That is fine.

 

i don't see anything wrong with what you propose,

that pump would probably be fine on a 15A dedicated circuit, but no harm in installing 20A if thats what your heart desires

 

Can you shine any light on what it means, though? From what little I understand about breakers, they prevent surges because a surge of power can overwhelm wiring and circuitry to the point that sparks and heat can create fires and or damage utilities, equipment, systems, etc... Am I right so far?

What I don't understand is the ratings and how people like you and my electrician come up with their appropriate breaker ratings. Why the 20A? Or the 15A? If the sump pump is rated at 10.4A, are the 15A and 20A suggestions due to an approximate idea of what those breaker ranges would get tripped at in the event of a surge? Because nobody would know how much a surge of amps would be in the event something like that happens, right? But it would imply then that the electrician is trying to reduce the margin of surge amount to be as close to the intended amp usage amount of the breaker as possible, which would make sense then... So if the pump is rated at 10.4, it would make more sense to use the 15A breaker as that would be closer to the "trip amount." Am I right in my thinking? I mean, I'll probably just stick with the 20A for the sake of consistency and having a wee bit more power to the plugs if ever needed, but I'm just trying to wrap my head around what this all means.

 

Breakers trip when too much current flows. They are not going to prevent surges.

Breakers are sized for the loads they need to serve. Your pump should be fine on either a 15 or 20 amp circuit. Regular duplex receptacles cannot be on circuits larger than 20 amps.

The receptacle should have gfi protection.

 

Thanks, Jim. That clears it up in my mind. You're absolutely right: I shouldn't have been looking at it from a perspective of something like a "surge" but more like how much water can go through this pipe (thinking of it like it's a pipe sized for a specific amount of water or volume [amount] of electricity).

 

Breakers are there to protect the wiring, NOT THE LOAD.
Residential breakers operate on heat/amps. The more you draw the warmer the breaker gets until it trips. It is possible for a breaker to draw more than the rated current for minutes some times hours, if the increase of amps is slow enough. I used to test breakers as a part of my job with an electrical MFG.

Installing an 20 amp circuit for a 10 amp pump is fine if you have the parts but a 15 amp breaker on the 12 wire would be a lot smarter. We are not talking about long distances or large loads.
Most sump pumps are ignored until they fail. Just like condensation pumps on HVAC.


Surges and spikes in the voltage service to your home are way to fast for the residential breaker to see it. Surges and spikes are handled by metal oxide varistors which are tested for a one time use. I change my panel protector ever other year. Right after the monsoons that we have. We are talking micro/nano seconds in speed

 

Residential breakers operate on heat/amps.

Just a reminder that a breaker not only trips on overcurrent but also on short circuit and ground fault. Short circuit is the unintended contact between the white (neutral) and the hot conductor, or in the case of 240v it would be the unintended contact between two hot conductors

A ground fault is an unintended connection between hot and the ground or the equipment. grounding conductor

While I was writing the explanation below C'est Moi beat me to posting. The extended explanation below will explain how the breaker detects the 2 different conditions.

Most residential circuit breakers are dual trip in that they have a thermal element and also magnetic element. The thermal element detects overloads were the temperature caused by that current flow through that size wire is higher than what the insulation can withstand without damage. When talking about motor loads the damage which can be caused by a long lasting overcurrent that continues beyond a short time is the dominant concern. That time temperature curve which shows at what temperature over what time will trip the thermal element of the breaker varies from one manufacturer to another. The magnetic element of the breaker is designed to open the circuit very quickly if a fault or short circuit occurs and the current flowing in the wire rises to a very high value relative to the breakers rating in a very short time. If the cord or cable supplying the pump were damaged far too much current will flow through the wire in less than a second. If the motor bearings are wearing out it would take gradually more current to turn the rotor against the physical load of the increased friction in the baring. When the current needed to turn the rotor gets beyond what the wire insulation can safely be subjected to a bimetallic strip in thermal element heats up and, because of the difference in how much each of those metals expands the strip bends when the strip gets hot enough it will bend to the place were it can unlatch the trip spring and open the breaker. A relatively high over current is needed to trip the magnetic element. A smaller overcurrent will cause the thermal element to trip but it takes a longer time for it to get hot enough that it will trip the breaker.

