[willc86]

Hey guys just been doing more and more research - so one thing I am a little confused about is, it is recommended for a single circuit of 15 amps with a 70% load of that circuit would be 1260watts

120 volts x 15 amps = 1800 watts x 70 % = 1260 watts

now, how is this possible? say you have lighting, a computer, printer, fan, chargers for phones all in that one circuit. So you are syaing, if I were to hook up dyson vacuum with about 1200 watts, this will exceed the recommendations? if thats the case, then hundereds of homes are exceeding this?

Most toasters and small ovens are already up to 1500 watts and they blog in to a normal 12v outlet.

would this be a concern?

Example would be, im pretty sure most kitchen lightings and outlets are on the same circuit. So we add light, phone charger, microwave and oven - thats over 3000 watts in a single circuit... See where I am getting at?

So, was wondering if you guys can educate me on this

 

[Oso954]

it is recommended for a single circuit of 15 amps with a 70% load of that circuit would be 1260watts

I am not sure where you found that recommendation.
But as a general response, nothing happens if you exceed 70%. You can even exceed 15 amps (1800w) for a short period of time. When the breaker trips is based upon how much you exceed the amp rating and for how long. The more you exceed it, the quicker it trips.

Example would be, im pretty sure most kitchen lightings and outlets are on the same circuit.

That might depend on where you live. IIRC, the requirement to provide two 20 amp circuits for counter top receptacles (aka SABCs) and prohibiting lighting on them was NEC 1959.
In my area, a lot of the housing built prior to the implementation of that code have had the kitchen remodeled once (or more)since then. If they did electrical work as part of the remodel, the electrical should have been upgraded to whatever code was in effect at the time.

 

[dmxtothemax]

Most places where your likely to come across large loads
such as heaters, hair dryers, etc etc
then you will usually have 20A circuits.
places like laundry, kitchen, bathrooms.
Other circuits that don't have large loads
can usually get by with 15A.

The 70% thing is not always manditory,
Rather it is industry best practice.

:vs_cool:

 

[willc86]

ahh thanks!! I am just a bit concerned, say my wife uses this high end hair blower, which is about 1500 watts. In that same circuit, I probably have lighting, a computer, and perhaps use my vacuum (dyson) while her doing her hair. So, we are talking about almost 2000 - 2500 watts in this single 15 amp circuit.

Should I be concerned?

 

[willc86]

forgot to add in also - would it be wise to hire an electrician to add a 20AMP in the garage if ill be using table saws, miter saw, computers connected? maybe peaking 2000 3000 watt? I have 1 outlet being connected to a 15 amp - but its just 1 outlet. i can take out 2 or 3 more out of that circuit

 

[AllanJ]

There is no way for the home builder contractor to know how much power you will be using in any given room at any given time.

You need to be disciplined (and knowledgeable about which receptacles are on which branch circuits) to not plug in the vacuum cleaner on the same circuit where, say, a small floor standing heater or a home theater with high powered sound system was in use.

Any one tool with a "regular" plug will run on a 15 amp circuit although in some cases no other things can be plugged in and turned on. A 20 amp tool will have a plug with a slightly different prong arrangement for which a 20 amp circuit and also a 20 amp receptacle is needed. (Thirty amp tools and 240 volt tools have yet different plug prong arrangements.)

The suggestions made by various books on wiring will cut down on the chances that any given branch circuit might be overloaded.

 

[Know A Little]

First a 20 amp molded case circuit breaker can carry 300% of it's rating (60 amps) for 15-60 seconds depending on the manufacture.


Second if I put every receptacle in a house on one 15 amp circuit breaker and then install a single 20 amp circuit breaker the home owner sure as heck will overload the 20 amp circuit breaker.

One cannot tell what anyone is going to utilize in their house. BUT the NEC has determined with the modern code what works for the typically home owner, and for the most part it works.

The problem is when home owners over think it.

 

[Oso954]

A couple of suggestions.
First, why don't you map the 120 volt circuits for your house? Turn a breaker off. You can test lights by flipping the switch. Receptacles can be tested with a 5 buck receptacle tester, a plug in radio, a lamp, or a clamp on utility light. Plug it in, if you have power it's not on that breaker, if it is dead it is.
I draw a floor plan sketch and mark the light switch and receptacle locations, labeling them by breaker number. Others might prefer use a list format.
It will help you figure out what is really on what circuit

Learn to convert amps to watts. You keep throwing out phone chargers. My cordless phone chargers are 350 mA at 6 volts or 2.1 watts. So, while they might draw a hair more at 120v, I don't worry about 2-3 watts.

Same with smart phones. iPhones are 1amp at 5v or 5 watts. Again, are you worried about 5-6watts.

If you don't like the math approach, consider buying a Kill-a-watt meter. You plug it in, then plug what ever item in you want to check into it. It tells you immediately what the power draw is in watts. You can also plug in a machine that runs intermittently, and detireman how many kWh it uses per day,week, etc. what is the standby draw of my tv,computer,etc versus power when operating, and what is the total power usage in a given period.

Computers, you threw that one at use several times. Is someone really operating a computer in the house that is on the same circuit as the miter saw in the garage ?

 

[dmxtothemax]

forgot to add in also - would it be wise to hire an electrician to add a 20AMP in the garage if ill be using table saws, miter saw, computers connected? maybe peaking 2000 3000 watt? I have 1 outlet being connected to a 15 amp - but its just 1 outlet. i can take out 2 or 3 more out of that circuit

I would consider putting in a dedicated 20A circuit for the hair dryer ?
Ditto for the garage, instal dedicated circuits as most power tools
can pull high currents.

Short term, you can probably get away with pulling 20A thru a 15A circuit
But long term it is NOT a good thing.

:glasses:

 

[Oso954]

Rather than a 20 amp circuit for the hair dryer, I would suggest a dedicated 20 amp circuit for each bathroom. That is unless she has a dedicated spot (other than in one of the bathrooms) where she does her hair.

Bringing your house up to, or closer to, current code should give you reliability for all the issues that you are worried about. And they add value to the house. Adding dedicated circuits in unusual places don't add value.

How many times have you actually tripped a breaker ?