Noob Installation Question (UK): Growatt SPF 5000 ES AC input 50a circuit breaker

[Philpo]

So my 2p worth...

Wiring looks pretty old and outdated. But, AFAIAA there is no legal requirement in the UK to update to modern standards unless you are going to rent the property out - in which case an EICR is required.

However, for your own / family safety I'd suggest:-

1) Check each MCB and main RCD, the Wylex and the old RCCB for a) correct operation and b) to identify (and document) what switch isolates which circuit.

2) Like @ThaiTaffy, the first thing that alarmed me is the "living room socket" circuit is not RCD protected. Whilst not a legal requirement, it would make sense to bring that up to modern standards which, in summary, is any socket that can have something plugged into should be on the safe side of and RCD. This could possibly be achieved by replacing the MCB with and RCBO to avoid (or at least delay) the complexity of upgrading the whole house CU.

3) It is common in the UK for light circuits to be not protected. This, I understand, is so that you can still see at night if the RCD trips.

I'd agree totally with @ThaiTaffy's suggestion of...

.. but with the warning that, IME, these days many such tradespeople have a vested interest in generating work, so finding one that will give you an honest opinion might be tricky.

Going back to your original questions about the garage circuit and inverter... it would be actually good if the garage is connected directly from the incoming supply, via the old fuse box - with presumably a wire-fuse in it and the stand-alone RCD - that will give you more options for the future if you are considering a grid-tied system.

Once you have worked out what is what and what connects to what from step 1 above, then you'll know if your garage circuit is indeed protected by and RCD from the house or not.

For an off-grid configuration IMHO you need an RCD on the output side of the inverter to protect your self-powered loads. If grid-tied, you will need to feed the solar input to the supply side of the existing circuits.

Thanks @SeaGal , you just answered some of the questions I posted only a moment ago in response to @ThaiTaffy. I'll look into getting an RCBO for the main consumer unit. I've got to get the tots some dinner now but will write back later

 

[ThaiTaffy]

No problem @ThaiTaffy I'd rather have your honest opinion and be told the bad news than be told what I want to hear. And having some accurate background info from you guys also helps when trying to find an honest electrician, as there are plenty of shysters about (as I'm sure you know) who will just make stuff up to get you to part with your hard earned £££...

Yep just wanted you to have a realistic view

Anyway, just to confirm, it is the grey 45 amp fuse box under the main CU that provides power to the garage. I switched it off, and it cut the power to the garage (and to the garden office that is fed from the garage). At least that portion of cable looks to be fused (and earthed if I understood you correctly in your previous message).

Well yes and no it has a earth but there could be a nail in the fuse carrier so fused might be a stretch.

Going back to your original questions about the garage circuit and inverter... it would be actually good if the garage is connected directly from the incoming supply, via the old fuse box - with presumably a wire-fuse in it and the stand-alone RCD - that will give you more options for the future if you are considering a grid-tied system.

The wylex board does seem to be wired directly into the meter but personally I would say this should be replaced with an RCD to protect an external underground cable it's pretty hard to damage swa but not impossible.

Another brief observation is that the MCBs on the left hand part of the CU do switch off and cut power to the sockets and electrics in the main part of the house, just not the garage or the extension. Does this still mean there is no protection for that part of the house?

Lighting previously wasn't required to be protected though modern day with fancy light fittings i would say it should be, don't want a shock changing a lamp bulb. But the sockets should really be on the right hand side of the board

Is there something else missing, e.g. an RCD after the mains switch on the left of the board? Please forgive my noobiness!

Nothing missing just wrong arrangement.

I'll have to save some money to get an electrician in and check the wiring for the main part of the house, but I'll deffo do it.

It would be wise.

In the meantime, I'll probably hook up the inverter, panels etc, using a 63a type b RCD as you suggested, followed by a 16a RCB in the garage before the inverter. The solar panels will of course also have (DC) circuit breaker protection, and the AC output going from the inverter will also have a circuit breaker before it goes out to the office and powers anything.

