Replacing a rusty old garage CU

[Googleberry]

Hi guys,

I have 2.5mm SWA going from a 32A MCB in the house's CU to the garage. The SWA goes into an old and rusty Wylex fuse box, where it is split into a 6A lighting circuit and a 32A ring.

I want to replace the rusty old fuse box with a nice unit like this: http://nextday.diy.com/app/jsp/product/productPage.jsp?productId=33248

The trouble is that this device is called a 'Consumer Unit', and I have been advised that replacement of all CUs requires notification. My question is that since this CU is a replacement for an existing unit, and is fed via an MCB from the house's CU, does it really require notification? It's not like it's fed directly from the meter, and would not adversely affect the existing circuit's safety in any way. The circuit's existing protection would remain unaffected.

Grateful for your thoughts.

 

[flameport]

Replacing or installing a CU is notifiable.

There is a way to complete this installation without fitting a CU in the garage, which would be to fit a metal clad double socket outlet instead of the CU and connect the lighting via an unswitched fused spur containing a 5A fuse.

However in your case, the 2.5mm SWA from the house is too small to be connected from a 32A MCB, so that would need changing to a 20A or less, and that would be notifiable, so you still have to notify either way.
There is also the issue that an RCD will be required either in the house or garage.

 

[Aragorn84]

2.5mm SWA is rated to 36A if its the XLPE type, so would be prefectly fine on a 32A MCB...

Sticking a double socket on the end of the SWA instead of the existing ring main seems a bit of a sloppy way to go?

I'd go with replacing the CU as you planned, you just need to sort out the notification, or get someone in to do it.

 

[ban-all-sheds]

2.5mm² SWA is rated to 36A if it's the XLPE type AND if everything it is connected to and runs through is rated for operation at 90°C...

 

[Googleberry]

2.5mm SWA is rated to 36A if its the XLPE type, so would be prefectly fine on a 32A MCB...

Sticking a double socket on the end of the SWA instead of the existing ring main seems a bit of a sloppy way to go?

I'd go with replacing the CU as you planned, you just need to sort out the notification, or get someone in to do it.

Thanks. It is the XLPE type, so I have no worries about the house CU MCB rating, and I agree that the double socket, presumably with built-in RCD, is a sloppy way to go compared with a garage 'CU' containing separate MCBs for lighting and ring.

It is my belief that when Part P refers to a 'Consumer Unit', it is in fact referring to a unit connected directly to the meter, i.e providing primary protection to the garage circuit. When connected via an MCB in the house CU, it would not in fact be acting as a 'Consumer Unit' in that sense. Protection is unaffected as this is provided by the house CU's MCB. It is certainly not in the spirit of the legislation that this be disallowed when other less neat solutions are permissible!

The important thing to note is that this is not in any way going to adversely affect the safety of the garage circuit. Quite the contrary in fact!

Again, grateful for further thoughts...

 

[flameport]

It is my belief that when Part P refers to a 'Consumer Unit', it is in fact referring to a unit connected directly to the meter,

You can believe whatever you want, but that item you are intending to install is a consumer unit, therefore the work is notifiable. What it is supplied from makes no difference.

A plastic CU won't be rated for use at 90C either.

 

[Googleberry]

It is my belief that when Part P refers to a 'Consumer Unit', it is in fact referring to a unit connected directly to the meter,

You can believe whatever you want, but that item you are intending to install is a consumer unit, therefore the work is notifiable. What it is supplied from makes no difference.

A plastic CU won't be rated for use at 90C either.

I think it does, but fine, whatever, if the law really is that stupid, bring it on! I'll simply CE mark the CU and re-define it! As a CEng with a 1st with honours in E&E Eng and a PhD in the same, I think I can wipe the floor with any crappy legislation if needs be! The law really is an ass if it seeks to prevent people from adding safety! It allows other work that is potentially more dangerous for pity's sake!

 

[ban-all-sheds]

My question is that since this CU is a replacement for an existing unit, and is fed via an MCB from the house's CU, does it really require notification?

Try reading Schedule 2B.

The circuit's existing protection would remain unaffected.

You are proposing to change the device currently providing protection to the garage circuits for a different one. How on earth will the existing protection be unaffected?

It is the XLPE type, so I have no worries about the house CU MCB rating,

What about the temperature rating of what the cable is connected to or passes through?

and I agree that the double socket, presumably with built-in RCD, is a sloppy way to go compared with a garage 'CU' containing separate MCBs for lighting and ring.

Putting 'CU' in quotes like that won't make it less of a one.

It is my belief that when Part P refers to a 'Consumer Unit', it is in fact referring to a unit connected directly to the meter, i.e providing primary protection to the garage circuit.

Well you are wrong. It just refers to a consumer unit.

When connected via an MCB in the house CU, it would not in fact be acting as a 'Consumer Unit' in that sense.

I agree, but that "sense" as you call it is actually a nonsensical invention of yours, so your argument collapses. It would be acting as a consumer unit because that's what it ******* well is.

Protection is unaffected as this is provided by the house CU's MCB.

Protection of what is unaffected? What is the house CU MCB protecting?

The important thing to note is that this is not in any way going to adversely affect the safety of the garage circuit. Quite the contrary in fact!

It's gratifying to know that you have all the necessary test equipment which you will need to make sure that you are not in any way going to adversely affect the safety of the garage circuits.

 

[ban-all-sheds]

I think it does, but fine, whatever, if the law really is that stupid, bring it on!

Perhaps you should read the law, and see if it does support your belief, and if not reflect on where any stupidity lies.

I'll simply CE mark the CU and re-define it! As a CEng with a 1:1 in E&E Eng and a PhD in the same, I think I can wipe the floor with any crappy legislation if needs be!

It's not the law which is an ass here...

The law really is an ass if it seeks to prevent people from adding safety!

Please show us where the law prevents you from making an electrical installation safer.

It allows other work that is potentially more dangerous for pity's sake!

As it doesn't disallow anything it's hard to see how that can be, but feel free to show us where you think it does.

 

[mikeyd]

As a CEng with a 1:1 in E&E Eng

I only have a BEng. in Elec Eng. Are you sure you have an upper first class degree, only there wasn't such a thing in my day.

 

[Aragorn84]

If it was my house, i'd just change the damn thing too.

Might well be against the law, but as a "crime" its pretty damn minor!

 

[ban-all-sheds]

If it was my house, i'd just change the damn thing too.

Me too.

 

[Googleberry]

As a CEng with a 1:1 in E&E Eng

I only have a BEng. in Elec Eng. Are you sure you have an upper first class degree, only there wasn't such a thing in my day.

And there wasn't in mine! I can't believe I typed that - too late/too tired! It's a 1st with honours.

But hey, what the heck, even my PhD is worth nothing at all alongside a Part P certificate!

 

[RF Lighting]

I've got a BSc
















(Bronze Swimming certificate)

 

[Googleberry]

If it was my house, i'd just change the damn thing too.

Might well be against the law, but as a "crime" its pretty damn minor!

Thanks, it's good to keep a sense of perspective.