x2000 + 2585 + 3410. So IDK where the 10.5 kW number comes from.

IDK that I've ever had every thing heating at once.
 

Jadnashua

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Code doesn't care about the actual device a the end of the wires...it specifies the protection device for the protection of the wiring in the wall that you may not be able to see, thus, the comment on the wire. It's perfectly okay from a safety viewpoint to use a fuse (or CB) that is smaller than the wiring would allow, but it is a definite violation to put a larger protection device on a circuit than the wiring can support.

You might think of it this way...you can plug your cellphone charger into the wall which might draw 20W or a space heater that might draw 1500W...as long as the wiring in the wall is correct, you won't burn down the house from the wiring fault, but the device plugged in could have its own issues and the fuse or CB may never trip or blow.

Some devices will have local, internal protection, and some will have installation instructions saying to use a dedicated circuit sized at X. In those cases, the fuses and or CB should be what the device's installation instructions call for.
 
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Thanks, guys. I'm with you so far.

I looked at the markings on the cable and measured the strands, and found the cable to be AWG 8 Aluminum, around 70 feet long. So that should handle about 40 amps?

And I have this question. If the two hot lines have two different-size fuses (in this case 35 and 60), does that give the same protection as when both fuses are of the lower value (in this case 35)?

I guess the answer must be 'no', for otherwise why would there be a fuse for each line?

But if the answer is 'yes', then maybe, upon an overload, one could avoid wasting a fuse, as only the lower-valued fuse would open.
 

Jadnashua

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Let's get back to basics...on a 120vac circuit in the USA, all of the power that goes out on the hot lead returns on the neutral (complete circuit).

On a 240vac circuit, all of the power that goes out on one of the hot leads must come back on the other hot lead (assuming there is no neutral at the device). But, if some power at the device uses 120vac, while power will still go out on (at least one of the) 120vac lines, some of it MIGHT come back on the neutral verses the other 120vac circuit (120+120 is where you get the 240vac that powers the heating elements - one or the other hot to neutral=120vac). In that case, the actual current load on one hot might not equal that on the other.

But, the fuse or circuit breaker cannot be larger than the wire will support. It would be unusual in a stovetop for a 120vac load to be very big (light, maybe some electronic controls, maybe a clock, etc.). The primary power users are the heating elements, and those are all 240vac...requiring all of the current to go from one hot to the other. As a result, both hot leads would need the same capacity for worst case scenarios.

Having a 60A fuse on one lead and 35A on the other would limit the maximum 240vac circuit to 35A since all power that went out on one hot MUST return on the other except as noted if there are any 120vac loads.
 
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Let's get back to basics...
Thanks. I followed that pretty well. Meantime I studied a little about 3-phase power and understood that for the first time, and looked at the power lines in the neighborhood, and learned how 250V is delivered from the center tap transformers, and why 250V is called one-phase power even though it has two hot wires half-a-cycle out of phase.
 
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