Is an RCD needed in a MH (1 Viewer)

Feb 24, 2013
13,148
101,692
Bolsover, Derbyshire
Funster No
24,833
MH
Hymer S800
Exp
not long enough
Our Hymer has never had one, not sure if ever fitted or removed by dealer or previous owner

It hasn’t crossed my mind to fit one or even worry about not having one, based on all U.K. supplies we will connect to will have an RCD, or am I wrong to think that as well 🤔

Only raised as query now as daughter is having a van converted and she asked me if we had one, her convertor asked her if she wanted one and she has said yes
 
Jul 28, 2008
822
753
Wiltshire, UK
Funster No
3,483
MH
Ducato Sportivo
Exp
Since 2005! 2000+ nights so far...
DIY, you don't need to do anything which is a little bonkers. But then DIY gas is fully permitted in vans too - which is scarier if you see some DIY installs!

But having one is no issue, and I'd recommend both RCD and dual pole breakers (as reversed polarity is fairly common abroad).
Bear in mind an RCD trips if "you" are carrying current to earth and thus stops you having a shock, not having one is madness really. Never trust your hookup connection to save you!
Should be part of the CU - but if hymer have their "own" then who knows!
I'd not want to say if its "law" or not, or if it only applies to UK made vans?

Edit: Something like the PO104 is excellent for purpose (I've used it on both vans I converted)

71DawY-WJeL._AC_SL1280_.jpg
 
Dec 2, 2019
4,165
9,348
South Lincolnshire
Funster No
67,140
MH
Rapido 7065+
Exp
Broken most bits now
Also interested to know if an RCD would work in the van as you are insulated from earth by 4 tyres so theory is you couldn't get a shock but no way am I going to try it🤔
 
Nov 30, 2009
6,548
149,623
Pickering
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9,521
MH
PVC the PUG
Exp
Since 2009 with motorhomes several caravans then tents before that.
Ralph fitted one in Pug David. We had one in the previous shop bought Mizar too.
He says are you sure you haven't got one ?
 
Apr 14, 2022
292
530
Carvoeiro, Portugal
Funster No
88,080
MH
Bavaria T71LP
Exp
50 years of boating, just one on motorhomes.
Someone far better qualified than me will answer I am sure but this is what I understand. If you don’t have one and you have connected the hook up earth then you are making the assumption that the external one is working and their earth is properly connected. Fitting your own is a good back up. If you are not connected to their earth then you are ‘floating’ so should not get a shock as there is no path to earth. Personally, I would fit one, it’s cheap, has no downside but might save your life. A more important question be ‘is the hook up earth connected to my chassis’. If yes then definitely yes. Of course bring an inverter into the picture and….. (reaches for paracetamol)
 

ctc

Oct 12, 2015
1,535
2,570
Crowle
Funster No
39,408
MH
Hymer b680
Exp
New
RCD's can protect you from shocks, which can be painful and unpleasant. But they are not reliable, good quality fuses of the right size should always be used. Too many leave the 13amp fuse supplied and don't change it to suit the appliance.
 
OP
OP
DavidG58
Feb 24, 2013
13,148
101,692
Bolsover, Derbyshire
Funster No
24,833
MH
Hymer S800
Exp
not long enough
He says are you sure you haven't got one ?

😁 fair question 👍

AB74E500-DA11-4FC1-B680-D5A503773313.jpeg


Fairly sure there isn’t one here, no test button 🤔👍

It’s also not something I will be doing myself, we have an electrician who looks after our house and rentals , he also has a MH , will get him to check it and fit one if needed

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Jan 31, 2022
278
131
Funster No
86,605
MH
70s camper,Weinsberg
Rcds are fitted to all hook ups for a reason, most probably dont work as they get tripped continiously so have your own and get it tested. Fault current jumps across the shortest path YOU !. Probably as Lenny says most abroad are reverse polarity so get a plug tester too, I bet you have extra security on your motorhome so it doesnt disappear or is that more important than being electrocuted !! Rant over...
 
Apr 14, 2022
292
530
Carvoeiro, Portugal
Funster No
88,080
MH
Bavaria T71LP
Exp
50 years of boating, just one on motorhomes.
An RCD is very simple, it looks at the current coming which should be identical to the power going out, if it is different then it must be finding another path to the line going out and will trip if it is more than 30ma which is considered to be the highest amount that won’t kill you. It was designed for appliances that have metal cases that could develop a fault that connects live to a metal case. If there is no path to earth than you can’t get a shock. However, the earth and neutral are connected together, usually where power comes into the premises, and to the ground so you need an RCD to protect you if you touch anything that is live, whilst you are connected to earth.
 
