Caravan suppły RCBO

[Bsharp]

Hi I haven't posted for a while but I'm having some issues with a caravan park I have recently carried out some work on and washoping somebody may be able to shed some light on the issue.
The problem is burnt out neutrals on out going side of RCBO, we have replaced 137 caravan suppły points I've the winter and now the camp is back open the problems have started, I have replaced 5 RCBO'S up to now all with the same BADLY burnt out neutral, now I know the obvious answer is loose connection on the neutral but was wondering if any body had come across the same problem with a different cause as we check all manufacturers connections. The supplies have been reduced to only 10amps!! (By instruction of camp owner to reduce electricity consumption as the camp pays for the electricity)
i can't see any overload issues apart from the standard "nuisance tripping" until caravan owners decrease the power they are using. The reason may just be the odd loose neutral but in my 25 years of work I have never seen so many in such a short space of time! Any ideas would be great fully recieved.

Thanks.

 

[Plonker 3]

Have you checked the resistance acroos the incoming and outgoing neutral connections to make sure it is not a hight resistance joint?

 

[Bsharp]

Hi Dillb,
not quite sure what you mean, are you saying there could be a high resistance joint between the suppły cable and the RCBO in suppły box?

 

[Plonker 3]

Well it seems there is high resistance joint somewhere, is it in the RCD itself?

 

[Bsharp]

Quite possibly I'll be carrying out a few resistance test tomorrow on a few random rcds around the site. I'm starting to think this could be a problem with the manufacturer

 

[davesparks]

If you put a load on the circuit and measure the voltage each side of the RCBO you will able to see what it's resistance is under load.

 

[Bsharp]

I'll do that tomorrow Dave.
Thanks

 

[Bsharp]

Do you think that the fact that no boot lace ferrules have been used in the boxes by the manufacturer that the fine cores of the fly leads which appear to be spread could cause a high resistance joint??

 

[davesparks]

Do you think that the fact that no boot lace ferrules have been used in the boxes by the manufacturer that the fine cores of the fly leads which appear to be spread could cause a high resistance joint??

It wouldn't necessarily cause an increase in resistance, but it can create a significant reduction in CSA at the point of the connection. But it depends on the type and design of the terminal. A cage type terminal such as you get in MCBs and din rail connectors where a flat plate traps the conductor against another plate is unlikely to suffer as much as a standard screw terminal.

 

[Bsharp]

The terminals are din rail connectors direct into RCBO, no screw terminals are used like we see in neutral bars, surely the decreased csa of the conductor could cause a high resistance taking into account these vans are only on 10amp supplies so are pulling very close to the maximum??

 

[driverman]

Might be a bad batch,has been known. Is it a particular make? Well known?

 

[Bsharp]

Rolec caravan hook up boxes, unsure of make of rcbo as they are labeled up as rolec but I doubt they manufacture them!!