PME carport

[marcuswareham]

Hello

Hope everyone if well with this cover-19 stuff going on

Quick question

I would like to put a power supply to a metal framed car port, the metal frame is buried into the ground so definitely introduces earth potential, the ground inside the carport is tarmac laid on top of soil

The power supply is coming from P.M.E house, I think the best option is to make the carport TT and install RCD protection, However I cannot achieve sufficient separation between PME bonded gas pipe and water pipes in the ground and the new earth electrode.

If I export the PME earth and bonding the metal structure then surely this is creating a large shock risk to anyone standing on the wet grass next to the car port and in contact with the metal structure if there was a PEN conductor fault.



Looking at 18th Edition Amendment 1 section on EV charging

722.411.4.1
(iv) Protection against electric shock in a single-phase installation is provided by a device which electrically disconnects the vehicle from the live conductors of supply and from the protective earth in accordance with Regulation 543.3.3.101(ii) within 5 s in the event of the utilisation voltage at the charging point, between the line and neutral conductors being grater than 253 C rms or less than 207 V rms. The device shall provide isolation and be selected in accordance with Table 537.4. Equivalent means of functionality could be included within the charging equipment. Closing or resetting of the device shall be possible only if the voltage between line and neutral conductors is in the range 207 to 253 V rms.



Maybe I could use a device like this but not for EV charging but instead to protect car port from open PEN

Although I cannot find anywhere to buy such a device

Many thanks

Marcus

 

[pc1966]

These folk make them, product list at bottom of the fairly crappy web site:

Installation Manuals

Installation Manual v1.10 Oct 2021Models: SP-EVCP-T (Cxx) SP-EVCP-M (Cxx)SP-EVCP-R (Cxx) SP-EVCP-B (Cxx)IP-EVCP-T (Cxx) IP-EVCP-M (Cxx)IP-EVCP-R (Cxx) IP-EVCP-B (Cxx)Download SP-EVCP Installation Manual May 21Models: SP-EVCP-T(Cxx) SP-EVCP-M(Cxx)SP-EVCP-R(Cxx) SP-EVCP- B(Cxx) SP-EVCP-...

matt-e.co.uk

I mean, WTF do they think you want to see the logo filling whole page and have to scroll down to see the useful stuff?

Manual for non-RCBO version:

https://matt-e.co.uk/wp-content/uploads/2019/02/SP-EVCP-T.pdf

If the pipes are close/accessible though (as I guess your TT rod issue suggests?) then under such faults you might still have step-voltage risk.

Edited to add: A quick search shows you can get them from CEF and Rapid for around the £100+VAT mark and with RCBO for about £30 more.

 

[Lister1987]

MyEnergi Zappi would be the product for just this.

zappi EV Charger | 7kW & 22kW Home charger | myenergi

Fast charge your electric vehicle at home or work using cheaper and greener energy, with the original eco smart zappi EV charger. Made in Britain.

myenergi.com

 

[buzzlightyear]

I will not require to be put on a TT.

 

[Midwest]

Just a thought, what is the power supply for? Would it be for Class II apparatus?

 

[marcuswareham]

These folk make them, product list at bottom of the fairly crappy web site:

Installation Manuals

Installation Manual v1.10 Oct 2021Models: SP-EVCP-T (Cxx) SP-EVCP-M (Cxx)SP-EVCP-R (Cxx) SP-EVCP-B (Cxx)IP-EVCP-T (Cxx) IP-EVCP-M (Cxx)IP-EVCP-R (Cxx) IP-EVCP-B (Cxx)Download SP-EVCP Installation Manual May 21Models: SP-EVCP-T(Cxx) SP-EVCP-M(Cxx)SP-EVCP-R(Cxx) SP-EVCP- B(Cxx) SP-EVCP-...

matt-e.co.uk

I mean, WTF do they think you want to see the logo filling whole page and have to scroll down to see the useful stuff?

Manual for non-RCBO version:

https://matt-e.co.uk/wp-content/uploads/2019/02/SP-EVCP-T.pdf

If the pipes are close/accessible though (as I guess your TT rod issue suggests?) then under such faults you might still have step-voltage risk.

Edited to add: A quick search shows you can get them from CEF and Rapid for around the £100+VAT mark and with RCBO for about £30 more.

Yeah nice idea, I have seen a matt-e video on youtube although not in this much detail and have never seen anywhere to purchase it.

