Fridge pops RCD

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1410 posts

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#2452853 2-Apr-2020 11:39

BlinkyBill:

Interesting. The Wiring Regulations were updated in 2018 and from November 2018 there were new RCD regulations to conform to. The regulations beefed up the requirement for RCD’s in many/most domestic circumstances and brought NZ more in line with AU requirements.

More interestingly, there are 294 new requirements as from Nov 2018, for wiring, compared with a very much smaller set of changes previously - 87 over the previous 30-odd years.

More good reasons for using an electrician, I guess.

The 2018 requirements, thankfully, exclude New Zealand. The new rules (which AU have adopted but we have held back for obvious amendment reasons) stipulate that anything 32A and under needs to be on RCD - this would cause all kinds of extra nuisance tripping with elements and compressors!

There are exceptions for having to install an RCD on power/light circuit -- if you are MOVING an outlet, or if you are replacing/joining cabling you do not have to put the item on RCD. Bathroom / wet area / spa [etc] power points have required RCD protection for many many years (>20), however.

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mdav056

605 posts

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#2452856 2-Apr-2020 11:43

Thank you all. Lots to think about here, and I think the general focus is -- a fridge problem. Wonder when I'll be able to get it fixed...

Some answers: Fridge is probably about 10 years old, making a fridge problem more likely. The RCD was a like-for-like replacement of a previous one which was popping off all the freaking time, and then stopped being able to be reset. Again pointing at a fridge problem. I've thought about putting a light in circuit, but it is in a downstairs flat, and it's hard to sleep with a light on (and easy to sleep if it goes off!).

I suspected back EMF, but I'm a DC person, and I would normally sling a diode across the offending solenoid to fix this. But I guess there may be some DC circuits in the fridge. Not something I want to futz with. Though I wonder if there is something, some appliance or wall wart I could hang in the circuit that would soak up the back emf?

Thanks again, stay healthy.

gml

elpenguino

3364 posts

Uber Geek

#2452862 2-Apr-2020 11:51

mdav056:

Thank you all. Lots to think about here, and I think the general focus is -- a fridge problem. Wonder when I'll be able to get it fixed...

Some answers: Fridge is probably about 10 years old, making a fridge problem more likely. The RCD was a like-for-like replacement of a previous one which was popping off all the freaking time, and then stopped being able to be reset. Again pointing at a fridge problem. I've thought about putting a light in circuit, but it is in a downstairs flat, and it's hard to sleep with a light on (and easy to sleep if it goes off!).

I suspected back EMF, but I'm a DC person, and I would normally sling a diode across the offending solenoid to fix this. But I guess there may be some DC circuits in the fridge. Not something I want to futz with. Though I wonder if there is something, some appliance or wall wart I could hang in the circuit that would soak up the back emf?

Thanks again, stay healthy.

Back EMF is a red herring.

There's only one reason why an RCD trips and that's due to an imbalance between the current in the phase and the neutral wires. The assumption is that current is leaking somewhere else = to earth (through your body lol).

So to stop this occurring you need to remove the connection to earth. There are dodgy options that we won't consider but your safe option is to run the fridge through an isolation transformer, if you can find one with a high enough VA rating.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

BlinkyBill

1443 posts

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#2452865 2-Apr-2020 12:00

snnet:

The 2018 requirements, thankfully, exclude New Zealand. The new rules (which AU have adopted but we have held back for obvious amendment reasons) stipulate that anything 32A and under needs to be on RCD - this would cause all kinds of extra nuisance tripping with elements and compressors!

There are exceptions for having to install an RCD on power/light circuit -- if you are MOVING an outlet, or if you are replacing/joining cabling you do not have to put the item on RCD. Bathroom / wet area / spa [etc] power points have required RCD protection for many many years (>20), however.

I don’t understand this - what is AS/NZS 3000:2018 then, why was there an amendment published in January this year, what are the obvious amendment reasons, why did the Master Electrician Authority have a roadshow, why are electricians working towards this standard?

