Butchering a consumer unit Part deux

[littlespark]

Heating system in a local church which is basically tubular heaters under a few pews.

A local company has already quoted thousands to rip all this out and start again. The committee are reluctant to spend massive amounts as the building only gets used for 2 hours once a fortnight.
It’s old, but it all works.

Main switch on left is always on to power everything here.
The silver box next is a contactor.... will get to that in a minute..
Next is the mainswitch for the fuseboard... they turn this on during the week before a service.... but only sends power to the top of the contactor.
Next is the fuseboard.... 6 fuses across 3 phases going out on the old twin and earths that disappear into the wall below it then go to heaters.
The rightmost MEM switch doesn’t get used. Neither does the circular mechanical time clock below.... which is marked as suppliers clock.
The electronic programmer beside it appears to have replaced another mechanical clock which energises the contactor coil.... the switch below that overrides the programmer.... which is now surplus to requirements as the electronic programmer has its own override button.

So, just to make things a little safer without tearing it all out, could I take the guts out the fusebox and install a DIN rail with rcbo’s?
Leave the box and lid as it is, but fix a Perspex shield with a hole for the rcbo’s to stick through so they can be reset, but all the connections are safely behind the barrier.

Whew... long post.
There’s a fairly modern 4 gang plastic CU elsewhere serving lighting and power, so I’m quoting to change this to rcbo as well.

ps, the other box a foot below the switch is a room thermostat, and if it’s also surplus, it’s coming out for LN.

 

[westward10]

Leave it why does it need replacing.

 

[littlespark]

Leave it why does it need replacing.

It doesn’t. I know that, but the committee are worried about how “safe” it is in regard to what the other company had said and I was suggesting what could be done without going overboard.

Their insurance may state that circuits must be up to a certain standard not just EICR satisfactory, which I assume this is.

 

[westward10]

Generally insurance requirements are that the Report comes back as satisfactory, I can't see that attracting anything more than a C3.

 

[littlespark]

Generally insurance requirements are that the Report comes back as satisfactory, I can't see that attracting anything more than a C3.

Yeh. Maybe.... but I can see whoever did the last check to push those C3’s up to a C2 just to make work for themselves.

the committee just looking for a second opinion, I’m looking for a third...

 

[westward10]

I know not ideal but you could divert the supply into an rcd.

 

[littlespark]

I still need to work out what the mech time clock actually does. It’s still ticking away so it has power, and there’s a really old handwritten instruction sheet by a previous committee stating it belongs the Electricity Board and shouldn’t be touched.
I think, there was off peak heating at some time, as some of that MEM switchgear is labelled as off peak.

The clock is mounted on a 4x4 adaptable metal box with the 6181Y single cables coming through unprotected holes in the lid.

 

[loz2754]

The time clock is on its original mounting box from the look of it, and also from the look of it it's not doing anything because the lever actuators on the dial are not there...

 

[MrPupsi]

As above, looks like an old Sangamo time clock which is no longer in use.

I imagine the terminals are still in use though and it’s just being used as a junction box now, hence why you can still hear the ticking as it still has power.

I think technically the din rail and RCBOs would work, but then you’d be the constructor of said ‘homemade’ DB, and whilst you’ll sign it off as safe, I’d imagine the next person carrying out an EICR may well fail it in 5/10 years time.

 

[littlespark]

As above, looks like an old Sangamo time clock which is no longer in use.

I imagine the terminals are still in use though and it’s just being used as a junction box now, hence why you can still hear the ticking as it still has power.

I think technically the din rail and RCBOs would work, but then you’d be the constructor of said ‘homemade’ DB, and whilst you’ll sign it off as safe, I’d imagine the next person carrying out an EICR may well fail it in 5/10 years time.

This has been part of the problem.... the most recent eicr said it needed changed, but all previous ones, it was fine.

ive not read the report yet, maybe they were just more “listy” with any C3’s and it just looked like there was a lot of problems.... that coupled with a quote to “put things right”

Of course, the ‘sbestos fairy will need a visit- there could be flash pads behind those fuses.

I believe I can make a tidier job adapting and building a CU than some people can with an all new board with all the right bits.

