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Possible earth problem

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large_ghostman

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Hi guys.
Got a bit of a strange problem, I have finished off the main room used for soap production. Its just about ready to Rock 'N' Roll (another coat of paint is all now), i have emailed my mate from here a few times but not getting replies.

So assuming he is
A) Busy
B) sensible and dosnt read my blab
C) I got yet more major Email problems...

Anyway the overview is like this......

Home electrical system is kind of in 3 parts.
Overhead cable into property, this cable enters upstairs into a outbuilding. Its a really bad place as its up stairs and not weather tight (never designed to be, as its a hay loft!!).

The overhead cable to the main fuse/electric meter, looks to have 2 of the 3 conductors joined on the overhead side, this is after the main transformer box that sits on a pole 10' from the building.

Enters building and goes behind a wall where I cant see a thing, pops out the bottom to the electric companies main fuse, this then connects to the pre paid key meter. The key meter has been here since we moved in, we decided to leave it as is rather than have a normal meter installed. the reasoning being we pay about the same as we would for the electric anyway, and its a great way to avoid chunky bills every quarter. Alot of the stuff I do is electric intensive, having a pre paid meter lets me see whats being used in money terms and not just KW amounts.

This main meter is open to the damp and a fair bit of moisture, the building its in was never really designed to be weather proof. From the main electric meter things get strange. One feed goes to the out buildings main consumer unit, this is in yet another building, this building is pretty weather tight. the consumer unit supplies all the other NON house buildings we have, including my outside lab and the new soap room thats just been built.

No electrics were touched during the build, some sockets were changed, but the configuration etc was left as it was.

The other feed from the main meter goes into the house, the house consumer unit is in the far end of the house. Lately we have had some problems with the electrics. I am not sure what earth system the instillation uses. i cant see any obvious earth rods, I cant see the actual cable on the main fuse, so I dont know if the earth is bonded to the outer supply sheath (doubtful as its an over head) or what is going on.

I know the out buildings were rewired a good 10 years after the house, looking at the consumer box and the way its been done, I would say its deff part P compliant. Its pretty high quality work and everything seems ok.

the house wiring is a bit older, cant use the main electric cooker now because it trips the main consumer box main switch. The top oven can be used and up until a couple of days ago we could use the electric shower. Current situation is.....

We had a shite load snow, when it thawed the shower was working. The main pull cord for the shower is pretty close to the shower cubicle, it gets alot of condensation to the fitting. It has become a bit stiff sometimes, so I assumed the pull cord switch was dead. I got a new one and went to change it, the cable tails into the switch are really really short, roughly just over an inch!! So you cant easily get to the terminal screws on the switch.

What I found with the multi meter has me puzzled.

First quick recap of some points.

Apart from the main cooker (will be replaced at some point) the house consumer unit main switch DOSNT trip.

The shower pull switch light dosnt come on and the shower dosnt work.

When I tested both side of the switch (Live/neutral) the feed side shows 2.1V RMS, this has me baffled. The consumer unit trip switches are badly labeled, someone dipped a spider in ink and wrote on them, you cant read what each trip is for. The distance from the main unit to the shower is from one end of the house to the other!

The trip switch hasnt tripped????

No Voltage on the feed side of the switch, except this strange 2.1V RMS.

So I dont have a clue whats wrong, its not the switch. No idea why the feed side shows a voltage that low, I am aware we probably got earth problems because now and then the lights will trip.

The side of the house the shower is on dosnt have a loft space as such, you cant get to most the cable. The other side of the house has great loft space.

So any ideas?? I intend to see if there is a live feed at the consumer unit trip switch, its actually in a bad place and hard to get to the screws to take the cover off. But none the trips have gone although I havnt a clue if the shower shares one or has its own.

Some how I got to try and identify what trip the shower is on, this is not easy due to distance etc etc.

If the trip switch shows mains voltage both sides, then its a ***** to change the cable and would cost a fortune to replace that lengh of cable!! Keep in mind its a electric shower, so the cable is pretty thick and expensive.


Any ideas how to test the earthing is Ok on the system overall? The main key meter is covered in bird shite by the way!

