# Forum Home Renovation Electrical  Separate MEN at Shed?

## Nifty1

I've had conflicting advice from a few sparkies regarding a separate earth connection at my shed. Situation is that the shed is 30m from the switchboard at the house, and the earth is run all the way back to the single earth point at the house. On its way it travels up the house wall, across the ceiling to the swbd, then across the ceiling and down another wall to the earth stake. All the time it is radiating noise from the solar inverter in the shed, which interferes with the poor AM radio reception we get here.
I thought a solution would be to have a separate earth at the shed  and an old sparkie told me it would require an MEN connection at the shed. Another said it would not be legal and he wouldn't do that, and another said just stick another earth at the shed and leave everything else as it is. Obviously by asking the question I am risking more different answers, but I'm looking for the right way to end up with a much shorter earth wire at the shed end to reduce radiated noise. The shed has its own sub board and its own breaker on the main switch board.

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## Vernonv

Here's what I would do ... and no I'm NOT a sparkie ... I would create a sub-board/sub-main in the shed that has it's own earth stake and MEN, and remove the earth connection going back to the house. 
Does the shed have it's own sub-board/sub-main?

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## applied

Buy a digital radio it will be cheaper. 
Your getting conflicting info because you could in do both but generally sheds don't have men links and I wouldn't advise it either you can't just bang eath stakes anywhere you like.
I would try grounding everything metal to the existing earth and get some split conduit and sheild the cable around the inverter.
Alternatively you may be able to re route the cable further from the inverter but altamately you will most likely find it is a external source of disturbance in the supply.

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## 2x4

Each installation shall only have one MEN. ( unless you have multiple substations dotted across your property)
Not sure that removing the earth stake/changing the location to the shed is such a good idea. Eg. The current owner moves on and the next owner bulldozers the shed.
Surely there is noise suppresion devices that can be added to counteract your radio problem. 
Any radio gurus out there?  
.

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## Vernonv

> ...but generally sheds don't have men links....

   

> Each installation shall only have one MEN.

  A MEN link needs to be installed on the main switchboard and any submains. Sheds are often setup as submains and as such will have their own MEN link and local earthing system.

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## chrisp

> I thought a solution would be to have a separate earth at the shed  and an old sparkie told me it would require an MEN connection at the shed. Another said it would not be legal and he wouldn't do that, and another said just stick another earth at the shed and leave everything else as it is. Obviously by asking the question I am risking more different answers, but I'm looking for the right way to end up with a much shorter earth wire at the shed end to reduce radiated noise. The shed has its own sub board and its own breaker on the main switch board.

  Don't add an extra MEN point. 
You could, however, add an *additional* earth to the shed and see how it goes.  It'd be easy to try - just bang in another earth stake and wire it up to a 3-pin plug (earth pin only) and plug it into a outlet in the shed.  If you find it makes no difference, it is easy to disconnect. 
Weak AM reception is very susceptible to noise so it might be hard to eliminate.  You could try (big) ferrite beads on the inverter AC and/or DC leads to see if it helps.

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## 2x4

> Sheds are often setup as submains and as such will have their own MEN link

  I have chopped your quote. I hope you dont mind. 
The above is the way I understand it. The MEN link being in the MSB. Not so sure on the extra earth stake. 
.

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## Vernonv

> The MEN link being in the MSB.

  True, there is a MEN link in the MSB, but there is also one in each submain's subboard - there is no earth cable running from the MSB to the subboards. 
The submain in the shed allows you to run multiple subcircuits (lights, power, 15a GPO, etc) without the need to run each subcircuit all the way back to the MSB.