 

[telectrix]

So, just to make things a little safer without tearing it all out, could I take the guts out the fusebox and install a DIN rail with rcbo’s?
Leave the box and lid as it is, but fix a Perspex shield with a hole for the rcbo’s to stick through so they can be reset, but all the connections are safely behind the barrier.

that would be my way also, if ,indeed, upgrading is desirable. nowt wrong with it as it is, although lack of RCD protection for sockets could be classed as a C2 - Mrs.Mop wth her dyson hoover.

 

[UNG]

So, just to make things a little safer without tearing it all out, could I take the guts out the fusebox and install a DIN rail with rcbo’s?
Leave the box and lid as it is, but fix a Perspex shield with a hole for the rcbo’s to stick through so they can be reset, but all the connections are safely behind the barrier.

My first thought would be to investigate fitting a skeleton CU into the existing DB enclosure rather than trying to use a homemade modification which may be called into question at the next EICR

 

[Rockingit]

So long as the cable hasn't degraded I'd trust that far more than some modern bish-bash-eicr-in-it-for-the-remedials mob. Just a question - why would you need to have the levers of the rcd/rcbo's actually exposed anyway? Mounted internally on DIN rail behind the original panel would be fine by me - it's not been made worse and affords a level of protection in keeping with the spirit of 133.1

 

[brianmoooore]

So long as the cable hasn't degraded I'd trust that far more than some modern bish-bash-eicr-in-it-for-the-remedials mob. Just a question - why would you need to have the levers of the rcd/rcbo's actually exposed anyway? Mounted internally on DIN rail behind the original panel would be fine by me - it's not been made worse and affords a level of protection in keeping with the spirit of 133.1

Rockingit has essentially posted just what I was going to post after reading page 1.
The main switch for the fuse enclosure is separate from it, so make sure the fuse enclosure is clearly labeled "isolate before opening" and the switch is equally clearly labeled as to its purpose.

 

[DPG]

So long as the cable hasn't degraded I'd trust that far more than some modern bish-bash-eicr-in-it-for-the-remedials mob. Just a question - why would you need to have the levers of the rcd/rcbo's actually exposed anyway? Mounted internally on DIN rail behind the original panel would be fine by me - it's not been made worse and affords a level of protection in keeping with the spirit of 133.1

People cannot operate the test button for one thing.

 

[brianmoooore]

People cannot operate the test button for one thing.

Very good point! I was reading RCBO, but thinking MCB. Makes all the difference.

 

[Rockingit]

People cannot operate the test button for one thing.

Yes they can, they just need to take the catches off the lid

 

[DPG]

Yes they can, they just need to take the catches off the lid

Ah sorry, I thought the lid was screwed on.

 

[Rockingit]

Ah sorry, I thought the lid was screwed on.

I think those units have two thumb screws?

 

[DPG]

I think those units have two thumb screws?

I can't tell if they are just slotted screws or thumbsrews. You may be right though yes.

 

[brianmoooore]

For the test buttons to work, then you would have to have it live with the cover off, exposing live terminals.
Lid should only be openable with a tool.

 

[Rockingit]

For the test buttons to work, then you would have to have it live with the cover off, exposing live terminals.
Lid should only be openable with a tool.

And this is where it gets interesting..... technically I'd argue that this is a commercial installation and therefore subject to a regime of testing and maintenance - by a skilled or instructed person.

 

[littlespark]

The lid is screwed with hinges. I could replace with thumb turn bolts.

I would be fitting a flat plastic plate properly screwed in place to shield the everyday user from live parts.

I did think of using a complete CU inside the box, but there would still be cables with only basic insulation exposed.

 

[DPG]

The lid is screwed with hinges. I could replace with thumb turn bolts.

I would be fitting a flat plastic plate properly screwed in place to shield the everyday user from live parts.

I did think of using a complete CU inside the box, but there would still be cables with only basic insulation exposed.

Sounds a bit too much like manufacturing custom equipment to me.

Don't get me wrong, I'm sure technically it is a good solution.

 

[streamer]

 

[streamer]

 

[streamer]

How about replacing the isolator and fuse box with something like the above. I know proteus isn't to everyone's liking but it was the first to come up when I googled.

