Why 2m max from EHU to the consumer unit?

[Nedge68]

My point was RCD'S do not guarantee safety, a little common sense has to be used. Unless you have other problems a240v shock won't kill. My wife recently had a severe shock when an expensive RCD shorted to earth, the earth stakes were dry and the taps were live. They were live because the regulators say taps must be earthed for safety even when the pipes are plastic. For safety I did away with the RCD.

Removing the RCD is not the correct solution. It is true RCDs detect the imbalance between Line and Neutral, however there is a trip threshold, which can be 30, 100, 300,… mA. the disconnection occurs when the current is exceeded. A high earth loop impedance can prevent the threshold trip current from ever being exceeded (Leaving you clinging on to a live component.) It was stated that the electrician turned of the system because you had no Earth, and he wanted to install another earth rod.
Earth checks are essential in any electrical power system, more so in TT system which relies on an earth spike, rod, plate, particularly during dry weather the resistance of earthing rods etc.. increases, meaning the earth loop impedance increases, meaning that protective devices will not operate as intended.
Your wife received a shock because there was a fault ( RCD socket?) the Circuit power was not interrupted because either there was no RCD protection installed and/or the earthing loop impedance was to high.
I don’t recommend that you ever remove a circuit protective device.

 

[Gromett]

Tripped over this; There is a downward trend since the introduction of RCDs into common use.

Electric Shock - Current | Voltage | Current Path | Let-Go Threshold

The severity of an electric shock is largely dependent amount of energy delivered to the body. A current exceeding 30mA is often fatal.

www.pat-testing-training.net

 

[The Wino]

As autorouter says. Why do you think so few people die from electric shocks these days? It is because of the very regulations and guidelines you are now mocking.

I'd have thought a major part of why there's so few deaths from electrocution is the fitting of RCD,s I know for years people laughed at continental regs allowing sockets in bathrooms etc but don't think they actually have a lot higher rate of electrocuted people and in motorhoming reversed polarity only seems to concern Brits. I'm no expert but weren't RCD common in europe way before they were here and double poll ones on motorhomes so removing the risk. In the context of the length of cable before the consumer unit it would be interesting to see if the continental regs vary.

 

[The Wino]

Tripped over this; There is a downward trend since the introduction of RCDs into common use.

View attachment 719439

Electric Shock - Current | Voltage | Current Path | Let-Go Threshold

The severity of an electric shock is largely dependent amount of energy delivered to the body. A current exceeding 30mA is often fatal.

www.pat-testing-training.net

They're really low numbers! It does make you wonder if we overdo worrying about electricity so much relative to other causes of death. In the pandemic we were probably getting more covid deaths in one day than the total from electrocution since ww2

 

[Gromett]

They're really low numbers! It does make you wonder if we overdo worrying about electricity so much relative to other causes of death. In the pandemic we were probably getting more covid deaths in one day than the total from electrocution since ww2

Low? OK.

The thing these figures miss out is serious injury, hospitalisations and long term damage caused by electric shocks.

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[The Wino]

Low? OK.

The thing these figures miss out is serious injury, hospitalisations and long term damage caused by electric shocks.

Couldn't find any figures for hospitalisation suspect it's too low to be counted compared to heart disease cancer etc.
The biggest cause of work related deaths is falling from height at about 120 a year going on the MH roof is probably more dangerous than the electrics.

This is the biggie mesothelioma from asbestos
"The figures show that 2,544 people died from the disease in 2020. This is in line with the average of 2,523 deaths over the previous 8 years."
And yet it was still being used relatively recently in artex!

 

[Gaston aires]

I don't know how many people have died from electric shocks in their vans but I think no matter what length cables the risk is nonexistent to minute. You are far more likely to be killed in your own home by a tea cosy (one in Suffolk some years ago)

That cosy had a teapot inside it.

 

[The Wino]

That cosy had a teapot inside it.

You have to look out for the details. I saw a quote that there a common plant so dangerous that if sit under it for 10 minutes you die










A water Lilly!

 

[Gromett]

Couldn't find any figures for hospitalisation suspect it's too low to be counted compared to heart disease cancer etc.
The biggest cause of work related deaths is falling from height at about 120 a year going on the MH roof is probably more dangerous than the electrics.

This is the biggie mesothelioma from asbestos
"The figures show that 2,544 people died from the disease in 2020. This is in line with the average of 2,523 deaths over the previous 8 years."
And yet it was still being used relatively recently in artex!

I have no idea where you are going with this or what point you are trying to make.

If you think RCDs are pointless and don't increase yours and your families safety then feel free to remove it. I will stick with them thank you very much.

 

[Gromett]

Spooky how these things happen. One of the channels I follow on youtube just had these videos show up in my "you might be interested" feed.

These are for domestic premises but might be of interested.

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[Nedge68]

I've seen this mentioned a few times in various places but have never got to the bottom of why it is recommended (required?) that the consumer unit should be no more than 2 metres from the EHU. Can any wizards enlighten me, please?....

