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Re: circuit breakers keep tripping

you said

The OP said he was having trouble with the "new" 50A breaker tripping so his electrician replaced it with a 40A. Which leads me to believe he saw the wire was only rated for 40A.

the electrician initially used a 50a breaker, so if the wiring was rated for 40 A, he made a serious error. If the 50a breaker was in fact the appropriate one for the wiring, then when he returned to put on a 40A breaker, he was intentionally putting on a breaker that was smaller then required, making it MORE LIKELY the oven would trip the breaker. he never told me that the wiring called for a smaller breaker, just that HE NEEDS TO BE SAFE, as opposed to he thinks I need to be safe. This leads me to think that he put on a smaller breaker just in case something should happen with the house, he does not want to be blamed. As described above, his behavior was somewhat irrational, in that he no showed 4 times, then when he finally comes, he is really angry toward me for asking him to do what he said he would do for the past 4 months!

The best solution is to hire a new electrician, as previously stated by myself and several others. Thanks again for all your thoughts.

Re: circuit breakers keep tripping
The Semi-Retired Electric wrote:

Leiko, did your electrician measure your voltage? 10Kw at 240V is 41.67A which will trip a 50A breaker over a long period of time. To pull this much power you would have to have the range really hot. A 50A breaker should not have over a 40A continuous load.

However, if you only have 208V it will only pull 36.1A. Maybe when they put in the new service they replaced a 208V transformer with a 240V.

Have you replaced any of the elements with hotter coils?

Did the electrician place an ammeter on the circuit to see if it's actually pulling 50A?

Have you looked at the label in your panel? It list the make and model numbers of acceptable breakers which may be used. Does the breaker feel hot after it trips? Can you tell what size wire (and is it copper or aluminum) is connected to the breaker? Does the range plug or receptacle get hot?

I suspect you would do well to call in a new electrician since the first one has already stood you up four times.

What sort of solar system did you install?

Good Luck from Columbiana, Alabama
Maurice Turgeon, http://thesemi-retiredelectrician.com

Maurice -- if I'm not mistaken with regards to residential electric ranges , the NEC as well as our CEC consider the calculated load is less than the total connected load listed on the model/serial rating plate.
In which case the op's rating of 10 kw would be acceptable on either a 40 or 50 amp breaker.

Re: circuit breakers keep tripping
leiko49 wrote:

I recently had a new service entry put on my house to replace an older one after I had a solar unit installed, requiring more capacity then the old service entry.

After the installation of the service entry, the circuit breakers trip regularly for the stove when I have maybe two burners on, or one burner and the oven.

Prior to the new service entry, I never had a problem breakers tripping on the stove.

My electrician is saying that my old service entry was old and not functioning properly, and now the breakers are functioning normally. He also said maybe I need a new oven (mine is only 10 years old). The breaker’s actually look used to me, but the electrician says they are new (the paint is faded, looked dented, compared with same at home depot, all of which look clean, undented, with unfaded white paint).

The specs on my oven 
10.0 kw at 120/240 volts 
7.5 kw at 120/208 volts. Its an Eaton Panel with Cutler Hammer breakers
On my service entry, it is hooked up to a 50 amp breaker, which I understand should handle the oven with every burner on.
The electrician does not seemed inclined to take responsibility for the work, saying it must be the stove, or something else with the internal circuits of the house. He no showed after making 4 appts with me to look the system over.
What thoughts do folks have about
a. whether I should cut my losses and call in a new electrician
b. expect him to fix the system for no extra charge, hold him accountable for an incomplete job
c. offer to pay him more money depending on whether he finds a problem with the internal circuitry of the home.
d. live with flipping the triggered breakers several times a week?

OK, he just (finally) came over after no showing for times over several months. He appeared quite irrate toward me, replaced the breaker, and on his way out the door stated, "o by the way, I put in a 40A breaker instead of a 50A breaker, to keep me safe".

Not sure what he meant by that!

Any thoughts would be appreciated.


some time has passed now since the breaker was changed -- have you experienced any tripping with the lower ampacity breaker ? If not then your suspicion may be correct that he installed a used 50 amp breaker.

In our part of the world --- a new service panel installation can not have used breakers installed -- period.
The only way a used breaker can be put into service is if it had been sent back to the manufacturer to be tested and re-certified --- which is likely cost prohibitive.

Around here the minimum code requirement for an electric slide in range is 40 amp circuit protection. Which means 8/3 AWG wiring -- 40 amp breaker in the panel -- NEMA Type 14-50R receptacle.
For most homes with modest kitchens this is adequate to accomodate the majority of slide in electric ranges that will be used.

When it comes to McMansions with huge magazine show piece kitchens, there is a greater possiblity of having massive electric slide in ranges. In which case a lot of sparkys will run 6/3 AWG cable --- install a 40 amp breaker. This makes future upgrade easy buy simply swapping the breaker with a 50 amp.

Keeping in mind the gauge of wire determines the maximum ampacity of the required circuit breaker.

For example in this case---

8/3 AWG dictates the maximum of a 40 amp breaker

6/3 AWG dictates a maximum of a 50 amp breaker

However, it is acceptable and legal to derate the circuit wiring with a lower ampacity circuit breaker ....... 6/3 with a 40 amp breaker.

