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Old 28th Apr 2022, 10:52 am   #21
ms660
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Default Re: Mains filtering

Quote:
Originally Posted by stevehertz View Post
My earth is of my own making. I drove a long copper earth bar into the ground and brought a wire from it up to the electrical distribution box.
I exported a PME supply from the house to the caravan in the garden, no problem until I decided to install a LPG gas appliance in it which meant that I had to TT the supply. Because of the nature of the ground here where I live I had to drive down a 2.4 metre earth rod to get the earth loop impedance low enough, 1st photo shows the mains voltage and frequency at the time of the test, the 2nd photo shows the results:

PE = Phase/Earth impedance.

PFC = Prospective Fault Current.


PN = Phase/Neutral impedance.

PSC = Prospective Short Circuit Fault Current.

Lawrence.
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Old 28th Apr 2022, 11:11 am   #22
Roger Ramjet
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Default Re: Mains filtering

Hi again Steve, despite the "fools errand:, comment in post [9], I still feel that switching off the house supply to see if the issue resolves or improves is worthwhile because:-

a) If reception improves then it can be concluded that the interference is emanating from the phase and / or neutral wiring of the ring main.

or b) If the reception does not improve then it can be concluded that the interference is emanating from the earth wiring (as also suggested in post [9]of the ring main) or maybe another source ?

This test should only take a minute or two and either way this will give us more info on the probable cause as opposed to just making assumptions.

Going off thread slightly & with your best interest in mind, I would be tempted to remove the ferrite clamps from the DNO's meter tail. I say this because they could be presumed as meter tampering to reduce bills (similar to the old magnet trick on the mechanical meters). Of course, this is clearly not the case but best not to leave yourself open to any presumption by the REC who may not fully understand the theory involved.

Rog
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Old 28th Apr 2022, 11:55 am   #23
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Default Re: Mains filtering

Given my earthing system, why would I want to improve the ELI? will it improve the noise issue or act as an aid to anything that I can do to improve it?
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Old 28th Apr 2022, 12:02 pm   #24
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Default Re: Mains filtering

Quote:
Originally Posted by Roger Ramjet View Post
Hi again Steve, despite the "fools errand:, comment in post [9], I still feel that switching off the house supply to see if the issue resolves or improves is worthwhile because:-

a) If reception improves then it can be concluded that the interference is emanating from the phase and / or neutral wiring of the ring main.

or b) If the reception does not improve then it can be concluded that the interference is emanating from the earth wiring (as also suggested in post [9]of the ring main) or maybe another source ?

This test should only take a minute or two and either way this will give us more info on the probable cause as opposed to just making assumptions.

Going off thread slightly & with your best interest in mind, I would be tempted to remove the ferrite clamps from the DNO's meter tail. I say this because they could be presumed as meter tampering to reduce bills (similar to the old magnet trick on the mechanical meters). Of course, this is clearly not the case but best not to leave yourself open to any presumption by the REC who may not fully understand the theory involved.

Rog
Thanks Roger. I actually 'began' a mains disconnect test yesterday but my partner was on the (mains powered) landline phone and got cut off, so I had to switch it back on again smartly! Will try again today.

Regarding the ferrite rings on my mains supply, thanks for the advice but I'm going to leave them on. I'd be more than happy to fight my corner with anyone who is suggesting that they are being used as a meter tampering device. It may well be that they are doing 'nothing' in which case I will remove them, but for now at least I'm leaving them in place. Thanks again.
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Old 28th Apr 2022, 12:07 pm   #25
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Default Re: Mains filtering

Quote:
Originally Posted by ms660 View Post
Quote:
Originally Posted by stevehertz View Post
My earth is of my own making. I drove a long copper earth bar into the ground and brought a wire from it up to the electrical distribution box.
I exported a PME supply from the house to the caravan in the garden, no problem until I decided to install a LPG gas appliance in it which meant that I had to TT the supply. Because of the nature of the ground here where I live I had to drive down a 2.4 metre earth rod to get the earth loop impedance low enough, 1st photo shows the mains voltage and frequency at the time of the test, the 2nd photo shows the results:

PE = Phase/Earth impedance.

PFC = Prospective Fault Current.


PN = Phase/Neutral impedance.

PSC = Prospective Fault Current.

