Sanity check on plan for CU replacement (MCB to RCBO AFDD)

[nicebutdim]

The Crabtree Starbreaker are nice, innards same as Wylex, and one of the original single-module AFDD. As for the RCBO they have the nice feature of neutral-switching.

And that lovely plug in live busbar.

 

[j0hnnn]

There's no reason not to fit AFDDs, but is there any benefit in doing so? Is the property used for commercial purposes?

It's a domestic property and not used for any commercial purposes. Aside from the inherit benefits from detecting arc faults, my thinking is that if a situation would arise, I'd be some what protected. Although it's not mandated for domestic installations, I'm going by the fact that if it's mandated for premises with sleeping accommodation, it must/should be good for domestic too. Also, if I'm replacing the MCBs and I have the option to go for RCBOs or RCBOs with AFDD, if money isn't a big factor, would you still settle just for RCBOs?

What is the earthing arrangement at the property? Buying what you think is best might be an ultimately pointless exercise. This ties in with my suggestion to engage the services of an electrician, rather than compile a shopping list on the basis of information gathered from various parts of the internet. Regardless of how good a source might be, they won't reimburse you for items bought that don't meet the requirements of your installation.

Standard earthing setup with bonding to gas and water pipes. I will definitely be engaging with an electrician but I wanted to get a feel for what I'm planning makes sense. I know there will be a lot of factors that will come into play on the actual installation but I wanted to have some understanding of all this before I blindly go and ask someone to do it. This is why I spent my time researching and hopefully the information I have presented is sane. I was hoping the collective feedback of many would be better at this stage than approaching an electrician locally. If everyone were to post saying this wouldn't be up to code or it's unsafe then at least I know I'm completely off track.

It is good that you have read up on this and familiarised yourself with the options, but I'd suggest you don't fix on a particular manufacturer or specific arrangement until you've spoken to the electricians who will be quoting the job.

The reason I've picked this particular manufacture is because I've spent that past few weeks looking into various manufacturers and I wanted to make sure I'm getting quality rather than going for cheaper options. I don't have an issue spending a bit more if I know the product is good and this is the impression I got with Hager on most posts/reviews. The specific arrangement was just put up for discussion as a first pass with the members of this forum before I go ahead and speak to electricians.

As @davesparks says many sparkys have favourite brands so might want to offer others, but if you are looking for high quality then Hager and Schneider are your best bets if affordable.

Totally understand that some will have brand loyalty. I'll just need to find someone that has a similar alignment to a brand I'm considering. If others posted saying Hager isn't a good choice then I would know not to be picky and let the electrician advice me on their preference but that's not the case, as you say, Hager is one of the higher quality brands and I'm leaning towards quality over value here.

For the electricians on the forum, if someone approached you with a similar request to mine, how would you feel and deal with the situation? I understand that it could come off as trying to tell one how to do their job but I'm hoping I've got some valid requests/thoughts for discussion/advice in there albeit being excessive? As I said before, I wanted to post here to get feedback from a larger pool of electricians first.

 

[nicebutdim]

It's a domestic property and not used for any commercial purposes. Aside from the inherit benefits from detecting arc faults, my thinking is that if a situation would arise, I'd be some what protected.

You would be afforded protection against certain types of earth fault, but not all.

Some protection would be better than none, should such a fault occur.

Although it's not mandated for domestic installations, I'm going by the fact that if it's mandated for premises with sleeping accommodation, it must/should be good for domestic too.
Also, if I'm replacing the MCBs and I have the option to go for RCBOs or RCBOs with AFDD, if money isn't a big factor, would you still settle just for RCBOs?

I'd consider the question on its respective merits for each individual installation. Arc fault protection is relatively new technology where UK electrical installations are concerned.

It has been used quite widely in US domestic installations for a longer period of time and opinions about its benefit are mixed over there, although negative opinions may stem from the sort of installation which might benefit most from atc fault protection.

