Help with a small off-grid garden office system (UK based)

[Forrester]

Hi all

I’m new to this forum, and there seems to be lots of nice, helpful and knowledgeable people here, so I’m hoping someone might be able to help me with advice relevant to UK solar systems

I’ve built a small garden office, which I plan to work in most days from spring to autumn (I’ll go in the main house during winter), and I would like to install a small solar off-grid system that powers a few devices (laptop, monitor for laptop, Wi-Fi extender, a few led lights).

When building the garden room I installed the lighting and socket wiring ahead, which is as follows:
- x1 ceiling light (x3 leds(
- x2 double standard sockets (on the one radial circuit)

I’m leaning towards buying a Renology kit with a few panels, charge controller and associated cables, then separately purchasing a lithium battery and inverter.

My questions that I don’t understand and would like some help with are:

1. From the inverter, can I wire straight to the socket and lighting circuit? Or do I need to go to some sort of consumer unit first?

2. The 1000w Renogy inverter I’m looking at only has 3 pin AC out sockets (nowhere to hard wire to). Is this okay to use to send out power to the sockets and lighting circuit (or consumer unit) by? Or would I need a different inverter that allows hard wiring?

It’s worth noting that I am not going to be connected to the mains at all.

I’d like to keep it as simple as possible and ideally avoid a consumer unit if it is not necessary, but I also would like to keep it safe and not do anything that raises eyebrows!

Many thanks in advance!

 

[SamDeleted]

.

 

[Rednecktek]

Summoning @SamG340 ! You're in his neck of the woods, could use your experience here.

Normally I would put in my giant Blurb but this is a pretty small system so I'll just throw out a few thoughts at ya:

Kits are a wonderful way for a company to take $400 worth of equipment and charge you $800 for the privelidge for the "convenience", AKA a waste of money. Since you're going to have to do all the same work to make the system run, you might as well spend your money the most efficient way possible.

Whatever size solar panels you think you need, double it. You guys get pretty krappy sun hours. Same for the battery capacity.

You'll have to do a Power Audit. There's a sheet in the Resources section that helps you walk through it, but basically you need to make a list of all the devices you want to run from the laptop to the light bulbs to the tea kettle (legally required in the UK as I understand it ), figure out how many watts they use in an hour, guesstimate how many hours a day you'll want to run them, and add it all up. This is going to tell you 3 important things: 1) how big does your inverter need to be, 2) how much battery do you need to have to make it through $n number of cloudy days, and 3) how much solar panel you need to recharge those batteries in 4-5 hours of good sun. Short change yourself on any of those and the system isn't going to do what you need it to do.

Figure out where you're going to stick the components. Physics is pretty unforgiving and you need to keep the batteries above freezing unless you want to spend $$RealMoney on heated batteries.

How are you planning on heating and cooling the place? When it comes to heating the general consensus is "Anything But Solar!!" because it's so power intensive. If you're just using fans, factor those into the power audit.

When it all boils down to it there's not a lot of things involved in a solar system. Some panels, a charge controller, an inverter, some fuses and some wires. The goal is making the right system that fits YOUR needs for the best value. Balancing in the cost of parts, the effort you're going to put into the assembly, and how it's going to get used and maybe expanded in the future is a lot of work, but it's FREE work that you can do yourself over a few cups of tea.

Edit: Typed too slow and Sam beat me here. ?

 

[Forrester]

Hi Froster

Sounds like good fun & very achievable project.

Renology don't have the best reputation , it's most cheap rebranded rubbish that you could buy a lot cheaper on eBay without the Renology sticker slapped on the front

I'm going to answer your questions in reverse lol



2) 90% of all inverters are plug in , not hard wired , it's ok


1) so there's 2 main types of protection you need on a AC system like your looking to make

A fuse (or MCB circuit breaker )

And an RCD

MCB protects the cable from too much current, RCD protects you from electric shock

, UK plugs have a fuse built in , your inverter will probably be a plug in , so you're sorted there

you could install a consumer unit for the RCD , but personally I'd get one of these

Masterplug 13A Fused Plug-Through Active RCD Adaptor - Screwfix

Order online at Screwfix.com. Added protection against electric shock. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

Thank you very much @SamG340 for your reply

Thant’s good to know about Renology being overpriced. I’ll check out eBay!

- If, as you say most inverters have a socket for AC out, how would I wire from the AC out socket of the inverter to a MCB/RCD? Is it okay to plug into the inverter AC out and then wire the other end of that plug wire into the MCB and consumer unit/RCD?