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## chrisp

AS/NZS 3000 (2007) states: *5.5.3 Particular methods of earthing* *5.5.3.1* _Outbuildings_
All parts of an electrical installation in or on an outbuilding that are required to be earthed in accordance with Clause 5.4 shall be earthed by one of the following methods: 
(a) Connection to the electrical installation earthing system The earthing system in the outbuilding shall be connected to a protective earthing conductor connected in  accordance with Clause 5.5.2.1. 
(b) *Separate MEN installation The earthing system in the outbuilding shall be connected to the submain neutral conductor supplying the outbuilding. In this case the submain neutral conductor supplying the outbuilding is a combined protective earthing and neutral (PEN) conductor.
The electrical installation in the outbuilding shall be regarded as a separate electrical installation, and shall be earthed in accordance with other relevant Clauses of this Standard and with the following requirements:* (i) There shall be not more than one MEN connection in any one outbuilding.
(ii) The distribution board in the outbuilding shall be regarded as a main switchboard for the purpose of effecting the MEN connection.
(iii) The earthing conductor between the distribution board in the outbuilding and the earth electrode shall be regarded as a main earthing conductor for the purposes of earthing of the electrical installation in the outbuilding.
(iv) The submain supplying the outbuilding shall be run either—(A) directly from the main switchboard; or
(B) from the main switchboard via distribution boards in one or more other outbuildings, to one distribution board only in the outbuilding.(v) Where the combined protective earthing and neutral (PEN) conductor supplying the distribution board in the outbuilding runs from the main switchboard via distribution boards in one or more other outbuildings, the terminals on such distribution boards shall
not be depended on for continuity of the combined protective earthing and neutral (PEN) conductor.
(vi) The combined protective earthing and neutral (PEN) conductor supplying the distribution board in the outbuilding should not be connected in parallel, by means of earthing or equipotential bonding conductors, with conductive pipes or structural metal
within the electrical installation.NOTE: Particular care is required where conductive pipes and such items as telecommunication cable sheaths, covered walkways, etc may be continuous between separate buildings and thus establish a parallel earth/neutral path.

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## 2x4

> there is no earth cable running from the MSB to the subboards

  In most , if not all domestic installs I reckon there is.  
For a shed out the back, probably a 6mm 2c+e that feeds a small DB. Why cut out the earth ? Only to run another. Not like SDI's are thrown in the ground for the average Joe. 
The MEN point for this DB is back at the MSB. Multiple MEN's should be back at the main board for a single property, should they not? 
Not that I am in a position to have multiple buildings on my property. Still waiting for Lotto :Tongue: 
.

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## Vernonv

I see, a difference in understanding/usage of the term "installation".  
Thanks for the clarification Chris.

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## Vernonv

> In most , if not all domestic installs I reckon there is.

  Maybe it depends on the usage of the shed. I know most of the sheds around here (rural/semi rural) are run as a submain and earthed separately to the MSB.   

> Multiple MEN's should be back at the main board for a single property, should they not?

  That is not my understanding - my understanding is that they should be in the switchboard of the main or submain concerned.

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## chrisp

> In most , if not all domestic installs I reckon there is.

  You're probably right, but the standard states that you can run the earth back to the main switchboard (option 'a' from the quote in the Standard above)  *or* use a PEN (and separate earth stake) and a MEN link (option 'b') - provided that is is a *separate* building.

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## 2x4

Well done chrisp. Ruined a potentially great argument/debate with actual fact and clause numbers. :Biggrin:    
.

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## 2x4

This is funny. Its like I'm in a time warp. 
Maybe it's my poor effort at stabbing fingers into my keyboard. 
By the time I re-post you guys have been, gone, and been again.
Cheers for the lesson by the way. :Snog:   
.

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## chrisp

> Well done chrisp. Ruined a potentially great argument/debate with actual fact and clause numbers.

  Psst, don't let anyone know, but I originally thought you were right about the restrictions on the number of MEN points.  However I decided to check the Standard just to be sure and it seems if it is a completely separate building you can call it a separate installation. 
It seems I've learnt something today.  :Smilie:

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## Vernonv

> It seems I've learnt something today.

   Me too.  :Biggrin:

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## 2x4

No No No. 
These threads are not supposed to end like this are they? :Rolleyes:   
.

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## elkangorito

Multiple MEN links within one supply are best be avoided if possible because if there is a problem, it may be complicated by having more than one MEN link.
Also, the part of the installation with the extra MEN link will need to comply with all earth/impedance requirements, which means that it must be tested (Earth Fault Loop Impedance). This is to ensure correct opreation of any OCPD's (circuit breakers). 
Usually, "noise" problems are made worse by having a PME/MEN system (TN-C+S) whereas the IT system is less noisy but not as safe as the TN-C+S system. 
My advice - do not introduce another MEN connection. Try to deal with the noise in another way.

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## Nifty1

Gee, I had a feeling this would happen. I've now got several more opinions to consider on top of the original three. Most impressed though, to get 18 replies in the first 3 hours and during the working day too. Don't any of you blokes go to work? 
I think the advice I like is from Chrisp and the regs, which tell me (I think) that I can have a separate earth point at the shed (not sure if this is a MEN or PEN). The shed sub board has all sorts of breakers and earth leakage safety devices, just like the main board, so I guess we can  refer to it as a separate installation. Am I on the right track here? 
I have tried attacking the problem from the other angle, but AM reception is poor on the stations we like, there is no digital radio here yet, and because the earth wire runs close to every radio in the house the only escape is to retreat to another part of the yard. Well, it is a very small house. I have had limited success making a tunable AM loop antenna too. No, I need to stop the noise entering the house on the earth line.

