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

[j0hnnn]

I'm planning a replacement for my existing domestic CU and would like to have it sanity checked before I get an electrician involved. The main reason for replacing the whole CU is that I would like to have an additional circuit to the attic which would be isolated from the existing one. 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. Second reason is that the current CU is using MCBs and also there is no more space left. Instead of planning for another smaller CU, I want to get this done properly and modernised.

Existing Setup

The existing CU is 14-way (all used up). The main fuse from the supplier is 60A.

• CPN IS2100 Isolater Switch (100A) - 100A, 2 Pole. | CPN Cudis - https://cudis.co.uk/product/100a-2-pole/
• 3x CPN MC110B MCB (10A) - 10A - B Curve | CPN Cudis - https://cudis.co.uk/product/10a-b-curve/
• 3x CPN MC116B MCB (16A) - 16A - B Curve | CPN Cudis - https://cudis.co.uk/product/16a-b-curve/
• 4x CPN MC132B MCB (32A) - 32A - B Curve | CPN Cudis - https://cudis.co.uk/product/32a-b-curve/
• 1x CPN RC263/030 RCD (63A) - 63A 30mA Type B | CPN Cudis - https://cudis.co.uk/product/63a-30ma-type-b/

Upgrade Plan

I have spent the last few weeks researching everything electrical related to CUs and tried to incorporate as much of the recommendations I have read online. Since I'm not an electrician, the following is likely to not make sense, completely wrong or "overkill", hence me seeking advice. I fully understand that this plan may require rewiring and won't be cheap so money isn't going to be the significant deciding factor here.

Having looked into the different brands, I'm have made the decision to go with Hager. As mentioned previously, my immediate requirement is to have a new circuit to the attic but would be looking to have an EV charging point installed in the future. So my thought is to get the main supplier fuse upgraded. If I'm reading correctly, going form 60A to 80A could be simple but going to 100A would require a service head replacement. Also, if the cabling into the home isn't adequate, there will be extra work involved. Ideally, I get the main supplier fuse upgraded from 60A to 100A giving me more flexibility for the future. I want to get an isolation switch installed at the same time as there currently isn't one between meter and the CU. I guess I just need to get in touch with my DNO to see what they can do and whether the tails need upgrading too.

For the new CU, I'm considering the following:

• Hager VM120K CU Enclosure (20-way) - VM120K | Hager UK - https://hager.com/uk/products/h/vm120k-conunitd3020w100asw-discknockouts
• Hager VME02SPD SPD Type 2 - VME02SPD | Hager UK - https://hager.com/uk/products/h/vme02spd-cu-surge-protection-kit-type-2
• Various RCBO AFDDs:
  • Hager ARR910U (10A) - ARR910U | Hager UK - https://hager.com/uk/products/h/arr910u-rcbo-with-arc-detect1m-10a-b-6ka-a-30ma
  • Hager ARR916U (16A) - ARR916U | Hager UK - https://hager.com/uk/products/h/arr916u-rcbo-with-arc-detect1m-16a-b-6ka-a-30ma
  • Hager ARR932U (32A) - ARR932U | Hager UK - https://hager.com/uk/products/h/arr932u-rcbo-with-arc-detect1m-32a-b-6ka-a-30ma

With this in place, I'm hoping to have a second circuit installed in the attic purely for the server rack. Currently it's powered using a single socket to a 13A PDU. Maybe I can separate the load here across two PDUs plugged into two different 13A fused sockets from the new circuit, at least I should have more options. I've looked into commando sockets but like I said, unlikely I'll have a load that would warrant it.

So, how does this all sound?

 

[davesparks]

Thanks! So what would be my other high quality/reliable options if I were to just stick to RCBOs and given that Hager ones are single pole?

Personally I have used contactum for domestic work since I was an apprentice and have not had any major issues with them.


Is there a particular reason you need double pole protection? There's not normally any need for it in the average UK installation.

 

[pc1966]

Thanks! So what would be my other high quality/reliable options if I were to just stick to RCBOs and given that Hager ones are single pole?

For most purposes the single pole switching RCBO are fine, it is only specific cases like EV charges that need double pole and for that you can fit a MCB and separate RCD.

You mentioned a lack of space, some (like Hager) do double-row CU enclosures and that might help if you are short of width but have height to spare.

Personally I would go with the main stream brands (Hager, Schneider, Wylex, Crabtree, etc) and avoid the own-brand ones (Proteus, Axiom, etc).

 

[j0hnnn]

Is there a particular reason you need double pole protection?

Ahh, there is a couple of posts earlier on in this thread where people recommended getting double pole so was just trying to follow the advice.

For most purposes the single pole switching RCBO are fine, it is only specific cases like EV charges that need double pole and for that you can fit a MCB and separate RCD.

I have plans to install an EV charger at some point in the future, in this case, what you suggest makes sense but could also save a module space here and go with their AFDD as it's already DP?

You mentioned a lack of space, some (like Hager) do double-row CU enclosures and that might help if you are short of width but have height to spare.

Good point! I saw the Hager double-row CU but didn't think much of it. These might make things less of a hassle to install given the space.

Personally I would go with the main stream brands (Hager, Schneider, Wylex, Crabtree, etc) and avoid the own-brand ones (Proteus, Axiom, etc).

Definitely, I'm happy to pay a bit extra for main stream brands with higher quality hence why I want to make sure if I'm getting the work done, the electrician is not just using any random brand.

 

[timhoward]

Is there a particular reason you need double pole protection? There's not normally any need for it in the average UK installation.

Ahh, there is a couple of posts earlier on in this thread where people recommended getting double pole so was just trying to follow the advice.

Single Pole, Single Pole Switched Neutral, and Double Pole are all different things. Hager RCBO's are Single Pole.
I was recommending Single Pole Switched Neutral as I favour devices the isolate the N. It makes it possible to ‘contain’ neutral-earth faults and any future diagnostics are so much easier.

Regarding choice, you need to talk to your electrician as different sparks have accounts at different wholesalers and can get different brands at good prices. We all have things we are used to and prefer to fit too.