Standard earthing setup with bonding to gas and water pipes. I will definitely be engaging with an electrician but I wanted to get a feel for what I'm planning makes sense. I know there will be a lot of factors that will come into play on the actual installation but I wanted to have some understanding of all this before I blindly go and ask someone to do it. This is why I spent my time researching and hopefully the information I have presented is sane. I was hoping the collective feedback of many would be better at this stage than approaching an electrician locally. If everyone were to post saying this wouldn't be up to code or it's unsafe then at least I know I'm completely off track.

This doesn't address the question I raised about earthing, but that won't be an issue if you intend bringing an electrician on board before buying materials.

As per my initial post; there's nothing flawed in your plan, although it does appear to be more risk averse than many would consider necessary.

Chances are we'll see boards filled with AFDDs in the not too distant future, but I'd expect they'll be considerably less expensive by then and possibly more refined. With brands like Hager or Crabtree, it's very likely that availability won't be an issue in the future as both have a great track record where backward compatibility is concerned.

The bare bones of your plan is sound, if excessive, and specific details can be ironed out when an electrician looks at the installation.

They may not bat an eyelid at your proposals, but nor should they have any issue fitting what might be considered an overly expensive option if you explain that it's what you want.

 

[Risteard]

The Crabtree Starbreaker are nice, innards same as Wylex, and one of the original single-module AFDD. As for the RCBO they have the nice feature of neutral-switching.

This (i.e. switching all live conductors) will be essential for adding an EVSE installation to this new DB later as stated.

 

[littlespark]

An earlier point raised. A 60, 80 and 100A main fuse all use the same fuse holder, so you may not meet a new head. (Although, you do imply money isn’t a problem)

The problem with upsizing the fuse is whether it would still offer protection to the supply cable coming into the property. (Very likely anyway)

 

[pc1966]

Long story short, I've got a server rack up there which is increasing in power consumption and had a trip when a computer on the same circuit got powered on.

How big are you planning this rack to be?

Are you using a UPS on this?

Generally computer racks can be quite leaky, more than the ~9mA max recommended for your usual 30mA additional protection RCD/RCBO used for general circuits.

If that is the case then hard-wiring the UPS supply without RCD on its input using a suitably protected cable like SWA to a FCU or similar, possibly with supplementary bonding to the rack, would be a better idea. Any RCD protection on sockets fed from the UPS ought to be on its output, say via an RCD FCU (or two, if splitting a lot of low power but leaky loads) to some block(s) of 13A or 10A IEC outlets..

Disconnecting the input to a UPS does nothing to protect some poor sod on its output!

 

[plugsandsparks]

To answer the Ops question - how would an electrician react to the home owner specifying the Cu design ?
TBH - it has never happened, lol
There is no brand loyalty, as such, it is just some brands have quirks in their products that grind your gears when you have to deal with them. I tend to settle on a brand that is supported by local wholesaler, a brand that does not have a key part in short supply, a brand whose quality of housing and fasteners is dependable and strong. Lastly a brand that supports options i may need, its very different in the commercial world, so i tend to be more brand conscious in commercial and industrial. Domestic, you have slightly different priorities.

I think the question may be more relevant to ask yourself how you are likely to react when the electrician proposes a different solution which you have spent hours of research on. Dont expect an electrician to engage in a lengthy conversation, we are not research bods, we are a trade with years of experience in both installations and fault finding / maintenance, this all comes into play when designing any solution.

E.g. I would recommend to get a quote for your installation upgraded to 100A , you may be lucky. A good strong CU housing, the bigger the better, over-size it by at least 20% from what you know today. All RCBO with DP switching, earthing system checked for best possible ZE. SPDs - cheap enough but need to be checked regularly, AFDDs if you really want them but i personally am in no rush to fit them in my own home, could be useful for an electric shower cct, car charger cct or any long duration high power loads.