If
 

Les Jones

Well-Known Member
Most Helpful Member
Hi LG,
Can you confirm the the mains switch in the house consumer unit is an RCD type ? (If it is an RCD it will have a test button on it) It is not an overcurrent trip. It detects any difference in the current in the live and neutral conductors such as if you touch the live and it has a path down to any earth. It does not have to be the earthed metal casing of the appliance. It can be through you via damp leather shoes to the ground. The trips as you are calling them will be MCBs (Miniature circuit breakers.) The shower will be on one rated at 32 amps or more. (More likely more.) That fact may help you narrow down which MCB feeds the shower. The 2.5 volts may be just from capacity coupling to another live cable. Measure the voltage between the earth conductor and both the live and neutral at the shower pull switch. Iwould expect a zero reading to neutral.

Les.
 

large_ghostman

Well-Known Member
Most Helpful Member
Hi Les THX
Its sorted! But to answer the questions.

The consumer unit dosnt have a RCD on it, it has a main switch. On closer look the main switch is a MCB type??? Its not easy to get to the unit. Anyway I wasnt sure if the MCB's (yeah around here farmers call them trips, i got into bad habits) were type B's or could be locked. So i went to look and see if the indicator was green or not, as it turns out the MCB's dont have indicators on. So this got me wondering....

How come there is no RCD??? Ok the RCD must be somewhere and it must be OK, but I dont know where it is. So hunting around I found another 2 MCB consumer unit in a under stairs cupboard. To the side of it is a RCD box, lifted the lid and inside is 2 RCD's. One RCD marked main and one marked SHOWER :D, the shower RCD had tripped. Odd that there isnt a RCD on the cooker circuit but there is on the shower, although I guess not so strange.

Did the test you said and I do get a reading on the neutral side.... So there is a problem somewhere but the shower is back in action.
 

large_ghostman

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Most Helpful Member
Its not easy getting to things at the moment, just after new year we had yet another bad storm. One the big Elms was in danger of coming down, it would have hit the building where I have done the soap shop. So didnt have much choice, I had to take the elm down during the storm. Huge thing but what I didnt know, the bottom was hollow. I got onto the final felling cut and it just went on me, caught my lower back with a large trunk and fractured a vertebrae.

No major problem, but I had to have a special plastic Brace I wear 20 hours a day for 12 months! Could of been alot worse, it hasnt stopped me doing much, but it has slowed me down alot. Doing the new soap area became difficult as I cant bend over properly, although on the plus side, its meant I have made the benches adjustable height. So it will be better to work in in the future. We have lost 100+ trees this year so far!! 30 odd the other week with the snow.
 

Les Jones

Well-Known Member
Most Helpful Member
Hi LG,
Sorry to here about your tree felling accident. I hope it has not done any permanent damage. I'm glad the shower is working again but if it had tripped the RCD the heating element could have corroded on the outside letting some moisture get into the insulation material between the eathed casing and the element itself. The neutral and earth are probably joined together where the mains cable enters your property. If there is a long run of cable between that point and where the shower is and there is a reasonably high load on the cable run then there will be a voltage drop on the neutral due to its resistance. But as there should be no current passing through the earth conductor you will be seeing the voltage drop along the neutral conductor. I had not considderd this effect when I asked the question.

Les.
 

large_ghostman

Well-Known Member
Most Helpful Member
Hi LG,
Sorry to here about your tree felling accident. I hope it has not done any permanent damage. I'm glad the shower is working again but if it had tripped the RCD the heating element could have corroded on the outside letting some moisture get into the insulation material between the eathed casing and the element itself. The neutral and earth are probably joined together where the mains cable enters your property. If there is a long run of cable between that point and where the shower is and there is a reasonably high load on the cable run then there will be a voltage drop on the neutral due to its resistance. But as there should be no current passing through the earth conductor you will be seeing the voltage drop along the neutral conductor. I had not considderd this effect when I asked the question.

Les.
Hi Les
The Trip of the RCD from what you have said, sounds more like the switch. The reason I say this is, the switch is too close to the shower unit. When you have a shower the room steams a fair bit and drops of water form on the ceiling by the switch. I cant see any evidence of this on the switch however, but its the cheaper option so for now I am going to think that until i got to replace the shower unit :D.
The feed side of the cable is long, but when i tested it there was no load on it. Its a 42A cable (or whatever is close to that size).

