RCD trip

Solarchaser

ispookie666 said:

@Solarchaser
If you have EPS you cannot rely on the earthing arrangement as is(TN-S or TN-C or TN-C-S).  You should have a separate earthing arrangement.  If the grid goes down(so will the earthing), and if there is a fault the RCD will not trip and anything metal would be at mains voltage. Hence the need for metal stake or equivalent. Floating neutral is not a nice proposition. Assuming the house to be good enough to provide earthing might be a bit too much as the impede can be variable. 

I hope I'm not talking porking, I have had to read up fair bit on this topic following my inverter failure, which theoretically can be caused by lack of earthing. 

Good point, well made 👍

70sbudgie

Martyn1981 said:

70sbudgie said:

Solarchaser said:

ispookie666 said:

@2nd_time_buyer if you have emergency backup power from your inverter you will need another source for earth. 
My knowledge on RCD trip is minimal other than having blamed victron for 6 months only to find the connected equipment was dodgy 🙈

I'm intrigued by this comment, your earth is essentially "your house only" and its there to get rid of any potentially harmful leakage and push it into the ground/ distribute it through everything to dissipate its wattage rather than give you a shock, so your whole house is on one earth, all your copper and metal in the house will be on it... or part of it is really more accurate, all your radiators, taps, electrical wire and it's unique to your house, I've never heard of anything where another earth is suggested, as it would in essence remove the effectiveness of the earth.
The only separate earth I've heard of is in relation to ev chargers and thats more an additional earth to ensure it can carry the full current of ev charging gone wrong. 

My eps uses the house earth, with no issue.

EV chargers don't have separate earths. However, when my EV charger was installed, they had to add extra earth rods. This was to reduce the impedence of the earth network of my house. (Esssentially making it easier for earth currents to be discharged). 

My understanding is that most EV chargers need (needed) a separate earth. In fact I asked about it when ours was fitted, because (you'll laugh!!!) 'they' didn't fit an extra earth. They explained that that model, didn't require one, but ~90% did. However, that was a year ago, so things may have changed, and more are like the one I got.

Clearly times are a changing, but Solarchaser's comment was correct for most chargers installed in the past.

Do you need an earth rod for an EV charger?

That is interesting. I hadn't realised that the earth rod created a separate earth. It was explained to me as being required to reduce the impedance. The electrician that fitted my charger ended up putting in 3! because the first one was too close to the foundations which are unusually deep and therefore the impedance was too high. 

Heedtheadvice

I do like it when people contribute to a thread with some, little or no knowledge....maybe based on a little personal experience but that is not good enough!!!

My comment is not to be antogonistic or upset anyone and even applies to sone good regular posters.

Let us be clear. RCDs, MBOs and RCBOs all have their individual purposes.

RCDs to detect an imbalance between the neutral and live currents flowing in that circuit. If there is not balance then the difference is going somewhere and this can be to earth connection via any or many routes including a person, or insulation (particularly heating coils that become faulty) via dampness etc. All the circuits and appliances connected through that RCD contribute to the imbalance and sum up. RCDs are fast acting (mS) and have specific sensitivities. But it is time and current imbalance that cause the trip. It may not detect a big imbalance that is of exceedingly short duration such as switching spikes or filters that are not themselves well balanced such as on poorly designed or faulty equipment. That though depends on the level and duration of that imbalance too. (Very old filters on equipment were not designed for balance and used to cause no end of problems at switch on but were fine once up and running!)

If RCDs trip, and are correctly installed to regulations and are not faulty themselves (rare) then that indicates a problem that needs fixing.....for safety reasons.

The fault could be to do with the live wiring/appliances etc. or nuetral or both.

It should be noted that a static test such as with a simple insulation tester is insufficient to fully test a circuit as the response time is also a factor. Further a static test will not reveal a problem that is dynamic such as appliance switching different loads (eg motor starts, heater switching, different cooker rings etc.) or different generation from solar and batteries.. That does not always get tested by an electrician involved in house wiring.

RCDs should not be swapped for ones of higher rating or slower responses without ensuring regs etc are still met. That might well impair safety.

It may well be that there are too many circuits connected to a single RCD. Whole house (the main RCD) trip kevels are often 100mA but it is far better to have several individual trips with the lower rating given thar 50microamps through the heart is enough to stop it! (That usually requires more through the body thankfully!). Agricultiural (and some other supplied property) have much more sensitive trips but 30mA is standard for house circuits and outside connections.

As I mentioned them:

MCBs(miniature circuit breakers) only trip with current overloads and are there to protect wiring and rarely domestic equipment though they may well trip with an equipment over current fault.