- If I install a consumer unit, won’t that need earthing/grounding? If so, what would that involve? Presumably into the earth outside of the garden office?

Finally, that plug you linked to in Screwfix, does that go into any 13a socket I need to use for my appliances? I’d like to keep the design of the system clean so it feels like using a regular plug in the house, so would like to avoid that if possible.

Many thanks

 

[SamDeleted]

Thank you very much @SamG340 for your reply

Thant’s good to know about Renology being overpriced. I’ll check out eBay!

- If, as you say most inverters have a socket for AC out, how would I wire from the AC out socket of the inverter to a MCB/RCD? Is it okay to plug into the inverter AC out and then wire the other end of that plug wire into the MCB and consumer unit/RCD?

- If I install a consumer unit, won’t that need earthing/grounding? If so, what would that involve? Presumably into the earth outside of the garden office?

Finally, that plug you linked to in Screwfix, does that go into any 13a socket I need to use for my appliances? I’d like to keep the design of the system clean so it feels like using a regular plug in the house, so would like to avoid that if possible.

Many thanks

Hi yes you can wire straight into the consumer unit from the plug

This looks good:

Metal Garage Unit 63A RCD (Type A) + 32A+6A MCBs

If you did want to use that RCD plug , it goes in the inverter first , then youd plug your loads in to the RCD - so everything is protected .







Grounding is a whole nother kettle of fish , it's safer , but some think it attracts lightening strikes to your solar panels. I'm not sure .. It's argued about a lot here .

But I do know one thing , I really don't fancy digging an 8 foot deep hole to fit a ground rod lol

You could tie onto your houses ground rod if you've got one ?

 

[Forrester]

Hi yes you can wire straight into the consumer unit from the plug

This looks good:

Metal Garage Unit 63A RCD (Type A) + 32A+6A MCBs

If you did want to use that RCD plug , it goes in the inverter first , then youd plug your loads in to the RCD - so everything is protected .







Grounding is a whole nother kettle of fish , it's safer , but some think it attracts lightening strikes to your solar panels. I'm not sure .. It's argued about a lot here .

But I do know one thing , I really don't fancy digging an 8 foot deep hole to fit a ground rod lol

You could tie onto your houses ground rod if you've got one ?

Thanks @SamG340! Very usefully stuff.

Ah I see, so the RCD plug goes directly into the inverter socket. I will not be plugging appliances directly into the inverter, so perhaps the Masterplug won’t be needed? Unless the Masterplug is still required between the inverter and the consumer unit?

Thanks for the consumer unit link. Can it be used stand alone? In the website description it states it “provides power supply from a main building consumer unit to separate garages…”. Presumably it’s fine to use on its own wired into my inverter, rather than connected to my house consumer unit?

Regarding the earthing, I don’t have an earth rod on the house to tie into, and I’m not sure I fancy installing an 8ft rod! Is it dangerous if I didn’t install one?

Basically I just want to wire an inverter into 2 wall plug sockets and a ceiling light circuit lol! Are there any other easier ways I’m missing?

Thank you!

 

[Forrester]

Summoning @SamG340 ! You're in his neck of the woods, could use your experience here.

Normally I would put in my giant Blurb but this is a pretty small system so I'll just throw out a few thoughts at ya:

Kits are a wonderful way for a company to take $400 worth of equipment and charge you $800 for the privelidge for the "convenience", AKA a waste of money. Since you're going to have to do all the same work to make the system run, you might as well spend your money the most efficient way possible.

Whatever size solar panels you think you need, double it. You guys get pretty krappy sun hours. Same for the battery capacity.

You'll have to do a Power Audit. There's a sheet in the Resources section that helps you walk through it, but basically you need to make a list of all the devices you want to run from the laptop to the light bulbs to the tea kettle (legally required in the UK as I understand it ), figure out how many watts they use in an hour, guesstimate how many hours a day you'll want to run them, and add it all up. This is going to tell you 3 important things: 1) how big does your inverter need to be, 2) how much battery do you need to have to make it through $n number of cloudy days, and 3) how much solar panel you need to recharge those batteries in 4-5 hours of good sun. Short change yourself on any of those and the system isn't going to do what you need it to do.

Figure out where you're going to stick the components. Physics is pretty unforgiving and you need to keep the batteries above freezing unless you want to spend $$RealMoney on heated batteries.

