Is this safe? UK household fuse box/RCCB reset edition
September 12, 2024 1:02 PM Subscribe
I just put my electric oven on for the first time in a long time (air fryer FTW!). Shortly after switching it on, a fuse switch (an RCCB) flipped on the main fuse board in the hall, and I need to know if what I’ve done was a safe reset.
After the fuse blew (there was a click and several appliances went off) I checked the fuse box in the hall, and the one that had flipped is marked RCCB. When I tried to flip it back up manually, it wouldn’t stay. There’s a yellow button on that fuse unit (it’s a Crabtree brand if that’s useful to know), so I pressed that, and then was able to flip the switch back to up to the on position and my appliances came back on.
I assume this is OK and I’ve just successfully reset the fuse after some kind of surge and my flat’s not going to burn down tonight as a result, but can anyone reassure me?
Online resources mostly assume more knowledge than I have (which is zero). I did find this video after having reset the RCCB using the yellow button. I tried the method he suggests and none of the three fuses alongside the RCCB cause it to switch off, but I don’t know if I’ve overridden something by pressing the yellow button? Switching it off as a precaution will switch off my freezer among other things, so I don’t want to do that unless I have to.
(Separately, I noticed the sticker on the fuse box that tells me to get it checked regularly, which I definitely haven’t done, and will do… but atm I just need to know if this is a dangerous emergency or totally fine). Thank you!
After the fuse blew (there was a click and several appliances went off) I checked the fuse box in the hall, and the one that had flipped is marked RCCB. When I tried to flip it back up manually, it wouldn’t stay. There’s a yellow button on that fuse unit (it’s a Crabtree brand if that’s useful to know), so I pressed that, and then was able to flip the switch back to up to the on position and my appliances came back on.
I assume this is OK and I’ve just successfully reset the fuse after some kind of surge and my flat’s not going to burn down tonight as a result, but can anyone reassure me?
Online resources mostly assume more knowledge than I have (which is zero). I did find this video after having reset the RCCB using the yellow button. I tried the method he suggests and none of the three fuses alongside the RCCB cause it to switch off, but I don’t know if I’ve overridden something by pressing the yellow button? Switching it off as a precaution will switch off my freezer among other things, so I don’t want to do that unless I have to.
(Separately, I noticed the sticker on the fuse box that tells me to get it checked regularly, which I definitely haven’t done, and will do… but atm I just need to know if this is a dangerous emergency or totally fine). Thank you!
Best answer: I think you’re fine.
The RCCB breaker compares the current coming back with the current going out and breaks if there’s a difference.
In all probability, the plume of smoke coming off a long disused and therefore organic film coated heating element provided an alternative path to ground for a very small current, and that tripped the breaker.
posted by jamjam at 1:18 PM on September 12, 2024 [3 favorites]
The RCCB breaker compares the current coming back with the current going out and breaks if there’s a difference.
In all probability, the plume of smoke coming off a long disused and therefore organic film coated heating element provided an alternative path to ground for a very small current, and that tripped the breaker.
posted by jamjam at 1:18 PM on September 12, 2024 [3 favorites]
Best answer: I am not an electrician at all but consumer units are designed to be failsafe. I too think you're fine.
The yellow button is a test button. It simulates a fault, and should switch off all circuits linked to that RCCB. This explains how it works.
I would probably try the screwfix forum if I wanted more reassurance tonight. I'm not sure how many mefites are good at British electrics.
posted by plonkee at 1:22 PM on September 12, 2024 [2 favorites]
The yellow button is a test button. It simulates a fault, and should switch off all circuits linked to that RCCB. This explains how it works.
I would probably try the screwfix forum if I wanted more reassurance tonight. I'm not sure how many mefites are good at British electrics.
posted by plonkee at 1:22 PM on September 12, 2024 [2 favorites]
Best answer: The one with the yellow button is a Residual Current Circuit Breaker, which trips if there's a difference in the current going towards the consumers (in this case the circuits behind the 'normal' circuit breakers) and the current coming back. It trips if that difference is greater than 30mA (milliAmps), which is commonly considered safe (for the short time it takes for the breaker to trip) in case that current flows through a human body.