RCBOs combine the functions of the above.

If one has an intermittent fault causing a trip on an appliance then noting what was happening at tge time can indicate the cause. As an example we had a bread maker that tripped part way though it's cycle (resulting in no bread!!!). That was when the cooking heater started. It was damp from condensation following the rising stage. I could test at that time (low impedance to earth) and disassembly showed the condensation. A static test prior to 'cooking' was fine as would be tested as such by an electrician doing a property check or even a PAT inspection. It would normally require an appliance technician to do a full check to locate but for most people logic might just tell them to replace it or the affected part.

Heedtheadvice

Note some EV chargers require a separate earth to prevent attached vehicles becoming ' live '. This can eminate where the supply utilises the Neutral connection as an Earth and there could be a fault elsewhere that makes that earth rise to higher than the local earth potential around the property i.e in the vicinity of the cars bodywork thus giving a higher risk of shock.

Some chargers have extra protection built in to them to prevent that possibility and do not need a separate earth other than the normal propert earth.

Solarchaser

Well while I agree mostly with what you said heedtheadvice, and I take on board you are obviously talking about me (as well as potentially others) i think you really point out the issue with the Internet, with life and with "professionals".

I am not a spark, never claimed to be either, but I have a fair amount of experience with specific things that are electrical.
White and brown goods engineer for a time. 
I'm also not a mechanic, never claimed to be, as I didn't finish my apprenticeship, got bored, but I know a fair bit more about cars and engine's than the average Joe or Jim.

I also have a fair amount of experience with inverters of many different types due to my own... DIY I guess, and helping others.

I've in the past hired several professionals to complete tasks to do with all of the above, and laterally found that I know more about the thing I'm paying for, than the person I'm employing.

I was advised by both growatt and sma to change my 30ma rcd to a 100ma rcd to solve nuisance trips, many on various forums have reported the same.
And for the record it did solve nuisance trips.
And so I pass that on to those experiencing nuisance trips.

You could definitely argue I shouldn't give that advice, they should contact professionals... but what happens when they do and its not resolved?

Finally, you have spoken with authority here, and an air of knowing what's what, but its the Internet, so you could just as easily be a 10 year old using Google.... as could I.
So of course every reply should be treated with caution by the reader.

None of us know who we are conversing with, and if the idea is that you should never comment unless you are qualified to do so would mean very very quiet Internet forums.

A quick look at professional forums will tell you that in many situations qualifications mean nothing anyway.
We have all worked with guys and girls who are !!!!!! hot, and also worked with guys and girls who you wonder if they tied their own shoe laces in the morning.

I will continue to "help" with my own experience where I can.
Every user is advised to treat any of my replies with caution.... just like every other user on the world wide Web 🌐 

2nd_time_buyer

Just to echo what @Solarchaser says above. I was/am somewhat sceptical of the chances of a typical sparky being able to identify my intermittent fault that may or may not be associated with a solar installation. I could foresee quite a lot of call outs and expense to get to the bottom of it.

I asked for advice and experience on here to narrow things down, which has been more than forthcoming. I now have plenty to discuss with the electrician to get to the bottom of it.

@Heedtheadvice I honestly wasn't sure whether your first paragraph was sarcastic:

I do like it when people contribute to a thread with some, little or no knowledge....maybe based on a little personal experience...

I think it must have been - but in my mind, this is the best of the internet.  

Thanks all

Heedtheadvice

You are both correct in much of what you write and yes I did include yourself solarchaser amongst others. For some of the 'advice' you gave. And yes that was a sarcastic comment I made!

 But as I wrote "My comment is not to be antogonistic or upset anyone and even applies to sone good regular posters."

You are both good posters and I am sorry if I struck a raw nerve and apologise for that. I too have had help from you at times for which I am gratefull. I am glad you will continue to post on this excellent forum.

 I do think we need to phrase things carefully in posts that are helpfull by aim but can have unintended consequences for those that take them as gospel and out of context.

I was really just wanting to highlight that not all advice is necessarily good (as you have correctly written) and I am particularly concerned where advice is given that might lead the uninformed doing something dangerous. Some other posters (on this site) have posted things that are, if not just ill advised, downright potentially dangerous.

Taking posts sensibly and advice as to potential possibilities is one thing. Doing something that increases risks of safety problems or contravenes things like wiring regs is another matter altogether. Many might not really understand enough to dicriminate or understand the context.