How would this fit in with the reg, as it is not being used for a EV charging point

The TT idea the earth rod would only be able to go a maximum of 1m away from bonded service pipes (and the DNO incoming cable). There has been some digging for other reasons which is why the location of these is known. I guess an insulation test between PME earth and the earth rod would indicate what PME fault voltages could be transferred to the TT?

Thanks



Thanks

 

[marcuswareham]

Just a thought, what is the power supply for? Would it be for Class II apparatus?

A mix, but definitely some Class I appliances, one being a mig welder (although the welding current is separated by a transformer). The chassis of the welder and all other metalwork is bonded to the CPC

 

[pc1966]

Yeah nice idea, I have seen a matt-e video on youtube although not in this much detail and have never seen anywhere to purchase it.

How would this fit in with the reg, as it is not being used for a EV charging point

I'm not sure. All it is doing is disconnecting everything (L, N & E) in the event of voltage going out of range (which is usually the symptom of a broken PME circuit). So in that sense it would revert your car port to the previous unconnected situation.

The TT idea the earth rod would only be able to go a maximum of 1m away from bonded service pipes (and the DNO incoming cable). There has been some digging for other reasons which is why the location of these is known. I guess an insulation test between PME earth and the earth rod would indicate what PME fault voltages could be transferred to the TT?

The separation of the earth rods (for example the 10m for caravans) is not so much about the resistance between them but more about the TT rod being at a low enough potential if the PME 'rod' (cable, pipes, whatever) becomes live and the ground around it shows a dropping potential with distance. In the caravan case that TT rod is connected to the caravans that could be some distance away, so the area around the caravan is close to true Earth and that is why the TT rod's separation from PME (and possible potential rise) matters.

In your case it is slightly different as the risk is the potential difference between the car port metalwork and the immediate surrounding area which as you say includes the pipework and so any possible PME effect.

You say the car port metal work is already grounded, have you tried making a bonding resistance check between it and, say, your house PME earth to get an idea of how well grounded it is?

It might serve as your TT rod, or you might consider digging a small hole in the tarmac at a far for a dedicated rod. As others have advised, if you can hand-dig down by around 1m (say using a fence post style of tool) then you can be sure of no cables/pipes befor driving a rod in and then back-filling it.

 

[marcuswareham]

I'm not sure. All it is doing is disconnecting everything (L, N & E) in the event of voltage going out of range (which is usually the symptom of a broken PME circuit). So in that sense it would revert your car port to the previous unconnected situation.

Yes I agree there could still be a situation of a broken PEN but the voltage remaining within that range, depending on the balance of loads on the other phases in the street. Strange how the regs say it is ok for EV charging, I guess the fact PME should have multiple rods along the supply and that it will detect a broken PEN in most cases it is enough mitigation.

I had also not thought about your comment on returning the carport to the current situation, i.e without a power outlet in it. So basically there could be a shock risk from the carport regardless due to the fact that the steel posts are in the ground in close proximity to the service pipes. Doh !

You say the car port metal work is already grounded, have you tried making a bonding resistance check between it and, say, your house PME earth to get an idea of how well grounded it is?

I have not done as you say to the PME MET, I have done an earth loop impedance test on it using a flying lead from the C/U, there are 5 posts and most are around the 150ohm range.

If I do manage to get a rod in far enough away (what separation would you suggest in this instance), would you bond the carport metal posts to the carport TT MET or leave un-bonded. I think this would bring the PME risk onto the TT CPC, but it could also reduce the touch voltage of the carport posts in a PEN fail

Thanks Marcus

 

[pc1966]

Are the posts all bonded together? I'm guessing they would be bolted to metal beams, etc, but that may or may not be giving a good resistance between them. Either way as you are seeing < 200 ohms then it would normally be considered good enough for a TT earth rod.

In fact having a set of posts spread out should mean that they are close in voltage to the surrounding soil, and that is all that really matters from a shock point of view. If your service pipes are not exposed outside then I guess there is a low risk of seeing enough step-potential for it to be dangerous (also given the relatively low risk of a PME fault).

Certainly you should bond the posts and any circuit earth in the garage together with 10mm or similar as the whole point is to achieve an equipotential zone. Should the whole zone be at, say, 100V up under fault conditions but your soil around it is within 25V or so of it then there is little real shock risk.

Off hand I don't know if you can use a structure as the TT earth (would have to look that up), but if you are sure there is nothing buried in the immediate vicinity of one of the posts then it would be safe to drill & drive a dedicated rod in even if you are really relying on the posts as the main earthing means. I would not worry about getting far away as, again, what matters is keeping the exposed metalwork voltage close to the surrounding soil.