We have 3 over head wire enter the property from the main pole transformer, I am pretty sure two of them are joined by a kind of spiral of solid wire. I cant see that overhead anymore from the ground, there is a kind of upper floor deck from the hay loft, this was done in the summer and I cant remember the cable now. I could get on the roof, but wont be doing that for a while lol. I am ok, the brace is 19mm solid plastic that was molded to my body, it's kind of hinged with elastic one side, and has straps the other. Alot like old days Armour!! But plastic :D, it didnt hurt when i did it, mainly because I didnt wake up for 24hours.

Anyone seen cowboy about? i been emailing him but no luck. I havnt been able to log in here for a while, I lost the login password! and the old email wasnt in existence anymore. Been so busy since September, tough choice at Christmas. I had to decide to hit the Christmas market, or upgrade the workroom.........I did a bit of both in the end. I havnt finished the website, but local sales were small but steady enough to cover me while I upgraded. It was one of those things, do i do a upgrade now while I grow, or wait until i am desperate but cant afford the time or loss in production.

I decided to take over the bigger downstairs building outside, that covers me for a couple of years growth at least. Cost wise it was almost as cheap as just doing a smaller upgrade, worked out roughly £1000 for a extra year or so of growing. Having spent £4,200 i thought was worth it, otherwise I would of been spending that again in a years time at this rate.

My main issue is the products that sell well, these take 7-8 weeks from start to finish. They also use a live (kind of) ingredient i grow in a bioreactor, so some the upgrade was lab based :D. But in another 6-8 weeks i should be registered for some products as totally natural, whats cool about it for me is, one the products is sold as anti microbial. So not only is it anti microbial but its completely natural, the only one on the market of its kind.

Dosnt sell huge amounts, but i havnt pushed it yet, all sales have been word of mouth. Next big job I have is automation. Alot of the process uses environment chambers and stuff like that, absolutely perfect for automating and IOT stuff. At the moment not everything is tied together. I have just added as i needed, but time now while its dead time to think about tying it all in.

Sorry for waffling on, seems like ages since i was able to post!

Bloody shower is really annoying, £17 for a new switch!! No wonder he smiled when he sold it to me.

I want proper three phase, the overheads for it are 50 meters away, they want £51,000 to connect me!! On what planet do these people live! They have offered split phase for £3.5k, not sure split phase would help much. We did get upgraded to 100A main fuse though.

Maybe its time to put the workshops onto generator main power, I can make enough fuel and my generator should handle most the 3 phase stuff I want.
 

Les Jones

Well-Known Member
Most Helpful Member
Hi LG,
Your condensation around the switch sounds like a plausable theory. I agree that to see how it works for the next few weeks is better than just replacing the shower. I'm not sure what split phase is unless it's like the American system where the two phases are 180 degrees out of phase. In other words the secondary of the transformer that feeds yoy is 480 volts with the centre tap being the neutral and the ends of the winding the two lives. If by cowboy you mean cowboybob then I have not seen him post on this forum or AAC for some time,

Les.
 

large_ghostman

Well-Known Member
Most Helpful Member
Hi LG,
Your condensation around the switch sounds like a plausable theory. I agree that to see how it works for the next few weeks is better than just replacing the shower. I'm not sure what split phase is unless it's like the American system where the two phases are 180 degrees out of phase. In other words the secondary of the transformer that feeds yoy is 480 volts with the centre tap being the neutral and the ends of the winding the two lives. If by cowboy you mean cowboybob then I have not seen him post on this forum or AAC for some time,

Les.
From my understanding of split phase, its the same as yours just different Voltages. Its classed on wiki as 230V / 460V, around here with nearly 210 wind turbines (some really big), the solar farms and so on.. The voltage is day to day! I would prefer true 3 phase, but the cost is a joke.

Cowboybob

Yes, thats really worried me. I was talking to him by email daily a little before Christmas. He has been helping me with setting up my business, various projects and a great sounding board for idea's. Then Christmas came and I assumed 'busy time of year', family and stuff. I fired off a couple of emails and no replies, unusual i have to say. But again I got injured and reading emails wasnt a priority, i had arranged to talk to him on skype, day or two before my accident. But storms knocked my internet out for a few days.

