EHU tripping

[two]

I’m trying to find out what might have happened to cause my domestic batteries to drain on a boat that I own. The EHU cable (shore-line in boating terms) was plugged-in with the cover vertical, rather than going into the inlet, so that a poor connection resulted. An RCD tripped in the bollard, leaving all power demands to be taken from the batteries instead. I’m trying to understand what would cause the bollard RCD to trip as I’m not convinced that a poor plug-socket connection should do that.
Maybe someone has experienced similar?

And, if there is more than one RCD along a supply line, could more than one trip?

 

[Phill D]

Poor connection will often result in high resistance and increased temperatures thus increased current so the RCD would very likely be caused to trip.

 

[Abacist]

Surely if the EHU plugin to the boat was not covered properly water could cause a short resulting in a trip? That can happen with my EHU with long persistent rainfall.

If you had a Bluetooth shunt and something like a Victron Cerbo GX you could monitor remotely on the internet and set up alerts to warn you of problems like this.

 

[Phill D]

Ps:

The EHU cable (shore-line in boating terms) was plugged-in with the cover vertical, rather than going into the inlet, so

Does this mean water / rain can get at the ehu connection? If yes then there is your probable cause

 

[matbic]

When I had a boat the most common reason for tripping the RCD was damp. Damp connectors, wires or other components in the boat. Causing a leak to earth and so tripping the RCD.

^{_{Subscribers  do not see these advertisements}}

 

[two]

When the RCD trips, will it necessarily be an 'upstream' one (towards the supply) or could it be the one in the boat?
I agree that water ingress might be the cause, as the connector was not fully engaged and not protected as intended, but am trying to understand the consequences.

 

[Abacist]

A Downstream trip does not solve the problem.

Upstream trip cuts off the supply and makes the cable and connection to the boat safe! I.e removes threat to life!

 

[autorouter]

And, if there is more than one RCD along a supply line, could more than one trip?

Once one of the RCDs has tripped, it will stop the supply to the faulty item, so other RCDs along the line won't trip. If there's two possible RCDs, they will probably have the same trip limit nominally, ie 30mA. One of them will be slightly lower than the other, due to production tolerances etc, so one will trip first, but it's not possible to predict which one.

 

[two]

I was told that when the EHU was plugged-in incorrectly once before, the inboard RCD tripped.
Is that likely to be possible? (I don't think so.)
It seems, to me, that only a 'supply-stream' RCD (eg in the bollard) could be tripped because the short is the wrong side of the one inside.

 

[autorouter]

I’m trying to understand what would cause the bollard RCD to trip as I’m not convinced that a poor plug-socket connection should do that.
Maybe someone has experienced similar?

An RCD doesn't trip if there is excessive current (amps). That's not its purpose, that's the job of an MCB, which will have a set limit written on it, like B10 (10 amps) or C16 (16 amps).

What an RCD (Residual Current Detector) does is compare the outgoing current to the returning current. They should be exactly equal. If there is a difference, some current (residual current) is leaking to earth. For example, if you touch a live wire, current will pass through you to earth. That shows up as a difference in the outgoing and returning current.

If the difference is greater than a very small amount - 30 milliamps usually - then the RCD will trip. It is designed to protect humans against electric shock, but also protects against other things too. That 30 milliamps is written on the RCD, usually '30mA' or '0.03A'.

So the likely scenario is that water gets into a plug or socket, and causes a small leakage to earth inside the plug, enough to trip the RCD.

If you look carefully at the plugs and sockets you will see the marking of the IP rating, usually at least IP44. IP = Ingress Protection, the second number (4) is for liquids. 4 means proof against splashes from any direction, and is normally considered rain-proof. It's not proof against hose jets or powerful splashes, and not proof against immersion. Of course this protection assumes that the plug is assembled correctly and inserted properly.

The standard round blue plugs and sockets found outdoors on campsite and marina hookup posts are usually IP44, and are rainproof. There is a version of these round blue plugs and sockets that are much more waterproof - IP67 or IP68. They have a sealing ring and rubber gaskets.

^{_{Subscribers  do not see these advertisements}}

 

[dash300]

Worth trying the YBW forum too!