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## applied

seems your out of luck. 
Do you have access to broadband internet you could consider a iphone or ipod touch with a docking station or a ipad connected to a wifi network. 
that would open up channels from all over the world.

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## Nifty1

Well, a quick test has blown my theory apart. We connected a temporary new earth stake at the shed and disconnected the existing earth. Still get interference radiated from the mains back at the house. So it was not just noise carried by the earth, but on the active and neutral too. What was someone saying about ferrites? How big should they be, and how many times should the cables be looped through them (I'm assuming they are just a bigger version of the ones on various small power supplies).

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## applied

i doubt the would do much to ease your pain. you really need to isolate the cause of the noise wether its even coming from your property or somewhere else. 
try shutting down your solar setup see if that stops it if it does its most likely caused by resonance and something like a 120ohm resistor in series with a 0.1uF capacitor would probably help.

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## chrisp

> Well, a quick test has blown my theory apart. We connected a temporary new earth stake at the shed and disconnected the existing earth. Still get interference radiated from the mains back at the house. So it was not just noise carried by the earth, but on the active and neutral too. What was someone saying about ferrites? How big should they be, and how many times should the cables be looped through them (I'm assuming they are just a bigger version of the ones on various small power supplies).

  Nifty, 
I'm not sure as to what standards solar inverters have to meet with regard to EMI (ElectroMagnetic Interference )emissions, but generally, for most electronic gear, the EMI emissions should be low. 
One trick I've been told about when seeking EMI certification - which is expensive - is to ensure that the equipment doesn't interfere with an AM radio before bothering to submitting it for testing. 
You might be able to use a radio as an indicator of the EMI strength - and emission source.  I'd suggest try setting the radio up so the interference isn't too bad and moving it closer to (i) the inverter; (ii) the AC wiring from the inverter; (iii) the DC wiring to the inverter (and/or solar panels).  Hopefully, you'd get a better idea of the 'mode' of the emission - i.e. is it AC born, DC born, or radiating directly from the inverter? 
If the emission is via the wiring (either AC or DC) then placing ferrite beads will help suppress the EMI.  The type of beads I'd be trying would be something like this style of ferrite bead: FAIR RITE|0431173551|SUPPRESSOR, CABLE, SNAP ON | Farnell Australia   Jaycar others may also have something similar 
It is a bit of a black art, but they will probably work better if they are used over both cables on the DC side (i.e. place the positive and negative through the one bead rather than use separate beads on each cable).  The AC side is similar - place one bead over the whole cable. 
Do you recognise these beads?  Have a look at most computer monitor cables, you will see a 'lump' in the cable- this is the ferrite bead. 
If you find that the interference is strong around the solar panels and/or DC wiring, post a picture of the wiring layout as I may be able to offer some other tips.

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## jago

If you own a plasma  or LCD they have a Ferrite choke on the power lead. 
I know with my radio a very good Henry Kloss model AM is affected not just by the housing circuits but by the   
Aircon
Old beer Fridge
CFL's 
Computer Screens
Doorbell transformers
Electric blankets
Certain Mobile and Cordless phones
Outdoor power lines 
Local CB radio hams etc 
the list goes on and on, as Chrisp suggested grab your best radio and tune it in to station with the least amount of static (quiet frequency)and walk around and check the  appliances in you listening rooms and you will get a feel for what in each room is causing RFI.
Once you have a map of which things are causing the problems you can either elminate them or choke them.   :2thumbsup:

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## Bedford

What about putting the radio in a Nu Metal shield ?

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## jago

> What about putting the radio in a Nu Metal shield ?

  
Pardon my ignorance is that similar to Farraday cage ? If not what is it?

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## Bedford

I don't know, but about 40 years ago I built an oscilloscope and it had to have one around the CRT to protect from interference.

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## Bros

Many years ago when I had to do switching in a large HV switchyard we were supplied with a small broadcast radio and had to tune it just off a station on the AM band and if we heard static above the background static it was time to get out of there. 
I never heard any static and nothing blew up.

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## chrisp

> Many years ago when I had to do switching in a large HV switchyard we were supplied with a small broadcast radio and had to tune it just off a station on the AM band and if we heard static above the background static it was time to get out of there. 
> I never heard any static and nothing blew up.

