Nightmare - Farm Electrics

[boyo24]

Just thoughts Id share my recent fun and games on my parents farm.. The electrics are old. Its a 400yr old house with outbuildings just as old plus steel framed buildings.

So the farm supply is a 80a single phase supply. The house also comes off the same pole outside and also has an 80a fuse and by both boards fuses it says it is a PME supply. The farm supply goes through a pretty old 100ma RCD but it does actually work...well it does if given a chance. The line and neutral than go to some henley blocks. The earth also goes into a henley block. 10mm tails and the earth then head out to the various old fuse boards, they are daisy chained one after the other but they are all basically on the 100ma rcd.

So my dad calls me and says whenever he turns the power on in one of the buildings on the old fuse board in one of the outbuildings, if he uses any tools he is getting a tingling on his hands. I tell him to stop and turn it back off. He did stop but he didn't turn it off. I arrive with and go out to the building where he was working and pick up the circular saw he was using and realise "oh yes the power is still on". But before I do I decide to have some fun and measure the potential difference. From the saw to my hand was 70v, to my dads hand (different boots) was 100v at which point I said it was bloody more than tingling you nutter. I then measured to the steel frame of the building and yes 232v. I then walked into every flipping outbuilding and found the entire farm except the house which is only the other supply was live. Probably the most scary was a metal clad switch, mounted on a board on the inside of a steel building. To go in the steel framed building you often hold open the metal gate and turn the light switch on at the same time! Alarm bells anyone? If there was ever an advert for understanding why extraneous conductive parts need bonding even if you have an rcd, this is it.

So after a while I have tracked down the offending lighting circuit that was causing the fault. It is a bunch of strip lights in a building mounted on wood but didn't have time to fix those so I have just removed the circuit for now. My next problem was determining why the RCD wasn't tripping. I'm sure there is a continuity issue on the earth on the feed to the fuse boards but I don't have a lead long enough to check. Also replacing the earth wire is going to be a nightmare.

My thoughts. Since the majority of the steel framed buildings are close to the supply pole for the farm. Is it possibly more straight forward to create a TT system and bond onto the frames which goes down a good metre into the soil. Seems pointless putting rods or providing sufficiently sized cpc when the frame provides hundreds of mm2 per post of steel back to the transformer on the pole and should provide enough fault current to trip the rcd. However I am then concerned if a fault occurs and for some reason, the rcd doesnt trip. Is this going to potentially elevate the voltage on the farmhouse neutral which also comes off the same pole. How can this be mitigated if this is a potential issue?

Many thanks

 

[Yozza19]

Should already be on a tt system look up agricultural in the big book

How old is the pme supply ?

 

[DPG]

I would definitely read the section on agricultural buildings in the wiring regs.

 

[UNG]

Just thoughts Id share my recent fun and games on my parents farm.. The electrics are old. Its a 400yr old house with outbuildings just as old plus steel framed buildings.

So the farm supply is a 80a single phase supply. The house also comes off the same pole outside and also has an 80a fuse and by both boards fuses it says it is a PME supply. The farm supply goes through a pretty old 100ma RCD but it does actually work...well it does if given a chance. The line and neutral than go to some henley blocks. The earth also goes into a henley block. 10mm tails and the earth then head out to the various old fuse boards, they are daisy chained one after the other but they are all basically on the 100ma rcd.

How have you tested the RCD is it just the test button or do you have the appropriate test equipment

So my dad calls me and says whenever he turns the power on in one of the buildings on the old fuse board in one of the outbuildings, if he uses any tools he is getting a tingling on his hands. I tell him to stop and turn it back off. He did stop but he didn't turn it off. I arrive with and go out to the building where he was working and pick up the circular saw he was using and realise "oh yes the power is still on". But before I do I decide to have some fun and measure the potential difference. From the saw to my hand was 70v, to my dads hand (different boots) was 100v at which point I said it was bloody more than tingling you nutter.

And a different body resistance as well

I then measured to the steel frame of the building and yes 232v. I then walked into every flipping outbuilding and found the entire farm except the house which is only the other supply was live. Probably the most scary was a metal clad switch, mounted on a board on the inside of a steel building. To go in the steel framed building you often hold open the metal gate and turn the light switch on at the same time! Alarm bells anyone? If there was ever an advert for understanding why extraneous conductive parts need bonding even if you have an rcd, this is it.

