I am running wire for a standard Kenmore stove/oven and wire for a stackable washer dryer unit. Both runs are less than 50'. What amp breaker and guage wire is needed?
A "standard" cooktop only, or a single wall oven, will typically be on a 30A-120/240V circuit, requiring 10/3 cable. Keep in mind, I have seen many newer cooktop models that require a 40A circuit. It all depends on the kW rating.
A free-standing range, rated 12kW or less, can typically be wired to a 40A-120/240V circuit using 8/3cu or 6/3al cable.
A typical electric dryer, and most combined stackable units, will require a 30A-120/240V circuit using 10/3 cable.
This chart indicates that for a common household electric stove/oven at 240V, up to 30A, a 10/3 wire is proper.
If it’s a gas range maybe, simple answer is what kind of range do you have if a induction ran range you need to dearth the cable so a 10/3 Wire will work. If you see the word induction think heat so a standard Romex or Soow cable then no the 10/3 will not work because of what you are run most ranges are induction run so your 10/3 is now only a 27 amp cable but if you use a 10/4 GGC cable then yes. But you need to match it with you breaker at the the main box so if it’s a 50 amp breaker then you need 8/3 if it’s 40 amp breaker you need 6/3 and if it’s a 30 amp breaker the you 10/4 GGC or a 6/3 Soow. Then on the Range side just put a DIN breaker or DIN 2 fused block with 2 30 amp 250Vac time delay midget fuses or if it’s 40 amps then it to a 40 it’s 50 amp oven then that is what you use. The wires from the main breaker only protected the wire from melting the fuses can protect your range.
Or you can simply look a the wire temp never just assume a wire gauge is the right answer. Always look at what degree of heat it can handle. Example nickel or nickel plated copper 10/3 Soow cables at 35 amps at 80c, 40 amps 90c, 58 amp 105c, 70amps at 125c. We have the same cable but now it’s tin plated copper 55amps 150c, 60 amp 200. These rules of thumb are referring to the amperage capacity or “ampacity” of the conductor (wire) and are often correct. Sometimes, these general rules lead technicians to believe that if an appliance is rated for 50-amp breaker/fuse maximum overcurrent circuit protector (MOCP), you must use 6-gauge wire and a 50-amp circuit breaker.
It’s not that simple according to National Electrical Code (NEC) NFPA 70 for several reasons. Here are some additional factors to be considered: What is the conductor made of? Is it aluminum, copper, or something else? What is the ambient rating of the conductor (wire) and its termination (connection) points? What type of load is being controlled? What other thermal de-rating conditions exist? Are there multiple conductors in a raceway, high ambient conditions, etc.? What is the allowable voltage drop based on wire length? This is not dictated by the NEC but rather by the requirements of the connected load. When we use a rule of thumb, we are missing two main areas as it relates to the conductor.
Is the conductor aluminum or copper, and is the insulation rating 60°C (140°F) or greater?
Aluminum wire has a lower ampacity than the same gauge copper wire, meaning aluminum must be larger to accomplish the same ampacity job as copper wire. The rule-of-thumb sizes rely on the lowest allowable temperature rating of the wire; in some cases, the circuit may have a higher ampacity if the insulation on the wire and the connection endpoints are all rated at 75°C (167°F) or 90°C (194°F).
All of these ratings can be found in NEC (NFPA 70) Table 310.15(B)(16) in detail, but as an example, according to this NEC chart, a 6-gauge copper circuit rated at 90°C (194°F) has an ampacity of 75 amps while a 6-gauge aluminum conductor rated at 60°C (140°F) has an ampacity of 40 amps. Of course, there are other considerations in addition to this, but it is clear the rules of thumb we often use can get us in trouble if we aren’t aware that exceptions exist and what those exceptions are. Keep in mind that for a circuit to have a rating above 60°C (140°F), the wire as well as the breaker, disconnect lugs, and connection lugs in the equipment must all be rated at a temperature at or above the temperature rating being used. If any portion of the circuit utilizes non-metallic (NM) cabling — often known by the trade name Romex® — it must be rated at 60°C (140°F) according to article 334.80 of the NEC.