 

[UNG]

I did think of using a complete CU inside the box, but there would still be cables with only basic insulation exposed.

That is why I suggested a skeleton CU as they usually come with a large cover which if needed could be cut down to suit the application

 

[brianmoooore]

Sounds a bit too much like manufacturing custom equipment to me.

Don't get me wrong, I'm sure technically it is a good solution.

I agree. It's fine to screw a DIN rail into an old rewireable fuse enclosure like the one in question and fit MCBs with semi exposed live terminals, as long as the lid is secured by screws that require a tool, and it is labeled appropriately, and I have done so on a few occasions, but RCBOs, with their test buttons, means this solution can't be used.

 

[littlespark]

I agree. It's fine to screw a DIN rail into an old rewireable fuse enclosure like the one in question and fit MCBs with semi exposed live terminals, as long as the lid is secured by screws that require a tool, and it is labeled appropriately, and I have done so on a few occasions, but RCBOs, with their test buttons, means this solution can't be used.

But if I make a “lid” which is screwed back.... but has a hole where the front of the rcbo’s protrude to access the test button and toggle switch.

The actual existing lid is a hinged door, which just happens to be held closed by screws at the moment.

 

[brianmoooore]

You possibly can, but you will be accepting responsibility for the design.

 

[pc1966]

If the right-most switch is no longer used, and the mechanical timer below it also obsolete, could you not just replace the box with the 6 rewirable fuses with a suitable DIN rail box and some RCBOs?

Space would be an issue, but you can probably take those cables in the rear of a box and the top mated to the trunking.

 

[Rockingit]

RCBOs, with their test buttons, means this solution can't be used.

What makes the test button on an RCD/BO any different to the trip mechanism on an MCB or even the pulling of the original ceramic fuse???

 

[brianmoooore]

Because you can, and should, reset an MCB or pull a ceramic fuse with the board dead. RCD test buttons only work when the circuit is live.

 

[littlespark]

What makes the test button on an RCD/BO any different to the trip mechanism on an MCB or even the pulling of the original ceramic fuse???

Because you can do those with the power isolated.... rcd test button needs power to operate


yeh what he said ^

 

[Rockingit]

I'll need some serious convincing that everybody isolates an entire board to 'reset' an MCB, especially when they're rated for functional isolation (as also are RCBO's).

 

[Mike Johnson]

I don't think any home owner will isolate the board before trying to reset any MCB etc: that has tripped.

 

[DPG]

What makes the test button on an RCD/BO any different to the trip mechanism on an MCB or even the pulling of the original ceramic fuse???

Because an MCB only needs to be operated if a fault has occurred. The test button on an RCD should be operated periodically without any fault being present.

 

[brianmoooore]

I'll need some serious convincing that everybody isolates an entire board to 'reset' an MCB, especially when they're rated for functional isolation (as also are RCBO's).

Whatever the manufacturers claim, closing a MCB live, against a short circuit, is neither good for the MCB nor my nerves.

 

[Mike Johnson]

The most common tripping event, In the days of tungsten bulbs MCB would trip whenever a bulb blew, if a home owner knew that and replaced the bulb, the short circuit had been eliminated so resetting the MCB would not be against a short circuit, not reliable for all events, but.

 

[brianmoooore]

e for all events, but.

'But' is the 10mm2 shower feed on a 40 or 45A MCB, crammed into a tiny ceiling switch box, with a terminal that has worked loose and melted the insulation of the cable, shorting live and neutral together.

 

[pc1966]

Whatever the manufacturers claim, closing a MCB live, against a short circuit, is neither good for the MCB nor my nerves.

Still, it could be worse. Closing a MCCB on a 50kA fault is definitely on my not-to-do-list!

 

[westward10]

I have no idea why you are intending to create an ad hoc dist board. I would give them two options, divert the supply into an rcd which isn't ideal or completely replace the board. The fact they are not keen on spending too much money would be of no concern to me.

 

[streamer]

I think if you replace the board with something like post #25 or #26 what ever the board costs you will save in time so it shouldn't cost the customer any more.