Firstly definitely not a wizard.
I don’t have a copy of the Regs. infront of me. I think this recommendation has come from the DNO requirements for meter tails, but you are not dealing with an electrical supply from a Distribution Network Operator, you are using a EHU from a ring final circuit, which should have adequate overload and shock protection, there are definately specific regs. about EHU on Sites.
So how safe do you want to be? Keeping the length to the CU as short as possible is sensible as is providing additional mechanical protection and ensuring the cables are adequately supported/fixed, Double pole RCD - Yes. Annual inspection to check installation. - Yes. Check RCD on post and in van everytime It is connected - Yes…
I am guilty of not checking the van RCD, (in external locker.)
I think the most likely failure will be the EHU cable or plug/ socket, which could mean that potentially you loose the Earth connection so now your RCD is not going to protect you. If your van RCD isn’t working check your EHU cable.

 

[The Wino]

I have no idea where you are going with this or what point you are trying to make.

If you think RCDs are pointless and don't increase yours and your families safety then feel free to remove it. I will stick with them thank you very much.

To the contrary what I'm saying is that the widespread use of RCD,s probably makes other regulations less important. Also we probably worry about electricity a bit too much and other dangers too little ( maybe because everyone has heard of the electric chair)

 

[autorouter]

Oh. Just checked and you can get single module dual pole RCBOs. I didn't realise they were a thing.

Unfortunately you can also get single module single pole RCBOs. They only cut the live path when they trip, even though they have a neutral wire built in. In the UK they are more common than double pole RCBOs, because most consumer units have breakers only on the live path, and a common neutral bus. Outside the UK it is more common to have double-pole breakers everywhere, and no neutral busbar. At least with RCDs they will nearly always be double pole. Single pole RCDs are very rare.

 

[Nedge68]

To the contrary what I'm saying is that the widespread use of RCD,s probably makes other regulations less important. Also we probably worry about electricity a bit too much and other dangers too little ( maybe because everyone has heard of the electric chair)

All the regs are important, they are there to prevent you getting the shock in the first place, an RCD is intended to limit your exposure and is the last level of protection If other measures have failed.

 

[DavidCh]

I'd have thought a major part of why there's so few deaths from electrocution is the fitting of RCD,s I know for years people laughed at continental regs allowing sockets in bathrooms etc but don't think they actually have a lot higher rate of electrocuted people and in motorhoming reversed polarity only seems to concern Brits. I'm no expert but weren't RCD common in europe way before they were here and double poll ones on motorhomes so removing the risk. In the context of the length of cable before the consumer unit it would be interesting to see if the continental regs vary.

Reverse polarity concerns Brits because our systems usually only switch the grid (Live) connector not both. In Continental Europe it is usual for circuit breakers to switch both so it does not matter. If you only switch live and the incoming connector is reversed then your internal live and neutral are reversed so, if the circuit breaker is off live is still going to the appliance. The appliance wont work as their is no neutral return but you can still get a live to earth shock.

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[The Wino]

Reverse polarity concerns Brits because our systems usually only switch the grid (Live) connector not both. In Continental Europe it is usual for circuit breakers to switch both so it does not matter. If you only switch live and the incoming connector is reversed then your internal live and neutral are reversed so, if the circuit breaker is off live is still going to the appliance. The appliance wont work as their is no neutral return but you can still get a live to earth shock.

I know that but is it better to fit better RCD or test for reverse polarity etc.

 

[DavidCh]

I know that but is it better to fit better RCD or test for reverse polarity etc.

Its an 'and', not an 'or'

 

[bigtwin]

Its an 'and', not an 'or'

What benefit do you get from testing if you have a double pole RCD?

Ian

 

[Gromett]

What benefit do you get from testing if you have a double pole RCD?

Ian

None of your van sockets switches are double pole for example.

 

[bigtwin]

What benefit do you get from testing if you have a double pole RCD?

Ian

None of your van sockets switches are double pole for example.

Struggling to understand the relevance of your response to the question asked.

Ian

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[Gromett]

Struggling to understand the relevance of your response to the question asked.

Ian

UK vans fitted with switched sockets will only have the live switched.

There is also the matter that in some system the neutral will be bonded to chassis via the earth I believe (victron for example)?

I would always want a reverse polarity test and a means of swapping if it were wrong, even in a vehicle with double pole RCD or RCBO.

 

[bigtwin]

UK vans fitted with switched sockets will only have the live switched.

Neither are switched on the sockets in my van.

Ian

 

[bigtwin]

I would always want a reverse polarity test and a means of swapping if it were wrong, even in a vehicle with double pole RCD or RCBO.

Why?

Ian

 

[Gromett]

Why?

Ian

I answered this in #81

I am not sure I am adding anything to this thread anymore. I will leave it to you all.


Not aimed at you bigtwin just a general response.