Lawrence.
Thanks Lawrence. Can you talk me through the results figures, as in isolation they don't mean a lot to me, I don't know what's good or bad. Cheers.
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Old 28th Apr 2022, 12:25 pm   #26
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Default Re: Mains filtering

My supply comes via a pole transformer 11kv to 240V> just outside the bungalow. AM reception used to be of similar quality to FM but over the last years it has become almost impossible to listen to AM at all and I only have a few neighbours! The mains appears to be loaded with it. The earthing is I believe 'local'. The neutral appears to be connected to a thick earth wire.
I have experimented with various mains filters but they all do practically nothing. I think we have to give up AM broadcasting, there are other means of reception. The earth wire that branches off to the right in the meter cupboard vanishes under a concrete floor, presumably the bungalow earth or a return to one of the wires rising on the pole. Anyway it works OK. John.
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Old 28th Apr 2022, 1:17 pm   #27
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Default Re: Mains filtering

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Originally Posted by Heatercathodeshort View Post
My supply comes via a pole transformer 11kv to 240V> just outside the bungalow. AM reception used to be of similar quality to FM but over the last years it has become almost impossible to listen to AM at all and I only have a few neighbours! The mains appears to be loaded with it. The earthing is I believe 'local'. The neutral appears to be connected to a thick earth wire.
I have experimented with various mains filters but they all do practically nothing. I think we have to give up AM broadcasting, there are other means of reception. The earth wire that branches off to the right in the meter cupboard vanishes under a concrete floor, presumably the bungalow earth or a return to one of the wires rising on the pole. Anyway it works OK. John.
Hi John, Your set up looks like a PME system, with the supply earth derived from a Neutral link bar in the service fuse. The Earth wire on the pole & subsequent ones also ties the overhead supply Neutral to Earth - hence the term Protective MULTIPLE Earthing. Normally there would be a PME alert sticker on each pole because if the Earth wire(s) were inadvertantly disconnected, this could result following a fault condition of dangerous voltages appearing on the customers appliance earthing / metalwork.

The Earth wire going into the floor could be a bonding connection to water pipe or similar rather than an earth electrode.

Useful to note that nothing you have tried seems to mitigate this mains borne interference on which is a very interesting topic.

Rog
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Old 28th Apr 2022, 1:49 pm   #28
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Default Re: Mains filtering

Quote:
Originally Posted by Roger Ramjet View Post
Hi again Steve, despite the "fools errand:, comment in post [9], I still feel that switching off the house supply to see if the issue resolves or improves is worthwhile because:-

a) If reception improves then it can be concluded that the interference is emanating from the phase and / or neutral wiring of the ring main.

or b) If the reception does not improve then it can be concluded that the interference is emanating from the earth wiring (as also suggested in post [9]of the ring main) or maybe another source ?

This test should only take a minute or two and either way this will give us more info on the probable cause as opposed to just making assumptions.

Going off thread slightly & with your best interest in mind, I would be tempted to remove the ferrite clamps from the DNO's meter tail. I say this because they could be presumed as meter tampering to reduce bills (similar to the old magnet trick on the mechanical meters). Of course, this is clearly not the case but best not to leave yourself open to any presumption by the REC who may not fully understand the theory involved.

Rog
Ok, mains test done. Mains socket wise my distribution box is zoned 'nearside' and 'far side' of the house, and lighting wise 'upstairs' and 'downstairs'. Otherwise there are separate circuits for the heating system, shower etc.

So I was able to isolate different parts of the house in order to locate the source of any interference. BTW, the vintage wireless under test and also the battery receiver used for this test are situated 'nearside' and not too far away from my desk that has my computer, printer, mains powered phone, mains powered USB hub etc on it. As stated, all of the aforementioned have ferrite clamps on their mains leads. This is what I found. Switching off the nearside sockets had the most drastic effect of reducing the interference. Switching off the far side sockets had a lesser effect. Strangely, switching off the upstairs lighting circuit (no lights on) also removed the higher frequency hash that was present and quite audible. I also lifted the battery receiver (Bush TR82) up to the vicinity of my long line AM aerial as it comes into the house and the noise very slightly increased.
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Old 28th Apr 2022, 2:09 pm   #29
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Default Re: Mains filtering

Quote:
Originally Posted by stevehertz View Post
Quote:
Originally Posted by Roger Ramjet View Post
Hi again Steve, despite the "fools errand:, comment in post [9], I still feel that switching off the house supply to see if the issue resolves or improves is worthwhile because:-

a) If reception improves then it can be concluded that the interference is emanating from the phase and / or neutral wiring of the ring main.

or b) If the reception does not improve then it can be concluded that the interference is emanating from the earth wiring (as also suggested in post [9]of the ring main) or maybe another source ?

This test should only take a minute or two and either way this will give us more info on the probable cause as opposed to just making assumptions.

Going off thread slightly & with your best interest in mind, I would be tempted to remove the ferrite clamps from the DNO's meter tail. I say this because they could be presumed as meter tampering to reduce bills (similar to the old magnet trick on the mechanical meters). Of course, this is clearly not the case but best not to leave yourself open to any presumption by the REC who may not fully understand the theory involved.

Rog
Ok, mains test done. Mains socket wise my distribution box is zoned 'nearside' and 'far side' of the house, and lighting wise 'upstairs' and 'downstairs'. Otherwise there are separate circuits for the heating system, shower etc.