So there's no need for multiple RCDs, what I would do is get the old small wylex board removed and fit a small metal clad board there with the type b and a appropriate MCB to protect the cable( see if you can see any writing on the swa cable in the house, the garden or into the garage we can let you know what size MCB) then fit a small unit in the garage to feed it and the office it might come with a RCD if you buy a complete board but don't feel you need one if you decide to buy things individually.

Am I right in thinking that at least that portion of the system would have a bit more protection with all these circuit breakers in place? The Growatt can't export electricity back to the grid, so I'm hoping that this mini solar system would only really be a minor-ish extension of what is already in place (and what is already in place hasn;t caused us any problems thus far). And just a further thought: should fit an isolator switch as well before the RCD? That way I could shut that half of the garage down if anything went wrong. Forgive me if that is a totally noob thing to ask

If you fit a new consumer unit in the garage best just put the office/inverter on its own MCB that should isolate. it's late now but rather than the type B RCD there might be a cheaper equivalent RCBO you can just put the office on, I'll take a look tomorrow for you.

Anyway, if I can get the solar system up and running it will of course help us save a bit of money on the electricity bill, which will go straight towards getting an electrician in (when I can find an honest one !

It's not so much honest just one that's not greedy.

For bedtime reading today though I'll read the article that @SeaGal sent me on MCBs

Might put you to sleep...

Thanks again, you guys are true heroes

No worries I'm a firm believer in karma.

 

[Philpo]

Thanks so much! I’ll keep you posted of any developments! A cheaper RCBO would be great, but I’ll keep looking for a reasonably priced type B in the meantime.
I’ll also have to look out for an honest looking electrician
Have a great evening! I’m sure we’ll speak again soon
Until then all the best!

 

[ThaiTaffy]

Sadly no, I haven't kept that up to date on switchgear but nothing I found RCBO wise protects against DC current in afraid maybe someone else knows of a product but as I said earlier the UK has poorly been left behind compared to the EU when it comes to advancements in electrical systems. We still have the best plugs/sockets in the world so we can say that atleast.

 

[Philpo]

Cheers @ThaiTaffy and no problem. The only sniff of a solution I found was on sites discussing EV chargers, where EVSEs (electrical vehicle supply equipment) are likely to produce DC residual current during operation. This may be a red herring, as it is somewhat over my head, but you might be able to find something of use in here:

3.101 of BS 7671:2018+A2:2022 states that “except where provided by the EV charging equipment”, protection against DC fault current shall be provided by a Type B RCD or a Type A or Type F in conjunction with an RDC-DD. This is further clarified in Note 3 to Regulation 722.531.
Source: https://electrical.theiet.org/wirin...s-for-electric-vehicle-supply-equipment-evse/

 

[SeaGal]

Few more thoughts from me - but note, as I said before, I'm not a sparky.

I am guessing that you already have the Growatt and are therefore looking for a configuration where the office is connected to the off-grid side of the inverter. If you haven't already got the Growatt, then a grid-tied setup to me would make more sense. I have Solis, btw.

Assuming that... then the office will be supplied from the Growatt and, as such, you will need to have an RCD to protect the output of the Growatt as the office will not be protected by an RCD on the input-side of the Growatt.

AFAII there is no legal requirement in the UK to have an inverter connected to the grid via an RCD, unless recommended by the manufacturer. From other threads on here, there can be issues - albeit with grid-tied inverters - with nuisance tripping of RCD's and also some inverter manufacturers recommend having an RCD with a 100mA trip current, rather than 30mA. Whereas a 100mA RCD would be OK for the inverter itself, you would then still need a 30mA RCD to protect any house, garage of office circuits.

So, if I was installing what you are installing, I'd connect the house->garage SWA via a suitably sized MCB, once the cable size of the SWA is known, but skip the RCD at that location.

Then, in the garage, have a new distribution box fitted that will supply
a) via a breaker (*), the inverter and
b) via an RCD and MCB's the garage light and socket circuits.

On the output side of the inverter an RCD and suitably sized MCB's (or RCBO's) to supply the office.

(*) If you are likely to ever replace the Growatt with a grid-tied inverter then, IMHO, it would make sense to install a 30A lockable AC double-pole rotary type isolator, rather than a the breaker for the inverter so you will be future-proofed for G98/G99 compliance.

