Should I get a new CU?

[NewFolder]

I have a MEM Memera 3 Fuse Box (don't think it's classed as a CU, it has fuses inside).

It has 4 fuses in it: 5A for lighting, 15A for 'Heating' (I think it means immersion heater, I don't think a timer and pump will draw 15A), 30A for the ring main, and a 15A for the cooker outlet. The fuses are cartridges with fuse wire inside them.

There is a CU in the loft, with a RCD and two MCB's. One MCB supplies the electric shower, and the other supplies one double socket in the loft (AFAIK it doesn't supply anything else).

I'd like to know whether this setup is dangerous or it should be replaced. The house was built in 1985, and we've been living there since 2005, and in that time, we've only had to replace two fuses, once because some guy tried to replace some wall lights and wired them up wrong (idk how) and caused a short circuit. The second time was when a shed installer decided to try to disconnect and move the shed socket without asking us to switch off the electricity first. Fortunately, he managed to blow up the fuse instead of himself!

Might it be better to just keep the current system and perhaps use those plug in RCDs on certain appliances?

Am I correct in thinking that the fuses will protect against an electrical fire, but not necessarily electric shock, and RCDs will do both?

Does anyone know around how much it would cost to replace this fusebox with a modern consumer unit with MCBs and RCDs, bearing in mind that there are only 4 outputs?

If anyone needs any more information please ask.

 

[PrenticeBoyofDerry]

As the saying goes "if it ain't broke don't fix it"
Firstly it's had to say if your set up is safe or unsafe without proper inspections and tests being done.
As it stands, by what you have said it is not unsafe, you have RCD protection shower which is important, if any socket outsets are used for outside equipment (including the shed) it would be wise to have RCD protection there.
*RCDs detect earth leakage and protect against electrical shock.
*Fuses/MCBs will protect against overloads and providing the cable of the circuit is rated in accordance to the fuse, that will help prevent fire.
* It's an RCBO that will help protect against both the above.

The changing of the board price, will vary from region to region.
It would be advantageous if you had a board with dual RCD protection as this would leave you with some power if one RCD tripped out.
They can be bought at around the £70 mark, some cheaper and expensive versions will be available.
You would require a EICR (electrical installation condition report) prior to any swap over, as not all systems are suitable for RCD protection and nuisance tripping or even complete power loss may occur.
CU change over, my area, about £350-£400 that's with EICR, new unit and signing off.

 

[NewFolder]

As the saying goes "if it ain't broke don't fix it"
Firstly it's had to say if your set up is safe or unsafe without proper inspections and tests being done.
As it stands, by what you have said it is not unsafe, you have RCD protection shower which is important, if any socket outsets are used for outside equipment (including the shed) it would be wise to have RCD protection there.
*RCDs detect earth leakage and protect against electrical shock.
*Fuses/MCBs will protect against overloads and providing the cable of the circuit is rated in accordance to the fuse, that will help prevent fire.
* It's an RCBO that will help protect against both the above.

The changing of the board price, will vary from region to region.
It would be advantageous if you had a board with dual RCD protection as this would leave you with some power if one RCD tripped out.
They can be bought at around the £70 mark, some cheaper and expensive versions will be available.
You would require a EICR (electrical installation condition report) prior to any swap over, as not all systems are suitable for RCD protection and nuisance tripping or even complete power loss may occur.
CU change over, my area, about £350-£400 that's with EICR, new unit and signing off.

Thank you very much for your detailed reply.

That is actually quite a reasonable price, was expecting it to be higher. But as you said, if it aint broke, don't fix it. How much would the EICR cost on it's own?

 

[PrenticeBoyofDerry]

EICR, again regional variations, based on your set up, £120-£200.
I have heard of some electricians changing less.

 

[sparkybird]

and more - it depends on size of property, no of circuits and location of property (ie London/SE more £). And just because you have 4 fuses doesn't mean you only have four circuits -I've seen up to 5 sharing a lighting fuse and 2 or 3 on a socket one!

 

[Taylortwocities]

There is a CU in the loft, with a RCD and two MCB's. One MCB supplies the electric shower, and the other supplies one double socket in the loft (AFAIK it doesn't supply anything else).

I'd like to know whether this setup is dangerous or it should be replaced. .

This is not a great place to locate a CU.
Where is this CU fed from?

 

[NewFolder]

This is not a great place to locate a CU.
Where is this CU fed from?

It is only for a shower and one double socket in the loft. Seems to make sense to put it in there as the stuff it supplies is within a few metres of it at the most. Or is there another reason why it's not ideal?

I don't know where it is fed from, it doesn't have a mains switch, just a RCD and two MCBs. I wouldn't have thought it'd be fed from the main fuse box.

 

[PrenticeBoyofDerry]

I don't know where it is fed from, it doesn't have a mains switch, just a RCD and two MCBs. I wouldn't have thought it'd be fed from the main fuse box.

