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.

 

[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.