To take just one example. I surprises me that the inverters you mention require 100mA trips and that you have been so advised. However I cannot disagree that you have been so advised or that it will have reduced nuisance trips as can be expected by utilising a less sensitive device. It should not however be the action to take just because any 30mA RCD trips frequently. I fear some readers would think 'great, that is what I will do' rather than clear a dangerous fault.

High sensitivity trips (10mA and 30mA) provide good protection against shock or electrocution and fire.

100mA trips do not give good personal protection but are effective at fire risk reduction. Do not take my word for it (I could be that person Solarchaser refers to using Google!). In fact I have Googled to find authoritative documentation as reference and everybody is free to read such as that by the IET which explains how to meet BS7671.

Simply using a medium sensitivity RCD (100mA upwards) to stop nuisance tripping seriously reduces personal protection. That approach is not allowed on domestic socket outlets such as for dishwashers, ring mains etc. I guess some readers might take that sort of action.

This particular forum of the site is generally very good but some forums on this site just give incorrect advice on matters of safety! That is against the site rules as well as, more importantly, being dangerous.

I am confident that you do not intend any harm and hope our posts not only help but also make readers aware of potential pitfalls!

Solarchaser

No raw nerves here, as I said I agreed mostly with what you said 

shibli

Heedtheadvice said:

I do like it when people contribute to a thread with some, little or no knowledge....maybe based on a little personal experience but that is not good enough!!!

My comment is not to be antogonistic or upset anyone and even applies to sone good regular posters.

Let us be clear. RCDs, MBOs and RCBOs all have their individual purposes.

RCDs to detect an imbalance between the neutral and live currents flowing in that circuit. If there is not balance then the difference is going somewhere and this can be to earth connection via any or many routes including a person, or insulation (particularly heating coils that become faulty) via dampness etc. All the circuits and appliances connected through that RCD contribute to the imbalance and sum up. RCDs are fast acting (mS) and have specific sensitivities. But it is time and current imbalance that cause the trip. It may not detect a big imbalance that is of exceedingly short duration such as switching spikes or filters that are not themselves well balanced such as on poorly designed or faulty equipment. That though depends on the level and duration of that imbalance too. (Very old filters on equipment were not designed for balance and used to cause no end of problems at switch on but were fine once up and running!)

If RCDs trip, and are correctly installed to regulations and are not faulty themselves (rare) then that indicates a problem that needs fixing.....for safety reasons.

The fault could be to do with the live wiring/appliances etc. or nuetral or both.

It should be noted that a static test such as with a simple insulation tester is insufficient to fully test a circuit as the response time is also a factor. Further a static test will not reveal a problem that is dynamic such as appliance switching different loads (eg motor starts, heater switching, different cooker rings etc.) or different generation from solar and batteries.. That does not always get tested by an electrician involved in house wiring.

RCDs should not be swapped for ones of higher rating or slower responses without ensuring regs etc are still met. That might well impair safety.

It may well be that there are too many circuits connected to a single RCD. Whole house (the main RCD) trip kevels are often 100mA but it is far better to have several individual trips with the lower rating given thar 50microamps through the heart is enough to stop it! (That usually requires more through the body thankfully!). Agricultiural (and some other supplied property) have much more sensitive trips but 30mA is standard for house circuits and outside connections.

As I mentioned them:

MCBs(miniature circuit breakers) only trip with current overloads and are there to protect wiring and rarely domestic equipment though they may well trip with an equipment over current fault.

RCBOs combine the functions of the above.

If one has an intermittent fault causing a trip on an appliance then noting what was happening at tge time can indicate the cause. As an example we had a bread maker that tripped part way though it's cycle (resulting in no bread!!!). That was when the cooking heater started. It was damp from condensation following the rising stage. I could test at that time (low impedance to earth) and disassembly showed the condensation. A static test prior to 'cooking' was fine as would be tested as such by an electrician doing a property check or even a PAT inspection. It would normally require an appliance technician to do a full check to locate but for most people logic might just tell them to replace it or the affected part.

Thanks everyone here for your valuable input I tested the dishwasher socket with a kettle and no issue so I am conducting a further test i.e. using a different socket in the house to power the dishwasher  to confirm if the dishwasher has a fault (perhaps water/steam getting into the electrics) which is causing the RCD to trip rather then then solar panel installation, which is a strange coincidence.   

Solarchaser

Heedtheadvice said:

To take just one example. I surprises me that the inverters you mention require 100mA trips and that you have been so advised. However I cannot disagree that you have been so advised or that it will have reduced nuisance trips as can be expected by utilising a less sensitive device. 

Purely as an FYI, this was my email from growatt in 2019, saves any question mark over what I was told from the manufacturer