As I (briefly) read it, the exceptions refer to situations where a nuisance trip is more life-threatening than is worthwhile, such as a life-saving medical device.

Bung

6359 posts

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#2452869 2-Apr-2020 12:07

A new edition of a Standard doesn't take effect until it is included in the NZ Regulations.

snnet

1410 posts

Uber Geek

#2452883 2-Apr-2020 12:26

BlinkyBill:

I don’t understand this - what is AS/NZS 3000:2018 then, why was there an amendment published in January this year, what are the obvious amendment reasons, why did the Master Electrician Authority have a roadshow, why are electricians working towards this standard?

As I (briefly) read it, the exceptions refer to situations where a nuisance trip is more life-threatening than is worthwhile, such as a life-saving medical device.

Just because it has a date on it, that doesn't mean NZ has adopted it yet. We are still working on the 2007 model (with ammendments).

I've read the 2018 version and it says all of the RCD stuff 32A and under and then it specifically excludes New Zealand. Therefore, as far as standards are concerned, we install RCDs as per 2007 edition (with ammendments). I.e. New power / lighting circuits, extending power / lighting circuits, etc etc (including some hardwired applications such as electric underfloor heating etc etc); 3 subcircuits to an RCD; One lighting circuit per RCD, etc EVEN WHEN the 2018 edition is written into regulations -- unless that section gets ammended (unlikely)

BlinkyBill

1443 posts

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#2452890 2-Apr-2020 12:33

Ok, thanks for the explanations.

sparkz25

750 posts

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#2452893 2-Apr-2020 12:38

mdav056:

Thank you all. Lots to think about here, and I think the general focus is -- a fridge problem. Wonder when I'll be able to get it fixed...

Some answers: Fridge is probably about 10 years old, making a fridge problem more likely. The RCD was a like-for-like replacement of a previous one which was popping off all the freaking time, and then stopped being able to be reset. Again pointing at a fridge problem. I've thought about putting a light in circuit, but it is in a downstairs flat, and it's hard to sleep with a light on (and easy to sleep if it goes off!).

I suspected back EMF, but I'm a DC person, and I would normally sling a diode across the offending solenoid to fix this. But I guess there may be some DC circuits in the fridge. Not something I want to futz with. Though I wonder if there is something, some appliance or wall wart I could hang in the circuit that would soak up the back emf?

Thanks again, stay healthy.

It could be a Defrost element on its way out or leakage in the compressor (the windings are starting to break down in the compressor)

I would suspect that it is the defrost element on its way out or has some moisture in the element.

gregmcc

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#2453084 2-Apr-2020 15:05

Without some investigation it could be the straw that broke the camels back, there may be several items with a little bit of earth leakage, the defrost element (for example) turning on adds that little bit more of earth leakage - enough to trip the beaker. But like I said some further checking will be needed to prove this.

Depending on how much your electrician has invested in tools they may have a mA meter that can read the earth current in the particular circuit and pin point it down to a particular item or a combination of appliances causing the trip.

Then again it could just be fridge, depends on how much money you want to spend to sort it out.

surfisup1000

5288 posts

Uber Geek

#2453123 2-Apr-2020 15:33

gregmcc:

Without some investigation it could be the straw that broke the camels back, there may be several items with a little bit of earth leakage, the defrost element (for example) turning on adds that little bit more of earth leakage - enough to trip the beaker. But like I said some further checking will be needed to prove this.

Depending on how much your electrician has invested in tools they may have a mA meter that can read the earth current in the particular circuit and pin point it down to a particular item or a combination of appliances causing the trip.

Then again it could just be fridge, depends on how much money you want to spend to sort it out.

This is what got us... so many power outlets going through 2 rcd's. We were getting a lot of RCD trips.

Fixing the fridge defrost element helped, but we still had one RCD trip every month or so.

In the end, we spent $2,000 a couple of years back putting every circuit on a dedicated RCD -- since then, not a single RCD trip.

RCD's are evil if not installed by someone who knows what they are doing!

