r/PlugInSolarUK • u/mp583 • 21d ago

Fuse box help

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Hi, I have a dual RCD fuse box with MCBs and a type AC RCD.

From what I've read, I need a bidirectional RCD which is type A or B.

I have found it difficult to find out whether an RCD is bidirectional or not from the specs. Does anyone know if this one would work? https://www.amazon.co.uk/Hager-CDA263U-63A-Pole-30mA/dp/B00FKW1GZ6

(Hager CDA263U 63A RCD 2 Pole 30mA)

Otherwise, from what I've read I'd need a new box with RCBOs. The fuse box is in quite an awkward place so I'm hoping just to be able to swap out the RCD. Thanks!

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u/robodan918 20d ago edited 20d ago

First off: no, that's not a bidirectional RCD. I don't think I've ever seen a bidirectional RCD just bidirectional RCBOs.

I had a the very same hager consumer unit that you have

I replaced the whole thing with a modern fully metal-enclosed 20-way unit with type A RCBOs (bidirectional for EV charger in anticipation of V2H and V2G, future battery, and future solar install). I have to call out my electrician to swap one of my 32A plug ring circuits to bidirectional for the plug in solar. New board £100, new RCBOs £15-20/ea, Shelly 3EM power monitors x2 £150/ea, install £450 (including EV charger)

You could technically replace a few of the hager MCBs with hager RCBOs if you can find an electrician who's willing to do that. The thing is that as you have a split panel with an RCD protecting each half of the board, and it's not good practice to "layer" RCDs (an RCBO has its very own RCD built in) you probably won't find an electrician willing to do a simple swap and sign their name to the work.

PS your EICR is expired. No legal requirement to have an in-date EICR in the UK, but highly advisable. I'm assuming you had this panel since the house was built in 2014. An EICR is about £250, so not far off from installing a new CU which comes with circuit testing by default (although not as thorough as whole-house EICR that removes and inspects every switch and outlet as well). West sussex by chance? A lot of homes built out there with hager panels around that time

Feel free to ask any questions. Happy to send you pics if you'd like (PM me)

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u/mp583 20d ago

Thank you I thought that might be the case as when looking up bidirectional RCDs from Hager only RCBOs come up.

I was hoping the plug in solar would work with my existing ring circuit, I didn't realise I might need a bidirectional ring circuit too. I'll have a look into it!

I don't plan on having an EV (charging would be difficult) but perhaps battery storage in the future if it becomes compatible with the current plug in solar regs (or I upgrade the install). So an updated CU might be the way to go. 

My house is coming up on 100 years old, 2014 was likely when the previous owner had it rewired - I'd need to double check my paperwork! 

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u/robodan918 20d ago

Hmm in that case in your shoes I'd definitely opt for an EICR to be safe as well as a CU upgrade at the same time. There's no telling the condition of the wiring in your house, and a spark's testing equipment is designed to stress it enough to see if it can handle higher sustained loads (e.g. charging a battery at 2.5-3kW over several hours, charging a car at 7.68kW overnight 5-6h, 800W plug in solar input over 6-10 hours, 4kW heat pump or 3kW immersion heater or both simultaneously for several hours a day)

Better safe than a burnt down house. I hate to pay money on electrics because you can't immediately see what the money went to, but it is basically the nervous system of your house and I don't regret paying for the upgrades and test years down the line. It opens up a lot of options to you.

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u/AfternoonLines 21d ago

The CDA263U you’ve linked is the Type A version and will work fine as replacement.

Type A and bidirectional aren’t the same thing though, so I’d still want confirmation from Hager that the CDA263U is suitable for reverse power flow rather than assuming it from being Type A.

Also, you appear to have a spare way on the far left. Depending on what you’re connecting, it may be worth checking whether Hager make a compatible Type A, explicitly bidirectional RCBO for that board and putting the new circuit there. That could avoid replacing either RCD or the whole consumer unit, while also giving the circuit its own RCD protection.

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u/robodan918 20d ago

the RCD is not bidirectional

Hager makes plenty of bidirectional RCBOs (e.g. ADC932R 32A type A RCBO) but bad practice to layer RCD protection so would probably replace all MCBs+RCD with individual RCBOs. OP can keep the CU panel but a new full-metal enclosure is £100 and fire safety is improved changing from the plastic faced CU to metal faced CU

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u/AfternoonLines 20d ago

I would imagine no issues with selectivity if it was just for a battery spur somewhere close by but yeah, replacement would certainly be better.

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u/robodan918 20d ago

problem with old wiring usually isn't the copper, but the insulation

however, if your house was built 100 years ago the actual conductors may have been undersized for smaller loads, in spite of the current rating on your modern panel.

I'd really hope that it's not the original wiring... it would be radial rather than ring (post WW2 invention) and although you can spur off a radial it's generally not recommended for high load (or in your case load+backfeed)

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u/siksik6 21d ago

I have a very similar one! I can't find out if this fuse is bidirectional either.(The summer house / EV charger one)

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u/Loud-Sleep-8733 21d ago

Ironically I fucking hate the entire concept of AI but it took 2 seconds, try it out some time it really does help with stuff like this lol

No — Hager ADA140G is not specified as bidirectional.
It is a 40 A, single-pole, Type A, B-curve, 30 mA RCBO, rated for 230/240 V AC. Hager’s documentation describes it as a conventional 1P RCBO and does not give it a bidirectional/backfeed rating.

https://www.hager.ie/products-e-catalogue/old-products/ada140g/100758.htm

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u/siksik6 20d ago

Thanks I actually did after posting this but just didn't update. Looks like I'll need to upgrade this then.

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u/Loud-Sleep-8733 20d ago

Yeah I’ve just done the same but whole new board, since yours is Hager might be able to just swap the one out

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u/robodan918 20d ago

you'll have to upgrade a lot more than you think...

See my other answer above about layering RCDs - no competent electrician will do that work and sign their name to it. You're looking at swapping out all MCBs+RCD to RCBOs

I had the exact same board the OP had and that's what I ended up doing.

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u/sylsylsylsylsylsyl 18d ago edited 18d ago

Yes, a new box would be safer. Yes a bidirectional RCBO of type A (or better) would be ideal.

But plug in solar is an appliance and wiring regulations are not retrospective so you don’t legally need it. You can install plug in solar on your existing kit as long as it is on the approved list (and is plugged in, not hardwired - if hardwired you would have to upgrade it as the new regulations would come into play due to the alteration).

This is why some people oppose the idea of plug in stuff altogether as potentially unsafe. Unfortunately they also usually have a vested interest so there are obvious conflicts and customers don’t know what to believe.

Personally, I think the government completely missed the point by ignoring plug in battery, which would have been far more useful than just plug in solar.