How are you planning on heating and cooling the place? When it comes to heating the general consensus is "Anything But Solar!!" because it's so power intensive. If you're just using fans, factor those into the power audit.

When it all boils down to it there's not a lot of things involved in a solar system. Some panels, a charge controller, an inverter, some fuses and some wires. The goal is making the right system that fits YOUR needs for the best value. Balancing in the cost of parts, the effort you're going to put into the assembly, and how it's going to get used and maybe expanded in the future is a lot of work, but it's FREE work that you can do yourself over a few cups of tea.

Edit: Typed too slow and Sam beat me here. ?

Thank you @Rednecktek for your helpful advice. I will check out those resources and also make those calculations.

I will not be heating the space. It’s well insulated and I won’t use it in winter months.

Thanks again!

 

[Sean Very North]

Save yourself time, energy and money and run a length of SWA to the shed, those "kits" are a waste of money, energy and time.

 

[SamDeleted]

Thanks @SamG340! Very usefully stuff.

Ah I see, so the RCD plug goes directly into the inverter socket. I will not be plugging appliances directly into the inverter, so perhaps the Masterplug won’t be needed? Unless the Masterplug is still required between the inverter and the consumer unit?

Thanks for the consumer unit link. Can it be used stand alone? In the website description it states it “provides power supply from a main building consumer unit to separate garages…”. Presumably it’s fine to use on its own wired into my inverter, rather than connected to my house consumer unit?

Regarding the earthing, I don’t have an earth rod on the house to tie into, and I’m not sure I fancy installing an 8ft rod! Is it dangerous if I didn’t install one?

Basically I just want to wire an inverter into 2 wall plug sockets and a ceiling light circuit lol! Are there any other easier ways I’m missing?

Thank you!

My pleasure ,


The absolute simplest way is to use the mains like Sean said , but that's not as fun ,

solar will take some setting up and cost you a bit , but it's a great hobby to get into , very satisfying to make your own off grid power . It all seems complicated but it's simple once you get your head round it

----

An RCD will protect all cables & appliances down stream of it , whether it's at the inverter, or built into a consumer unit , it's all good

RCD will protect against earth faults too so I wouldn't worry too much about it.

But that said I'm just some bloke on a forum lol.... when in doubt, consult a qualified electrician

----


Yes consumer unit is fine for stand alone , all of them are , providing it's got a suitable MCB & RCD . ,

But if you really want to keep it simple ( I would! ) forget the consumer unit all together you don't need it. Save £30 and use that RCD plug

inverter > RCD plug > fused UK 3 pin plug > cable > plug sockets > loads




And then we've got to talk about the DC / solar side of things!



Hope that all made sense, I am tired

 

[mikefitz]

Since perhaps your knowledge and that of some of the replies, is unsafe and against regulations, I suggest you get professional advice.

You need an inverter with neutral to protective earth bond, designed for permanent Instalation, a consumer unit with MCBs and RCD. A dedicated earth point, example earth rod, is needed for the protected earth. If any AC is imported from the main dwelling then there are other requirements.

Once you have distributed circuits with multiple cables, outlets and appliances connected to an inverter, there is an increased risk of electric shock. Regulations for a permanent installation (UK) with distributed wiring regard an inverter as an 230v AC power source, and as such needs the same protection as utility power. Incorrectly installed inverters can, and have, killed.

Mike

 

[SamDeleted]

Since perhaps your knowledge and that of some of the replies, is unsafe and against regulations, I suggest you get professional advice.

You need an inverter with neutral to protective earth bond, designed for permanent Instalation, a consumer unit with MCBs and RCD. A dedicated earth point, example earth rod, is needed for the protected earth. If any AC is imported from the main dwelling then there are other requirements.

Once you have distributed circuits with multiple cables, outlets and appliances connected to an inverter, there is an increased risk of electric shock. Regulations for a permanent installation (UK) with distributed wiring regard an inverter as an 230v AC power source, and as such needs the same protection as utility power. Incorrectly installed inverters can, and have, killed.

Mike

It's all true I'm sure. .... but at a guess out of 10 off-grid systems in the UK , I'd bet only 1 is done strictly to building regs

Probably less than that!


A system can be electrically safe without being to regs


But you're right , it's always best to get an electrician in ?

 

[SamDeleted]

But you're right , it's always best to get an electrician in ?

That's if you can find a sparky that's willing to touch an off grid system , might find a solar installer that'll do it , but your small fry at that and they're mostly not going to be interested