Electrical connection to macerator

[Rogeranerley]

The macerator spur connection will be beyond zones 1 & 2. The fitting instructions require an unswitched 5 amp fused unit with a flex intake port. Also, I understand that all bathroom electrics now require a link to an RCD. It's impractical to try and connect with the RCD side of my consumer unit. However, the integral RCD spurs I've so far uncovered are specified for 30 amp, for example:
http://www.ebay.co.uk/itm/PowerBrea...UK_BOI_CircuitBreakers_RL&hash=item2c726d2f5b

Can a 5amp catridge fuse befitted into such a unit or is there a lower rated fused RCD spur I could use?

Thanks

 

[PrenticeBoyofDerry]

Can a 5amp catridge fuse befitted into such a unit or is there a lower rated fused RCD spur I could use?

Swapping out the 13A fuse for 5A, will be fine.
But it is also a requirement that any cable buried in the wall less than 50mm, if not mechanically protected is protected by 30mA RCD. The FCU/RCD combination will not protect the supply cable. So I assume you are taking a spur from an existing socket outlet on either a ring or radial circuit. I would place the FCU/RCD next to this socket, then that would cover both appliance and cable. Unless you install a cable in metal conduit or use ali-tube or flexishield type cable.
The appliance could then be connected via a flex outlet.

 

[Rogeranerley]

Thanks for your quick reply PrenticeBoyofDerry

I'm taking a 2.5mm spur off from the upstairs ring main which goes back to the mcb side of the consumer unit.

The wire is running within the floor void then up to an intended PowerBreaker-30mA-Safety-RCD-Fused-Spur unit sited some 60mm back from the face of a tiled, dry lined wall.

From your comments, have I understood correctly that this setup is OK?

Thanks again for your time.

 

[PrenticeBoyofDerry]

The cable is required to run in permitted safe zones in walls and floor voids (through joist)
links here:
http://www.diynot.com/wiki/electrics:installation_techniques:walls
http://www.diynot.com/wiki/electrics:installation_techniques:route

Cables buried within walls less than 50mm will require 30mA RCD protection.
This is both sides of the wall, not just the side of the accessory.
You stated that you do not have this circuit RCD protected at the consumer unit and you intend to introduce a FCU/RCD, to protect the appliance.
If you install the FCU/RCD at the appliance, this will only protect the appliance and the flex to it, it will not protect the cable used to take the spur.
If the unfused length of cable taken from the ring circuit socket, is greater than 3 metres, it would be recommended to down-fuse at the socket outlet anyway,
I would suggest this FCU/RCD is installed next to the socket where you are taking the feed from, this would then protect the newly installed cable and the appliance, you can then either install a second isolator within the bathroom or a flex outlet plate.
An alternative would be to swap out the MCB for a 30mA RCBO, to achieve 30mA RCD protection, if the board type allows.

 

[Rogeranerley]

Many thanks for the very detailed, informative attachments. The cable inside the 60mm dry lined surface is running up the exterior wall which is 260mm thick, so I seem to be OK on that. However, I will need to rerun the cable in the floor void through holes at least 50mm deep as this is presently running in pre-existing notches.

Installing a 30mA RCBO is not so easy as this will require 2 gangs of the bus bar where only the current mcb is presently on offer.

If I locate the intended FCU/RCD beyond the shower room close to the ring main to protect the cable, what unit do I need for connecting the macerator's flex to the 2.5mm spur cable? So far, other than the intended FCU/RCD, Ive not located any unswitched, fused spur socket that's rated for a bath/shower room.

Again, thanks for your time.

 

[PrenticeBoyofDerry]

Many thanks for the very detailed, informative attachments.

No problem, I do my best!

The cable inside the 60mm dry lined surface is running up the exterior wall which is 260mm thick, so I seem to be OK on that.

If that is the case, seems fine

However, I will need to rerun the cable in the floor void through holes at least 50mm deep as this is presently running in pre-existing notches.

Pre-existing notches can be capped with safe plates.
http://www.screwfix.com/p/protecta-galvanised-safe-plate-pack-of-20/30038

Installing a 30mA RCBO is not so easy as this will require 2 gangs of the bus bar where only the current mcb is presently on offer.

What type of MCBs are they, make and code?
Don't confuse RCCB with RCBOs, you can get single pole RCBOs.

If I locate the intended FCU/RCD beyond the shower room close to the ring main to protect the cable, what unit do I need for connecting the macerator's flex to the 2.5mm spur cable? So far, other than the intended FCU/RCD, Ive not located any unswitched, fused spur socket that's rated for a bath/shower room.