Jul 28, 2008
822
753
Wiltshire, UK
Funster No
3,483
MH
Ducato Sportivo
Exp
Since 2005! 2000+ nights so far...
Also interested to know if an RCD would work in the van as you are insulated from earth by 4 tyres so theory is you couldn't get a shock but no way am I going to try it🤔
You are sort of correct. The CU should be bonded to the van chassis as earth, so it will actually stop you carrying voltage to the van metalwork. It likely a EHU will have earth connected (lol - not always) and that is to "earth" - so thats your path.

Thats why you don't use the "camping EHU" cables in vans (despite many saying "hey, its fine in tents, why not a van". Slamming cable in door, splitting it, could get you a shock as the cable isn't bonded to the chassis.
 
Jul 28, 2008
822
753
Wiltshire, UK
Funster No
3,483
MH
Ducato Sportivo
Exp
Since 2005! 2000+ nights so far...
😁 fair question 👍

View attachment 717013

Fairly sure there isn’t one here, no test button 🤔👍

It’s also not something I will be doing myself, we have an electrician who looks after our house and rentals , he also has a MH , will get him to check it and fit one if needed
Odd - (a) thats missing, and (b) that will allow you to draw 23A from the hookup - yet the cable and socket is rated to 16A only regardless of what the supply could give. So you could max the 23A through an unrestricted EHU post and overload cable, socket and get into a right mess.

There is a reason the one I posted above has 10+6!

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OP
OP
DavidG58
Feb 24, 2013
13,148
101,692
Bolsover, Derbyshire
Funster No
24,833
MH
Hymer S800
Exp
not long enough
3crispies

I am guessing you have electrical qualifications which give you very much more knowledge than me on this , hence my question 🤔

However I can’t imagine Hymer have fried many customers or for that matter broken any laws when they sold our MH into the U.K. in 2008

I will look to improve the electrical safety in my MH by a qualified tradesman, but we have survived 10 years to date

(exactly 10 years , we picked it up on 14th Feb, our anniversary ❤️ 2013, I joined MHF the following day 😁)
 
Mar 11, 2013
1,288
1,701
Gillingham
Funster No
25,056
MH
coachbuilt
Exp
since 2005
Also interested to know if an RCD would work in the van as you are insulated from earth by 4 tyres so theory is you couldn't get a shock but no way am I going to try it🤔
When using your hook up cable so long as the earth is connected within the plug and socket the van is no longer insulated from ground.
 
OP
OP
DavidG58
Feb 24, 2013
13,148
101,692
Bolsover, Derbyshire
Funster No
24,833
MH
Hymer S800
Exp
not long enough
Odd - (a) thats missing, and (b) that will allow you to draw 23A from the hookup - yet the cable and socket is rated to 16A only regardless of what the supply could give. So you could max the 23A through an unrestricted EHU post and overload cable, socket and get into a right mess.

There is a reason the one I posted above has 10+6!

I am easily confused and your reply has done just that, so not only do I not have an RCD do I also have over rated breakers? 🤔
 
Nov 30, 2009
6,548
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Pickering
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PVC the PUG
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Since 2009 with motorhomes several caravans then tents before that.
Happy Anniversary Love GIF by Hallmark Gold Crown

Happy Anniversary Bev n David 👍

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Lenny HB

LIFE MEMBER
Oct 18, 2007
54,095
152,695
On the coast in West Sussex
Funster No
658
MH
Hymer B678 DL
Exp
Since 2008 & many years tugging
I seem to remember when I bought a Hobby caravan in 2002 it didn't have an RCD but if you bought from the UK importer they fitted one.
All my Hymers have been self imports so British dealers were probably fitting them before Hymer started fitting them.
 
Jul 28, 2008
822
753
Wiltshire, UK
Funster No
3,483
MH
Ducato Sportivo
Exp
Since 2005! 2000+ nights so far...
I am easily confused and your reply has done just that, so not only do I not have an RCD do I also have over rated breakers? 🤔
Sorry
One is 10A.
One is 13A.
Each will protect "something", a circuit, fridge, a number of sockets? Who knows. (documentation/manual?)

