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How can I check that a house cct can deliver 15 amps

3K views 26 replies 9 participants last post by  oleguy74 
#1 ·
Hi,

I want to know that a house cct can continuously deliver 15 amps (or, say, some derated amount like 12 amps) without tripping the breaker.

Is there some kind of loading device made where I can control the the number of amps that it will load the outlet with?

Failing that, what household appliance could I plug in to test it? I guess a microwave is a good start, at about 8 amps.

Thanks for any suggestions!

Peter
 
#4 ·
What does the Canadian Electric Code (or even NEC for that matter - I'm guessing they're similarly derated) say about 15A house cct derating?

Canadian Tire's highest-wattage heater is 1500W. Is there a 15% derating factor for continuous use?

Is 1800W draw for short periods allowable per spec?
 
#6 ·
You have a washer tripping a breaker, then there is more than just the wash machine or laundry convenience outlets on that circuit. How many circuits are in the home, and what is the total load on each circuit. That you are going to have to do, to determine a load calculation.

De-rating has nothing to do with your problem, your problem is typical of older homes, and wiring that is done by someone that does not know what they are doing. A circuit does not deliver amps, it delivers voltage. The amps is the "load" on the circuit.
 
#7 ·
You have a washer tripping a breaker, then there is more than just the wash machine or laundry convenience outlets on that circuit. How many circuits are in the home, and what is the total load on each circuit. That you are going to have to do, to determine a load calculation.

De-rating has nothing to do with your problem, your problem is typical of older homes, and wiring that is done by someone that does not know what they are doing.
I mapped the house ccts, I put the washer on a cct which I am sure is dedicated (I mapped out all the house ccts) and it still pops. The breaker panel is new. The front-load washer always trips upon entering the spin cycle. Previously, an old top-load washer worked fine on the same cct. I would have guessed that a front-load spin cycle uses less power, but maybe not since it is high rpm.

The home uses 18 ccts.
 
#8 ·
You do not need to map the circuits, you need to do a load calculation on the circuits. That means sitting down with pencil and paper, adding everything that connects to that circuit. If the breaker is tripping when something runs, that means that there is either something wrong with the wiring, or there is too much load on the circuit.

You have some homework to do. You also need to get a Clamp-On Ammeter, to measure each circuit, to see what the total load is.

How old is this house, how many amps is the breaker panel, can you post a picture of the breaker panel, meter & drop.
 
#9 ·
By mapping, I meant that I know what loads are on each cct, but I have not measured the individual loads or the aggregate load at the panel.

I have a Kill-A-Watt (http://en.wikipedia.org/wiki/Kill_A_Watt) which I hope can accurately measure loads that are plugged into a receptacle which should be the case for the ccts in question.

House is 50-60 years old (no aluminum), 100A panel. Don't have pics. What is the "drop"?
 
#10 ·
Ditch the Kill-a-watt, and invest into a Ted 5000. You can see more effectively the particular loads, and over time, it gets better with how it reads. I use it in conjunction with the Plotwatt.com & myenersave.com websites.

The drop is from the power company to the meter. Depending on what the previous owners have done with the wiring, you may find out that there could be some questionable junctions, or additions to circuits. Only way without investing in a whole-house meter like a ted, you can use a clamp-on meter placed on each circuit. As you run stuff, it will tell you the amp load on it. Also keep in mind, depending on the panel you have, you could just have also some bad breakers.

Post a picture of the panel, meter and entrance drop, as requested before, along with model & manufacturer of the power panel.
 
#12 ·
Thanks Greg, the TED 5000 looks pretty cool.

Anyways for now I bought a 1500 W space heater, plugged it in, verified it was actually drawing 1500 W, and the breaker didn't trip. I'd be surprised if the washer is using > 12.5A for spin.

I checked the washer manual, all it says it that it needs 15A standard cct. I haven't had a chance to check the name plate yet.
 
#13 ·
I think this might be getting a little overcomplicated. You say the washer trips the breaker when it starts the spin cycle? Does it do it instantly when the spin cycle tries to start, or after a while of spinning? Either way, my money's on a fault in the washing machine.
 
#22 ·
Yes my $$'s been on the washer the whole time. But it got me thinking of what would be the best way to ensure a cct can handle max load without trial-and-error. I think I've got some good answers to that now.