Hope that makes sense.

 

[ThaiTaffy]

Cheers @ThaiTaffy and no problem. The only sniff of a solution I found was on sites discussing EV chargers, where EVSEs (electrical vehicle supply equipment) are likely to produce DC residual current during operation. This may be a red herring, as it is somewhat over my head, but you might be able to find something of use in here:

3.101 of BS 7671:2018+A2:2022 states that “except where provided by the EV charging equipment”, protection against DC fault current shall be provided by a Type B RCD or a Type A or Type F in conjunction with an RDC-DD. This is further clarified in Note 3 to Regulation 722.531.
Source: https://electrical.theiet.org/wirin...s-for-electric-vehicle-supply-equipment-evse/

Likely a rdc-pd would be even more expensive than a type b

 

[ThaiTaffy]

Few more thoughts from me - but note, as I said before, I'm not a sparky.

I am guessing that you already have the Growatt and are therefore looking for a configuration where the office is connected to the off-grid side of the inverter. If you haven't already got the Growatt, then a grid-tied setup to me would make more sense. I have Solis, btw.

Assuming that... then the office will be supplied from the Growatt and, as such, you will need to have an RCD to protect the output of the Growatt as the office will not be protected by an RCD on the input-side of the Growatt.

AFAII there is no legal requirement in the UK to have an inverter connected to the grid via an RCD, unless recommended by the manufacturer. From other threads on here, there can be issues - albeit with grid-tied inverters - with nuisance tripping of RCD's and also some inverter manufacturers recommend having an RCD with a 100mA trip current, rather than 30mA. Whereas a 100mA RCD would be OK for the inverter itself, you would then still need a 30mA RCD to protect any house, garage of office circuits.

So, if I was installing what you are installing, I'd connect the house->garage SWA via a suitably sized MCB, once the cable size of the SWA is known, but skip the RCD at that location.

Then, in the garage, have a new distribution box fitted that will supply
a) via a breaker (*), the inverter and
b) via an RCD and MCB's the garage light and socket circuits.

On the output side of the inverter an RCD and suitably sized MCB's (or RCBO's) to supply the office.

(*) If you are likely to ever replace the Growatt with a grid-tied inverter then, IMHO, it would make sense to install a 30A lockable AC double-pole rotary type isolator, rather than a the breaker for the inverter so you will be future-proofed for G98/G99 compliance.

Hope that makes sense.

This makes sense and @SeaGal has far more experience with me when it comes to solar

 

[ThaiTaffy]

When I eventually fit my on-grid I'll buy a type B and do some testing but my off-grid AiO hasn't had any issues with the rccb we have fitted, luckily the one we have has a setting wheel to select what mA you want it to cut out on but 30 has been fine.

 

[SeaGal]

This makes sense and @SeaGal has far more experience with me when it comes to solar

Thanks! Experience and common sense has worked for me... I'm still alive, but that's only a sample of one! I can totally see the reasons for all new regulations but, IMHO, they have to be put into context.

In the OP's situation, my biggest concern is nothing to do with solar... it's the fact that the old house sockets are not protected by an RCD at all (the far left MCB). Whilst that's not to current standards for a new installation, it's still totally legal in the UK for an existing one. However, with wiring of an unknown condition and young children in the house (ref post #26), fixing that would be my first priority.

 

[Philpo]

Thanks guys, this is amazing. I just wish I could help you as much as you have helped me!
I can't find any writing on the SWA at the moment (the previous owners painted over the sections of cable entering the garage), but the overall outside diameter is 15mm
I'll see if I can find anything on the cable inside the house.
@SeaGal 's recommendations sound good to me. I'll see if I can get an electrician in to connect the house>>>garage
SWA via an MCB, and then install a new consumer unit along the lines she suggested.
Just one question - would the breaker that comes before the inverter (in the new garage consumer unit) be an MCB, or would maybe an RCBO be better?
Will be back soon with any more details I can find about the SWA

 

[ThaiTaffy]

Thanks guys, this is amazing. I just wish I could help you as much as you have helped me!
I can't find any writing on the SWA at the moment (the previous owners painted over the sections of cable entering the garage), but the overall outside diameter is 15mm

10mm² 2 core swa is 18mm overall diameter so maybe it's 6mm but without a code I'm not 100%

I'll see if I can find anything on the cable inside the house.