Are they H-section beams or similar? Getting a good bond should be as simple as drilling and using a ring tag. If rusted and/or painted then a bolt serrated flange nut can be used first to clear it off and then some Vaseline or proper contact grease used to avoid galvanic corrosion afterwards.

 

[Wilko]

Hi - re the carport bonding to the house PME MET vs it’s own TT - there is always a risk introducing two systems if they can be simultaneously touched. If there’s an outside light on the house adjacent to the carport etc. If the carport is adjacent/attached to the house and it’s just an outlet planned (for a vacuum cleaner for example) I’m thinking I’d just extend the house installation earthing system in the usual way and probably not bother to bond the carport. Am I a bad person?

 

[Strima]

If you're getting 150 ohms from the steel work one rod isn't going to be much better.

 

[pc1966]

Some useful feedback there! Is there any risk for touching the two system simultaneously?

If you do go down the TT route then you don't need 10mm bonding, only 4mm or phase size (which ever is greater), and 542.2.2 allows foundation structures to be used, though 542.2.4 has the proviso they are deep enough so drying/freezing causing a rise in impedance is not a risk.

 

[marcuswareham]

Are the posts all bonded together? I'm guessing they would be bolted to metal beams, etc, but that may or may not be giving a good resistance between them. Either way as you are seeing < 200 ohms then it would normally be considered good enough for a TT earth rod.

The posts are only joined via timber beams across the top of them, so they would all need bonding in that case, one of the posts is about 70cm away from the gas pipe which is bonded to PME and enters the house about 1.5m away above the soil.

I have tested a spare rod in the garden, about 1m away from potential PME bonded stuff in the ground. I get about 60ohms from it, doing an earth loop impedance test in the same was as conducted on the posts.

Hi - re the carport bonding to the house PME MET vs it’s own TT - there is always a risk introducing two systems if they can be simultaneously touched. If there’s an outside light on the house adjacent to the carport etc. If the carport is adjacent/attached to the house and it’s just an outlet planned (for a vacuum cleaner for example) I’m thinking I’d just extend the house installation earthing system in the usual way and probably not bother to bond the carport. Am I a bad person?

There is not much potential of touching outside lights on the house and the carport at the same time. (although should outside lights on PME supply really be class I, like you see everywhere, surely that is a very large shock risk from touching outside light while standing on wet garden grass etc).

Extending the PME installation might be the best way, although I know class I appliances will be used in the carport and possible in contact with soil/grass on a rainy day

So not sure whether it is better to go TT or use the Matt-e device

Thanks Marcus

 

[pc1966]

Why not convert your house to TT supply and then you can bond the car port beams, etc, all together with your main earth & service pipes, etc?

Of couse said service pipes might be bonded to neighbours PME...
[automerge]1586529768[/automerge]
I guess it would cost you a 100mA type-S delayed RCD as incoming protection and an identifiable earth rod, but it should be a reasonable solution to this.

 

[pc1966]

These days many service pipes will be plastic in the street, so if you are unsure and can safely/easily manage it then you could disconnect your PME earth and check the impedance between that and the rest of your home's earth (i.e. including the service pipes). If it is 1 ohm or so then obviously they are shared/bonded at neighbours!

 

[davesparks]

I have tested a spare rod in the garden, about 1m away from potential PME bonded stuff in the ground. I get about 60ohms from it, doing an earth loop impedance test in the same was as conducted on the posts.

Is that a single 4' rod giving you 60 ohms? If it is then you should be able to get a pretty good Ra when you've gone up to 2x 8' rods.

Have you considered adding supplemental earth electrodes connected to the MET to gaurd against the risks?

 

[Ian1981]

Some useful feedback there! Is there any risk for touching the two system simultaneously?

If you do go down the TT route then you don't need 10mm bonding, only 4mm or phase size (which ever is greater), and 542.2.2 allows foundation structures to be used, though 542.2.4 has the proviso they are deep enough so drying/freezing causing a rise in impedance is not a risk.

TT requires a minimum of 6mm csa for a bonding conductor. No less that’s half the size required for the earthing conductor and no less than 6mm copper

 

[pc1966]

TT requires a minimum of 6mm csa for a bonding conductor. No less that’s half the size required for the earthing conductor and no less than 6mm copper

Yes, should have looked it up!
[automerge]1586541492[/automerge]

Have you considered adding supplemental earth electrodes connected to the MET to guard against the risks?