When the op's service panel was upgraded from 150 - 200 amps and if the old panel had a 50 amp breaker with 6/3 circuit wiring , then a 50 amp breaker could been installed. Many times when a panel is to be upgraded, sparkys will get a package which includes an assortment of breakers and typically has one 40 amp breaker for the stove ( since 40 amp is minimum code ). In which case the electrician would have had to purchase a 50 amp breaker seperaetly to be installed into the new panel.

Whether or not a new or used 50 amp breaker was installed is just a guess at this point. The description the op provided as to the visual condition of the breaker could very well be a used breaker or it could be an unused breaker that was in the sparky's vehicle for some time getting dirty and scuffed --- who knows.

Although, when the inspector was checking the installation and saw the other shinny clean breakers I would think he would have questioned the sparky about the breaker in question.

To say the stove is faulty -- well -- let's just say it's possible but, a heck of coincidence in timing. Regardless, if the replacement 40 amp breaker is not tripping with the same normal use of the range then it's likely the 50 amp breaker in question was faulty --- used or not.

I would suspect his reluctance to get back to you and resolve the issue in a timely manner along with his attitude when he did get back to you , would indicate he may have known about that breaker being suspect . In which case he didn't want to be out of pocket for a new replacement 50 amp breaker and instead swapped with the 40 amp he may have had on hand or that may have come with the kit orginally.

2 cents worth ( or is it 5 cents )

Re: circuit breakers keep tripping

Let me add a couple of things here. A 120/208 service is not generally used in residential service, it is a commercial 3 phase service. Back in the 50's, there were some houses with large AC units that got this service, but that is very very rare. Residential service is 120/240. They do not make a 120/208 volt single phase transformer. Note: do not confuse that with a 208Y/120 volt single phase transformer which is meant to be used in a three phase bank. Those are not used in residential service.

The problem may have nothing to do with the circuit breaker or the stove. It may have everything to do with the inverter. Before jumping on this, I would like to know from the OP if the 40 amp breaker has been blowing.

It is possible that the 50 amp breaker was simply defective.

Back to the inverter. For the system to feed excess energy back into the grid, it has to have the same or slightly higher voltage as measured at the primary of the transformer hanging out there on the pole. If the utility is overvoltage, as they often are, then the inverter may be generating 260 volts to compensate.

If this is the case, and the 40 amp breaker is blowing, the utility company should reset the tap on their transformer to a higher rated voltage. If the utility is not using a transformer with taps, they should install one for you and make the necessary adjustments.

Re: circuit breakers keep tripping

keith3267 --- I doubt any inverter issue would only affect the stove breaker.

Re: circuit breakers keep tripping

It would affect any circuit that was being used near its limit. If only one circuit was being pushed, then only one circuit would be blowing the breakers on a regular basis.

There would be issues with all the appliances though. Light bulbs would have a short life.

The OP has not indicated whether the circuit has been tripping the 40 amp breaker. I suspect that the original breaker was just defective or worn out. I threw the rest in just in case.

Re: circuit breakers keep tripping

Sam, the calculated load is useful in obtaining the permit but the actual connected load must always be at least 20% less than the continuous load, in the US.

I wondered about the wire size and type (AL or CU) romex or THHN etc. in conduit. All have different ratings and acceptable breaker sizes.
Which is why I asked the OP if any of the devices or breakers felt hot.

Even with the correct breaker/wire/range combination if the electrician didn't use no-lox or torque the connections the heat from the bad connection could cause the breaker to trip.

I suspect the OP has found his answer, which is why we haven't heard from him lately.

Good Luck from Columbiana, Alabama
Maurice Turgeon, http://thesemi-retiredelectrician.com

Re: circuit breakers keep tripping

I think there is one point everyone is missing. The stove is label rated at 10kw which should be the maximum draw. Every stove I have seem has had at least four "burners", an oven, and a broiler and yet the OP said the breaker was tripping with two "burners" or one "burner" and the oven which should not be even half the full load draw. The first test is to see if it is one particular "burner" that is involved when the breaker trips which would indicate a problem with that "burner" circuit. If another burner and the oven doesn't trip the breaker it would be solid evidence that the first burner is the problem.


Re: circuit breakers keep tripping

Sound thinking Jack. I looked up what an 18.5" x 14.5" oven element draws and 2300 watt was average (9.6 A.

A typical 8" surface element was 2350 W (9.8 A).

An interesting fact about resistive elements like burners and light bulbs is that their cold resistance is quite a bit lower than their hot value (at least 20%) so if every element is turned on real quick the inrush current could trip a weak breaker.

Looks like if both oven elements and two surface elements were turned on together (38.8A) a 40A breaker would be running real close to the trip point, even considering the fact that breakers are "inverse time lag devices" and can stand an overload for a short period of time.

Good Luck from Columbiana, Alabama
Maurice Turgeon, http://thesemiretiredelectrician.com

Re: circuit breakers keep tripping

Good point, Jack. The thought was in the back of my mind but never poked its way forward.

The Semi-Retired Electric wrote:

Looks like if both oven elements and two surface elements were turned on together (38.8A) a 40A breaker would be running real close to the trip point, even considering the fact that breakers are "inverse time lag devices" and can stand an overload for a short period of time.

Unlikely that both oven elements would be on at the same time. Most ovens are one or the other. Some ovens will turn them both on during a preheat cycle, but I haven't seen too many like that.

I agree, If the breaker is tripping with only a couple of burners on, either it's a weak breaker or a bad element or switch.


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