The section just outside the house looked like a good length

@SeaGal 's recommendations sound good to me. I'll see if I can get an electrician in to connect the house>>>garage
SWA via an MCB, and then install a new consumer unit along the lines she suggested.
Just one question - would the breaker that comes before the inverter (in the new garage consumer unit) be an MCB, or would maybe an RCBO be better?

According to @SeaGal an MCB would be better to prevent nuisance tripping

Will be back soon with any more details I can find about the SWA

 

[Philpo]

And I forgot: yes, I already purchased a Growatt (got a good deal on it but didn't envisage putting up a breaker would cause so many problems
and the question of the house sockets lacking an RCD will need some urgent attention. I'll see if the electrician I find can offer some kind of reasonable solution...

 

[Philpo]

OK so I dug up a section of cable as there were no discernible markings on the above-ground sections.

All I can find is the following:

"Electric Cable 600/1000v Delta Enfield Basec"

At least that's all I can make out. I'll go and get my specs and have another look

 

[ThaiTaffy]

And I forgot: yes, I already purchased a Growatt (got a good deal on it but didn't envisage putting up a breaker would cause so many problems
and the question of the house sockets lacking an RCD will need some urgent attention. I'll see if the electrician I find can offer some kind of reasonable solution...

In theory he should be able to move the living room sockets MCB to the protected side but there maybe faults or issues that prevented them doing so in the first place

 

[Philpo]

I'm guessing the cable is one of these:

https://www.enfieldelectrical.co.uk/assets/file/pdf/untitled.pdf

 

[SeaGal]

would the breaker that comes before the inverter (in the new garage consumer unit) be an MCB, or would maybe an RCBO be better?

Depends on cables sizes. I'd go for an MCB there (if at all) and an RCBO on the output from the inverter.

 

[Philpo]

So yes, now spectacles verified, the marking reads

"Electric Cable 600/1000v Delta Enfield Basec"

The overall diameter of the cable reads more like 15.5 or more with my calipers (it's easier to take a reading from the dug up sections).

 

[ThaiTaffy]

I'm guessing the cable is one of these:

https://www.enfieldelectrical.co.uk/assets/file/pdf/untitled.pdf

Going off this and your original 15mm measurement I can deduce it's between 2.5mm and 10mm I would think it's either 4 mm or 6mm but there's two ways to tell either the cable has a code or the brass glands if they have 20s stamped on them it's likely 4mm if 20(no s) it's 6mm.

 

[SeaGal]

I'm guessing the cable is one of these:

LOL, yes one of them, but def not the 400mm2

 

[SeaGal]

Going off this and your original 15mm measurement I can deduce it's between 2.5mm and 10mm I would think it's either 4 mm or 6mm but there's two ways to tell either the cable has a code or the brass glands if they have 20s stamped on them it's likely 4mm if 20(no s) it's 6mm.

Best is to measure the actual copper core diameter with your calipers to work it out (after isolating it, of course). I have got 25 glands on 4mm2 and 20 on 1.5mm2. It will also depend on whether it is 2, 3, or 4 core.

 

[Philpo]

It looks like Delta Enfield cables are no more...

DELTA ENFIELD CABLES (HOLDINGS) LIMITED overview - Find and update company information - GOV.UK

DELTA ENFIELD CABLES (HOLDINGS) LIMITED - Free company information from Companies House including registered office address, filing history, accounts, annual return, officers, charges, business activity

find-and-update.company-information.service.gov.uk

 

[ThaiTaffy]

 

[SeaGal]

Just took a look at my supplier and the nearest is 2 core 6mm2 at 15.4mm. But outside diameter can vary quite a bit between different suppliers IME.

 

[ThaiTaffy]

Best is to measure the actual copper core diameter with your calipers to work it out (after isolating it, of course). I have got 25 glands on 4mm2 and 20 on 1.5mm2. It will also depend on whether it is 2, 3, or 4 core.

It's 2 core