How much can I practically/legally DIY, and other newb questions

[Oldgreybeard]

Do you have a suspended timber floor?

What about hitting a rod inside the property under the floor?
That’s what I’m planning as it means I can put the rod virtually under the consumer unit, no visible conductor to see, no slabs to lift..
works for me in my Victorian property as it’s just sand under the boards.. it’s accessible for inspection so just thought I would mention it in case it’s an option..

Used to be very common in older homes to have an indoor earth electrode, often just a length of galvanised water pipe driven into the ground inside the foundations and below where the meter or fuseboard was located. Our first two homes had this type of earth electrode, probably fitted when they first got electricity sometime in the 1950's at a guess. The second home we owned had the meter and supply wiring changed by SWEB (as they were then) when the original brick of an ELCB stopped working and they converted the installation to PME. Should have kept the ELCB, as it was one of the very early VOELCBs, massive electromechanical thing that was supposed to trip if the voltage on the house earth got 50V above the earth electrode.

[openspaceman]

Used to be very common in older homes to have an indoor earth electrode, often just a length of galvanised water pipe driven into the ground inside the foundations and below where the meter or fuseboard was located.

Our earth is bonded to the galvanised water pipe that runs under an extension just in front of the consumer unit. As it extends outside into the damp soil I expect it has better ground contact than the earth rod.

[dangermouse]

Do you have a suspended timber floor?

What about hitting a rod inside the property under the floor?
That’s what I’m planning as it means I can put the rod virtually under the consumer unit, no visible conductor to see, no slabs to lift..
works for me in my Victorian property as it’s just sand under the boards.. it’s accessible for inspection so just thought I would mention it in case it’s an option..

Nice idea but my house is quite modern and the floor is solid concrete! Built on reclaimed land too, and I think under the veneer of topsoil there's a fair amount of hardcore rubble, hence my scepticism about being able to install a decent earth. I can worry about that later

[AE-NMidlands]

Do you have a suspended timber floor?

What about hitting a rod inside the property under the floor?
That’s what I’m planning as it means I can put the rod virtually under the consumer unit, no visible conductor to see, no slabs to lift..
works for me in my Victorian property as it’s just sand under the boards.. it’s accessible for inspection so just thought I would mention it in case it’s an option..

Used to be very common in older homes to have an indoor earth electrode, often just a length of galvanised water pipe driven into the ground inside the foundations and below where the meter or fuseboard was located. Our first two homes had this type of earth electrode, probably fitted when they first got electricity sometime in the 1950's at a guess. The second home we owned had the meter and supply wiring changed by SWEB (as they were then) when the original brick of an ELCB stopped working and they converted the installation to PME. Should have kept the ELCB, as it was one of the very early VOELCBs, massive electromechanical thing that was supposed to trip if the voltage on the house earth got 50V above the earth electrode.

Interesting... our house was built with gas only (lead pipes for lighting buried in the plaster, all later wiring surface mounted still with earth continuity in junction boxes connecting the lead sheathing when we moved in) but we found a massive bit of heavy wall copper pipe about 2 1/2" diam driven deep into the ground just outside the breakfast room window. It took a lot of getting out and I am afraid it has gone to the scrappie. I had assumed it was for a battery-powered radio.

Re indoor earths, wouldn't the soil be too dry?

[Oldgreybeard]

Interesting... our house was built with gas only (lead pipes for lighting buried in the plaster, all later wiring surface mounted still with earth continuity in junction boxes connecting the lead sheathing when we moved in) but we found a massive bit of heavy wall copper pipe about 2 1/2" diam driven deep into the ground just outside the breakfast room window. It took a lot of getting out and I am afraid it has gone to the scrappie. I had assumed it was for a battery-powered radio.

Re indoor earths, wouldn't the soil be too dry?

