Crabtree RCCB Question

[junglistmatty]

What is the difference between a Crabtree RCCB 363/S030 and a Crabtree 363/030 (other than their size)?

Source

Starbreaker RCCBs are specifically for use in conjunction the Starbreaker plug-in
busbar system. The three module wide devices have two pin connections and are
related to split load applications. The two module wide devices have a single pin
connection and are related to main incoming applications.

Having done some reading it appears my consumer unit contains 2x bus bars, the circuits on the first bar are protected by the S030 and the circuits on the second bar are protected by the 030. What makes the 2x RCCBs different? What is different between "main incoming applications" and "split load applications" in the paragraph above?

Note: here's a photo of my consumer unit:



Thanks in advance

 

[plugwash]

It sounds to me like the "split load applications" version is designed to pick up the incoming live from a busbar at the bottom, while the "main incoming applications" version is designed to have the incoming live fed by a wire entering from the top. In the context of a "16th edition" split load layout this would save the need for a live link wire from the main switch to the RCD.

When the 17th edition of BS7671 came along, requirements for RCD protection were expanded significantly meaning most domestic circuits would need RCD protection. However, putting a full install on the same RCD was frowned upon and RCBOs were expensive. So we saw the introduction of the dual RCD split.

Since the first RCD is next to the main incomer it can be supplied by a section of busbar from the main incomer and a "split load" style RCD can be used. On the other hand feeding the second RCD from the first RCD would defeat the object of having two RCDs, so it's incoming live has to be fed by a wire and a "main incomer" style RCD used (even though it isn't actually the main incomer.

 

[EFLImpudence]

A split load system is simply some of the circuits supplied by one RCD and some from another or from no RCD.

I don't really know why the Starbreaker three-module RCCB is itself said to be related to split-load applications as it will be the same whether there is a break in the busbar (for another RCD) or not.

 

[junglistmatty]

I don't really know why the Starbreaker three-module RCCB is itself said to be related to split-load applications as it will be the same whether there is a break in the busbar (for another RCD) or not.

Thanks - this is what confused me.

What I wanted to know was if there is a possibility to add a non RCD protected MCB to the unit (i.e. between the Main Switch and the 3-module RCCB in my CU), for a circuit to provide some power to an outbuilding with it's own small CU.... Maybe my only option (unless upgrading the CU) is to have a sparky add henley blocks to the meter tails with a switched fuse supplying the SWA.

Reason I'm asking is that I want to understand the different quotes I've got coming my way (have a few sparkys coming out next week).

 

[ericmark]

The picture on the data sheet shows the split load RCCB in the centre and the RCCB picture shows the split load has neutral only connections, where the non split load has a line input. But the text tells us the non split load has one pin and the slip two pins, so in total same number of connections, so I am as intrigued as you are as to what the difference is? I know the first RCD's I worked with were 4 module width, it always seemed odd to me to have DIN rail which is a German standard, then move away from the standard by using clip in buzz bars or half DIN rails.

But it depends on the consumer unit this shows two neutral bars, this shows three neutral bars, and to have a non RCD protected section it needs to have three neutral bars. I note Starbreaker RCBO's are available but at £40 darn expensive, so my work out cheaper fitting something like FuseBox CU instead. I wonder myself what the answer is, clearly likely can do some botch, but for a CU to be a CU it needs to be to manufactures design, any change and it is no longer a consumer unit, it is only a DB.

 

[EFLImpudence]

What I wanted to know was if there is a possibility to add a non RCD protected MCB to the unit (i.e. between the Main Switch and the 3-module RCCB in my CU), for a circuit to provide some power to an outbuilding with it's own small CU....

Yes, you can do that by altering the busbar if they are still available, or by some other means.

I once used a Loadstar MCB which does not have the plug-in terminal and supplied it with a wire from the main switch but I suppose no one will do that.

Maybe my only option (unless upgrading the CU) is to have a sparky add henley blocks to the meter tails with a switched fuse supplying the SWA.

That would be better.

 

[junglistmatty]

That would be better.

My supplier is Octopus so I've sent them a request to fit an isolator switch on the meter tails as I have no way to isolate my main switch... I'm under the impression this is needed for the Henley block method as there's no way to isolate those tails and I'm not sure any electrician will be pulling my main fuse as it's a smart meter (I've read that notifies the DNO and someone will come to inspect, plus it's illegal unless explicitly premitted by the DNO).

I think octopus will be happy to install the isolator for me, not sure if or how much cost that will involve but it seems to me to be a sensible necessity for anyone to safely work on my electrics.