Advice on using FCU instead of CU in garage conversion

[bongos]

Hello. I've recently had a garage conversion. The spark has removed the old sockets/lighting and has rewired the new sockets and lights back to the existing garage consumer unit.

The consumer unit is fed from an old metal fusebox, which goes direct to the main CU in the house. The cable run start at the house CU in twin and earth, with an old junction box under the kitchen floor (I found this when running some cat 6 but wouldn't have expected the spark to). SWA then runs from the junction box under the floor to the old fusebox in the garage.


So I have:

House CU (32A MCB & 30mA RCD) > twin & earth > junction box under the floor > SWA > old fusebox > twin & earth > garage CU (32A & 6A circuits, also with 30mA RCD).

I don't see anything inherently unsafe in this set up, though it doesn't seem ideal (or necessary) having two 30mA RCDs & 32A MCBs in circuit. It also leaves a scruffy large space that will need a large door fitting due to allowing access to the garage CU and fusebox. As I have protection at the house CU could I ask the spark to terminate the SWA in a suitable small junction box with access still but in place of the metal fusebox. He could then also fit a FCU to supply the circuit for the lights?

TIA

 

[flameport]

Both of those fuseboxes/consumer units are scrap and should have been slung away during the conversion.

Did this electrical work involve any kind of certificates being provided?

 

[Sureitsoff?]

is the junction box under the floor accessible and how has the swa been terminated into this box

 

[bongos]

Both of those fuseboxes/consumer units are scrap and should have been slung away during the conversion.

Did this electrical work involve any kind of certificates being provided?

It's suppose to have. Still waiting to see any though...

is the junction box under the floor accessible and how has the swa been terminated into this box

Not particularly accessible to be honest. It's a suspended floor and I crawled under to run the Cat 6. That's when I came across it. But no it's not been particularly well installed IMHO. Not sure when it dates from though.

I'd rather they ran twin and earth back to the junction box (or ideally all the way back to the main house CU) min place of the SWA but it goes through the concrete ground/floor that was previously the driveway. Would be a PITA to run a cable through might be best option.

 

[Murdochcat]

That’s a very poor, badly designed and installed set up …..

 

[Taylortwocities]

It does not look possible to remove the cover from the bottom CU. Is it?

 

[bongos]

It does not look possible to remove the cover from the bottom CU. Is it?

Good point. I think it probably could be done...with a bit of a wiggle. But as already mentioned, the whole set up is a mess.

I went back under the floor to see if I could locate the SWA & twin and earth connection at the junction box. Here it is...

 

[Murdochcat]

Oer thats rough

 

[Ivor Windybottom]

.

 

[ebee]

Those pics might be good to send to PE (Professional Electrician ) magazine for their "Caught on Camera" section.
www.professional-electrician.com
or Voltimum UK, www.voltimum.co.uk
etc etc.

 

[Ivor Windybottom]

I posted above to suggest getting an actual electrician in then decided that was a bit harsh so deleted it.

It's not ideal. But, given that there's already a single cable feed to the room, it would have been a major expense to replace an already working system with another that may be neater but wouldn't actually give any improvement other than omitting the two units.

The junction looks bad, it also looks like it's hanging by a wire that may be at risk of cutting into a pipe or the cable. Definitely improve that. Also is there a terminal block under that tape?

I'd improve the edges of the access holes by adding more insulation to ensure the interior surface doesn't get a draught from the outer surface. The insulation needs to be contiguous other than the units themselves.

If two flush access hatches are added where indicated by the pencil lines with plasterboard between then it will end up looking passable. There are off-the-shelf white plastic hatches available from various places. It should all turn out OK.

 

[bongos]

It's not ideal. But, given that there's already a single cable feed to the room, it would have been a major expense to replace an already working system with another that may be neater but wouldn't actually give any improvement other than omitting the two units.

This was my view really though I felt that it could still could have been done better than it has been .

The junction looks bad, it also looks like it's hanging by a wire that may be at risk of cutting into a pipe or the cable. Definitely improve that. Also is there a terminal block under that tape?

It doesn't look great - there's no tape on it but the earths are terminated outside the box I think. It looks like the earth core from the t&e has been 'tied up' with one of the SWA cores. I've seen this done a bit before but always assumed it was an old school way of doing this. My guess would be this was done many years back, perhaps when the the garage was given its original supply.

I'd improve the edges of the access holes by adding more insulation to ensure the interior surface doesn't get a draught from the outer surface. The insulation needs to be contiguous other than the units themselves.

So the builders should bring the insulation right up to surround the CU & fusebox, not covering them though?

If two flush access hatches are added where indicated by the pencil lines with plasterboard between then it will end up looking passable. There are off-the-shelf white plastic hatches available from various places. It should all turn out OK.

Thanks. I'd decided this was probably the least bad solution noting that my builders have been pretty crap and this is part of the snagging that I raised in late autumn which still hasn't been done. Where is a good place for me to get these if I end up doing it, or i'm at least able to provide them a specific example of what I want them to do.

 

[SUNRAY]

I caught a glimpse of this previously but missed the replies.

Without knowing what has been done with the rewiring I can only make a guess that there is a ring final circuit for the sockets on the 32A MCB.

If that is correct then the consumer unit is effectively only providing protection for the lighting circuit and as the original post questions.

I don't see anything inherently unsafe in this set up, though it doesn't seem ideal (or necessary) having two 30mA RCDs & 32A MCBs in circuit. It also leaves a scruffy large space that will need a large door fitting due to allowing access to the garage CU and fusebox. As I have protection at the house CU could I ask the spark to terminate the SWA in a suitable small junction box with access still but in place of the metal fusebox. He could then also fit a FCU to supply the circuit for the lights?

I think that could be the nicest solution. I'd suggest extending the feed, just as you describe with a maintenance free junction box and fit the SFCU where the current CU is located, that ugly hole would then simply be one electrical accessory and the insulation will be installed without any cold spots

And of course it doesn't have to be within the existing hole

 

[bongos]

I caught a glimpse of this previously but missed the replies.

Without knowing what has been done with the rewiring I can only make a guess that there is a ring final circuit for the sockets on the 32A MCB.

If that is correct then the consumer unit is effectively only providing protection for the lighting circuit and as the original post questions.

I think that could be the nicest solution. I'd suggest extending the feed, just as you describe with a maintenance free junction box and fit the SFCU where the current CU is located, that ugly hole would then simply be one electrical accessory and the insulation will be installed without any cold spotsView attachment 331922
And of course it doesn't have to be within the existing hole

I like what you've done here! There's already a light switch for the room so perhaps i'd be better with an unswitched FCU?

But yes it is a 32A ring final circuit he's installed on the 32A MCB. I've not come across maintenance free junction boxes before but guessing from their name that they can be covered over. Thanks again all for your help. I shall ask the spark/builder to rectify. And provide my certificate...

 

[SUNRAY]

I like what you've done here! There's already a light switch for the room so perhaps i'd be better with an unswitched FCU?

But yes it is a 32A ring final circuit he's installed on the 32A MCB. I've not come across maintenance free junction boxes before but guessing from their name that they can be covered over. Thanks again all for your help. I shall ask the spark/builder to rectify. And provide my certificate...

Ah, does that mean you have only one light?

Another possibility could be to replace the switch with a sfcu as a spur from the ring.