Old black box near consumer unit

[h4r00n]

Hi, My electrics keep tripping.. this black box in the picture seems to be the culprit. Slight touch of it and it trips. The electrician suggested removing this and connecting two main cables from main switch to the consumer unit with connectors. He said this black box is very old and not needed. Plus it looked melted in the inside. Is this OK to do?

 

[James]

I would take your electricians advice.
the black box is an isolator (switch)
you have a shiny new switch just below it to use instead.

if it were me, I would change the cables between the new switch and the consumer unit for new instead of putting any joints in the middle of the old cables.

 

[littlespark]

It’s a switch fuse.

I’m wondering why it was left when the service isolator below was fitted. They’re doing the same job.
Can you clarify what is tripping? Is it the RCD mainswitch on left of your consumer unit?
Removing the black switch fuse may not actually solve the problem.

There is a home for old things like that. So don’t throw it away.

 

[snowhead]

Littlespark, see pic for why it's possibly doing as stated,

this black box in the picture seems to be the culprit.
Slight touch of it and it trips.
Plus it looked melted in the inside.

 

[littlespark]

I know it’s early… but what I’m suggesting is the rcd main is tripping through cumulative earth leakage.
Taking the switch fuse away may not remove the fault completely.

Overloading the 45A would blow the fuse inside, unless it has had higher rated fuse wire fitted. The melting mentioned is likely a loose connection.
The rcd is also downstream of this switch fuse. N-E fault anywhere would trip the rcd.

What is melting though? The cable? Or is it just black burn marks from blowing fuses.

It’s all metal in those things, and some porcelain fuse holders.

 

[h4r00n]

Any sockets switched on and it trips.. sometimes nothing on and trips. Nudging the black box and it definitely trips. Yes its just the RCD that trips. Also seem to have a faulty mcb constantly staying down, nothing plugged in this circuit.

 

[swaRRR]

Any sockets switched on and it trips.. sometimes nothing on and trips. Nudging the black box and it definitely trips. Yes its just the RCD that trips. Also seem to have a faulty mcb constantly staying down, nothing plugged in this circuit.

You need someone who is experienced and qualified in inspection and testing to test your system. If MCB's and RCD's are disconnecting then you need to have your wiring tested, just removing that black isolator isn't going to solve the problems.

 

[JBW175]

As above, if you’re getting nuisance tripping just from plugging things in, it’d be a good idea to get an EICR carried out. This will give a good indication as to the condition of the fixed wiring.

 

[Avo Mk8]

Looking at other examples on the web, it's clear the "black box" is made of bakelite, not metal, and as pointed out, is only rated at 45A.
lt seems to me there is no valid reason to leave it in circuit.

I do agree with the comments above, there's likely another issue as well, needs checking out.

 

[nicebutdim]

Littlespark, see pic for why it's possibly doing as stated,

this black box in the picture seems to be the culprit.
Slight touch of it and it trips.
Plus it looked melted in the inside.

View attachment 99061

Maybe sheath & insulation damaged on entry to CU? Unlikely that's causing the problem with a plastic board, but post #2 seems like a good start followed by advice in post #7.

 

[Lucien Nunes]

If there is a faulty connection inside the switchfuse especially on the neutral, then tapping it could be causing momentary glitches in the supply. If the total functional leakage on the system is near the tripping point of the RCD, then an intermittent neutral can push it beyond and cause a trip, as the load side of the intermittent jumps momentarily up towards line voltage, passing a current spike to earth through suppression capacitors in appliances etc.

As above, the switchfuse is surplus to requirements and a weak link. If you remove it, I would be grateful and would reimburse you if you had a chance box it and send it to us for the museum. We have the 15A version of the Bill Insulok and possibly the 30A although IIRC one of them is broken. We don't have the 45A though.

