two radials into an RCBO

[John-SJW]

No spare ways in the consumer unit. There are two low current radials on their own RCBOs. Do the regs forbid putting the two radials onto the same RCBO - that is two L wires into the one RCBO?

 

[brianmoooore]

I thought we'd laid this one to rest a couple of months ago!
Doesn't matter how many wires from however many radials connect to one MCB or RCBO, as long as their total cross sectional areas doesn't exceed the maximum capacity of the device's terminal and they are all properly secured. They will all form ONE circuit in total.
Connecting multiple radials like this can make fault finding much easier. The last case of RCD tripping I sorted out was caused by a lighting circuit with six individual wires connected to the MCB. Within ten minutes of arriving at the property I'd identified the wire with the poor IR, connected the other five back up, been around the house to see what didn't work,and discovered it was the feed to the light in a boiler house.
Problem was a leak in the shower in the room above directly above the conduit to the switch.

 

[timhoward]

@brianmoooore I agree in this case, and must have missed the previous thread on this.
Out of interest, would your comment mean that 314.4 can never actually be broken if combining radial circuits?

 

[John-SJW]

The idea is to make a way for an SPD by joining two circuits. The SPD will be a single way unit. The BG SPD looks OK. Can it fit into a Wylex CU?

Type 2 Single Phase SPD (Surge Protection Device) | BG (CUSPDT21-02)

 

[brianmoooore]

By the letter of the regs. , no, but it depends if you're an engineer or a sheep. I have no problem mixing different makes in a full DIN rail CU, as long as they fit properly.
This doesn't connect to the busbar, so no pulling out of shape. The only possible issue is to make sure the front part projects through the front panel enough to meet the IP rating, which it almost certainly will.

 

[SJD]

I'd make one more comment - perhaps the reason the boiler and the fridge were on separate radial circuits was because they are either (a) somewhat important circuits that could be problematic if tripped, or (b) the loads (at least the boiler or associated valves/pump) are prone to faults. I know most properties don't provide that luxury, pity to take it away.

 

[GBDamo]

Whenever I swap out a board I look to put everything on its own OCPD and leave space for expansion, so there's often more breakers than the original board.

However if I come to a full board, needing a low power radial, I'll always put it to the customer that I can do a "Spur at source" (which some electricians frown on) or I can put in a new board and a dedicated OPCD.

Guess which option they choose.

 

[John-SJW]

You certainly can if you like, but it's not actually required as per other posts as it is legitimately one final circuit with a branch.
There isn't a right answer here - we'd all prefer not to add joints if not required, and we'd prefer not to stick two legs in an RCBO.
I'd probably gravitate to the latter option personally.

It would also give DP isolation to an integrated fridge.

 

[timhoward]

Is this Wylex single module type 2 SPD of any interest:

Wylex NMT2SPD3W/1 Surge Protection Devices

Buy Wylex NMT2SPD3W/1 Surge Protection Devices online at Shop4 Electrical & get FREE Next Day UK Delivery when you order by 2pm & spend £60

www.discount-electrical.co.uk

It is a bus-bar connection too....no breaker needed for it

 

[John-SJW]

I'd make one more comment - perhaps the reason the boiler and the fridge were on separate radial circuits was because they are either (a) somewhat important circuits that could be problematic if tripped, or (b) the loads (at least the boiler or associated valves/pump) are prone to faults. I know most properties don't provide that luxury, pity to take it away.

People like a fridge on their own circuits so if another circuit is at fault the fridge is not taken out,

 

[John-SJW]

Is this Wylex single module type 2 SPD of any interest:

Wylex NMT2SPD3W/1 Surge Protection Devices

Buy Wylex NMT2SPD3W/1 Surge Protection Devices online at Shop4 Electrical & get FREE Next Day UK Delivery when you order by 2pm & spend £60

www.discount-electrical.co.uk

It is a bus-bar connection too....

The Wylex is £70 (taking the mick) to BGs £38. If two radials are joined there is another way available. Not sure if the BG will fit a Wylex.

 

[7029 dave]

People like a fridge on their own circuits so if another circuit is at fault the fridge is not taken out,

But your adding the boiler to this circuit ?, so it is not on its own anymore.

 

[timhoward]

The Wylex is £70 (taking the mick) to BGs £38. If two radials are joined there is another way available. Not sure if the BG will fit a Wylex.

In my experience it's usually the bus bar alignment that is the biggest issue, which as someone said wouldn't apply to an SPD which connects to an MCB.

 

[John-SJW]

By the letter of the regs. , no, but it depends if you're an engineer or a sheep. I have no problem mixing different makes in a full DIN rail CU, as long as they fit properly.
This doesn't connect to the busbar, so no pulling out of shape. The only possible issue is to make sure the front part projects through the front panel enough to meet the IP rating, which it almost certainly will.

The BG can fit onto a Din rail. Not sure if it fits a Wylex busbar, or any busbar.

"Can be fitted on DIN rail directly into the consumer unit."

 

[John-SJW]

But your adding the boiler to this circuit ?, so it is not on its own anymore.

Yep. A compromise.

 

[westward10]

@brianmoooore I agree in this case, and must have missed the previous thread on this.
Out of interest, would your comment mean that 314.4 can never actually be broken if combining radial circuits?

I always follow this, it is two final circuits therefore separate circuit protection.