A house from history

[sevuk]

There's this old house with multiple old fuse boards with BS3036 fuses. It was wired to be two flats, but was never used for that purpose. Anyway I'm starting to bring the electrics up to date. I'd like to get rid of the upstairs wilex board and the downstairs MEM board into the kitchen, but that probably won't be feasible right now.

There are two fuseboards in the intake cupboard, one supplies all the other boards, one has fuses for the circuits in the front part of the downstairs.
I was thinking of just swapping the two boards in the intake cupboard to one modern one, then supplying the other old fuseboards for now off 32amp (currently supplied at 30amp 3036 with a 4mm2 twin and earths going out.) With a new 17th edition board then the old boards will be protected by an RCD.

Excluding any further problems I might find in further investigation, this should be acceptable in principle as everything will be RCD protected and the bonding will be upgraded? I don't really want to go through changing all the boards, as it would be much more sensible to bring all the circuits back at a later date, as I can't do that right away due to the property being inhabited.

 

[westward10]

A 30A, BS3036 fuse is oversized for a 4.0 cable when correction factors (0.725) are applied and installation methods of the existing 4.0 cables will dictate whether your proposed 32A devices are also oversized.

 

[sevuk]

A 30A, BS3036 fuse is oversized for a 4.0 cable when correction factors (0.725) are applied and installation methods of the existing 4.0 cables will dictate whether your proposed 32A devices are also oversized.

Sorry I made a mistake they are 6mm, its the radial circuits that are 4mm and they are on 20amp fuses.

How does the upgrade sound though, is it ok to leave the bs3036s supplied on the board? I can't think why not when they are protected by and rcd, and as you pointed out, I should actually look at the tables in the regs book.

 

[westward10]

If you protect the existing boards which incorporate BS3036 fuses with an mcb you are likely to lose discrimination between devices. Have you tested any of this installation.

 

[sevuk]

I haven't testing anything yet, I think I see what you're getting at though, if the loop impedance is high the MCB might trip before the 3036 does.

I'm just trying to think of a solution where I can make a start without telling the occupants to bugger off for a few days while I sort the mess out. It's possible I might have to do that anyway, depending on how the testing goes...

 

[westward10]

Are you doing this for yourself or a client, if the latter what is the scope of works they are wanting you to do.

 

[sevuk]

Alright I'll fess up, I don't like to admit it but it's actually my parents house and I should have done it years ago. I've finally got around to looking, mostly because I ordered a shiny new tester. Also a project just finished and I'm not starting a new installation as I've got inspection and testing starting at one of these horrible skills colleges next week (I did do everything else the proper way), so I've got some time to kill.

My parent's are old and I'm trying to cause them minimum fuss.

 

[DPG]

Honesty is the best policy. It makes things easier in the long run.

 

[sevuk]

Honesty is the best policy. It makes things easier in the long run.

To begin with whose house it was didn't really seem relevant. It's still a house that needs an upgrade, that's not completely straight forward.

 

[westward10]

Best thing to do is give a test and a good visual and then you can see what is required.

 

[sevuk]

Best thing to do is give a test and a good visual and then you can see what is required.

Black Friday is delaying my tester arrival. Delivery man is up to his eyeballs.

I think I just have to just do the survey and get the schedule of circuits drawn up, and as you say do a good visual as I'm jumping ahead. I can't really be sure of the best course of action until I've got some test results and done further investigation.