With potentially a hundred of more amps to play with you would be hard pushed to keep the potential down. You might at least keep the potential gradient around the car port low enough which I guess is the critical thing.

In that case the earth between house and garage, etc, might need to consider the worst-case current that might flow, though if we are looking at something in the 10 ohm region then 6mm or more should be adequate.

 

[marcuswareham]

Why not convert your house to TT supply and then you can bond the car port beams, etc, all together with your main earth & service pipes, etc?

Of couse said service pipes might be bonded to neighbours PME...
[automerge]1586529768[/automerge]
I guess it would cost you a 100mA type-S delayed RCD as incoming protection and an identifiable earth rod, but it should be a reasonable solution to this.

I like this option as I am not the biggest fan of TN-C-S. However I am not Part-P I work setting up temporary power for events. I am not sure if changing the house supply to TT is notifiable work, or if you need to notify the DNO.

The water pipe is definitely plastic, although the gas pipe if definitely copper, this runs underground to gas bottles (out in the countryside), where the gas bottles are stored is shared with 2 other houses (presumed to also be PME)

I have considered adding supplemental earth electrodes connected to the MET to guard against the risks, however I am very limited on outside space to do as such unfortunately,

Thank you all very much for the replys. So I figure that the carport being TT and having all of the posts bonded is no worse than the carport not having power supply inside it, as posts are close to PME earth in the ground.

 

[pc1966]

So I figure that the carport being TT and having all of the posts bonded is no worse than the carport not having power supply inside it, as posts are close to PME earth in the ground.

That would be my take on things, but worth checking.

If you only need a small amount of power then the simplest option is a TT supply fed from a 13A plug in the house. Not too expensive to put in a small garage CU for it, and no Part P to worry about. Ultimately the metalwork is no less safe than it currently is in respect to the risk from nearby PME faults.

 

[marcuswareham]

That would be my take on things, but worth checking.

If you only need a small amount of power then the simplest option is a TT supply fed from a 13A plug in the house. Not too expensive to put in a small garage CU for it, and no Part P to worry about. Ultimately the metalwork is no less safe than it currently is in respect to the risk from nearby PME faults.

Yes I was going to spur out of C/U on one of the socket rings and do a minor works cert for it.

I might put a new circuit in and notify building regs, but shall see.

Just can't seem to get a straight answer from the council's documentation about if changing from TN-C-S to TT would be notifiable

Yes think TT is the way to go, getting that earth rod as far away from the gas pipe as I can.

Thank you very much for your advice,

 

[Wilko]

Hi - for what it’s worth, my understanding is a change to the installation’s earthing arrangements is not a notifiable activity in England.

 

[pc1966]

I guess if your CU is already all-RCD then it is simply a matter of changing how the MET is connected to "earth"

 

[shaun1]

If the water pipe is plastic then would it help to change the gas pipe to plastic also (even just a small section where it enters the house?

 

[westward10]

You cannot have a plastic gas pipe entering a property, think about the risks.

 

[marcuswareham]

I guess if your CU is already all-RCD then it is simply a matter of changing how the MET is connected to "earth"

I have a memera 2000 split C/U. However I do have RCD protection on all circuits, I have a sub C/U for electric shower containing RCD, and down stream RCDs for lighting circuits.

They are all rated at 30mA and I have done disconnection time on all of them and they are within spec. If changing to TT would I not also need a 100mA RCD for the whole system. Also what to do with the DNO (TN-C-S) earth from the service head just terminate it?

 

[pc1966]

Yes, if you have any non-RCD circuits at all then you would need an overall RCD to meet disconnection times on them. To achieve discrimination with your 30mA ones it would have to be a higher current (e.g. 100mA) and a delay S-type.

As far as I understand it, you should not touch the DNO cut-out so if changing the cable I would simply put a terminal block or similar on the end removed from your MET to insulate it and label things so anyone in the future knows why it was disconnected.

 

[marcuswareham]

Yes, if you have any non-RCD circuits at all then you would need an overall RCD to meet disconnection times on them. To achieve discrimination with your 30mA ones it would have to be a higher current (e.g. 100mA) and a delay S-type.

As far as I understand it, you should not touch the DNO cut-out so if changing the cable I would simply put a terminal block or similar on the end removed from your MET to insulate it and label things so anyone in the future knows why it was disconnected.

