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

Hi All, I am building a small 2.6KW system for my home office / garage (6 x 425w solar panels, although I will probably expand it with more panels at a later date).

For an inverter I have a Growatt SPF 5000 ES. This unit cannot export energy back to the grid (I don’t want to with this small set up), but does have an AC input which allows for pass through energy from the grid to charge the system battery and also provide power for running applications (when the sun doesn’t shine etc) through the AC output.

To install the inverter, the manual recommends putting a 50 amp circuit breaker BEFORE the AC input.

AC input for the unit would come from a power cable that runs from the garage consumer unit (on the other side of the garage). At present this cable runs across the garage walls, out the garage, and under the ground, to power our small garden office (which has about 12 standard double wall outlets).

Does anybody have any recommendations on what kind of AC breaker to use (specific brands/models would be helpful)? Would it be suitable to put another garage consumer unit with a 63 amp RCD (I think that’s what the garage consumer unit has) and a 50 amp breaker before the inverter?

I hope this is clear, I’ll try and clarify further if needed.

Thanks in advance for your help, you guys rule

Philpo said:

Hi All, I am building a small 2.6KW system for my home office / garage (6 x 425w solar panels, although I will probably expand it with more panels at a later date).

For an inverter I have a Growatt SPF 5000 ES. This unit cannot export energy back to the grid (I don’t want to with this small set up), but does have an AC input which allows for pass through energy from the grid to charge the system battery and also provide power for running applications (when the sun doesn’t shine etc) through the AC output.

To install the inverter, the manual recommends putting a 50 amp circuit breaker BEFORE the AC input.

AC input for the unit would come from a power cable that runs from the garage consumer unit (on the other side of the garage). At present this cable runs across the garage walls, out the garage, and under the ground, to power our small garden office (which has about 12 standard double wall outlets).

Does anybody have any recommendations on what kind of AC breaker to use (specific brands/models would be helpful)? Would it be suitable to put another garage consumer unit with a 63 amp RCD (I think that’s what the garage consumer unit has) and a 50 amp breaker before the inverter?

I hope this is clear, I’ll try and clarify further if needed.

Thanks in advance for your help, you guys rule

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I always liked hagar when working in the UK but there's many good brands what I would point out is if the breaker is being fitted to an RCD your best checking it's a type B RCD the UK has been left behind when it comes to earth fault safety and we were using type A RCD`s until recently which only protect against AC faults type B covers both AC and DC. The 50amp breaker covers surges of upto 10kw but as the system is rated at 5000w and your likely not going to be using even 3000w you can safely use a 32amp breaker and 4mm cable to power the inverter.

Cheers ThaiTaffy! That’s very helpful. I’ll check out Hager and type B RCDs.
I assume the RCD would be double pole?
If I installed a 50amp breaker that would allow me to upgrade the system safely with more panels at a later date?
Peace and thanks again!

Philpo said:

Cheers ThaiTaffy! That’s very helpful. I’ll check out Hager and type B RCDs.
I assume the RCD would be double pole?

Click to expand...

Yes double pole rcd

Philpo said:

If I installed a 50amp breaker that would allow me to upgrade the system safely with more panels at a later date?

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It's your load current more than PV panel wattage the 50amp MCB covers the 10kw peak current draw but that's more for large motors/compressors say you were going to add a chest freezer or something.

Just note if your going upto 50amp your going to need 10mm cable also.

Philpo said:

Peace and thanks again!

Click to expand...

No problem and welcome to the forums

Thanks ThaiTaffy! That's very helpful again. Happy to be part of this group!

Philpo said:

AC input for the unit would come from a power cable that runs from the garage consumer unit (on the other side of the garage). At present this cable runs across the garage walls, out the garage, and under the ground, to power our small garden office (which has about 12 standard double wall outlets).

Click to expand...

Not sure exactly how you intend to connect the unit to the existing cable, but as @ThaiTaffy pointed out above, if you're going to use a 50A MCB on that circuit you will need to ensure the cable is at least 10mm2.