But basically anything that cause those 30mA to take a path to ground not via the RCCB will trip it too, in this case some dirt and grease in the long-unused oven. Once tripped, the situation that caused it to trip may still persist such as with greasy dust so that trying to reset the RCCB will just trip it again. But at every attempt, a bit of the (in this case) greasy dust is burned away until there's little (or nothing) left and the RCCB stays put. Once it does, the setup works, and protects, like before.
The yellow button is a test button simulating such a 30mA current leakage, and does nothing to reset the RCCB after a trip.
posted by Stoneshop at 1:42 PM on September 12, 2024 [3 favorites]
But basically anything that cause those 30mA to take a path to ground not via the RCCB will trip it too, in this case some dirt and grease in the long-unused oven. Once tripped, the situation that caused it to trip may still persist such as with greasy dust so that trying to reset the RCCB will just trip it again. But at every attempt, a bit of the (in this case) greasy dust is burned away until there's little (or nothing) left and the RCCB stays put. Once it does, the setup works, and protects, like before.
The yellow button is a test button simulating such a 30mA current leakage, and does nothing to reset the RCCB after a trip.
posted by Stoneshop at 1:42 PM on September 12, 2024 [3 favorites]
Oven heating elements often fail in a way that causes the live wire inside to touch the outer metal casing and trip the circuit breaker. It may only do this after it gets hot, and then it may disconnect when it cools down, which is what would have allowed you to reset the breaker.
If it trips again the next time you try switching the oven assume you need a new element.
As others have said, your system is safe and if it were unsafe the breaker would quickly trip again. The yellow test button is a red herring. It would literally do nothing if the breaker is already tripped.
posted by grahamparks at 2:20 PM on September 12, 2024 [2 favorites]
If it trips again the next time you try switching the oven assume you need a new element.
As others have said, your system is safe and if it were unsafe the breaker would quickly trip again. The yellow test button is a red herring. It would literally do nothing if the breaker is already tripped.
posted by grahamparks at 2:20 PM on September 12, 2024 [2 favorites]
The typical usage for a breaker is that it trips into a middle position (between on and off), and then won't turn on again, until you manually push it to the off position, not just "tripped off". So the recovery steps are 1) find breaker in tripped position, 2) turn it off and 3) turn it on. After turning it off and on, you'll find it stays on. (Unless of course the trouble condition still exists, in which case it will trip off again.)
posted by intermod at 3:35 PM on September 12, 2024
posted by intermod at 3:35 PM on September 12, 2024
If it trips again, turn off the MCB (Miniature Circuit Breaker) labeled "cooker". This will disable the power to your cooker (oven/range). Reset the RCCB once more. Verify that your freezer and other important appliances are still running. Everything else should be up and running, except for your cooker. If operating the cooker keeps tripping the RCCB, it should be inspected and serviced by a professional.
posted by xedrik at 4:04 PM on September 12, 2024 [1 favorite]
posted by xedrik at 4:04 PM on September 12, 2024 [1 favorite]
The typical usage for a breaker is that it trips into a middle position (between on and off)
Circuit breakers of this kind are rare-to-non-existent in the UK. Every breaker here simply trips to the off position.
posted by grahamparks at 4:22 PM on September 12, 2024 [2 favorites]
Circuit breakers of this kind are rare-to-non-existent in the UK. Every breaker here simply trips to the off position.
posted by grahamparks at 4:22 PM on September 12, 2024 [2 favorites]
Response by poster: Thanks, everyone - all the answers were helpful but I've marked a few that got there first (I did also ask in the Screwfix forum, where everyone concurred, and I now have a whole new place to go with my clueless DIY questions, thanks plonkee).
Now I just have to come to terms with the fact that I evidently have an oven full of greasy dust.
posted by penguin pie at 3:47 AM on September 13, 2024
Now I just have to come to terms with the fact that I evidently have an oven full of greasy dust.
posted by penguin pie at 3:47 AM on September 13, 2024
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posted by penguin pie at 1:10 PM on September 12, 2024