Yes fair enough,


All this has also got me thinking about my outside lights, I have 2 class I each side of my front door at about shoulder height. That is probably not a good idea being PME hahaha

 

[Ian1981]

Yes fair enough,


All this has also got me thinking about my outside lights, I have 2 class I each side of my front door at about shoulder height. That is probably not a good idea being PME hahaha

Class 2 are non metallic.
opps 2 class 1 doh!!??‍

 

[pc1966]

All this has also got me thinking about my outside lights, I have 2 class I each side of my front door at about shoulder height. That is probably not a good idea being PME hahaha

To be fair PME faults are not very common, and the real risk is for stuff that people are likely to be in good contact with while also outside. Electric cars being washed while on charge are an obvious risk, metal caravans on nice wet grass, boats on marinas being fed power while engines off, etc.

I guess most outdoor power or gardening tools these days are double insulated so no earth to worry about.

Thought there was a school fence that gave some kids shocks (thankfully none fatal) in the news not that long ago, so it is not unknown!
[automerge]1586604142[/automerge]

I have a memera 2000 split C/U. However I do have RCD protection on all circuits, I have a sub C/U for electric shower containing RCD, and down stream RCDs for lighting circuits.

Is the sub-CU fed from the main one, or split meter tails?

If fed from the main one, is the main switch one that could simply be replaced with an RCD?

 

[marcuswareham]

To be fair PME faults are not very common, and the real risk is for stuff that people are likely to be in good contact with while also outside. Electric cars being washed while on charge are an obvious risk, metal caravans on nice wet grass, boats on marinas being fed power while engines off, etc.

I guess most outdoor power or gardening tools these days are double insulated so no earth to worry about.

Thought there was a school fence that gave some kids shocks (thankfully none fatal) in the news not that long ago, so it is not unknown!
[automerge]1586604142[/automerge]

Is the sub-CU fed from the main one, or split meter tails?

If fed from the main one, is the main switch one that could simply be replaced with an RCD?

Yeah I hear what you are saying about limited risk, I guess the easiest option is to move the lights higher up, so the risk is even less, unfortunately I cannot do that, but I will not lose sleep over it just yet.

Maybe there needs to be a device like the matt-e thing which offers a little more protection by measuring the voltage but which fits in a single gang backbox, for use for outside sockets with low demand etc feed from F.C.Us

The sub C/U is feed from a 40A MCB from non RCD side of the main C/U, so yes replacing main switch with a RCD would be an option although I am limied as you cannot get the MEM breakers for my C/U anymore, doh

 

[pc1966]

The sub C/U is feed from a 40A MCB from non RCD side of the main C/U, so yes replacing main switch with a RCD would be an option although I am limied as you cannot get the MEM breakers for my C/U anymore, doh

Ah, that sucks A quick search found this 2nd hand one, the earth tail is cut short but it might just be worth a try if you have a MFT to check the trip characteristics, etc, on some simple test bed before deciding if it could be fitted:

MEM RCD 100 Amp 100ma Double Pole 100a Time Delay RCCB MEMERA 2000 A100MET for sale online | eBay UK

Find many great new & used options and get the best deals for MEM RCD 100 Amp 100ma Double Pole 100a Time Delay RCCB MEMERA 2000 A100MET at the best online prices at eBay UK! Free delivery for many products!

www.ebay.co.uk

Failing that the obvious solution is a new CU but that opens a whole can of part P worms...
[automerge]1586606757[/automerge]
Or you could fit a small metal enclosure with a separate RCD in it. I think I have seen isolator switch & SPD combinations so why not RCD?

Yes, it is separating the meter tails and without an isolator switch you are in to the dodgy business of getting the DNO to pull the fuse (if it did not "fall out" accidentally...) but it is another way that avoids a new CU for now.

 

[marcuswareham]

Ah, that sucks A quick search found this 2nd hand one, the earth tail is cut short but it might just be worth a try if you have a MFT to check the trip characteristics, etc, on some simple test bed before deciding if it could be fitted:

MEM RCD 100 Amp 100ma Double Pole 100a Time Delay RCCB MEMERA 2000 A100MET for sale online | eBay UK

Find many great new & used options and get the best deals for MEM RCD 100 Amp 100ma Double Pole 100a Time Delay RCCB MEMERA 2000 A100MET at the best online prices at eBay UK! Free delivery for many products!

www.ebay.co.uk

Failing that the obvious solution is a new CU but that opens a whole can of part P worms...

