Supply conductor size for 8 bedroom Victorian house

[James Neilson]

Hi folks,

I've recently visited a large 8 bedroom Victorian house. It has a three phase supply. One of the phases feeds the main house, its wired through a 100 amp main switch/ isolator. The Suppliers Side is 25mm tails but the customers side to the main house consumer unit appears to be 16mm. The run is around 20 metres or so and it looked like FP200 CABLE. Surely this should be 25mm going to the main house consumer unit?

 

[westward10]

Any chance of some pics of the set up.

 

[LewisM]

Are you sure its not MICC cable, I'm sure they don't make FP cable in that size.

 

[James Neilson]

Any chance of some pics of the set up.

Sorry I've not taken any pictures yet.

 

[James Neilson]

Are you sure its not MICC cable, I'm sure they don't make FP cable in that size.

Your probably right, I've not dealt with either. I was surprised to see it, I thought it was used for industrial installations.
Regardless of the cable type, would you not agree that it should be 25mm conductors for the L and N?

 

[James Neilson]

Are you sure its not MICC cable, I'm sure they don't make FP cable in that size.

It is MICC cable for sure.

 

[123]

No. MICC has a much higher CCC than say SWA

 

[James Neilson]

No. MICC has a much higher CCC than say SWA

Okay thanks. Still not sure why it's been used in a house. I'm thinking about replacing it with 25mm SWA to the consumer unit and using pvc for the house circuits. Everything is done in MICC.

 

[123]

Why would you replace the MICC with inferior cables? Correctly installed MICC is a job for life

 

[Strima]

If its MICC then leave it. It will last longer than the house.

 

[Des 56]

If you haven't dealt with it before,be wary of attempting to make any alterations that involve disturbing the terminations

 

[sarky spark]

MICC is the best cable ever.

 

[PEG]

Hi,why not test it? Then you may be able to leave in,what will invariably be,the best choice of cable

 

[James Neilson]

Hi,why not test it? Then you may be able to leave in,what will invariably be,the best choice of cable

I'm going to test the whole installation but the consumer unit needs up dated and the customer would like additional sockets and lights etc. They said they wanted a rewire but testing the installation is probably the best option. I have no experience with MICC so now's the time to get it!!

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[westward10]

Those protective devices are BS3871 type 3 for the orange ones and type 4 for the brown ones. The type 4 have never been recognised by BS7671 so you need to compare readings with manufacturers data, Federal Electric.
Take care working on them as they have a lot of exposed live parts. I see you are an apprentice so have you any testing experience.

 

[Strima]

Much VIR on the installation?

 

[davesparks]

Your probably right, I've not dealt with either. I was surprised to see it, I thought it was used for industrial installations.
Regardless of the cable type, would you not agree that it should be 25mm conductors for the L and N?

What do you mean regardless of cable type? Different types of cable have different current ratings.
MICC has a higher current rating than most plastic insulated cables for the same size conductors, 16mm is probably suitable for 100A, especially if you actually do the calculations rather than just using the tabulated values Uncorrected.

 

[davesparks]

I have no experience with MICC so now's the time to get it!!

You will need help from an experienced electrician, it’s not something you can just have a go at or make up as you go along.

 

[Squid]

MICC is used in houses as I had it in my flat renovation, had to remove it as the CU was being located elsewhere and the if it was jointed then the run would have been longer then replacing the cable.

I loved PYRO back in the day, nothing more sexier then stripping 6 core Pyro in a hot sweaty basement with 6ft tails just in your boiler suit, sorry digressing a bit........... but the older members will remember....

 

[James Neilson]

You will need help from an experienced electrician, it’s not something you can just have a go at or make up as you go along.

Thanks I'm aware of that, I'm doing my research and getting advice from older, more experienced colleagues before I make any decisions.