You have a couple of options:
*Keep FCU/RCD at 13A and install a standard unswitched FCU at appliance and down fuse that to 5A (per manufacturers instructions)
*Or down fuse FCU/RCD to 5A and fit a flex plate at the appliance, this will allow you to joint the cables together in backbox and run the flex to the appliance.
http://www.screwfix.com/search.do?fh_search=Flex+plate&fh_view_size=20

 

[Rogeranerley]

The 2 ring main MCBs on the non-RCB side of the consumer unit are both Hager:

B40 MT140 450145
&
32A type2 M632 13085

I fitted the consumer unit 20 years back.

Not sure I understand the difference between RCCBs and RCBOs. Is the one shown at http://www.electricalcounter.co.uk/...C/2011754054?gclid=CL-406GmwbkCFfQetAodMy8AsA the type I should use to bring both mcb-only ring mains up to RCD grade?

On the options you've suggested, I'm OK with these, but might still take the upgrade of the consumer unit as an alternative as it will provide a more comprehensive solution .

Thanks again.

 

[PrenticeBoyofDerry]

RCCBs are double pole earth leakage devices, they do not protect on overload current.
Where as the RCBO, detects both earth leakage and overload.

The RCBO linked is a type C, in domestic installation a type B woukd be used.
With the board being 20 years old, not sure if they new ones retro fit the old boards.
Does the board have an RCCB that is protecting over circuits and if so are there any spare ways? AS you could move the 32A MCB of the ring circuit over.

 

[Rogeranerley]

Thanks for clarifying the difference between RCCB & RCBO. With one spare slot on the RDC side of the CU, I'm going to look at moving the MCB based ring main across. Also, I'm planning to check out whether RCBO 32 Amp Single Pole Type B can be accommodated as this would seem to be a good upgrade.

We're likely to sell the house in a year or sos time, and with the FCU/RCD already on order, I'm minded to install this in the shower room to give comfort to any prospective buyer that the macerator is adequately protected (if the CU can accommodate the switched or upgraded ring main). Would that compromise any RCDs or RCBOs on the CU?

Thanks again

 

[PrenticeBoyofDerry]

There would be no need to have two 30mA RCD units on the same circuit, protecting the same appliance or accessory.
They often cannot discriminate against each other, which could lead to an earth leakage fault at the macerator, by-passing the RCD/FCU at the appliance and tripping the RCBO at the board.
But will not harm the situation.

 

[Rogeranerley]

Many thanks for clarifying on this.

I'm away this weekend, so will try the CU switch over next week.

Cheers!

 

[Rogeranerley]

Finally made time to switch the upstairs ring main to the RCD side of the CU, only to find this is constantly tripping off, indicating a leak to earth somewhere.

On disconnecting all appliances on that ring main, the MCB stays in the open position but immediately clicks off whenever an appliance is reconnected and switched on in any of its sockets.

I'm laboriously checking each socket (all with switches), but wonder whether there's an easier, quicker way as there's much heavy furniture to move to reach some of them.

Most have metal boxes, and I'm wondering if a simple screwdriver tester would show up the faulty socket connection by just touching the plate retailing screws

Also discovered similar problem on the downstairs, front of house ring main. These MCBs were installed 20 years ago. Is it possible they've become too sensitive with age, as I've no problems with the downstairs back of house ring main installed on the RCD side of the CU just a few years back in the new kitchen.

Grateful for your thoughts.

 

[b13kal]

Hi

You will need to swop over the neutral to the correct RCD buz bar.

You need to check if the ring is complete (r1 , rn and r2)

If you have done this then split the circuit, but you will need a megga?

 

[Rogeranerley]

Thanks for your quick reply. However, the situation has become a bigger mystery (to me, anyway!).

To test matters, I first moved one of the more recently installed 6a lighting mcbs from the non-rcd side to the rdc side of the cu. This caused no problems. I then repeated this with another more recently installed 6a lighting mcb. Again, with no click off.

Checking further, I then moved one of the 6a lighting mcbs installed 20 years ago to the rcd side, which immediately activated the rcd safety click off. I repeated this with the other originally installed 6a lighting mcb which immediately also clicked off.

So, it looks as if I have a fundamental issue effecting the 2 ring mains and 2 lighting circuits installed 20 years ago on the non rcd side of the cu.

When looking more closely at the cu, I noticed that the 63a rcd switch (which has no guide marks) has the live feed in on the right, whereas the main 100a cu switch is wired with the live on the left as marked. Both of these connections were made by United Utilities 20 years back.

The cu set up is:

63a RCD:
16a - auxiliary emersion rod
32a - induction hob
32a - double oven
32a - garage R/M
32a - kitchen R/M
1 spare slot to which trying to connect upstairs R/M for 5a macerator fused spur

100a Main Switch:
40a - downstairs lounge/hall/utility room R/M (should be 32a) - original installation
32a - upstairs bedrooms/office R/M - original
6a - garage lighting - recently added
6a - kitchen lighting - recently added
6a - downstairs lighting - original
6a - upstairs lighting - original

Any ideas?

 

[b13kal]

There might be shared neutrals in the lighting circuit. Is the wiring singles?