From what point were you measuring to the builidings steel frame

So after a while I have tracked down the offending lighting circuit that was causing the fault. It is a bunch of strip lights in a building mounted on wood but didn't have time to fix those so I have just removed the circuit for now. My next problem was determining why the RCD wasn't tripping. I'm sure there is a continuity issue on the earth on the feed to the fuse boards but I don't have a lead long enough to check. Also replacing the earth wire is going to be a nightmare.

So what other checks or testing have you done to prove this installation is safe for continued use when you have doubts about the earth continuity

My thoughts. Since the majority of the steel framed buildings are close to the supply pole for the farm. Is it possibly more straight forward to create a TT system and bond onto the frames which goes down a good metre into the soil. Seems pointless putting rods or providing sufficiently sized cpc when the frame provides hundreds of mm2 per post of steel back to the transformer on the pole and should provide enough fault current to trip the rcd. However I am then concerned if a fault occurs and for some reason, the rcd doesnt trip. Is this going to potentially elevate the voltage on the farmhouse neutral which also comes off the same pole.

Have you tested or are you assuming that the building frames are one contiguous structure it is not unusual to find portal frames connected with timber purlins
You are assuming that because the frames are in the ground they will provide an earth path with a low enough resistance have you actually tested the this

How can this be mitigated if this is a potential issue?

Many thanks

Not sure how long you have been investigating this problem but you post suggests that this has taken some time to get to where you are now. You seem to be quite knowledgeable on electrics but your profile says you are an electrical enthusiast, given the problem you have identified unless you have the necessary test equipment I would suggest getting an electrician in who has a good knowledge of agricultural installations before someone is seriously injured

 

[boyo24]

How have you tested the RCD is it just the test button or do you have the appropriate test equipment

And a different body resistance as well

From what point were you measuring to the builidings steel frame

So what other checks or testing have you done to prove this installation is safe for continued use when you have doubts about the earth continuity

Have you tested or are you assuming that the building frames are one contiguous structure it is not unusual to find portal frames connected with timber purlins
You are assuming that because the frames are in the ground they will provide an earth path with a low enough resistance have you actually tested the this

Not sure how long you have been investigating this problem but you post suggests that this has taken some time to get to where you are now. You seem to be quite knowledgeable on electrics but your profile says you are an electrical enthusiast, given the problem you have identified unless you have the necessary test equipment I would suggest getting an electrician in who has a good knowledge of agricultural installations before someone is seriously injured

I used to work for HVAC installation company but i got out of that years ago. Didnt like the numbers of unqualified doing qualified work! I dont do electrics in any professional way but i keep myself reasonably well informed. I dont live there now but growing up on a farm, any of you electricians know farmers.... Do i need to say more lololol
Regarding safety its safe because the entire feed out to all of the buildings is now off until further notice.

At the end of the day im doing the donkey work. Putting the time in so a sparky will spend less time when they do eventually come because its likely to be a costly exercise.

Picking up on a few points...

I was measuring with my martindale electrical tester but from the handle of my dads saw which is metal to the steel frame. Getting full mains potential between the two!
When i say i think there must be an earth continuity problem, correction i know i do because the earth loop impedance test failed.

The electrician my parents will likely call is actually responsible for most of the electrics that have me so concerned so....

Why would the Dno supply pme to a farm when it isnt a safe system for farms?

Is it even pme? Overhead cables? I generally thought they werent pme. The pole immediately outside the house used to have a earth running down the side of the pole to the ground but after a tree feell down about 15 years ago they replace the pole but it no longer had the earth down the side.

The steel frames are joined by lattice trusses but yes one building is only joined by timber purlins. You can see some old braiding joining them but it looks very rusty.