Anyways, new washer's coming on Tue ...
If you can get your hands on a clamp on meter would tell you just how much is being pulled at any given time. You do need to build a break out box so you can test the individual conductors. :)
 
#15 ·
Yes, a washer has a peak amount of amps, when the pump cycles, and the motor changes the transmission direction or speed for spin. My washer spec. plate states 10 amps. On a dedicated 15amp circuit, with just a overhead light, I am fine. If you are into upgrading the wiring to #12 to make the outlet just for the wash machine a 20 amp circuit, you can do that. Keep in mind, that any convenience outlets in the laundry room can also feed off of that 20 amp circuit. You can have though a second circuit in that space if you wish for other use.

I have for my basement, a dedicated for the wash machine, a dedicated for our bar-fridge and upright freezer, and a dedicated for the outlet on the side of our panel. I went that way, so that I knew if there was any chance of needing to use either the wash outlet or fridge/freezer outlet for something like a sewer auger down there, I would have no problems. All of my dedicated outlets are 15 amp for down there, and have never had any problems. Of course, I also have a basement that is wide open, so it makes it easy to change wiring and see what has been done down there for next person.
 
#17 ·
oleguy74, You may want to re-read that section again. There is actually a loop-hole in that section for utility spaces, that are used as laundry rooms. In my case, my whole basement is a utility space and is not considered a dedicated laundry room for where the washer sits, because of the dual/multi-use of that space.
 
#21 · (Edited)
Oleguy, you need to go back and read everything pertaining to section 210, specifically 210.23 There is more than one subsection that pertains to a laundry space. Yes, the machines can only plug into one outlet, but there are exceptions to what can also be done. And yes, you can use them as a convenience for an iron, and for a utility light. But what the OP wants to do, by plugging in a heater, they need to wire a Small Appliance Branch Circuit into that space. Whether it and the outlet for the washer/dryer is part of a multi-wire branch circuit, like I said before, there is a loop-hole in section 210, that you can wire a convenience circuit into the space.

In my case, my whole basement is a utility space, which means that the washer is not in a dedicated room, but I have a dedicated outlet for it. And trust me, the circuit is code, along with every other circuit in my house. When I leave, what the next person plugs into them is their business, but I know that how they are wired is by the NEC.

The only thing about the code, is that it does not stop a person from what they can and can not plug into the circuit, as long as they remember not to overload it, the circuit is still in code. If you overload the circuit, the OPCD needs to operate within manufacturer spec's, and needs to be sized properly for the circuit. Now as for what stops a person from swapping out a lower amp breaker to a higher rated amp breaker, is how soon the wiring melts from the overload. I have also seen 400 amp circuits melt bus bars, and the breaker looked like someone shot a 12ga through it.

I have seen properly sized breakers for the proper gauge wire melt & the circuit catch on fire. Why, because of the inrush of current caused by a surge, and the breaker will stay open, until it either gets too hot, or the circuit completely shorts, then it will close. That in case, is what a space heater will do on a 15 amp circuit. They should only be operated on 20 amp circuits, protected by a AFCI breaker, and with working smoke detectors in the home.
 
#20 ·
Have people fogotten about clamp on amp probes?

Get a clamp on amp probe....clamp it around the wire coming out of the breaker feeding the appliance....measure the current....if it's more than 15a....the problem is downline....less than 15a and the breaker is tripping? Then the breaker is bad.
 
#23 · (Edited)
you still miss the point.per code,the laundry ckt is a dedicated ckt.and shall have no other outlets.call your basement what you want but you still need a laundry ckt by it's self.no lites or convienance out lets.get off this loop hole stuff.ckt overload goes with all ckts.again 210.11(c)(2)is all i am talking aboutIT SAY'S THE CKT SHALL HAVE NO OTHER OUTLETS.BY THE WAY,PER YOUR LAST PARAGRAPH,breakers open on a fault.not close.
 
#24 ·
Yes it is a dedicated circuit, and once it is wired, there is nothing to stop a resident from using it how they want. The code covers the concept, and the use. Again, because of interpretation everyone looks at that particular use a different way, and you really need tolook at the whole big picture of what they are saying.

Again, there is more than one sub-section that covers the laundry room, than just 210.11(c). But you are more than welcome to keep your mind set on just that one sub-section and not look further.
 
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