Failing RCBOS In "TT" caravan park install

Main supply neutral hr (fizzing/intermittent)

 

Hi Barry can you post any photographs? Would be interesting to see the result.

 

Sounds like loose connection at the melted terminals, either internally, or your torque made ones. If using a torque driver, you do need to make sure your conductors have spread/settled/been arranged prior to torquing.

Photos would be good, and the report from the manufacturer

 

Who is the manufacture ? Are they good quality in the first place .
I would not trust them on their word either , We have a on going dispute with ABB at the moment on a 1MW solar install we carried out about 20 months ago . We have already had two of their 3ph boards go up in smoke from a faulty rivet on the internal buss bar .
The first was sent away for inspection , only for them to tell me after 8 months , it was a lose connection on our side ( even though three different members of staff including myself had inspected and torqued them up ! ) .
And on the second one to go up I went out and brought near on £3 grand's worth of thermal imaging camera just to prove them wrong , only to find that they have lost the offending fuse board with their internal couriers whilst sending it back to Egypt for testing !!!!!! This second one has been going on for about 10 months now .
I am due to go back to site and check for more any day as the sun is threatening to show its face again soon .

 

I have fitted loads of Rolec stuff, and not had issues like this. The RCDs and RCBOs are known to fail trip tests after a while out in the wind and rain, but I've never seen this. They are only around £7 each, so you can see they are budget. Perhaps a dodgy batch?

Serial numbers will differ (that's the point of them), part numbers shouldn't.

The VKL RCBOs are fitted in all their recent kit. These are almost consumable items on large sites, to replace those that won't trip. I've never seen them do that.

 

Looking a Mk RBCO I have here, it has a 'Ambient temperature range' of 5-40 degree centigrade, is it possible yours are exceeding their temperture rating, (overheating) due to the loading,& in a enclosure & maybe a bad batch?

 

Couple of questions that might be relevant. Is it always the neutral? Do you try tightening up the screw terminal without a torque screwdriver?

Multi-strand copper wire is not the best metal for using a torque driver on. This point has been sorely missed by the industry. I know a fair bit about metals as I did a structural engineering degree and torqueing of bolts is designed for high tensile steel! If you torque copper it is at best unreliable because it will yield under the high pressure from the bolt being malleable and ductile. The properties of the copper that enable it to be drawn in to thin wire works against it when it is terminated in accessory terminals. IMHO unless you bo!!ock the terminal screw up and then again and even a third time you cannot guarantee the tightness of the screw. I don't use torque screwdrivers for this very reason. Don't get me wrong, I am sure you have used the torque driver correctly, but, all I'm saying is don't rely on it as a primary measure, also tighten it without and see if there is much difference in tightness.

 

Any multistrand copper cable can come loose if not unwound and flatened off first.

When in DNO employment I encountered countless 16/25mm tails that had burnt out as they'd been installed by Sparks full wound.

I've seen screwdrivers/meter/Iso terminals snapped under tightening but if the inserted cable is not unwound then a few swings left and right can see the cable almost pull straight out.

 

I would advocate using the torque screwdriver last. You tighten up the terminal until you are satisfied then use the torque screwdriver to be sure. I am also wondering whether the crimped lug method of securing tails on to domestic CU switch incomers should be adopted like the industrial switches. Crimping a lug on to the tail then securing the lug with a nut and bolt would be infinitely more secure than trying to pinch up strands of copper in a useless screw terminal. It seems that the method of securing copper wire in to terminals is long overdue for review and rather than take measures to enclose fires that occur as a result of this manufacturers should be looking at ways of improving the method of terminating wires thus eliminating the cause of the fire instead of accepting it will occur and trying to contain it.

 

Brilliant idea!

What about using a pin crimped connectors.

 

Having RCBO'S with tails pre-attached only available, would save a lot of grief.

With those Rolec RCBO's shame there isn't a pin crimped connector you could use on the cable,would having given a more secure connection than presently used.

 

Hi
You've said they fail on the outgoing side.
If that's where the cables are fitted on the images, then I would say they are being fed backwards.
You can see the arrows pointing into the top of the device on the schematic, that should be the line.

i would ask them to confirm line /load side on them before going much further

 

If the terminals were round instead of square and the correct size then it would help a lot. Look at the earth bars in consumer units, a 16mm cable is the perfect size for the hole usually, if you untwist that cable you won't get it in.

Half the time the screws are too soft on mains switches and don't take much rounding off. I will admit to using an impact driver on a main switch in some cases, better than any torque screwdriver if you are delicate with it.

 

Ferrules are more appropriate, but still more designed for screw type terminals and not particularly the "vice" type.

I'm not a fan of torque drivers at all - They don't want you under or over tightening. You really do need to "settle" the conductors in before you make the "torque tweak".

 

Impact driver Peter? that's well ott, impact drivers are for undoing things not assembling!

 

Hmm. I use my impact driver for both.

 

Hi UP, I must say I've never considered using an impact driver for tightening things, I can't even imagine using one on a c/unit main switch, it must knock the sh** out of the plastic enclosure and bus bar attachment points! I have used impact drivers quite a bit in my time but always in connection with working on motorcycles and cars, the Philips and pozidrive screws on *** bikes are immovable with a hand held screwdriver.