  It is also a good way of spotting leaking or cracked insulators on power poles - if you listen to AM radio in the car and drive around, you can sometime come across areas where there is notable noise - it can simply be dust collecting on the insulators causing leakage 'tracking' on the insulators.  Usually, the next rain storm washes off the dust and they come good again.

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## chrisp

> Pardon my ignorance is that similar to Farraday cage ? If not what is it?

  Close! 
A Faraday shield shields from an electric field.  It is essentially an equi-potential, highly conductive, shield that stops the electric field. 
Mu metal is highly magnetic permeable metal (i.e. it is highly magnetic 'conductive') that can be used to shield an object from a magnetic field. 
It is much easier to stop electric fields than to stop magnetic fields. 
It would be better to shield the inverter (to contain the noise) than to shield the radio  :Doh:

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## elkangorito

Is the inverter enclosed in a metal case? If it is, is the case earthed? 
AM radios, particularly the ones enclosed in plastic & not earthed because they are 'double insulated' (just about everything these days), will pick up anything. A higher quality radio (enclosed in a metal case & earthed) may partly solve the problem. Your only other option is to choose a similar style radio station that is FM. 
It's easy to spend a small fortune to solve this problem.

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## Lordy

> I've had conflicting advice from a few sparkies regarding a separate earth connection at my shed. Situation is that the shed is 30m from the switchboard at the house, and the earth is run all the way back to the single earth point at the house. On its way it travels up the house wall, across the ceiling to the swbd, then across the ceiling and down another wall to the earth stake. All the time it is radiating noise from the solar inverter in the shed, which interferes with the poor AM radio reception we get here.
> I thought a solution would be to have a separate earth at the shed  and an old sparkie told me it would require an MEN connection at the shed. Another said it would not be legal and he wouldn't do that, and another said just stick another earth at the shed and leave everything else as it is. Obviously by asking the question I am risking more different answers, but I'm looking for the right way to end up with a much shorter earth wire at the shed end to reduce radiated noise. The shed has its own sub board and its own breaker on the main switch board.

  Well the answers have been very interesting in this thread and it seems you have several issues to deal with Nifty. 
Re the MEN: 
Being a licenced sparkie and former contractor the best advice I can give you is to *call your local electrical inspector (LEI)* who will be advertised in the local phone book (or ask a local contractor for his number) and get him to tell you if you can have your shed classed as a separate outbuilding. From my experience 30M is not far and it would be classed as a part of your main installation. As someone else mentioned too you can end up with more problems having another MEN point too. So it is best to avoid it. *Ultimately the inspector will have the final say as to what can and can not be done.* i.e. it will be his interpretation of the rules. They are usually very approachable. 
Crisp put up a part of the earthing regs and really if he's going to do that he should place the entire section regarding earthing up as there are some other relevant parts in it. But thanks Crisp... not being critical. 
Re the Interference: 
I like the answers put up so far especially walking around with a radio to get a map of your property as to what is the best and worst offenders. After doing this (isolating your problems) take their advice to get rid of the RF interference noise.  
PS - NEVER DO ELECTRICAL WORK YOURSELF!!! TOO DANGEROUS!!! Always get a licenced electricial contractor (LEC) in and ask to see his licence and get a safety certificate for his work. 
Good luck.
Lordy

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## candoit

Chrisp is spot on. seperate buildings/installations with sub boards can and usualy do have their own men/earth system. If your house is on the grid and you have a solar system on the shed and the service meters are on the house and  you intend to install a net grid infeed tarrif meter to make money then  you will need that earth  !! but that is a another story.You will need a sparks for any of this work. Regards.

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## Bedford

There was an article in the Serviceman section of the "Radio, Television and Hobbies" magazine in the late 60's, in reference to poor signal and interference. It seems that the homeowner found that by putting his finger on the aerial it increased the signal to the point he could listen comfortably. 
Not wanting to be restricted in his movement while listening, he came to the conclusion that it must be the meat that was improving the reception, so to improve his mobility he tied a sausage to the aerial, which worked admirably until such time as the sausage dehydrated and the signal diminished. That's when he called the serviceman. :Biggrin:  
On a serious note, you could try to get in touch with an amateur radio club for some advice, these fella's can usually get reception with some aerial tuning and filtering. :Smilie:

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## Glot

It's scarey that 3 different electricians didnt know a very basic and very important thing such as this. Chrisp got it right but take note of the note. VERY IMPORTANT. The out building must be sufficient distance away from the main building ( as yours is) and there must not be any conductive pipes between. In a nutshell, in your situation, delete existing earth and install new main earth and MEN link at shed. Second bit of advice. Stay away from the electricians that could not tell you this!