Mine, 10A + 6A. generally the 6A controlls the fridge + charger; 10a is the sockets. But AFAIK no real rules. The idea if you trip the 10A overnight, you can still charge up and your fridge is fine.

Anyway, on yours, if socket 1 is on the 10A breaker, and socket 2 is on the 13A breaker, then if you pull 10A on (1) and 13A on (2) then you could pull 23A through the CU. Generally the cable supplying is rated at 16A. The hookup plugs/sockets are only rated at 16A and generally most hookup cables are rated at 16A.

In UK, its likely you'll trip the site breaker - but not all sites have individual breakers.

If your 10A breaker is charger+fridge (2-3A?) and your 13A is sockets, then you will only pull 13+3 so will be fine.

But yeah, looks like breakers are sized generously....
 

Langtoftlad

LIFE MEMBER
Apr 12, 2011
8,901
152,345
Langtoft, South Lincs
Funster No
16,024
MH
WildAx Aurora FB [PVC]
Exp
Since 2015
I think even my Wildax, which has the cheapest, lowest specification, electrical system, has one ..
But I could be mistaken.

Happy Anniversary.
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
54,095
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On the coast in West Sussex
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658
MH
Hymer B678 DL
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Since 2008 & many years tugging
Too many leave the 13amp fuse supplied and don't change it to suit the appliance.
Fuses are to protect the cable from overload not the appliance, as long as the cable is of a higher rating than the fuse it is OK
When using your hook up cable so long as the earth is connected within the plug and socket the van is no longer insulated from ground.
Correct, a lot of people forget that.
Also interested to know if an RCD would work in the van as you are insulated from earth by 4 tyres so theory is you couldn't get a shock but no way am I going to try it🤔
Tyres aren't an insulator they have a high carbon content. If you remember it was quite common to get a static shock when you got out of a car hence the reason for the higher carbon content nowdays
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
54,095
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On the coast in West Sussex
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658
MH
Hymer B678 DL
Exp
Since 2008 & many years tugging
Yes David's MCB's are a bit odd I've had 3 Hymers all they have ever had is a single 10 amp MCB.

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OP
OP
DavidG58
Feb 24, 2013
13,148
101,692
Bolsover, Derbyshire
Funster No
24,833
MH
Hymer S800
Exp
not long enough
Sorry
One is 10A.
One is 13A.
Each will protect "something", a circuit, fridge, a number of sockets? Who knows. (documentation/manual?)

Mine, 10A + 6A. generally the 6A controlls the fridge + charger; 10a is the sockets. But AFAIK no real rules. The idea if you trip the 10A overnight, you can still charge up and your fridge is fine.

Anyway, on yours, if socket 1 is on the 10A breaker, and socket 2 is on the 13A breaker, then if you pull 10A on (1) and 13A on (2) then you could pull 23A through the CU. Generally the cable supplying is rated at 16A. The hookup plugs/sockets are only rated at 16A and generally most hookup cables are rated at 16A.

In UK, its likely you'll trip the site breaker - but not all sites have individual breakers.

If your 10A breaker is charger+fridge (2-3A?) and your 13A is sockets, then you will only pull 13+3 so will be fine.

But yeah, looks like breakers are sized generously....
No apology needed, I just don’t get ‘technical’ , but thanks for the explanation 👍

This doesn’t make sense though, for convenience last summer I plugged a garden chipper into a socket in MH and tripped the MCB 🤔 works fine on house sockets 🤔
 
Jul 28, 2008
822
753
Wiltshire, UK
Funster No
3,483
MH
Ducato Sportivo
Exp
Since 2005! 2000+ nights so far...
No apology needed, I just don’t get ‘technical’ , but thanks for the explanation 👍

This doesn’t make sense though, for convenience last summer I plugged a garden chipper into a socket in MH and tripped the MCB 🤔 works fine on house sockets 🤔
It does make sense.
Maybe the socket you used was the on the 10A MCB and you were pulling more (10A = 2500w ish). So a 3000W thing would trip it.

If it tripped the 13A, then your MCB is knackerd lol as a normal 3-pin plug is rated at 13A so will have (max) 13A fuse.

So you ONLY have a van issue if, say, you plug in a 2200W something on the socket protected by the 10A MCB and a 3000W something in a socket protecting the 13A thing. Then the TOTAL draw is 23, which is "fine" from your CU, but not from your hookup which is only rated at 16A max.

(MCBs can fail and trip below their rating, or just randomly if they see fit!)

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