The other options would be a new, independently fused, circuit directly from the garage CU or reduce the MCB size to match the cable's capacity.

Thanks @SeaGal, yes sorry that wasn’t too clear. Attached are some photos:

Picture A


Above you can see the mains cable coming into the garage from the ground into a junction box, and then below that is the garage consumer unit. I’ll open that junction box and take a photo, but I can’t do it just yet as my partner has the tumble dryer on and I can’t shut the electricity off before it’s finished (lest she should attack me with a blunt object).

Below is a close up of the consumer unit:

Picture B


So it appears the unit has a 63a mains switch and standard 6a and 16a mcbs for lights and appliances.

It is the dark grey cable coming out of the top of the metal junction box (in picture a) that goes around the garage, and then feeds into another junction box. From that box a thicker cable is fitted that continues around the wall and finally exits the garage and goes outside to feed the garden office (pics below):

Picture C



Picture D


I’ll open up the junction box by the consumer unit a bit later, and send another pic.

Until then, my (tentative) idea was to run the thick black cable shown in pics c and d into another consumer unit, with a 63a RCD and 50a—or lower—mcb as you both suggested. The exit cable from this new consumer unit would feed into the Growatt 5000 ES inverter. The Growatt manual recommends using 1 * 8 AWG cable for the AC input - in addition to its recommendation of a 50a circuit breaker, although no further info is given.

Of course, it might be simply that I need a new consumer unit with a dedicated circuit for the inverter, as you suggested. I suppose that will depend on how that grey cable is wired to the consumer unit. I only have a basic understanding of electrics so defer to your better judgment!

Pics to follow!

Thanks very much again, I love you guys

Ok the tumble dryer has stopped. Here is spaghetti junction:

The grey cable on the top right of the pic is the one that goes round the garage and feeds the office.
Looks like it is running on 16a mcb, but not entirely sure.
Any advice greatly appreciated!
Thanks in advance and have a great evening

Great pics, thanks. First of all please note I am not a certified sparky - just a degree in electronic engineering and a lot of experience over too many years !

Where to begin?...

The wiring and use of those metal boxes is not the best I've seen - though far from the worst - I guess they have been added DIY after the house/garage was built.

From what I can see - and it is difficult to be exact with pictures alone, you have:-

a) Incoming SWA , presumably from the house's CU - the painted thick round cable bottom right of pic A. That is pre-2004 being red-black coloured. I _suspect_ that cable is 2.5mm2, but may only be 1.5mm2 (giving total current capacity of 24A or 16A depending on size). It would be good to check to see what MCB size is in your house CU for the circuit that supplies the garage, and also to verify that that MCB is on the protected side of the house's RCB. It should be as there is no RCB in the garage dist box.

b) The wiring in the junction box is a mixture of pre and post 2004, with the existing light and power outlets red-black and the newer grey cable to the 2nd box being blue-brown. Looks like the box was added to connect the new cable into the system, but DIY, rather than by a sparky as it doesn't have proper cable glands. A pic of the underside of the MCBs and garage isolator would be interesting to see too.

c) The grey cable around the garage _looks_ likely to be 2.5mm2 T&E, protected by the 16A MCB.

d) The second box is there to connect from the grey T&E cable to the SWA that goes underground to the office.

So, just as the weakest point of a chain is its weakest link then, IMHO, there is no gain in putting in a 50A MCB and 10mm2 cable to and from the inverter when the rest of the circuit will have a maximum capacity either due to a 16A limit from house->garage wiring and/or the 16A MCB in the garage dist box.

Assuming you are only intending to power the existing loads with your inverter, then a 16A circuit would suffice, as that is all you already have.

But here's some food for thought as you appear to be considering expanding the system in the future...

If it were me, I'd first of all verify what size SWA you have from house to garage and what size T&E from SWA entry point to house and size of MCB in the house's CU. If that is at least 2.5mm2, rather than 1.5mm2, then you have the option of increasing house to garage capacity to 24A - or more if it is 6mm2 (but doesn't look likely from pics).

