Replacing an old fuse box

[KungFooBob]

I know the answer is get a qualified sparky to do it, the BiL is one, but the wife fell out with him yesterday so I'm going to ask you lot first.

I have an old school fuse box in the garage. It has two populated fuses. A 5amp for the lights and a 20amp for the sockets.

It's fed from the house via 6mm Twin and Earth.

In the house it's connected to the RCD side of the consumer unit into it's own 32amp MCB.

I want to replace the fuse box with a new consumer unit.

Should the feed from the house connect in to an RCD or should it just be a master switch?

The pre-populated Garage CU's all seem to have RCD's in them, but none of them have enough room for the modules, I need to add an additional two circuits (garden bar MCB and EV Charger RCBO).

[Silly Car]

From my dated and limited knowledge:

You should be careful with one RCD feeding another RCD further down the line due to something called RCD selectivity which is all about which device trips out first.

6mm may be under-rated for distance from main DB and running multiple circuits including a EV charger. IIRC I’ve got 10mm feeding my garage (20m from main DB) to serve a future EV charger, lights and sockets.

Don’t bother with a garage board, mine has a small full purpose DB in it with RCDs and loads of space for expansion for EV, solar (if I’m ever allowed) , etc.

You can do the work yourself but you’d have to get local building control sign off as I’m guessing you aren’t a “competent person”. I’d check whether your local authority has someone who can do the inspection/ sign off as I can’t imagine a local electrician would be happy certifying someone else’s / DIY work. IME, the fees for inspection/sign off aren’t too dissimilar to cost of getting someone to do the entire job.*

* I enquired about getting building control to sign off a Logburner installation, their quoted fee was more expensive than getting my roofer to drop the flue liner in while doing the roof and the local HETAS guy / regular chimney sweep to connect everything up.

Any electrician who does any work on your property should really check / test everything associated with the property rather than just replacing a DB which will likely boost the overall cost though.

[KungFooBob]

6mm 'should' be ok for the EV charger, if there's not a lot of load on the other circuits, most can be tuned, so rather than pulling the full 7kw, they can be tweaked to 5 or 6 if it trips.

I had read about the RCD selectivity, which was why I haven't been to Screwfix yet

[Taff]

understanding that every house is going to be different, and there's regs that have to be met on the install......I had 2 sparkies here yesterday to look at our electrics to wire in an ev charger and neither would take a feed off the garage circuit and quoted for a new cable from the main ciruitboard. The charger needs 32A by itself so anything else running on the 32a circuit could overload it.

So instead we have to lay nearly 70 meters of 10mm cable on a dedicated circuit

You've already said it, you need a qualified sparky

[ogri]

If you do bodge it, dibs etc

[mangocrazy]

Alternatively, £1000* in used notes and you can claim on your fire insurance...

* Cost of living, innit?

[wheelnut]

Just to echo SCs comments which are all spot on. 6mm is not really enough if you have an EV charger and other circuits on the CU. Also bear in mind you will need some sort of feed back to the house for the CT clamp (I’ve got 10mm swa to mine with an Ethernet cable built in which goes back to the CT clamp).

As also said you presumably can’t certify it yourself and no spark will sign off another persons work - with that in mind the best and easiest course is to probably find another spark.

[cheb]

Use secondhand gear and it won't look like you been fiddling with it

[Noggin]

Ask @Couchy ?

[KungFooBob]

If we ignore the EV, I think I'd still like to replace the fusebox, even if it's just to get the garden bar working (it's running on a 15m extension at the moment).

I think this would do the job, I'd just fill the blank with another 32a MCB...

https://www.screwfix.com/p/british-gene ... unit/453vf

The only concern is that's RCB protected... as is the MCB in the main house CU it will be connected too.

[KungFooBob]

I thought I'd try my granny charger today, had the car two months and had never had it out the bag.

Got an alert from the app that charging had stopped after 10mins.

Checked the charger and a red thermometer was flashing.