Being really busy, I just assumed he was letting me get stuff done. Hearing he hasnt posted for a bit, thats different. I will try and contact him this week, i got a couple of avenues to try. I hope he is just busy, for someone retired he seems to find plenty to do lol.
 

JimB

Super Moderator
Most Helpful Member
Cowboybob

Was alive and well and visited ETO yesterday (Sunday).

JimB
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
LG:

Nice to see you back. Although you have a uk distribution system, I SUSPECT these to still be true. The uk uses main RCD devices, fuses in plugs and higher currrent distrubution and real single phase. Not the split phase stuff.

1. Neutral and ground is connected together in one place. It remains separate in the sub-panels.
Only if the sub is in a detached structure, there is an additional ground rod. This is primarily for lightning protection.

Potentials of EARTH may actually be different at each structure, which is another reason to connect ground to earth at the structures.

Your fuse location boxes are in bizarre locations.

A reminder is that RCD devices don't require a ground to work. They sense the difference of the current passing through neutral and hot. Easy to. A basic current transformer wound in two directions (cancel) and a winding to amplify.

RCD devices in the US are called GFCI (ground Fault Circuit Interrupter). We are seeing more combination AFCI/GFCI where AFCI is an Arc Fault Circuit Interupter. An Arc fault is something that checks for the signature of an ARC.

I don;t know much abut the ground rod stuff.but sometimes more than one is required and lots of requirements concerning bonding.

Strange things happen when the neutral/ground bond gets broken. That becomes the reference for the entire house. Telephone, cable and plumbing fixtures.

It was permissible to use underground copper for the ground rod. In systems that do, water meters and heaters may have to be bypassed due to plastic pipe
Ground is supposed to provide a reference and it carries current just during a fault.

In the industrial environment, we have availabe what;s called an outlet with an "independent ground" for sensitive electronics. These outlets are usually orange. The ground pin on these devices then have a separate ground fault path and reference path.

it's super easy to pick up stray voltages/ meaning they measure something small, but if loaded to say 1 mA, the phantom voltages go away and there isn't anything wrong with this.

In the US, it's possible to have 60 V where 120 is supposed to be. Our home distribution is 240/120 single phase. More properly called split phase or just a 120-0-120 V center tapped transformer near the home. The primary is probably around 10 kV. We have overhead and underground distrbution.

The ground-Neutral voltage is important and needs to be close to zero.

When that bond get's compromised, other paths can exist like from your house to ground to the neighbors water line to neutral. it may seem to be not connected, but it is. Just not very well.

Loose connections can be identified by color and even the voltage drop across the connection or breaker as long as current is flowing in that circuit.

Good luck!
 

large_ghostman

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Most Helpful Member
Yeah until yesterday I didnt know we had a RCD! I have since found a 3rd consumer unit. The units make sense when you know the house, it has alot of separate structures to it overall. I can sort of understand why they just put the fuse by the pole, but the facts its pretty un weather tight worried me a bit.

I need to hunt down the earth rods, apparently we are TT earth system according to the electric company. They think we would/should have at least 4 rods, again this only makes sense if you see the entire property. Whats rattled me is having things in different places. Why put the main RCD so far from the consumer unit? Why stick them somewhere you would never think to look.

The old part of the house i discovered had lazy electricians in, when they rewired that part of the house (says 20 years ago on the board), they left alot of the older wires in place. So it can get confusing when working on the electrics here. I am willing to bet we have at least one, probably more earth rods that are broken connections. Finding them is the nasty bit!

The entire bathroom needs redoing, so many things my mum hates about it. But its likely we will move in the next couple of years, depending on Brexit,independence,interest rate,income tax rate,how many banks close etc etc etc.
 

large_ghostman

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Thx Jim, good to hear he is about. Might even be a email problem, the company email address i use alot is often called spam!! Cheek of it, yahoos email is the worse for flagging the address up as spam.
 

Mickeysat17

New Member
When you say shower and240 ac I cringe. Scary that shower fixture could be your open ground be eXtremely cAreful .!!! Are feet in a metal shower with unknown electrical proublems can put you 5 feet under in 5 seconds. Shower in the river until it’s fixed for SURE !!
 
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