In the case that you have 2.5mm2 to the garage, then I'd look into replacing the existing garage dist box with a new, removing the dubious metal box of spaghetti in the process. You can then have a 6 or 8 way box with separate circuits for garage lights, garage sockets and inverter/office.

If you do that, it looks like the wires will be long enough to have a new dist box where the metal box is, without having to replace the wires.

I'd recommend getting a sparky in to do that for you if you don't have the skills to do it yourself.

But, if it were me, having invested in a solar installation, I'd deploy a grid-tied, G98 approved hybrid inverter that could power the house as well as the office up to the 3.6kW capacity of the simple "notify-only" process for connection to the grid. That way you can benefit from powering the house as well as the office from solar and/or battery.

Everything seagal posted above is spot on the only thing I would say is the cable coming into the garage could be 4mm or 6mm but definitely not the 10mm you would expect to use for a 50amp breaker to power the inverter also not sure how it's earthed there doesn't seem to be a CPC coming into the garage so even with all pretty green and yellow sleeving is there you may not infact have a decent earth.

Edit: I should add using the armour of the swa as a CPC is fine but you would expect to see a banjo and bolt to give you a decent connection, too many problems just expecting a steel box to play nice with a brass gland.

Good point about the earth. It "looked" like the armour of the SWA was providing the earth, but as I'm sure that metal box has been DIY'ed, there may not be a good connection, or a connection at all - can't see in the pics.

SWA may be 4mm (or even 6), but I'd be surprised if the original house builder added such a fat cable for a garage with only a 16A power circuit. Needs to be checked, together with wiring and MCB in the house.

I'd bite the bullet and replace the lot in the garage - for the sake of about 50 GBP worth of parts + recommend a sparky to do that as the OP said "I only have a basic understanding of electrics".

@SeaGal and @ThaiTaffy, wow, thanks so much for these incredibly detailed and helpful responses. You guys should both be awarded a medal for public service

It seems odd to me also that the garage and office appears to be run off a 16a mcb, especially considering the number of appliances we power (chest fridge freezer, tumble dryer, lights, power tools with 1000w shop vac, computers, monitors, table lamps, a dehumidifier and a heater in the office when it’s cold. I even have some 60w guitar amps in the office for when I want to annoy the neighbours True, not all those appliances are running simultaneously, but we’ve never had a circuit breaker trip, or any other problems for that matter.

I’ll deffo get a sparky in to replace the garage consumer unit, it’s beyond my capabilities to get it all done to spec, and I’d rather have the peace of mind knowing that it’s all done properly.

Out of interest though, and partly as you are both such great educators, I’ll take some pics of the house consumer unit as I’m curious what you think.- it’s not as bad as spaghetti junction above, but it’s not exactly clear either (some of the labels by the mcbs are outdated, and after a very brief perusal I’m not 100% sure what is powering the garage).

Also, and out of interest again, if I were to connect the Growatt inverter temporarily onto the existing 16a circuit in the garage, would I then use a consumer unit with a 63a, type B RCD followed by a 16a MCB before the inverter (to partially meet the manufacturers’ recommendation)? I got a bit confused looking for the type b RCDs that @ThaiTaffy recommended, as there don’t seem to be many on the UK market, and those that I could find were very expensive!

Overall I’ll try and complete this (my first) experiment in solar power to get a rough idea of how things work, but at a later date I think I will definitely follow @SeaGal ’s recommendations and build a bigger grid tie unit! I’ll have to finish some other projects first though, and also save up a bit more cash

I’ll post some more pics a bit later. Until then, THANK YOU both again, you guys are awesome!

Philpo said:

@SeaGal and @ThaiTaffy, wow, thanks so much for these incredibly detailed and helpful responses. You guys should both be awarded a medal for public service

It seems odd to me also that the garage and office appears to be run off a 16a mcb, especially considering the number of appliances we power (chest fridge freezer, tumble dryer, lights, power tools with 1000w shop vac, computers, monitors, table lamps, a dehumidifier and a heater in the office when it’s cold. I even have some 60w guitar amps in the office for when I want to annoy the neighbours True, not all those appliances are running simultaneously, but we’ve never had a circuit breaker trip, or any other problems for that matter.

