BANG!

[Julie.]

Oops.

Neighbour at the door early hours (04:00 ish)

Sparks and flame from cu.

Somewhat panicked!

By the time I got around there, the main fuse had gone, most damage to the spd, but full of arc residue on the rcbos around it.

Managed to save most of the board, but need new rcbo x 4 and the spd itself - at least I think it's not well!

Got most of it sorted in time, spen just round and replaced fuse, so some circuits back up now.

Rushed home to check my spd - all fine, so assume we are on different phases.

 

[davesparks]

It would be good if all manufacturers could change their terminals to prevent conductors from being inserted behind the clamp instead of in it.
Some terminals have a flat piece behind the clamp which travels with it to cover the hole when it is not open so you can't end up in this situation.

Even for the majority of us who do check every connection properly it is still very annoying when you find one which has gone behind the clamp, especially with the removable busbar normally found in domestic CUs.

 

[radiohead]

Now it’s getting down to who installed the Cu, cut corners and didn’t even do a tug test.

A loose connection could have caused a fire even without soapy bubbles

Mistakes happen, everyone drops a clanger sometimes, and in our game that can mean a dangerous situation is created. This could be an innocent error by an otherwise conscientious electrician. I'm afraid it gets my back up when this sort of thing immediately results in an assumption that corners were cut, a cowboy, without any real evidence that this is the case. This could also be a manufacturer fitted unit, of course even manufacturer connections should be checked, but let he who is without sin cast the first stone.
[automerge]1592249547[/automerge]

It would be good if all manufacturers could change their terminals to prevent conductors from being inserted behind the clamp instead of in it.
Some terminals have a flat piece behind the clamp which travels with it to cover the hole when it is not open so you can't end up in this situation.

Even for the majority of us who do check every connection properly it is still very annoying when you find one which has gone behind the clamp, especially with the removable busbar normally found in domestic CUs.

Indeed, had a board which had been installed almost at ground level to add an MCB to recently, the whole busbar had to come out and the only way to make sure it was back correctly was with a mirror.

 

[wheeto]

... the only way to make sure it was back correctly was with a mirror.

But the point is that you did....

 

[radiohead]

But the point is that you did....

I did......but I'm not going to claim that I've never made an error of similar magnitude in my 40 odd years as an electrician.

 

[davesparks]

Indeed, had a board which had been installed almost at ground level to add an MCB to recently, the whole busbar had to come out and the only way to make sure it was back correctly was with a mirror.

I used to keep a mirror in my toolbox for doing this and for looking under floorboards and into voids, these days I use my phone camera or a wireless camera on the end of cable rods.

 

[radiohead]

One of the reasons I like crabtree starbreaker is the plug in busbar. Never ever seen a burnt out busbar connection. The main switch terminals though are just as rubbish as all the rest!

 

[happysteve]

Indeed, had a board which had been installed almost at ground level to add an MCB to recently, the whole busbar had to come out and the only way to make sure it was back correctly was with a mirror.

Sometimes you can't even get a mirror in. In these circumstances my method is:

(1) loosen all the terminals, push the screws in with a non-magnetic screwdriver so hopefully the cages are all at the back, in the right place

(2) put the bus bar in, hold it there with one hand

(3) starting at one end, tighten the furthest terminal until it nips the bus bar

(4) still holding on to the bus bar, loosen that one slightly, until the bus bar would drop if my hand wasn't holding it up

(5) go through all the terminals, confirm that tightening each of them will hold the bus bar up. So confirming that each terminal will actually grip the bus bar, meaning the cage is in the right place

(6) once all checked, tighten all the terminals, then torque them up.

Takes a while to do, and I kick myself if I drop the busbar at any point and have to start again! But it was the only way I could think of, of confirming that every terminal is correct, if you can't see any of them.

 

[radiohead]

That's great idea, worth remembering.

 

[static zap]

(I worry about my mental health at times)
... Am I part of the Truman show...
Coincidences youtubing 25kA testing yesterday.
Selling class J fuses !
(The arcing noises used to promote -Electrician things - does bug me)

 

[ipf]

I did......but I'm not going to claim that I've never made an error of similar magnitude in my 40 odd years as an electrician.

I

(2) put the bus bar in, hold it there with one hand

(3) starting at one end, tighten the furthest terminal until it nips the bus bar

(4) still holding on to the bus bar, loosen that one slightly, until the bus bar would drop if my hand wasn't holding it up

Also like when a new breaker is needed in say, a Wylex unit, you have to remove the bus bar altogether to fit it.
Similar to above but instead of (4), go along by nipping at the next breaker before slackening the previous, proving they're fastened one by one and holding in position. That way you're not depending on hand holding, it's constantly fixed.

 

[pc1966]

Coincidences youtubing 25kA testing yesterday.
Selling class J fuses !
(The arcing noises used to promote -Electrician things - does bug me)

That is an impressive demo.

Thankfully the PFC on our local bus-bar chamber is just under 12kA and we are using fuses are our primary OCPD so a little less sphincter clenching when powering on via the big leaver...

 

[R-fur]

So it looks like having overcurrent protection on a SPD is a good idea, but that means an extra MCB in the board with cost and space considerations. Is there any reason why the SPD could not be doubled up with say a shower?

 

[Julie.]

So it looks like having overcurrent protection on a SPD is a good idea, but that means an extra MCB in the board with cost and space considerations. Is there any reason why the SPD could not be doubled up with say a shower?

There are a few issues, the first is that going via additional impedance can reduce the effectiveness of the spd, but as many others do go via a MCB it does show this is manageable

The second is really about availability, if the shower circuit is off for any reason, then the spd is also out of circuit

The big one though is that almost all circuits these days need rcd protection, and the circuit to a spd must not!

 

[R-fur]

Fair enough, I forgot about the RCD issue. If its a choice of no MCB or doubling up with a submain I think I would prefer to double up.

 

[pc1966]

Usually incomer delay RCDs are rated for kA sized surges, but not all downstream types are.