THanks for all the responses

 

[Vortigern]

Not too sure what you are asking. The picture you present is that the wiring is in a very poor condition with multiple faults throughout. Costly? what price a life? Get a spark in I would say. Maybe you could post some pics of the farm layout/equipment if you feel like it? It is impossible to imagine what you are talking about or visualise it. Is this an active farm, livestock or crops? Personally if I were to come and have a look it would not cost much to recommend some sage actions/remedies etc. You are saying an electrician is responsible for the electrics, would it make any sense to discuss this with him or is that a doubtful way to go?

 

[boyo24]

Not too sure what you are asking. The picture you present is that the wiring is in a very poor condition with multiple faults throughout. Costly? what price a life? Get a spark in I would say. Maybe you could post some pics of the farm layout/equipment if you feel like it? It is impossible to imagine what you are talking about or visualise it. Is this an active farm, livestock or crops? Personally if I were to come and have a look it would not cost much to recommend some sage actions/remedies etc. You are saying an electrician is responsible for the electrics, would it make any sense to discuss this with him or is that a doubtful way to go?

Im not really looking for specific advise. It was mainly to share the experience and my horror at seeing the voltages on everything. It will all be resolved in a safe way soon. The farm is 'semi active' but no animals in the buildings otherwise we might have some home cooked roast beef or lamb or roasted farmer....

 

[DPG]

Im not really looking for specific advise. It was mainly to share the experience and my horror at seeing the voltages on everything. It will all be resolved in a safe way soon. The farm is 'semi active' but no animals in the buildings otherwise we might have some home cooked roast beef or lamb or roasted farmer....

Be interesting seeing how things get resolved. Keep us updated. With photos if possible.

 

[boyo24]

Be interesting seeing how things get resolved. Keep us updated. With photos if possible.

There are some interesting old bits of kit...maybe 1990 era to isolate the incoming when the big generator was used. Each one has three positions. Mains, off and magnate for the genny. We used to have a 40kW pto generator we used for the parlour if the mains failed. From my memory there was no earth rod on the genny.... Any its never used now.
Amazing how reliable the grid is today. It used to frequently go off in the 90s. No good wheb you have 100 cows to milk.

 

[UNG]

I used to work for HVAC installation company but i got out of that years ago. Didnt like the numbers of unqualified doing qualified work! I dont do electrics in any professional way but i keep myself reasonably well informed. I dont live there now but growing up on a farm, any of you electricians know farmers.... Do i need to say more lololol
Regarding safety its safe because the entire feed out to all of the buildings is now off until further notice.

Yes I've seen quite a few electrical installations on farms some good and plenty you just want to run away from

At the end of the day im doing the donkey work. Putting the time in so a sparky will spend less time when they do eventually come because its likely to be a costly exercise.

Before you start you may be better getting an electrician involved before you start no point jumping in with both feet when getting some initial guidance from an electrician may give a better end result for both parties
From what you have said upto now I think a good starting point would be an EICR and / or a good amount of testing to verify what is good or in need of repair / updating to meet the requirements of the regs

Picking up on a few points...

I was measuring with my martindale electrical tester but from the handle of my dads saw which is metal to the steel frame. Getting full mains potential between the two!
When i say i think there must be an earth continuity problem, correction i know i do because the earth loop impedance test failed.

So what was providing the earth path the saw or the steel frame
At what point in the installation was the earth loop impedance checked and when you say it failed what was the actual reading as a fail would suggest that there is no earth path while the combination of an OCPD that is of a higher rating than needed for a circuit that has undersized cable my give reading higher than the maximum permissable Zs which is generally classed as unsatisfactory

The electrician my parents will likely call is actually responsible for most of the electrics that have me so concerned so....

Good luck with that one

Why would the Dno supply pme to a farm when it isnt a safe system for farms?

That would be something to ask the DNO

Is it even pme? Overhead cables? I generally thought they werent pme. The pole immediately outside the house used to have a earth running down the side of the pole to the ground but after a tree feell down about 15 years ago they replace the pole but it no longer had the earth down the side.

That is difficult to ascertain without pictures what you are looking at the fact that the DNO replaced a pole without replacing the earth cable would have me checking that the house supply has a good earth

The steel frames are joined by lattice trusses but yes one building is only joined by timber purlins. You can see some old braiding joining them but it looks very rusty.

Time to get the wander lead out and check all the steelwork links