I’ll deffo get a sparky in to replace the garage consumer unit, it’s beyond my capabilities to get it all done to spec, and I’d rather have the peace of mind knowing that it’s all done properly.

Out of interest though, and partly as you are both such great educators, I’ll take some pics of the house consumer unit as I’m curious what you think.- it’s not as bad as spaghetti junction above, but it’s not exactly clear either (some of the labels by the mcbs are outdated, and after a very brief perusal I’m not 100% sure what is powering the garage).

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Judging off the cable it could have been taken off another circuit possibly the main ring, check the side of your home where the garage is adjacent too look for any boxes on the external wall where the swa cable may enter. If it is being soured off a internal socket I wouldn't go poking around too much judging off the age of your install poking around in sockets in that area you could end up disconnecting something socket terminals will tend to get loose over time and the act of simply pulling off a socket front could lead to cables coming out. Ask your electrician when he comes atleast he can rectify any problems if they occur.

Philpo said:

Also, and out of interest again, if I were to connect the Growatt inverter temporarily onto the existing 16a circuit in the garage, would I then use a consumer unit with a 63a, type B RCD followed by a 16a MCB before the inverter (to partially meet the manufacturers’ recommendation)? I got a bit confused looking for the type b RCDs that @ThaiTaffy recommended, as there don’t seem to be many on the UK market, and those that I could find were very expensive!

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Type B are a new thing to the UK we sadly fell behind the rest of the EU and as I said specifically for AC/DC I can check some stockists when I'm more awake and try to suggest something.

The MCB/RCD amperage rating is more for protection of the cable they generally won't even blow when above that rating unless the power is past it for a prolonged time anything you fit just needs to cover the cable, in theory breakers earlier on in the chain will open even if you fitted 10mm and a 50 amp breaker.

Philpo said:

Overall I’ll try and complete this (my first) experiment in solar power to get a rough idea of how things work, but at a later date I think I will definitely follow @SeaGal ’s recommendations and build a bigger grid tie unit! I’ll have to finish some other projects first though, and also save up a bit more cash

I’ll post some more pics a bit later. Until then, THANK YOU both again, you guys are awesome!

Click to expand...

No problem and welcome to the forum.

Philpo said:

I got a bit confused looking for the type b RCDs that @ThaiTaffy recommended, as there don’t seem to be many on the UK market, and those that I could find were very expensive!

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Wow holy batman the UK market is taking advantage of the solar boom type B RCDs are 6x the price there to a comparable model here. I don't know what to suggest maybe @SeaGal or someone can suggest what's needed as far as the UK regs now and what they did as far safety.

ThaiTaffy said:

Wow holy batman the UK market is taking advantage of the solar boom type B RCDs are 6x the price there to a comparable model here. I don't know what to suggest maybe @SeaGal or someone can suggest what's needed as far as the UK regs now and what they did as far safety.

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@ThaiTaffy Yes I got a bit of a shock when I saw the prices! The only more reasonably priced ones are this series "Tongou" off Alibaba Express. I've never heard of this brand, let alone shopped from Ali Express, but this at least comes from the Tongou store. They are also sold on Amazon and eBay at approx. double the price. This series comes in a variety of amperages:


An independent seller on eBay also offered me this 63A Type B Rcd Wev263b-030 for £40 + £3.99 postage:


If @SeaGall has any further advice I'd be very happy to hear it!

I'll post some details of the main circuit board in the house in a few moments!

Cheers and thanks again!