So I was able to isolate different parts of the house in order to locate the source of any interference. BTW, the vintage wireless under test and also the battery receiver used for this test are situated 'nearside' and not too far away from my desk that has my computer, printer, mains powered phone, mains powered USB hub etc on it. As stated, all of the aforementioned have ferrite clamps on their mains leads. This is what I found. Switching off the nearside sockets had the most drastic effect of reducing the interference. Switching off the far side sockets had a lesser effect. Strangely, switching off the upstairs lighting circuit (no lights on) also removed the higher frequency hash that was present and quite audible. I also lifted the battery receiver (Bush TR82) up to the vicinity of my long line AM aerial as it comes into the house and the noise very slightly increased.
Nice one Steve,

I am assuming that you used the main isolator which switches the Phase & Neutral to each circuit in which case we can safely assume that the house wiring is re radiating the interference that must be coming in via the mains supply.

That said, it would still be useful to switch all mains leccy off to your house in one go & retest. This would completely rule out any secondary interference from your "in house"' equipment.

As John indicated his local mains supply is loaded with all sorts of interference so I reckon this is nigh on impossible to resolve apart from maybe's going off - grid ?

Rog
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Old 28th Apr 2022, 2:31 pm   #30
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Default Re: Mains filtering

Roger, In the tests previously described I used the individual switches on the RCD units to isolate each circuit individually.

I just switched the 'main' incoming mains switch on the disty box to 'off' and it killed virtually all noise. I then took my trannie outside and moved it near to the house mains feed as it came up the outside of the house from underground. The increase in interference was massive. Anything I can do?! I already have those clip on ferrite clamps on the incoming cables - see previous photo - and that makes little if any difference.
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Old 28th Apr 2022, 3:39 pm   #31
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Default Re: Mains filtering

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Originally Posted by stevehertz View Post
Roger, In the tests previously described I used the individual switches on the RCD units to isolate each circuit individually.

I just switched the 'main' incoming mains switch on the disty box to 'off' and it killed virtually all noise. I then took my trannie outside and moved it near to the house mains feed as it came up the outside of the house from underground. The increase in interference was massive. Anything I can do?! I already have those clip on ferrite clamps on the incoming cables - see previous photo - and that makes little if any difference.
Ta for the update Steve,

Switching off at the RCD only diss's the phase whilst the neutral remains connected). Switching off at the mains isolator diss's the phase & neutral which has clearly killed all interference. Sure you will agree that proves that your problem is not with the EARTH connection (as previously suggested) but solely with the incoming mains phase & neutral *on the proviso that your own home equipment is not adding.

John has tried all sorts of filters already with no resolve so we may be on a hiding to nothing. Just for the hat though:-

1. The bolt on capacitors connected across the mains supply on washing machines were designed to reduce interference from the motor feeding back into the mains. You say dissing the lighting circuit led to a good improvement so in theory, it is possible that one of these connected across the lighting 5A mcb + neutral + earth within the consumer may give similar result in which case could then repeated on all other mcb circuits. EXTREME CAUTION - These would have to be fitted by a competent person and / or electrician.

2. I have seen large permanently running UPS units in computer server rooms that completely isolate's the raw mains but these would be a very expensive solution.

Rog
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Old 28th Apr 2022, 5:43 pm   #32
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Default Re: Mains filtering

Thanks Roger. It's been an interesting exercise but I can't help but think that there is no cost effective solution to the digital hash problem that blights AM these days. I remember prior to digital TV I would equip my AM aerial leads with a croc clip and removing a shard of the outer plastic shrouding, clip them on to the coax of my TV download with truly excellent results. Not now! It's like feeding in a hurricane!

BTW, can you tell me a bit more about the bolt on caps, value etc? Thanks.
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Old 28th Apr 2022, 5:50 pm   #33
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Default Re: Mains filtering

Quote:
Originally Posted by stevehertz View Post
Quote:
Originally Posted by ms660 View Post
Quote:
Originally Posted by stevehertz View Post
My earth is of my own making. I drove a long copper earth bar into the ground and brought a wire from it up to the electrical distribution box.
I exported a PME supply from the house to the caravan in the garden, no problem until I decided to install a LPG gas appliance in it which meant that I had to TT the supply. Because of the nature of the ground here where I live I had to drive down a 2.4 metre earth rod to get the earth loop impedance low enough, 1st photo shows the mains voltage and frequency at the time of the test, the 2nd photo shows the results:

PE = Phase/Earth impedance.

PFC = Prospective Fault Current.


PN = Phase/Neutral impedance.

PSC = Prospective Fault Current.

Lawrence.
Thanks Lawrence. Can you talk me through the results figures, as in isolation they don't mean a lot to me, I don't know what's good or bad. Cheers.
First I made an error, apologies for that, I was in a rush because at the moment I'm doing a 5 days a week hospital run down to Truro and back, it should have read PSC = Prospective Short Current.

