Dear Dave,
I am new to this camper and although most things are going well, I had a problem when I tried to use a toaster oven in the kitchen. After turning it on and trying to make some toast, it ran for about 30 seconds and then turned off. My multimeter was not handy, but I soon realized that the bathroom GFCI had tripped. There were no other appliances in use at the time. I had an electric toothbrush plugged into the bathroom outlet, but it was not in use.
I reset the GFCI outlet and the kitchen outlet was back live. I made a pot of coffee (on the same outlet) with no problems. Later, I disconnected the tooth brush, and tried the toaster oven again. Same thing happened. It ran for 20-30 seconds and then tripped the bathroom outlet again. Should I replace the outlet, the toaster oven, both, or look elsewhere? —Mark, 2016 Highland Ridge Open Range Light 215RBS
Dear Mark,
Just to clarify, the button on the bathroom outlet GFCI tripped, not the circuit breaker you provided in the photo? As I have posted earlier, the GFCI outlets used in RVs are the cheapest possible. There is typically only one with the test/reset button and the others are what we call “dummy outlets” ganged and protected by the single outlet with the test/reset button.
Replace GFCI outlet
The first thing I would do it replace the GFCI outlet with a quality outlet that is hard-wired rather than the spade connections (below) often found in RVs. I would also change the kitchen outlet with a hard-wired outlet, as well, to ensure a good connection.
Next, purchase a watt meter to figure out what your toaster oven is doing. You can find one on Amazon here.
According to the Energy Star website, toaster ovens can use from 1,200 – 1,800 watts since it uses a heating element that is an electric resistance coil. Plug the watt meter into your kitchen outlet, then plug in your toaster oven and turn it on just like you did previously. Watch the wattage being used. My guess is the toaster oven starts off with a moderate wattage and then in 20-30 seconds ramps up the temperature and the wattage goes up.
Wattage does not trip GFCI
The wattage is not what trips a GFCI outlet as these are designed to protect by tripping when it detects a small amount of electrical current “leakage”—typically at 4-6 milliamps. It should, however, help determine why it takes 20-30 seconds to create the issue.
We ran into a similar situation with the Winnebago motorhome tripping the GFCI circuit breaker in storage in this post.
In that article, we referenced a post by electrical expert Mike Sokol, who went into further detail on leakage issues within RVs.
According to Mike, appliances are allowed to leak current to some degree and RV components are typically above average. However, you have identified the issue is the toaster oven.
This description by Fluke can help identify how much:
A GFCI uses a current transformer to detect the difference between the line current supplied to the load and the neutral current returning from the load. Ideally, this difference should be zero because both currents cancel. If there is a current differential, it becomes the input to a comparator within the GFCI, which changes states when the differential is around 6 mA. When the comparator changes states, it triggers a silicon-controlled rectifier, which disconnects the power from the output of the GFCI.
Here, also from Fluke, is another description of why the GFCI trips and how to diagnose the issue:
Leakage Current: Another term for a ground fault is leakage current. All insulators, including wiring insulation, have some conductivity which can cause leakage current. If insulation is old or damaged, its resistance is lower and leakage current could become substantial.
Diagnosing GFCI trips
Start by measuring the leakage current and then identify the source. Use a leakage current clamp meter to make these measurements. Leakage current clamp meters are similar to clamp meters used for measuring load currents; however, leakage current clamp meters perform much better when measuring current below 5 mA.
Test single-phase circuits by clamping the phase and neutral conductors. Test three-phase circuits by clamping around all phase conductors. If a neutral is present, clamp it too. The measured value will be any current flowing to ground. To measure the total leakage flowing to the intended ground connection, place the clamp around the ground conductor.
Measure leakage current
Measure the leakage current on each leg of the circuit to identify which one has considerably more leakage than the others. If one leg has a suspiciously high leakage current, ensure that the equipment is operating properly. Remember that surge suppression filters and capacitors on the power input of some electronic equipment can increase the overall circuit capacitance, which can increase leakage current. Determine loaded circuit leg leakage with the equipment “on”—switching the equipment “off” allows you to determine just the circuit wiring leakage.
If equipment on all legs is operating properly and the wiring is acceptable, it could be that the cumulative leakage current due to electronic equipment input filtering is just high enough to trigger the random GFCI tripping. In this case, consider redistributing the load on each circuit leg or adding circuits to provide more capacity.
As Mike stated in his post, this is beyond what you and I would be able to test. If the toaster oven continues to trip the new GFCI outlet, it would seem you will need to find a new method of making toast.😉 Or it might be possible to find a smaller toaster oven or one that is more efficient.
You might also enjoy this from Dave
Powering your RV: Essential 120-volt electricity tips and gadgets for every RVer
This is Part 3 of Dave Solberg’s “Everything you need to know about RVing” series. Today, Dave looks at 120-volt electricity and tells you just about everything you need to know.
In our homes, we plug in the vacuum, heat up cold coffee in the microwave, and turn on the air conditioner without thinking about where that power comes from. It’s easy—it comes from the local municipal company and is wired throughout the house. In an RV, we use 120-volt AC, 12-volt DC, and even liquid propane (LP) for the various components. It is important to understand what powers what and how much power everything uses. Continue reading.
MORE ELECTRICITY-RELATED POSTS FROM DAVE
- Why does an RV fridge work on LP but blow a fuse on electricity?
- Some fun facts I learned about electricity this week
- Follow-up on delayed converter charging and tripping GFCI issue
- All GFCI outlets work; why did 4 on other side quit working?
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
Read more from Dave here.
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