Philpo said:

@ThaiTaffy Yes I got a bit of a shock when I saw the prices! The only more reasonably priced ones are this series "Tongou" off Alibaba Express. I've never heard of this brand, let alone shopped from Ali Express, but this at least comes from the Tongou store. They are also sold on Amazon and eBay at approx. double the price. This series comes in a variety of amperages:

https://www.aliexpress.com/item/1005003095164494.html?src=google&src=google&albch=shopping&acnt=494-037-6276&slnk=&plac=&mtctp=&albbt=Google_7_shopping&gclsrc=aw.ds&albagn=888888&isSmbAutoCall=false&needSmbHouyi=false&src=google&albch=shopping&acnt=494-037-6276&slnk=&plac=&mtctp=&albbt=Google_7_shopping&gclsrc=aw.ds&albagn=888888&ds_e_adid=&ds_e_matchtype=&ds_e_device=c&ds_e_network=x&ds_e_product_group_id=&ds_e_product_id=en1005003095164494&ds_e_product_merchant_id=109019673&ds_e_product_country=GB&ds_e_product_language=en&ds_e_product_channel=online&ds_e_product_store_id=&ds_url_v=2&albcp=17866112291&albag=&isSmbAutoCall=false&needSmbHouyi=false&gad_source=1&gclid=Cj0KCQjwhb60BhClARIsABGGtw_ycPKcbEYs6oUZQkXKvXdG_kt-7KmXhDZDcYzIpD4NK3lijg2FH6waAstSEALw_wcB&aff_fcid=d0def7e85e9c4988a142c5866b3c475a-1720694267513-07345-UneMJZVf&aff_fsk=UneMJZVf&aff_platform=aaf&sk=UneMJZVf&aff_trace_key=d0def7e85e9c4988a142c5866b3c475a-1720694267513-07345-UneMJZVf&terminal_id=b8cbe489c3fd4e43b75c9f591b9c0997&afSmartRedirect=n

An independent seller on eBay also offered me this 63A Type B Rcd Wev263b-030 for £40 + £3.99 postage:

63A Type B Rcd Wev263b-030 | eBay

The Rcd is designed to provide protection against ground faults and other electrical hazards, making it an essential component for any circuit breaker or disconnector.

www.ebay.co.uk

If @SeaGall has any further advice I'd be very happy to hear it!

I'll post some details of the main circuit board in the house in a few moments!

Cheers and thanks again!

Click to expand...

Not sure of what quality control certification is applicable sorry but that would be my only worry about buying some unknown brand I tend to buy chint,suntree or Schneider if my wallet allows but I have limited choice here in asia

Ok so here is the main CU in the house. Apologies for the poor quality of the image, the light is pretty bad in that corner of the house:




On the basis of this I assume the garage power runs from the 2nd mains circuit (on the right of the CU), under which you can see this fuse box and circuit breaker:





Here is a close up of what looks like a Hackbridge Faraday RCD, rated at 40a with 30ma Trip:



However, as for where the SWA exits the house, I can't see any obvious exit points from the side of the house - so the SWA must run from here, under the driveway, to the garage (approx 20 metres away). The only evidence of the SWA I can find is where it exits the ground to enter the side of the garage and up to "Spaghetti Junction":



Thanks again for all your input, I'm humbled and learning so much!

ThaiTaffy said:

Not sure of what quality control certification is applicable sorry but that would be my only worry about buying some unknown brand I tend to buy chint,suntree or Schneider if my wallet allows but I have limited choice here in asia

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For everyone's reference, here is a forum post I found on Tongou RCDs.

According to this thread some UK sparkys tested them in 2019/2020. Tongou claim these units are compliant with IEC/EN62423 and IEC/EN51006-1 and the participants in the thread all seem to think they are legit:

Philpo said:

Ok so here is the main CU in the house. Apologies for the poor quality of the image, the light is pretty bad in that corner of the house:


View attachment 227925

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Can't really make out the board sadly but the trim to make that one MCB is making me chuckle, on the plus side it's a metal box which was considered old but now is back within regs.

Philpo said:

On the basis of this I assume the garage power runs from the 2nd mains circuit (on the right of the CU), under which you can see this fuse box and circuit breaker:



View attachment 227928

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Yep so atleast Its independent and not tied onto a ring or some malarkey though the earth cable feeding into the fuse board is far too small

Philpo said:

Here is a close up of what looks like a Hackbridge Faraday RCD, rated at 40a with 30ma Trip:

View attachment 227929

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Not sure what's going on with this RCD as it only has one cable it may not be doing anything.

