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RCD test.Explanation please

Jul 30, 2007
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Having had its service recently,among a couple of minor problems,our 2015 Unicorn Cadiz failed on the RCD test.
The engineer did try to explain but I'm not sure what he meant.
The service sheet states the following.....
RCD test X 1 Milliseconds...300 (this was flagged up red)

RCD test X 5 milliseconds....30.3
(this had a green pass).

Would appreciate an explanation in simple terms please.
Thank you
 
Mar 14, 2005
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Caravan RCD's should trip if it detects a fault current of 30mA. It should take less than 40mS to do it. The bigger the fault current the faster it should operate.

The standard tests include checking the trip time with an induced
30mA fault current (x1)
150mA fault current (x5)

Your RCD was reacting too slowly at 30mA hence it failed the test.

RCD's don't stop you from getting a shock, but the thy should limit the duration of a shock so its not lethal.

You should get the RCD replaced.
 
Oct 8, 2006
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An RCD should trip within 200mS at the rated trip current and within 40mS at five times the rated trip current. Ergo the RCD is out of spec at the rated trip current.

To get a pass will require replacing the RCD which is not a major issue if you are competent with mains electricity. If the MCBs and RCD are the horrible Chinese things - the name escapes me at this instant - in my case on my last van (Pegasus 462) a Schneider (formerly MEM) RCD was an exact fit albeit the outlet side wiring had to be changed.
 
Jul 30, 2007
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Many thanks for replies.
Are you saying that the RCD is working,but reacting too slowly?
If so,looks like a new unit when I take it to supplying dealer on June 14th.👍
 
Last edited:
Oct 8, 2006
1,139
170
19,235
Many thanks for replies.
Are you saying that the RCD is working,but reacting too slowly?
If so,looks like a new unit when I take it to supplying dealer on June 14th.👍
The only catch is that the dealer will probably fit like for like (especially if it is still under warranty) so you cannot be sure the replacement will be any better. It is something any electrician can replace for you which will give you a choice of fitting something better.

In terms of current flow, it is generally regarded that 40mA flowing across the heart could be lethal. Across the heart means hand to hand or hand to opposite foot. Foot to foot current and hand to same side foot are less likely to be lethal but still won't do you any good. It comes down to you personal conductivity and skin resistance. Some people can get a shock off a 12V battery, but IME most people will not feel much until you get around the 90-100V area, which is why 110V is used for on-site power tools. In reality it is not 110V but 55-0-55 with a sensitive RCD in the centre tap. You will feel the shock (a bit at least) but the RCD will go before any damage is done.
Electricity makes you muscles contract - try touching a cattle-type electric fence by resting a finger on it: when the next pulse comes along your arm will fly upwards as your arm muscles contract (been there, done that etc etc) without the owner of the finger actually doing anything - it is an automatic reaction. This is where fatalities occur: if someone with internal resistance on the low side holds something that is or becomes live, the arm and hand muscles will contract, they cannot then let go of the live item and it rapidly becomes a serious burn issue if not a fatality.
 
Mar 14, 2005
14,157
987
40,935
Many thanks for replies.
Are you saying that the RCD is working,but reacting too slowly?
If so,looks like a new unit when I take it to supplying dealer on June 14th.👍
If the RCD is reacting too slowly it is not working correctly, and that could put you or your family in danger if an appliance goes faulty

Quite simply get it changed.
 
Jul 30, 2007
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205
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Just an update.....
Took van to main dealer today for a new tyre(bulge on inner wall) and they also checked the rcd.

Oh......when it was serviced I had highish damp readings around rear of wheel arch and around the shower cubicle.
As the service at the storage compound found it wasn't the rear roofstrap,they put it down to the rear offside locker door leaking(which I promptly taped up with gaffer tape).

Anyway.....had a phone call from main dealer this morning to say they have replaced the rcd.......changed defective tyre......plus re-sealed the rear roofstrap and fixings as they were very rusty with a lot of mould present!!!!!!

So much for the diagnosis at the compounds service centre.

Main dealer has also washed,waxed the sides,front and rear and vacuumed the interior.
All done under warranty....
Well happy.
Just have to find something to remove all the gooey mess from the gaffer tape when I collect it🤔
 
Jun 16, 2020
1,513
489
1,935
Just an update.....
Took van to main dealer today for a new tyre(bulge on inner wall) and they also checked the rcd.

Oh......when it was serviced I had highish damp readings around rear of wheel arch and around the shower cubicle.
As the service at the storage compound found it wasn't the rear roofstrap,they put it down to the rear offside locker door leaking(which I promptly taped up with gaffer tape).

Anyway.....had a phone call from main dealer this morning to say they have replaced the rcd.......changed defective tyre......plus re-sealed the rear roofstrap and fixings as they were very rusty with a lot of mould present!!!!!!

So much for the diagnosis at the compounds service centre.

Main dealer has also washed,waxed the sides,front and rear and vacuumed the interior.
All done under warranty....
Well happy.
Just have to find something to remove all the gooey mess from the gaffer tape when I collect it🤔
Good news, (mostly}. Re the sticky mess. Most pound shops sell sticky stuff remover. Brilliant stuff.

John
 
Jul 30, 2007
1,195
205
19,435
Thank you John.
Ive also read that wd 40 and Auto Glym tar remover is supposed to be good.
Will try the pound shop first👍
 
Jul 30, 2007
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205
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Bargain!!!!!

I've also given my present storage compound 1 months notice that I'm leaving so I won't be tied to their servicing anymore.
I have a space at another compound available to me now,so thats where its going when we come back off holiday.
 
Nov 11, 2009
11,440
1,999
40,935
Just an update.....
Took van to main dealer today for a new tyre(bulge on inner wall) and they also checked the rcd.

Oh......when it was serviced I had highish damp readings around rear of wheel arch and around the shower cubicle.
As the service at the storage compound found it wasn't the rear roofstrap,they put it down to the rear offside locker door leaking(which I promptly taped up with gaffer tape).

Anyway.....had a phone call from main dealer this morning to say they have replaced the rcd.......changed defective tyre......plus re-sealed the rear roofstrap and fixings as they were very rusty with a lot of mould present!!!!!!

So much for the diagnosis at the compounds service centre.

Main dealer has also washed,waxed the sides,front and rear and vacuumed the interior.
All done under warranty....
Well happy.
Just have to find something to remove all the gooey mess from the gaffer tape when I collect it🤔
You seem to have a good dealer there. As JC says sticky stuff remover is gentle and effective.
 
Jul 30, 2007
1,195
205
19,435
Collected caravan from dealer this morning.
On my way there,I called into Poundland to buy some "sticky stuff remover".
As they were a smaller store,they didn't stock it so I continued over to get the caravan armed with a tin of WD 40.
To cut a long story short,one of the mechanics brought out about half a tin of "SAS label and gum remover".
What a nice chap.
Have a look at the picture below.
Absolutely brilliant.
The gaffer tape had well and truly left its residue (especially in this heat).
Sprayed on a section at a time and leave for 2-3 minutes.
I used a plastic car filler scraper and it just seemed to melt off.
Washed locker door after with warm soapy water then a coat of Auto Glym polish.
That tin of remover was excellent.....highly recommended.20210615_120226_compress67.jpg
 

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