 

[timhoward]

Also, if I'm replacing the MCBs and I have the option to go for RCBOs or RCBOs with AFDD, if money isn't a big factor, would you still settle just for RCBOs?

I've read this quite quickly, but I'll throw in that while Hager are excellent, unlike other brands their RCBO's only switch the live, not the neutral.
(Also beware that CEF say Hager Single Pole and Neutral, but they aren't, as the photo shows )

So I'd rather have the highly expensive Hager AFDDs or a lesser brand with RCBOs that switch both poles.

If it were me and I was splashing out I'd go the Crabtree route myself. I actually installed Fusebox in my own house but that is because no one was paying me to do it....and I think their perfectly adequate.

 

[j0hnnn]

Chances are we'll see boards filled with AFDDs in the not too distant future, but I'd expect they'll be considerably less expensive by then and possibly more refined. With brands like Hager or Crabtree, it's very likely that availability won't be an issue in the future as both have a great track record where backward compatibility is concerned.

That's a good point. It certainly feels risky opting for what's essentially a new product which most likely can be refined and be cheaper. Given all the feedback so far, I'm now on the fence of going all out AFDDs here, especially since this isn't going to be my final home.

How big are you planning this rack to be?

Are you using a UPS on this?

It's 20U, mostly networking gear with a few servers that could theoretically pull up to 700W individually but idle is around 100W and average during moderate use has been around 150W - 200W. So it's not really a that big considering how big and power hungry racks can be so I haven't planned in anything complex for power here other than the two PDUs (one IEC outlets and other standard UK). Up until recently, the PDUs came off the an APC UPS that had its battery fail so I'm still looking at options to replace that but on hold until I figure out what I'm going to do with the new CU/circuit. Currently, everything is powered off the mains socket. Nothing running is mission critical and everything is backed up (3-2-1) so I'm pondering whether I'll need a UPS again with proper protection in place.

E.g. I would recommend to get a quote for your installation upgraded to 100A , you may be lucky. A good strong CU housing, the bigger the better, over-size it by at least 20% from what you know today. All RCBO with DP switching, earthing system checked for best possible ZE. SPDs - cheap enough but need to be checked regularly, AFDDs if you really want them but i personally am in no rush to fit them in my own home, could be useful for an electric shower cct, car charger cct or any long duration high power loads.

Yea, hopefully going from 14 to 20 ways is enough for what I'll be needing as long as I'm in this house. Already struggling to find space where the existing CU is to replace with something bigger so will potentially need to a new mounting board above the current one, I'll leave this up to the electrician to figure out though. Are earthing system checks for ZE standard part of CU installs or is this something I would have to request the electrician carry out?

I've read this quite quickly, but I'll throw in that while Hager are excellent, unlike other brands their RCBO's only switch the live, not the neutral.
(Also beware that CEF say Hager Single Pole and Neutral, but they aren't, as the photo shows )

So I'd rather have the highly expensive Hager AFDDs or a lesser brand with RCBOs that switch both poles.

This is the unfortunate thing. I had this all planned out with AFDDs which are single module double pole and neutral. As you say, their RCBOs are not, although, their commercial breakers are DP (ADA932U | Hager UK - https://hager.com/uk/products/h/ada932u-rcbo-1pn-6kab-32a-30ma-a) but then at this point it's even more excessive, double module and I would be better off AFDDs with regards to protection and cost.

So, with all the feedback so far, it's clear this is a pretty excessive and an overly risk averse setup for what I'd consider is a "typical home" then I'm back to the drawing board again to consider what my options are for high quality DP RCBOs... Schneider? I've not really came across Crabtree but there seem to be a lot of positive chat about them in this thread so far.

 

[pc1966]

Are earthing system checks for ZE standard part of CU installs or is this something I would have to request the electrician carry out?

They should be. Checking the supply Earth nature & quality, and bonding of extraneous parts like service pipes, would be an essential aspect of any change to a CU, let along complete replacement.