The PE (Phase to Earth impedance) was 58.5 Ohms and the mains supply voltage was 238 Volts which means the Prospective Fault Current would be 238/58.5

The PN (Phase to Neutral impedance) was 0.47 Ohms, that means the Prospective Short Current would be 238/0.47

The difference between the current displayed and that calculated is probably due to the tolerance specs of the tester.

With all the appliances I could disconnect disconnected I plugged the tester in and those were the results I got.

At the time I was after a maximum figure of 200 Ohms, which was mentioned in the regs at that time, a 1.2 metre rod wouldn't do it but a 2.4 metre rod brought it down to well below that figure as can been seen in the test display.

https://martindale-electric.co.uk/pr...h-loop-tester/

Lawrence.
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Old 28th Apr 2022, 6:01 pm   #34
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Default Re: Mains filtering

Thanks Lawrence.
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Old 29th Apr 2022, 8:44 am   #35
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Default Re: Mains filtering

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What is TT? ELI? My distribution unit does use RCDs.
In my personal opinion, unexplained Multiple-Letter Acronyms (MLAs) are discourteous at best - and a PiTA at worst 😉
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Old 29th Apr 2022, 9:03 am   #36
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Default Re: Mains filtering

That would be fair comment but back in post #14 I linked to a Wikipage that explained all the MLA's and showed diagram of what they meant in practice.

I again suggested in post #20 this link was followed.

https://en.wikipedia.org/wiki/Earthing_system

The trouble is when there is good clear guidance so readily available do you spell it out bearing in mind how many of the members here know exactly what they mean already.

If the page was deemed difficult to understand then that's when I feel explanations are in order.

Google* is your friend.

* Other search engines are available

Cheers

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Old 29th Apr 2022, 9:20 am   #37
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Default Re: Mains filtering

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Switching off at the RCD only diss's the phase whilst the neutral remains connected
RCDs switch all poles, in this case both line and neutral.
RCBOs exist in both SP and DP versions. Obviously they sense the residual from both poles but switch only the line.
MCBs are normally single pole in the UK, but there are SPSN types that sense the current only in the line but switch both poles. There are also DP MCBS.

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Old 29th Apr 2022, 9:48 am   #38
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Default Re: Mains filtering

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Thanks Roger. It's been an interesting exercise but I can't help but think that there is no cost effective solution to the digital hash problem that blights AM these days. I remember prior to digital TV I would equip my AM aerial leads with a croc clip and removing a shard of the outer plastic shrouding, clip them on to the coax of my TV download with truly excellent results. Not now! It's like feeding in a hurricane!

BTW, can you tell me a bit more about the bolt on caps, value etc? Thanks.
Sorry Steve, I may have over egged this.... by a bolt on capacitor I mean ones I have come across fitted just under the lid on older washing machines that are connected across the incoming mains flex. The look like normal capacitors but have a piece of threaded rod on the end cap. The thread goes through a hole in the washer back & is secured with a nut. Most appliances with motors normally have some kind of suppressor capacitor. The bolt on ones seemed better suited to my suggestion.

Rog
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Old 29th Apr 2022, 9:55 am   #39
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Default Re: Mains filtering

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Quote:
Originally Posted by Roger Ramjet View Post
Switching off at the RCD only diss's the phase whilst the neutral remains connected
RCDs switch all poles, in this case both line and neutral.
RCBOs exist in both SP and DP versions. Obviously they sense the residual from both poles but switch only the line.
MCBs are normally single pole in the UK, but there are SPSN types that sense the current only in the line but switch both poles. There are also DP MCBS.
Yep sorry Lucien that was a typo.... I meant to write mcb (not at my best yesterday).

Rog
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Old 29th Apr 2022, 12:51 pm   #40
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Default Re: Mains filtering

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Originally Posted by Roger Ramjet View Post
Quote:
Originally Posted by stevehertz View Post
Thanks Roger. It's been an interesting exercise but I can't help but think that there is no cost effective solution to the digital hash problem that blights AM these days. I remember prior to digital TV I would equip my AM aerial leads with a croc clip and removing a shard of the outer plastic shrouding, clip them on to the coax of my TV download with truly excellent results. Not now! It's like feeding in a hurricane!

BTW, can you tell me a bit more about the bolt on caps, value etc? Thanks.
Sorry Steve, I may have over egged this.... by a bolt on capacitor I mean ones I have come across fitted just under the lid on older washing machines that are connected across the incoming mains flex. The look like normal capacitors but have a piece of threaded rod on the end cap. The thread goes through a hole in the washer back & is secured with a nut. Most appliances with motors normally have some kind of suppressor capacitor. The bolt on ones seemed better suited to my suggestion.

Rog
Thanks Rog.
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