Tom Horne

 

Lots of great info about all this. Thanks, guys.

The piece about heat and how that's how breakers get tripped is really interesting and puts a lot into a functional perspective. But I think I'm going to stick with the 20A breaker because while I have the pump plugged into the respective receptacle, it would be nice to have a little more buffer to accommodate a light or something for whenever I need to hook something up to the same receptacle (just something minor if and when it might be needed) because the receptacle I'm planning to use is just like the other one I used last time: it can accommodate 2 plugs. I figure it would be akin to having something and not needing it vs. needing it and not having it...

 

Just a reminder that a breaker not only trips on overcurrent but also on short circuit and ground fault. Short circuit is the unintended contact between the white (neutral) and the hot conductor, or in the case of 240v it would be the unintended contact between two hot conductors

A ground fault is an unintended connection between hot and the ground or the equipment. grounding conductor

 

I wish some of this could've been explained during an electronics course I once took back during undergrad... I think they overcomplicated a lot of what was discussed, but in the professor's defense, it was more of an electronics course and not something more inline to home wiring (one being mostly about computer circuits and the other knowing which lines not to cross--ha).

 

Let's make it complicated. Most small motors have built in thermal protection. If the motor runs hot- not overcurrent of the circuit but lets say the motor is drawing 12 amps instead of 10.4 amps as stated. The thermal protect at some point will trip and shut the motor down.

If the motor has TP then the circuit breaker in this case can actually be 250% higher than the actual motor amp. This means you could have a 25 or 30 amp breaker on a #12 wire. The breaker in this case is there for short circuit or ground fault. The overloads in the motor will protect the motor and wiring from currents a bit higher than the motor amps.

Understand this is an unusual case and it involves motors and you cannot, in general, install a 30 amp breaker on a #12 wire. I just thought I would mess with your brain.

 

Let's make it complicated.

Absolutely not! Ha! I've been at my wits end with this little home trying to make its basement as dry as possible (which isn't easy to do when it's built from back in the 20s or 30s using vitrified clay block). It's been a quest of mine that's involved replacing 2 entire sides of the basement that cost no less than $36k, so there's no way I want to drive myself over any sanity ledges anytime soon as I'm almost bankrupt on sanity as it is.

 

You are using a general purpose receptacle (socket). It's not dedicated, you already said you may plug other loads in there. That simplifies things. You must follow the general-purpose receptacle rules in Article 210 (and see also 240.4(D)(1-7) which also ties your hands on the wire size).

• On a 15A breaker, #14 or larger wire and 15A receptacles only.
• On a 20A breaker, #12 or larger wire and 15A* or 20A receptacles allowed only.
• On a 30A breaker, #10 or larger and 30A receptacles ONLY

And that's the end of the matter.


* 15A sockets allowed under an exception, if there are more than 1 total socket in the circuit. A garden-variety receptacle has 2 sockets, so auto-win. Result: you can use common socket for almost everything.

 

And that's the end of the matter.

A back fed circuit is much like a ring main circuit that would be installed in the United Kingdom. The difference is that it occurs by accident instead of as a deliberately looped conductor. It is true that both source breakers must be on the same phase but that can happen quite easily and can be the devils personal prank to unravel. You have to find the cross connect and open it in order to restore control of the circuit to it's original single pole breaker and to bring the available amperage of the conductor down to it's US National Electric Code imposed limitation. I don't see it as hijacking the thread because it is related to the work under discussion. That it is not in the main thrust of the subject does not make it somehow evil.

--
Tom Horne

 

Don't worry, guys: I plan on being safe with all of this... But if I do die, just know that I went out in a blaze of glory.

Thanks again.