The soil under a house isn't usually very dry, dig down a few inches and the moisture content is probably close to that of the soil outside. One reason for underfloor voids needing to be ventilated (and the reason we use damp proof membranes) is to reduce the risk of moisture rising up and to keep the humidity level under the floor space below that which will support mould growth. Earth electrodes are typically 4ft long, so go down far enough to make content with moist enough soil to get a fairly low resistance. If that isn't the case, then the standard fix is to just use a coupler to add a second earth electrode to the first one, making it around 8ft long overall, and that will pretty much be guaranteed to get down into moist soil in most places.

Not sure what that bit of thick copper pipe was, doesn't sound like an earth electrode. Your guess that it may have been for a radio sound reasonable, used to be pretty common to use an earth with a lot of early radios. I remember making a crystal set as a boy, and that needed an earth electrode as well as a fairly long length of wire as an antenna. I spent hours with a pair of headphones on in bed, surreptitiously listening to Radio Luxembourg on the home made crystal set when I was supposed to be asleep.

[dangermouse]

100mA RCD and type C mcb spec is to provide discrimination. Ideally an earth fault or overcurrent on a final circuit will trip their protective devices before the ones feeding the inverter, important where like mine it feeds the whole house.

If you are never going to do that, only at most a few of its circuits for EPS, then a 30mA RCD is arguably better (and AFAIR specified somewhere), in that case you could just use a type C rcbo which would take up only a single way.

Must have switched neutral e.g. https://www.tlc-direct.co.uk/Products/WYNHXS1C20.html or you will need a separate lockable d.p. isolator.

Sharpener thanks for the very helpful info.

Is there any reason why I can't connect the inverter through a single 32A 100ma RCBO? That will take only a single way in the CU and minimise the amount of messing about required. I'm envisioning an additional 2 pole 32A isolator switch between CU and inverter for good measure.

[Oldgreybeard]

Should be a 30mA trip current RCBO, rather than a 100mA trip current one I believe. 100mA RCDs are just for the incoming supply, usually with a TT installation, where they will also have a time delay, so there is some discrimination between the 30mA RCDs that protect the consumer side appliances and the supply side. I'm pretty sure it also has to have a Type A residual current characteristic, rather than the Type AC one in that photo.

[dangermouse]

Should be a 30mA trip current RCBO, rather than a 100mA trip current one I believe. 100mA RCDs are just for the incoming supply, usually with a TT installation, where they will also have a time delay, so there is some discrimination between the 30mA RCDs that protect the consumer side appliances and the supply side. I'm pretty sure it also has to have a Type A residual current characteristic, rather than the Type AC one in that photo.

I'm afraid you've confused me (again) with that comment. Are we talking at cross purposes? I'm talking about the inverter-grid connection via my existing CU. I don't intend to use the inverter's EPS output.

[Oldgreybeard]

Pretty sure that all connected equipment needs 30mA RCD protection now, and I believe that needs to be Type A, rather than Type AC. Certainly our inverters are both connected with 30mA, double pole, Type A RCBOs at the consumer unit.

I believe you can only use a 100mA RCD at the incoming supply, ahead of any 30mA RCDs downstream, the idea being that the 30mA RCDs or RCBOs provide the protection to anyone that may come into contact with equipment when there is a fault condition, and the 100mA RCD upstream won't normally trip and knock out all the power because of the discrimination between it and the downstream RCDs/RCBOs.

[Stinsy]

Pretty sure that all connected equipment needs 30mA RCD protection now, and I believe that needs to be Type A, rather than Type AC. Certainly our inverters are both connected with 30mA, double pole, Type A RCBOs at the consumer unit.

I believe you can only use a 100mA RCD at the incoming supply, ahead of any 30mA RCDs downstream, the idea being that the 30mA RCDs or RCBOs provide the protection to anyone that may come into contact with equipment when there is a fault condition, and the 100mA RCD upstream won't normally trip and knock out all the power because of the discrimination between it and the downstream RCDs/RCBOs.

This is my understanding too.

30mA Type A RCD protection is now required on all circuits. 100mA time delay RCD protection exists as a backup where the 30mA fails and the TT earth loop impedance isn't low enough to trip the overcurrent protection.

Interestingly this is a situation where adding the inverter onto an existing Type-AC RCD could cause a dangerous situation due to "blinding".