Philpo said:

However, as for where the SWA exits the house, I can't see any obvious exit points from the side of the house - so the SWA must run from here, under the driveway, to the garage (approx 20 metres away). The only evidence of the SWA I can find is where it exits the ground to enter the side of the garage and up to "Spaghetti Junction":

View attachment 227930

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This is another good sign really a single unbroken length of cable is always better.

Philpo said:

Thanks again for all your input, I'm humbled and learning so much!

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No problem just want to request two more photos if I can one of the top board on its own a little more closer can't make much out from the big photo and one of the spaghetti cables beneath with the door shut.

Philpo said:

@SeaGal and @ThaiTaffy, wow, thanks so much for these incredibly detailed and helpful responses. You guys should both be awarded a medal for public service

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YW - thanks for the appreciation I hate it when feedback is given and the OP never gets back.

Philpo said:

It seems odd to me also that the garage and office appears to be run off a 16a mcb, especially considering the number of appliances we power (chest fridge freezer, tumble dryer, lights, power tools with 1000w shop vac, computers, monitors, table lamps, a dehumidifier and a heater in the office when it’s cold. I even have some 60w guitar amps in the office for when I want to annoy the neighbours True, not all those appliances are running simultaneously, but we’ve never had a circuit breaker trip, or any other problems for that matter.

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When was the property built? 16A would be common for supply to garage via RCD protected 16A MCB in house CU. 16A can power a lot of things; it's 3680 Watts worth! And as @ThaiTaffy mentioned, a 16A MCB won't trip unless there is significant or sustained load over current. A surge with your power tools will not be an issue... if you're bored, here's a succinct article on MCB's.

Philpo said:

I’ll deffo get a sparky in to replace the garage consumer unit, it’s beyond my capabilities to get it all done to spec, and I’d rather have the peace of mind knowing that it’s all done properly.

Click to expand...

Philpo said:

Out of interest though, and partly as you are both such great educators, I’ll take some pics of the house consumer unit as I’m curious what you think.- it’s not as bad as spaghetti junction above, but it’s not exactly clear either (some of the labels by the mcbs are outdated, and after a very brief perusal I’m not 100% sure what is powering the garage).

Click to expand...

Sure - please post the pics.

Philpo said:

Also, and out of interest again, if I were to connect the Growatt inverter temporarily onto the existing 16a circuit in the garage, would I then use a consumer unit with a 63a, type B RCD followed by a 16a MCB before the inverter (to partially meet the manufacturers’ recommendation)? I got a bit confused looking for the type b RCDs that @ThaiTaffy recommended, as there don’t seem to be many on the UK market, and those that I could find were very expensive!

ThaiTaffy said:

I don't know what to suggest maybe @SeaGal or someone can suggest what's needed as far as the UK regs now and what they did as far safety.

Click to expand...

Click to expand...

Was just about to write something here, but your response and pics have just popped in, so will look at those and get back below.

Philpo said:

Overall I’ll try and complete this (my first) experiment in solar power to get a rough idea of how things work, but at a later date I think I will definitely follow @SeaGal ’s recommendations and build a bigger grid tie unit! I’ll have to finish some other projects first though, and also save up a bit more cash

Click to expand...

ThaiTaffy said:

Not sure what's going on with this RCD as it only has one cable it may not be doing anything.

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Agree.

ThaiTaffy said:

No problem just want to request two more photos if I can one of the top board on its own a little more closer can't make much out from the big photo and one of the spaghetti cables beneath with the door shut.

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I can't read what is above the MCB's. You say "I assume the garage power runs from the 2nd mains circuit (on the right of the CU)," can you clarify how you deduce that? Have you turned the MCB off and verified garage power is disconnected.

Similarly, for the "RCD-that-is-going-nowhere"

Thanks again guys!