Good job these chargers have temp sensor in the three pin plug part ...

PXL_20251004_155348854.jpg (1.01 MiB) Viewed 2046 times

Fitted a different face plate I had laying around and it's done the same (this is a socket in the garage near the main door).

Assume I really just need a brand new decent quality socket and it's nothing to do with the wiring?

[mangocrazy]

Hmmm, so £1000 was too spendy, so you decided to do it yourself?

[KungFooBob]

Hmmm, so £1000 was too spendy, so you decided to do it yourself?

No.

I've not done anything except change a face plate when the first one melted.

From using the 13a granny car charger.

[mangocrazy]

In which case I'd suspect the granny charger is pulling more than the rated 13A. You might also check the wiring to the socket to see if that has overheated.

[KungFooBob]

In which case I'd suspect the granny charger is pulling more than the rated 13A. You might also check the wiring to the socket to see if that has overheated.

The wiring all looked good and cool, the first face plate was full of dead spiders when I took it off and to be fair, there was always slight discoloration near where the live pin enters.

The 2nd was one left over from when I ripped the kitchen out, so was also 20+ years old.

I think I'll buy something much newer and try dropping the rate in the car from 13 to 10 amps.

[Sunny]

FWIW my garage consumer unit runs off a 32a RCB in the main house board, and the workshop consumer unit runs off another 32a RCB also in the main house board.
Nothing's burnt down yet.

The chap who came to fit our EV charger put a split on the incoming eleccy before the main house board and then put in a separate unit purely for the charger, with a 10mm cable running from it to the charger.

[KungFooBob]

FWIW my garage consumer unit runs off a 32a RCB in the main house board, and the workshop consumer unit runs off another 32a RCB also in the main house board.
Nothing's burnt down yet.

The chap who came to fit our EV charger put a split on the incoming eleccy before the main house board and then put in a separate unit purely for the charger, with a 10mm cable running from it to the charger.

In an ideal world the EV charger would be fed from the house CU or a tail from the meter cabinet, but they're about as far from where the car is parked as is possible, hence trying to work out if it could be fed from the garage. Her in doors doesn't want a thick black cable clipped to the outside of the house.

I could probably get away with using the granny charger instead... if it didn't melt the socket

[KungFooBob]

FWIW my garage consumer unit runs off a 32a RCB in the main house board, and the workshop consumer unit runs off another 32a RCB also in the main house board.
Nothing's burnt down yet.

The chap who came to fit our EV charger put a split on the incoming eleccy before the main house board and then put in a separate unit purely for the charger, with a 10mm cable running from it to the charger.

In an ideal world the EV charger would be fed from the house CU or a tail from the meter cabinet, but they're about as far from where the car is parked as is possible, hence trying to work out if it could be fed from the garage. Her in doors doesn't want a thick black cable clipped to the outside of the house.

I could probably get away with using the granny charger instead... if it didn't melt the socket

[Sunny]

FWIW my garage consumer unit runs off a 32a RCB in the main house board, and the workshop consumer unit runs off another 32a RCB also in the main house board.
Nothing's burnt down yet.

The chap who came to fit our EV charger put a split on the incoming eleccy before the main house board and then put in a separate unit purely for the charger, with a 10mm cable running from it to the charger.

In an ideal world the EV charger would be fed from the house CU or a tail from the meter cabinet, but they're about as far from where the car is parked as is possible, hence trying to work out if it could be fed from the garage. Her in doors doesn't want a thick black cable clipped to the outside of the house.

I could probably get away with using the granny charger instead... if it didn't melt the socket

I thought they'd run it from the garage one, but nope.

17m of black cable is now clipped to the side of the house/wall/run through the garage.

[MrLongbeard]

Her in doors doesn't want a thick black cable clipped to the outside of the house.

Have it mounted low and go buy some plants to, erm , plant in front of it, our garage feed run is clipped to the front of the house, in summer you can't see it for the flowers and in winter it's dark anyway.