 

[G1ZQC_David]

Hi, My electrics keep tripping.. this black box in the picture seems to be the culprit. Slight touch of it and it trips. The electrician suggested removing this and connecting two main cables from main switch to the consumer unit with connectors. He said this black box is very old and not needed. Plus it looked melted in the inside. Is this OK to do?View attachment 99057

The Old BILL switch is an isolator. The Electric board has fitted their own isolator below. You do not need the BILL switch.
You can wire the tails directly from the output of the board's isolator.

 

[pc1966]

As above, your electrician's advice is sound - it is not rated for a modern house (at 45A) and way past its designed lifetime. It ought to be a simple job for them to remove and bypass it given you have a modern isolator switch below it.

However you also appear to have a single RCD protecting the whole house (leftmost device in your board above it). That is not modern practice as (a) if it trips you loses all power, and (b) modern electronic appliances all leak a little, so the accumulation of a whole house of equipment often pushes the total leakage current to close to the trip threshold.

First step is to have the old Bill unit removed, if that leave thing satisfactory then OK, but you might be advised to look at a new CU (consumer unit = fuse box) that has ideally RCBO (individual over-current MCBs with RCD protection) or, as a minimum, dual RCDs so you still have some power when it trips. It should also have a surge protection device (SPD) now, another minor step in improved reliability and lifetime of electronics such as LED lights, as well as the more obvious PC/TV/etc.

The cost difference between the two is modest and personally I would always go for RCBO as less trouble from accumulation of leakage, and far easier to diagnose any future faults.

 

[h4r00n]

Thanks for the advice guys.. the black isolator box has been bypassed and new mcb to replace faulty. But still trips. Electrician replaced the rcd with a main switch to test and it all stayed on. But I did inform him that we cant simply leave a main switch (same red switch as shown at bottom of pic). Just incase there is a fault and rcd doesnt trip.. he mentioned mcb will still trip but still I thought we need an rcd too for safety. He then replaced old rcd with new and lo and behold it still trips!

 

[h4r00n]

Heres what he did after i told him no thank you and to replace isolator red switch with rcd and see if still trips which it did

 

[Avo Mk8]

Heres what he did after i told him no thank you and to replace isolator red switch with rcd and see if still trips which it did

Well done for insisting that the rcd should not be replaced with a switch. You did the right thing!
The next step is to find out what is causing the tripping, as per previous predictions!!
That is something I would have expected your "electrician" to have done already!

 

[Lucien Nunes]

Yes your next quest is to discover whether the tripping is caused by a specific fault, which could be equally be in an appliance as in the house wiring, or whether it's simply a result of the total normal leakage in the house being close to the tripping threshold of the sole RCD supplying it.

Did the old switchfuse get saved by any chance?

 

[James]

With suggestions like replacing rcd with main switch etc, I would recommend getting a new electrician (one that knows what he / she is doing)

 

[h4r00n]

Yes still have the old black isolator.. stuck on wall. Will take it down and send.. PM me address.

Issue still persists.. even switched all mcbs down other than just upstairs and downstairs lights and it tripped RCD after around 30 mins with lights not switched on. Any power on any sockets trips the RCD. The RCD is 80amp covering all MCBs it thats worth noting. Maybe some earth leakage somewhere?

Also wanted to ask... have old dishwasher and cooker hob still plugged in. Very difficult to get to as I believe its on an extension lead hidden behind kitchen counter. I did manage to just switch the plug switches off by removing Oven and reaching around. It still tripped. Just thought that the fact that the RCD still trips with all MCBs down and just 2 light MCBs up might mean theres no point ripping out kitchen counter?

Bit annoying because dont want to spend too much sorting it out as in a couple months we have builders in for an extension which includes full rewire.

 

[James]

It sounds like you might have a fault on a circuit between N and earth.
unfortunatley if it is in one of the appliances like the hob or dishwasher, switching the socket off will not remove the fault.
it can still cause problems even when the mcb is switched off.

most likely suspects to are
outside lights
immersion heater
oven or grill
electric hob
fridge freezers
anything with a heater element in it.