Here’s a bit more detail:

1) The main part of the property was built c. 1900, but 2 extensions were built later, I assume in the past 20-30 years. I’d have to dig out the property deeds for a clearer history.

2) I retract all assumptions about my hypothesis re the garage RCD unit from and to nowhere Here’s some more pics as @ThaiTaffy requested. First the main consumer unit. The garage isn’t in fact powered from the right hand block as I thought (this circuit block provides power to the extensions)! I switched it off to check, but the garage lights remained on.

I also switched off all the circuits on the left of the unit, and the garage lights remained on. The mains switch on the far left was pretty stiff so have left that for now

I suppose the final test would be to switch off the RCD from nowhere and see what happens. I’m out atm but will try that a bit later!


Next is a photo of the main CU unit’s spaghetti:



The white box on the right is for the doorbell. Maybe you guys can make more sense of the rest!

Let me know if any more tests/photos are needed.

Thanks again - as always you guys rule

Philpo said:

Thanks again guys!

Here’s a bit more detail:

1) The main part of the property was built c. 1900, but 2 extensions were built later, I assume in the past 20-30 years. I’d have to dig out the property deeds for a clearer history.

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Makes sense that the metal box that feeds your garage was likely a very early part of the electrics maybe even the main distribution board(two circuits one sockets one lighting) that's likely being fed directly from the incoming.

Philpo said:

2) I retract all assumptions about my hypothesis re the garage RCD unit from and to nowhere Here’s some more pics as @ThaiTaffy requested. First the main consumer unit. The garage isn’t in fact powered from the right hand block as I thought (this circuit block provides power to the extensions)! I switched it off to check, but the garage lights remained on.

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The upper distribution board might not have anything to do with the garage to tidy it all up and bring it to current code might be a massive undertaking but something that slightly concerns me is the house sockets bar the kitchen ones seem to have no protection.

Philpo said:

I also switched off all the circuits on the left of the unit, and the garage lights remained on. The mains switch on the far left was pretty stiff so have left that for now

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These are all your unprotected circuits generally older wiring that had nuisance tripping were seperated like this without an RCD to protect them. Many houses still have wiring like this but I will warn you don't fit fancy metal light fittings, their not pretty but white plastic pendants are far safer with your current electrics

Philpo said:

I suppose the final test would be to switch off the RCD from nowhere and see what happens. I’m out atm but will try that a bit later!

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Best guess is this was an old unit that originally had your shower on which was discarded later when the shower was added to the above board.

Philpo said:

View attachment 227945
Next is a photo of the main CU unit’s spaghetti:

View attachment 227948

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Seems the garage might have a 10mm earth feeding from that connector block above that's all I was really concerned about.

Philpo said:

The white box on the right is for the doorbell. Maybe you guys can make more sense of the rest!

Let me know if any more tests/photos are needed.

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I really wouldn't go poking around much more than this for your own safety the current electrics aren't exactly what you would call up to code and anything an electrician does might end up meaning you have an electrical safety notice though getting one in to clear up any faults/junk would most certainly be a good idea but then again they might say "the whole place needs a rewire".

Philpo said:

Thanks again - as always you guys rule

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Might not think so after this post.

You need an honest electrician preferably one with plenty of experience (not too old) to tell you straight if:
- The cables are degrading
- if the sockets bar the kitchen ones can be made safe
- what's going on with the old wylex unit(box below) can be removed and something more modern fitted to feed the garage

It's likely not going to be cheap you could have a full inspection and testing done on the property and see if a whole new fuse board could be fitted without a rewire but it's unlikely.

Don't hate me I'm just trying to make sure your informed.

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...

ThaiTaffy said:

You need an honest electrician preferably one with plenty of experience (not too old) to tell you straight if:
- The cables are degrading
- if the sockets bar the kitchen ones can be made safe
- what's going on with the old wylex unit(box below) can be removed and something more modern fitted to feed the garage

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.. 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.

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 £££...

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).

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

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.

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.

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

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 !

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

Thanks again, you guys are true heroes