Ahh thats the puppy, yes I have MFT and I spend alot of my working life testing RCDs so thats fine :- D

Yes I have before now though it might be time for a new C/U, I will wait until I need to do other additions etc, then kill all the birds with one stone

Just had another thought on the outside lights, Another workaround could be to use B22 12v bulbs in the fitting and supply the fittings via a 12v transformer, providing electrical isolation and extra low voltage, so no need for the earth bond, and no risk of touch voltages, maybe :- S

 

[pc1966]

If there is any simple way to TT supply the whole house and car port then all of the PME risk problems go away in one step.

I would try to ascertain if the service pipe work is bonded to the PME of neighbours first as that would negate any TT benefits. Some gas pipes now have insulated sections for this reason, and often the gas main is plastic even if the pipework in to the home is metal, so you might be OK there. Otherwise the trouble of sorting gas pipes is way too much and unlikely to be done during lock-down as not essential work!

 

[marcuswareham]

If there is any simple way to TT supply the whole house and car port then all of the PME risk problems go away in one step.

I would try to ascertain if the service pipe work is bonded to the PME of neighbours first as that would negate any TT benefits. Some gas pipes now have insulated sections for this reason, and often the gas main is plastic even if the pipework in to the home is metal, so you might be OK there. Otherwise the trouble of sorting gas pipes is way too much and unlikely to be done during lock-down as not essential work!

Yes I agree,

I am not on mains gas nor is any of the village, so the metal gas pipe runs to a shared (with neighbours) gas bottle storage which is bonded to all services supplied from it, Although that said bottled gas is so expensive I actually don't use it (haven't done for 2 years) as I have economy 7 and a log burner works out cheaper to heat the house with logs and the water at night time.

I do like having the gas option there as a back-up but in reality I could probably do away with it, meaning no metal service pipes entering the house.

It would still need it to be capped correctly by a gas safe person, and like you say with lock-down. However I am in no rush it can wait till after, whenever that may be

 

[pc1966]

It might be worth asking a gas safe person if they could install an isolation section so you can keep the gas but not the bonding.

If you search for "Insulation inserts in metallic gas service pipes to consumers' premises" you should find an IET article on this sort of thing (pasting links to the IET site seem to get borked on this forum).

 

[marcuswareham]

MyEnergi Zappi would be the product for just this.

zappi EV Charger | 7kW & 22kW Home charger | myenergi

Fast charge your electric vehicle at home or work using cheaper and greener energy, with the original eco smart zappi EV charger. Made in Britain.

myenergi.com

Sorry I missed your replay,

Just had a look at this product it would appear to me that this device instead of monitoring the voltage. It uses a sensing coil round the earth conductor and once it detects a few 10s of mA it disconnects line, N and PE , correct?

Thanks Marcus

 

[Lister1987]

Sorry I missed your replay,

Just had a look at this product it would appear to me that this device instead of monitoring the voltage. It uses a sensing coil round the earth conductor and once it detects a few 10s of mA it disconnects line, N and PE , correct?

Thanks Marcus

It has inbuilt RCD protection and uses the current clamp to monitor overall load on incoming supply and lowers/increases its power consumption during time of high/low demand, if I'm remembering correctly it monitors current instead of voltage and being the only one (apparently) to work on this manner it will isolate correctly in the case of a broken neutral, whereas others won't

Of course rereading your post your just after sockets, not an EV Charger, my bad.

 

[marcuswareham]

If there is any simple way to TT supply the whole house and car port then all of the PME risk problems go away in one step.

I would try to ascertain if the service pipe work is bonded to the PME of neighbours first as that would negate any TT benefits. Some gas pipes now have insulated sections for this reason, and often the gas main is plastic even if the pipework in to the home is metal, so you might be OK there. Otherwise the trouble of sorting gas pipes is way too much and unlikely to be done during lock-down as not essential work!

Looking at the gas bottle store, It will be very easy to disconnect earth links between gas pipes to the other house and the separation between the pipes is around 1.2m. the gas bottles themself cannot easily touch the others and they are also connected via rubber hoses. Will this be enough separation in the ground, I could do a resistance test between the gas pipes for the other houses.

If I do convert to TT, what tests would I need to do in addition, I am thinking measure Ze, earth rod impedance, test all RCD's disconnection times and that it? , and all of the bonding already in place for PME will be oversized but that's no problem

It looks as if I should be able to get earth rod resistance down to around 15-20ohm using 2 rods and the gas pipe

Also I do minor works certs for the work I do on my house, would a minor works certs for changing to TT do, and if so the format of a minor work cert doesn't lend its self to this, so what documentation could be better instead