If you don't think the RCDs add anything to your safety don't use them.
If you don't think polarity matters in a UK van, don't test and fix.
If you think an RCD doesn't need to be close to where the inlet is. Don't put it there.

You have free choice. But ALL those things are recommended for a reason. If you don't like them don't do them, but don't come crying to us when they bite you.

 

[ambulancekidd]

I don't know how many people have died from electric shocks in their vans but I think no matter what length cables the risk is nonexistent to minute. You are far more likely to be killed in your own home by a tea cosy (one in Suffolk some years ago)

After many years as a paramedic, I can tell you that people die all the time from risks which appear to between negligible & non existent.
Its like the perfect storm scenario, a number of years ago I was at a fatal collision in which a guy who was cycling round the coast of the UK was killed on the A78 near Prestwick.
The car which hit him has a sudden tyre blowout, lost control, slid across a dual carriageway which had no barrier.
The road was ready for an upgrade & the barrier was due to be installed the following day & if the guy had set off a few seconds earlier or later the errant car would have missed him?
I've often wondered about the odd's of this collision even happening must have been astronomical, probably many billions to one against.

The best way to stay alive is to negate the chances of death to as close to nil as possible, this wouldn't have helped the unfortunate cyclist, but you pays your money & takes your chances in life!

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[3alpacas]

That is not where I would have started from sadly. I hate integrated things like that because if one bit goes wrong you are stuffed for the whole system. I always go with separate components.

But you have already committed so I am afraid I can't advise on the Tetris project.

If you do have it any distance from the hookup inlet here is what I would do.
Ensure it is not in any cupboard or alcove where anything could be dropped or shoved into it.
Protect it in at least copex/kopex flexible conduit and try to secure it off the floor. Do not leave it flopping around.
I would do it in such a way that you can get to it after the build is finished so you can inspect it if necessary.
Make sure that if it is damaged it cannot touch any exposed metal work that is connected to the chassis.

Just a silly question. You may not be able to move the EC155 to the EHU inlet. BUT can you install an inlet nearer where the charger is going to be? ie can you move the inlet?

Thank you
Not a silly question at all; that had also occurred to me....I can relocate the EHU, to the other side of the van (the Sargent was going to be slap in the width-wise middle of the van, so the tail would be 1 metre rather than just over 2) though it would be close to the rear of the sliding door when its fully open (of course, not necessarily a problem if there is sufficient clearance)....the remaining challenge would be thinking of what to use the existing EHU hole in the wall for!
...oh, and I'd have to relocate the water pump and accumulator to create the space

 

[Gromett]

Thank you
Not a silly question at all; that had also occurred to me....I can relocate the EHU, to the other side of the van (the Sargent was going to be slap in the width-wise middle of the van, so the tail would be 1 metre rather than just over 2) though it would be close to the rear of the sliding door when its fully open (of course, not necessarily a problem if there is sufficient clearance)....the remaining challenge would be thinking of what to use the existing EHU hole in the wall for!
...oh, and I'd have to relocate the water pump and accumulator to create the space

If I was to relocate it. I would be tempted to leave the existing EHU in place but not connected on the back. It wouldn't look odd or out of place. Cover the hole with anything would perhaps look a bit odd?

As for clearance on the sliding door. That is a judgement call only you can make I am afraid.

Sounds like you are having fun though

 

[Hoovie]

If I was to relocate it. I would be tempted to leave the existing EHU in place but not connected on the back. It wouldn't look odd or out of place. Cover the hole with anything would perhaps look a bit odd?

An interesting option for a redundant EHU connection could be to replace it with an AC OUTLET instead. The wiring for this is virtually in place already, with the only change being to move the cable at the consumer unit from the RCD in to an MCB out.
Having a 240V external out on a van can be very useful. (I have one tucked behind a skirt behind the rear wheel but I am considering changing it for a flush mount outlet with flap actually.)


As far as decisions regarding the location of the Sargent Unit or Consumer Unit and the location of the EHU, if their current positions both suit, I personally would not be concerned about a supposed 2 metre maximum distance from EHU to RCD if that distance was longer.
IF their positioned suited but you were adament about not going longer than 2M, you could easily fit an RCD closer to the EHU and then continue the cable to the main CU/Sargent. There is no reason why you cannot have multiple RCDs between supply and outlets (this will be the case already with a EHU hookup as there will be an RCD on the pitch supply post).
In my own setup, I have a Sargent Unit with RCD and 3 MCBs, but that is actually supplied via another RCD and MCB courtesy of the Victron Easyplus unit I added.

 

[autorouter]

the remaining challenge would be thinking of what to use the existing EHU hole in the wall for!

You can get various connections to fit the hole - a 13A socket for outside use, an external gas point for a barbecue, a hot/cold water mixer for an external shower, etc.

 

[Nedge68]

Can anyone tell me where the 2m guidance comes from? as I mentioned before we are not talking about meter tails in the scenario given by the OP.

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