Electrical connection to macerator

[Rogeranerley]

All circuits are separate on the live feeds, with R/M mcbs running two wires in both directions. All other circuits are radial, with the heavy loads on one line to specified appliances (oven, hob etc.) and with the lighting being a mix of 2 and 3 wire switching.

Some of the lighting on the original cu installation is without earth lines due to being ancient installation whose location makes it difficult to add an earth.

Neutrals run back to one or other of two blocks in the cu. Is it possible, I've cross connected rcd neutrals with non-rcd neutrals?

 

[b13kal]

Yes , if you mix neutrals it will trip

 

[Rogeranerley]

Many thanks, b13kal, for your and PrenticeBoyofDerry's help with this macerator installation.

Changed neutral to the RCD block (as you'd already indicated) and all is working well with no trip outs. Sometimes takes us 70 year olds a little longer to work through the logic of the situation!

As I've now got RCD protection to the shower room all the way from the CU, I'm planning to connect up with MK's K377 FUSED+UNSWITCHED+SPUR as this has a neon, giving confidence that the macerator is 'live' before flushing, and also has the flex inlet port at the base, making for a safer and a more attractive link back to the macerator.

Again, many thanks to you both

 

[Agile]

I thought that the general good practice advice is to fit the RCD/isolator for a macerator outside of a bathroom ( regardless that it would be outside zones 1+2 ) ?

 

[b13kal]

Glad it all sorted

 

[b13kal]

Agil you are correct, unless there is seperation in the room or the the bathroom is more than 3 meters then you can put a socket in the room if you wish

 

[Rogeranerley]

Just to clarify, Agile, my set up is an unswitched 5a fused spur in the old zone 3 area. This is spurred in the wall and floor voids at 60mm, connecting to the upstairs R/M in the hallway beyond the shower room. The R/M is now located on the RCD side of the CU which is situated under the stairway in the hall.

However, I did consider installation within zone 3 using GREENBROOK's PowerBreaker Safety RCD Fused Spur H92WPA-C, which is specifically designed for wash/shower room situations.

The suggestion by PrenticeBoyofDerry to convert the R/M at the cu seemed, though, a more comprehensive solution....and is proving to be less expensive

 

[Agile]

Hopefully the RCD at the CU will now mean that the kitchen is included as well!

The cost of the hardware may be less than the cost of anyone losing their life following an electrical accident!

However, the electricians may have views on an 18A 2.5 mm2 spur coming directly off a 32A 2.5 mm x 2 ring main.

I find it difficult to follow the current preferred practice when I see so many examples of bad work and when so many are not up to date!

Tony

 

[PrenticeBoyofDerry]

Hi Rogeranerley, can you just clarify where you have taken the spur from and this was part of complete RFC and not an existing spur and the distance of this spur from the feed socket?
As you have already found out, you cannot have a live to a RCD side and neutral on the other side, as it will detect an imbalance and trip.
Shared neutrals often course this to become a bit of a headache.

Agil you are correct, unless there is seperation in the room or the the bathroom is more than 3 meters then you can put a socket in the room if you wish

Not quite correct, your bathroom could be 10m X 10m and requirements would not allow a socket outlet to be installed.
A socket outlet (if installed) must be at least 3m horizontally from any zone one and again 30mA RCD rule applies.

 

[Rogeranerley]

Thanks, chaps, for all your recommendations and comments so far.

The unswitched 5a fused spur unit for the macerator is located 75 cm from the shower. It's fed by a 2.5mm line entrenched more than 50mm beyond wall and floor surfaces, connecting to a 30a junction box on the upstairs RM. The JB is located in the floor of the upstairs hallway some 2 M beyond the shower room. This RM runs from to the CU located some 5 M away downstairs via the stairwell. Being upstairs, this RM generally feeds radios, phones, pc, tv etc.

I selected this RM as it was the nearest to the shower room and have now moved it's 32a MCB across to the 63a RCD side of the CU.

A separate 32a RM from the RCD buz bar serves the 13a wall sockets in the kitchen, with all other feeds from 63a RCD switch radially supplying hob, oven and other higher-demanding equipment.

Is this all OK?

 

[Agile]

The experts will pronounce on the 750 mm from shower! But seems too close to me!

I would also think it better to have a fuse device at the beginning of the 2.5 mm spur as that's being supplied from a 32A circuit. But the regs experts will pronounce on that too.

Tony

 

[PrenticeBoyofDerry]

The junction box should be easily accessible for maintenance, inspection and testing, unless a maintenance free joint is made.
If it is a shower with a fixed basin 750mm will take you outside the zones. if it a shower with fixed water outlet but without basin, then zone one is increased to 1200mm from the water outlet, but there is no zone two.
When taking a spur from the RFC, it is recommend that if the length of the spur is to exceed 3 metres, it should have a FCU fitted within the first 3 metres, as close to the intersection of the spur as possible would be advised.

 

[Rogeranerley]

Thanks guys.

The shower cubical is within a tray, so 750mm somes OK.

The 2.5mm run from the unswitched 5a fuse unit is some 4 M to the JB which is some 2 M from the shower room. This JB was originally used as a 13a spur the the room now being converted. It's your standard 3 terminal bakelite type round box and is easy to access as the floor boards in this part of the hallway are screw fixed. If I insert a FCU into the spur run at 1 M from the shower room, do I rate this at 5 or 13a.

Also, would be grateful for clarification on the difference between 32a & 30Ma.

Thanks again