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To B or not to B the RCCB


The Ents
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2 minutes ago, Alan de Enfield said:

That is very low - a typical 30Ma MUST blow by 30ma, and most blow around 23ma, I guess that the 10ma would blow at about 7 or 8 ma. - almost nothing.

 

It is cumulative so all the other boats are not quite taking it over the edge but when your 'comes on line' it goes over the top.

 

See if you can get the marina to try with everybody disconnected and then re-connect you, then one by one all the others, it could well be the 'last one; pushes it over the edge,.(whoever the last one is)

Yes, it all somewhat backwar in priorities i think.The Electrician is coming to the marina tomorrow....

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2 minutes ago, The Ents said:

That would be interesting. I shall try to.

Mike.

Specifically, having two RCDs in series is always a bad idea, and if the first one is of a higher sensitivity (lower fault current) than the subsequent ones then the subsequent ones might as well not be there because the high sensitivity one will always trip first. 

 

It’s also worth noting that the reason that 30mA RCDs are much more common than 10mA RCDs is because the 10mA ones are far too prone to nuisance trips. 

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I had a fairly similar problem on my last mooring. Single RCD protecting three boats. Situation seemed to develop over a period of time but it was only ever when I was connected that the RCD tripped. Whenever I connected to a supply elsewhere , no problem. I stripped out every bit of 230v wiring and equipment and either checked with an insulation tester or permanently disconnected the item. Found nothing. I always felt it was a suspect RCD but could never get the site owner to change it (even when I offered to pay)  In the end I was forced to give up an absolutely idyllic mooring in favour of a soulless marina. No issues since.  

Charger in question was (and is) a Mastervolt 100/2000 Combi

Edited by Slim
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12 hours ago, Keith M said:

Typical the Master RCD will be  100 mA or variable.

This would be a standard configaration 

 

Exactly, I have never seen a 10mA RCD on a domestic or industrial electric supply.

 

Rusty's suggestion of moving the boat to another supply is the only one likely to result in a definitive identification of the cause of the problem.

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Some years ago we had a similar problem with 4 liveaboards on one pole and the RCBO tripping due to combined earth leakage. The marina were very good, first changing the RCBO in case its spring had weakened and made it over-sensitive. Didn’t help, so one boat had its supply moved to a different pole with fewer boats on it.

 

That worked, but it was part of my reason for getting the IT. Once that’s in place, if this sort of thing starts happening you can put your hands up and say “Not me, guv!”

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1 hour ago, BruceinSanity said:

That worked, but it was part of my reason for getting the IT. Once that’s in place, if this sort of thing starts happening you can put your hands up and say “Not me, guv!”

Yep, it’s good to have that smug feeling when the fingers start pointing ;) 

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3 hours ago, cuthound said:

 

Exactly, I have never seen a 10mA RCD on a domestic or industrial electric supply.

 

Rusty's suggestion of moving the boat to another supply is the only one likely to result in a definitive identification of the cause of the problem.

We used to fit 10ma RCD's in science labs etc in schools, but 10mA seems very low for a setup such as this.

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Yes guys you are correct. The RCD at the supply into the marina is rated 100ma. My error I’m afraid, should have gone to specsavers..

But interesting meeting with the Electriciam.

He first tested our bowt which passed with flying colours! Yippee!

at that instant the whole marina tripped! (Yippee, but I didn’t say that.) with our boat not connected.

So this poor bloody electrician has a real problem. The boat next to ours has a shoreline plugged into a galvanic isolator and the euro plug is full of rainwater. He disappeared and changed some RCD stuff and unplugged other suspects’ boats.

Later, much later, he came to our pod and tested the earth which was OK at 60ohms. However as soon as he put his tester into our pod socket and began to test the RCD at the pod the main RCD at the marina tripped at a very low current, I couldn’t see what sadly. Sorry.

So we have what my dad would have called a right pig’s ear. I left the poor fellow still working his socks off at 4.30pm!

At least I know it is not our bowt!

I must thank you for your comments so far and look forward to reading some more of your thoughts this evening!

Mike.

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1 hour ago, The Ents said:

I must thank you for your comments so far and look forward to reading some more of your thoughts this evening!

Methinks he has accumulated leakage right across the site and he’ll simply have to go through it methodically. 

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4 minutes ago, Keeping Up said:

I wonder what the switching current rating of that RCD is, if it switches the total consumption of the entire marina.

Back in the 70’s I visited the catering kitchen in a large Birmingham venue. The main 3-phase breaker for the kitchen feed had a 30 pound stage weight hanging from it on a piece of string. When I queried it I was told “Well if we turn on all the ovens as well as the dishwashers and driers it turns off without that weight on it.”

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Although the problem seems to have been identified as being somewhere other than your boat I will make one observation.

 

A possible cause of tripping at 3:30 am in cold weather could have been your webasto kicking in at 3 am

heater kicks in at 3 am and boat starts to warm up
warming up boat causes condensation to form on cold metal parts

condensation in mains powered equipment or fusebox trips mains.

 

We used to have a ride where for the first 5 minutes each day it could sometimes (maybe once every 2 weeks) trip our supply if it had been humid the night before, after those first 5 minutes all the motors were warm and their cooling fans had taken any moisture out. after 3 years we gave up trying to find out which one of 50 motors was causing the problem.

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16 hours ago, The Ents said:

Wow, that is food for thought. Thank you.

 

So what would be the fix for that? Silicone spray?

 

Mike.

in our case the solution was either spend several thousand on getting a spare of each type of motor and hundreds of hours in down time while we went through each one or run the ride empty for 2 full cycles each morning instead of the 1/2 cycle required for the daily safety check.

 

we never placed any faith in extra sprays since we didn't want any extra coating that could hold the fine sand that used to get blown in, if left dry the sand falls away but with a lot of coatings it stayed and turned into a very effective grinding paste, I still have a swivel from another ride that got oiled because it had an annoying squeak from new, 1 week later we had to replace the swivel because we found the sand and oil had cut almost halfway though the unit (they usually lasted 2 years)

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