SomeoneSomewhere

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#2453701 3-Apr-2020 12:33

If you have one floating around, a UPS could be an option. It doesn't even have to power the fridge; it will just start beeping when the power goes out. Another option could be an old cellphone with some automation app to start screaming when it's unplugged.

NZ has required RCD protection of all residential sockets excluding those for fixed cooking equipment since ASNZS3000:2000 + Amendment 3 was adopted in 2003, but only for new circuits. The requirements for additions to existing circuits came in when we adopted 2007+A2 in 2010. It's also worth noting that these standards have specific provisions for Australia and New Zealand that differ greatly, particularly in regards to RCDs.

The 2018 standards have no weight until the government amends Schedule 2 of the [url=http://www.legislation.govt.nz/regulation/public/2010/0036/latest/DLM2763782.html?search=sw_096be8ed8183224c_3000_25_se&p=1&sr=14]Electrical (Safety) Regulations 2010].

mdav056

605 posts

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#2513771 27-Jun-2020 21:56

Um, more help needed here...it gets more and more curious.

The F&P tech came and replaced the defrost element ($$$), but the problem did not go away. Another F&P tech came, tested everything, and it all passed, and he suggested that it was something in the circuit that was tripping the RCD, not the fridge.
So, after a week or so of it still tripping off, I put the fridge onto a different circuit with an RCD in it, and it hasn't missed a beat. However, the problem RCD still keeps tripping on average once a day _with no load on the circuit at all_.

The problem RCD controlled circuit comes from a sub board with it's own dedicated contact breaker on the board, so I wondered whether it might be the contact breaker doing something odd (the contact breaker has never tripped), so I replaced it with a 15-amp fuse to test. The RCD still trips off at the same rate.

This suggests the wiring of the only 2 outlets on this circuit could be faulty. But if the wiring was faulty, why does it trip randomly about once a day? This I do not understand...

Can one of you explain this to me (and suggest my next step)?
Thanks...

gml

Jase2985

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#2513775 27-Jun-2020 22:05

next step, talk to an electrician

surfisup1000

5288 posts

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#2513779 27-Jun-2020 22:18

mdav056:Can one of you explain this to me (and suggest my next step)?
Thanks...

Could be a faulty RCD? You need an electrician :)... a decent one who knows how to diagnose RCD trips.

They should have diagnostic equipment .

gregmcc

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#2513793 28-Jun-2020 07:12

mdav056:

Um, more help needed here...it gets more and more curious.

The F&P tech came and replaced the defrost element ($$$), but the problem did not go away. Another F&P tech came, tested everything, and it all passed, and he suggested that it was something in the circuit that was tripping the RCD, not the fridge.
So, after a week or so of it still tripping off, I put the fridge onto a different circuit with an RCD in it, and it hasn't missed a beat. However, the problem RCD still keeps tripping on average once a day _with no load on the circuit at all_.

The problem RCD controlled circuit comes from a sub board with it's own dedicated contact breaker on the board, so I wondered whether it might be the contact breaker doing something odd (the contact breaker has never tripped), so I replaced it with a 15-amp fuse to test. The RCD still trips off at the same rate.

This suggests the wiring of the only 2 outlets on this circuit could be faulty. But if the wiring was faulty, why does it trip randomly about once a day? This I do not understand...

Can one of you explain this to me (and suggest my next step)?
Thanks...

It could be something as simple as ants in behind the socket, eventually they will cause a nuisance trip on the RCD, maybe there is a mouse chewing away at the wiring and getting a small shock tripping the RCD only to return later and have another go, the RCD could be faulty.

Step 1 check behind the sockets for ants

Does removal of the ants fix it?

Step 2 get your electrician to replace the RCD

Does the replacement RCD fix it?

Step 3 get your electrician to check out the wiring and replace if necessary.

A fault like this is hard to pinpoint and can become expensive really quickly so some basic checks and then move on to replacing likely causes from the cheaper to more expensive, an RCD may not seem cheap, but it's way more cheaper than an electrician spending hours trying to track down a fault that only happens sometimes.

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