Current , AWG question - Page 1
Forum section: electronics / beginners

author: bootloader9800
author_rank: Contributor
timestamp: February 18, 2021, 01:36:52 pm
content: Hi everyone!I was reading on the Home Depot website that,"A 20-amp circuit, protected by a 20-amp breaker or fuse, must be served by 12-gauge or 10-gauge wire.".I also have a RC motor that is a BLDC motor that draws around 30 Amps but has only a19AWGwire.Why is my motor performing properly without issues even though I am not using a 12 gauge or 10 gauge wire (as recommended by home depot) ? Shouldn't my motor wires burn out?A picture of my motor is below.Thank you

author: Vovk_Z
author_rank: Super Contributor
timestamp: February 18, 2021, 02:03:05 pm
content: That can be ok.There is a difference (different requirements) between stationary wiring and flexible short connecting wire. It may have a different type of isolation, a more heat-resistant one.Anyway, it is not home mains wiring, but it is just a part, so the manufacturer can make it as he wants. Possibly the manufacturer wants it works only several hours - we can't blame it (if it doesn't have those Safety Certificate markings, as on X2 caps, for example). We may choose to buy an item or not.

author: CaptDon
author_rank: Super Contributor
timestamp: February 18, 2021, 02:24:35 pm
content: They probably used the same gauge wire that the motor is wound with. There is some loss with the thinner wire and if you race competitively the winners probably replaced the wire with heavier and did away with those banana plugs!!! House wiring is far different!!!! It must survive stupid mistakes and dead shorts without even the slightest chance of a fire. It must survive 150% overloads for a minute or two until the breaker/fuse trips without danger of fire or even excess momentary heat rise. The manufacturer of your little motor/RC car really couldn't care less if it burns to the ground!!!

author: Siwastaja
author_rank: Super Contributor
timestamp: February 18, 2021, 02:29:29 pm
content: The wires hang around loose and are in the airflow of the propeller which cools them down.Look at some Chinese "LiPo" packs! They can use massively undersized wire gauges, and these wires sometimes end up inside a cramped case, not in the airflow. Their secret is they use silicone insulation, not PVC, so can take higher currents. Silicone is fine even if the wire inside runs at 150-200 degC, PVC would melt immediately. Also because they are HobbyKing stuff, they don't care if your house just burns down.House wiring must have ample safety margin because the PVC insulation degrades if subject to long-term temperature rise. It's not acceptable if your house burns down after 40 years. No one is interested in the long-term safety of the RC hobby project, it's more likely it burns down due to a shitty low-quality li-ion battery.Also 20A house fuse is guaranteed to blow up starting at 30A and even that may take tens of minutes. 20A is the nominal current allowed for the loads, the fuse is guaranteednotto blow at 20A, they are not precision devices. That's why the wire after the 20A fuse must be safe for extended periods of time at 30A.

author: Nerull
author_rank: Frequent Contributor
timestamp: February 18, 2021, 07:01:12 pm
content: Voltage drop in a wire is proportional to length, there may be hundreds of feet of wire in a house. Excessive voltage drop can damage appliances, so wires are sized to both remain under a certain temperature at their rated current and avoid excessive voltage drop. There's only a few inches of wire going to your motor and it isn't operating in an enclosed space surrounded by fiberglass insulation for years at a time.

author: TimFox
author_rank: Super Contributor
timestamp: February 18, 2021, 08:10:11 pm
content: The safety ratings for wire are based on temperature rise and insulation material, and depend on the environment (cable bundle, appliance, conduit, free air, transformer winding, etc.). The Home Depot statement is based on normal US standards for house wiring, where the conductors are in conduit or in cables that are considered to be equivalent. Those circuit breaker ratings are designed to protect the wires against overheating, and were codified by the fire-prevention authorities.