The RCD is considered as the main isolator in this case. There must be a distribution from your supply somewhere, do you have an additional isolator or connection box at your incoming supply.
Could you post photos of your set up?

 

[ban-all-sheds]

Or is there another reason why it's not ideal?

Because it is not easy to safely and properly have a CU that far away from the meter. Suppliers generally have a maximum limit on how long cables can be, and unless you have a fuse or MCB protecting the cable it's going to have to be large and expensive.

Hence the request for photos...

 

[NewFolder]

Thank you for all your replies. The pics are here:

//www.diynot.com/network/NewFolder/albums/13230

First pic is the meter box. The wiring in here is a bit messy, so I have also provided a block diagram which will hopefully make it a bit more clear.
The other pic is the loft CU.

I haven't included a photo of the main fusebox as it's a bit of a pain to get to, there are no visible wires around it, it's just a plastic enclosure with 4 fuse cartridges and a big main switch on it. Max load is 80A if I haven't already said. If you still want me to upload a photo of it, please ask.

 

[Taylortwocities]

OK
It seems clear.

The black cable, bottom right is your incoming power from the DNO with a 100amp service fuse.
This feeds the meter.
From the meter the feed splits
1) to your fusebox
2) to a switchfuse (the box top right with a red label on it). I'm guessing that feeds the mini CU in the loft?.

So that bit looks OK assuming the cable up to the loft box is not too small for the fuse in the switchfuse.

Where do you get 80amp as the maximum load?. The incoming fuse is 100amp.

SO, going back to your original post...

To add further features (eg RCBO or RCDs) would mean a change of the fuseboard and (itf it were me) I would want to do away with the loftbox and have all circuits connecting to the new consumer unit.

Cost should be about the same as a weekend break.
Wether the weekend break is in a Premier Inn or Le Manoir aux Quat' Saisons can only be determined by a site visit and a quotation.

Get three registered electricians to do this and you're ready to make a decision.


PS Re the "shed socket". I really do hope that this is RCD protected. That has been a requirement for a long time.

 

[NewFolder]

I have no idea for certain which one goes to the main fuse box and which one goes to the loft CU, but it seems more likely that the one from the switch goes to the one in the loft. I suppose I could switch it off and see what happens.

The wire to the loft CU seems the same thickness as the one that goes from the CU to the shower, which should be OK as the likelihood of the socket in the loft being used as the same time as the shower is virtually zero, the loft socket hasn't been used at all for at least 12 months, and the shower isn't working currently anyway.

80A is the maximum current for the main fuse box. The fuses in it only add up to 65A however.

Is the RCD on the shed socket a legal requirement?

 

[Taylortwocities]

I have no idea for certain which one goes to the main fuse box and which one goes to the loft CU, but it seems more likely that the one from the switch goes to the one in the loft. I suppose I could switch it off and see what happens.

Yes you should do that

The wire to the loft CU seems the same thickness as the one that goes from the CU to the shower, which should be OK as the likelihood of the socket in the loft being used as the same time as the shower is virtually zero, the loft socket hasn't been used at all for at least 12 months, and the shower isn't working currently anyway.

That isn't how it is done. The fuse in the switchfuse MUST be smaller than the maximum current than the cable (going to the loft) can carry. It propbably is but can only be determined by on-site inspection.

80A is the maximum current for the main fuse box. The fuses in it only add up to 65A however.

Yes, the actual maximum demand on your fusebox is much less than the total of the fuses, however.

Is the RCD on the shed socket a legal requirement?

It has been a requirement of Wiring Regulations since well before you moved in so and RCD should be on the shed socket AT LEAST. You should get that sorted if nothing else.
In 2001 the (then) new wiring regulations stated that RCD must be fitted to all sockets that could be used to power portable equipment outdoors.

Today's regulations more or less dictate RCD on every circuit in a house, including ligts, sockets, etc. But wiring regulations are not retrospective and only apply to "new" work.


Which brings us back to your Memera fuseboard, which is the subject of your thread.
When this was installed it would have met the safety requirements of that time. It won't get more dangerous than that. You may want to get the fuseboard upgraded to today's safety standards if you are having new electrical work done, or for your own peace of mind.

 

[securespark]

In 2001 the (then) new wiring regulations stated that RCD must be fitted to all sockets that could be used to power portable equipment outdoors.

I thought the "RCD to all sockets rule" was earlier than that. The introduction of the 16th (1991) or 7671 (1992) rings a bell.

Certainly the 1987 Amd 15th demanded "at least one socket" should have RCD protection, as well as being suitably placed and marked as to be used, to supply portable equipment outdoors.

 

[Taylortwocities]

You may be right on the date, I only had the 16th 2001 (2004) to hand in my pyjamas.
Doesn't change the rest of it though.