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## Bedford

> The out building must be sufficient distance away from the main building

  What is this distance?

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## elkangorito

> In a nutshell, in your situation, delete existing earth and install new main earth and MEN link at shed.

  I strongly suggest that you not follow the advice in the above quote. 
Lordy has the best advice so far, which is to consult an inspector. Generally speaking, it's up to your supply authority to decide whether your idea is acceptable or not. From experience, most supply authorities do not easily approve the use of multiple MEN connections nor the relocation of an MEN link in domestic installations (because it interferes with your AM radio). 
If you do manage to get approval for your idea, be prepared to have the system re-tested (earth fault loop impedance etc) & a C.O.C. issued. The cost of this exercise will not be small. 
More info from regs:
1.4.69 Outbuilding.
A structure completely separated by an area of land from another structure containing the switchboard from which supply is obtained. 
5.5.3.1 (b)
The electrical installation in the outbuilding shall be regarded as a *separate electrical installation*, and.... 
2.3.4 Additional isolating switches.
2.3.4.1 Electrical installation in an outbuilding.
An electrical installation in an outbuilding shall comply with the following: *(a) General. An electrical installation in an outbuilding shall be treated as a separate electrical installation if the electrical installation in the outbuilding
(i) has a maximum demand of 100 A or more per phase; and
(ii) is provided with a switchboard.* 
My advice is to adopt a "I can't decide what I want. The supply authority can decide what I can have or not have" attitude. 
It may be easier to put up with crappy radio reception.

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## NigeC

Well I've been on holidays and will now throw in my 1 cents worth (holiday's have cost me a lot so I don't have 2 cents) 
I would say No. and would agree with elkangarito, it won't be above 100A, even if it contains a switchboard. 
It is part of a single installation (ie one customer meter) so the MEN will be at the main board.
The installation should be a sub circuit supply cable which will contain an earth conductor suitable enough for the max demand of the shed. 
inverters are noisy, period (like VSD's) seeing they are hooked into the mains you will get noise. there is a long way to go on this technology me thinks 
check that the earth stake is not in dry soil, they like a little bit of water like plants! ( i think that is in the regs too) 
I'm confused that the existing supply cable has no earth conducter?? and is there an earth conductor run seperately to the earth bar of the main switchboard?? 
All conductors should be the same length and ran in the same manner of a sub circuit if they aren't part of the one cable (obviously)

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## Nifty1

I've done a bit more investigation. Turned off all the breakers on the main swbd except the incoming main, removed battery from laptop computer, turned off all the breakers in the shed including the the solar system. Acceptable radio reception, even from 300km away. Turned on the solar breaker, and after a couple of minutes the noise started. So it's pretty clear to me that the inverter is creating the problem. I added earths from the inverter case and the shed itself (steel shed) to the earth point in a 3 pin socket, but this made no difference so removed them. The RFI is worst close to the inverter, but is still a problem as you walk along the path the power cable takes up to the house. Cable is buried 600mm I think, and the radio is about 1.5m above ground level. If you walk away from the path of the cable, the interference fades. In the house, there is almost nowhere where the RFI fades out, because the power cable to the shed runs up the wall, across the ceiling, and down the opposite wall to the swbd. The earth from the swbd goes back up, across the ceiling, and down the third wall to the stake. RFI is bad if the radio is anywhere along this earth path, which is why I thought the separate earth at the shed could be a fix, although we eliminated that approach a few days ago.
So it seems these inverters are quite noisy, and both radiate RFI, and insert it into the mains power cable. The only practical approach I can see now is to look at suppressing the noise in the power cable with something located close to the inverter (is there a product that will handle all 3 wires?). I'll improve the aerial on the tuner in the hifi too. Most probably we will just put up with it for the portable radios - it's not the biggest problem in the world. 
I do appreciate all the suggestions and advice that you've put up - more than I ever thought I'd get. Thankyou.

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## chrisp

> The only practical approach I can see now is to look at suppressing the noise in the power cable with something located close to the inverter (is there a product that will handle all 3 wires?).

  Nifty, 
RS Components have a good range.  For example: Fair-Rite | Passives | Magnetics | Ferrite Core | Round Split RIngs |0431177081  
How big is the mains cable to the inverter? 
Also, see this web site - I think we are on the right track.  Radio Noise Suppression Ferrite Filters 
Good luck!

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