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Power - Earth-RCD's- ISO/TX's and workshops.

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TVJON74
(@tvjon74)
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My workshop is about 60 yards from the house in the back garden.
I installed armoured cabled underground in 2 inch ducting from the house to the workshop. At the house end I installed an RCD to protect the cable and at the workshop end I have my own consumer unit with built in RCD and my own earth stake, so I am totally separated from the house.
On the decorating side I have foil backed plasterboard with butted joints, the joint gaps were just filled with decorators caulk and painted.
In an earlier post it was mentioned about using plug in Ethernet devices, does anyone know if they will work over a mains install like mine?

Jon

Jon
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Posted : 31/01/2013 9:17 pm
Red_to_Black
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Hi Jon,

It is usually better to supply the outbuilding using armoured cable, and non RCD'd at the supply end, the RCD being at the remote end.

It would be better not to be on any RCD that the house is also using, as this can lead to nuisance/unwanted tripping the house out.

This is for two reasons.

1) two RCD's in series will not discriminate, ie. you cannot guarantee which one will trip first.
Unless the one at the supply end is a 100mA time delayed type, and the remote one is a 30mA type, a 30mA type required now for sockets for general use, or outdoor use.

2) the incovenience/danger in the dark of having to walk to the house to reset the RCD after it has tripped.

I see no reason why your network over mains would not work.

 
Posted : 31/01/2013 9:25 pm
Anonymous
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The Network over mains is a Transmitter and Receiver. It's a LIE. it uses the mains mainly for power. A pair lighting loops will couple one on a generator and one on public mains.

Older ones only wreck Short wave and high end of MW. Newer faster ones put out muck up to 200MHz!

If these are tested properly (i.e. on actual domestic wiring as a pair, transferring data) they are ALL 20dB above the interference limit. "Tricks" to pass them include only plugging one in or not connecting ethernet data.

 
Posted : 31/01/2013 9:31 pm
TVJON74
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Thanks for the replies,
I forgot to mention that my workshop supply comes from the house before the consumer unit so I'm totally separated, ie my causing a fault can not blow the house trip. Yes my supply is the same phase as the house, but I had heard somewhere that the Ethernet adaptors didn't like RCB's

Jon

Jon
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Posted : 31/01/2013 9:34 pm
Red_to_Black
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However there is still the thorny problem of whether to export the earth from the house to the shed or run the shed as its own TT system with an earth rod.

Depends on the earthing system in use at the supply end, and if there is any metal water or gas pipes in the outbuilding.

If you already have an accessible duct, then I would pull in some cat5 cable (or similar) too.

 
Posted : 31/01/2013 9:34 pm
TVJON74
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Unfortunately this was all about 13 years ago now and although I can get to both ends of the underground duct I won't be able to pull more cables through now!

House supply is overhead cable with earth stake, the cable armour is joined to house earth, the workshop then uses its own earth stake.

I'm currently using WiFi devices for internet connect via the house but distance and location slow things up a bit.

Jon

Jon
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Posted : 31/01/2013 9:47 pm
Red_to_Black
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House supply is overhead cable with earth stake, the cable armour is joined to house earth, the workshop then uses its own earth stake.

I'm currently using WiFi devices for internet connect via the house but distance and location slow things up a bit.

Jon

So your house supply is more than likely a TT system, so by rights the supply cable to the out building should be protected with a 100mA time delayed RCD (30mA at the shed end), if it has two 30mA cascaded it is only really a problem Jeffrey and I mentioned further back (lack of discrimination/inconveniance) but is safe, also having another stake at the shed end is good, as this will work in conjunction with the house stake lowering the overall RA (the rods resistance to earth) which is a good thing. :thumbl:

Ethernet over power is something I have very little experience in, so I cannot really advise if RCD's affect this or not.

 
Posted : 31/01/2013 9:58 pm
Anonymous
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Red to Black is correct about cascaded RCDs and the hassle of having an RCD trip at the house. However there is still the thorny problem of whether to export the earth from the house to the shed or run the shed as its own TT system with an earth rod.

Here every house has neutral bonded to earth and earth rod at the meter.

The HF transmitter earth connects to several earth rods and it's connected to mains earth too. I can't see how else you run 80W at 3.7MHz on a metal chassis / metal cased Radio set designed to use mains Earth. I suspect a problem in some countries? France?

Years ago in Norn Iron (1970s) the Bungalows all took three wires from pole and I presume the Earth and Neutral bonded at substation. But "earth" was also bonded to pipe (not plastic) in kitchen, at Hot tank and also at central heating pipe at boiler in garage.

 
Posted : 31/01/2013 10:01 pm
Anonymous
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Thanks for the replies,
... I had heard somewhere that the Ethernet adaptors didn't like RCB's

Maybe some models don't like some RCBs, but I'd honestly be surprised if it mattered much as the adaptors will work with a 2m or more gap between ISOLATED circuits! They will work badly or not at all if one end is on a properly filtered socket strip.

 
Posted : 31/01/2013 10:05 pm
TVJON74
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Thanks again all,
Maybe I will get a set and try it.

Best regards
Jon

Jon
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Posted : 31/01/2013 10:34 pm
Anonymous
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Please run Cat5e.

The Powerline Ethernet are horrible RF wise. Worse than any SMPSU, CFl or TV by up to 20dB :sad:

I install extra Cat5e and can run "IR" Remote, DC, Audio and even HDMI on it.
http://www.techtir.ie/howto/hdmi-via-cat5-cable

You can run SCART RGB, but that needs more cables and Baluns.

Shielded Cat5e is best if you don't have metal / shielded trunking.

 
Posted : 31/01/2013 11:38 pm
TVJON74
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Running any cables is a no go without digging up a patio and 60 yards of garden.
I will have to stick to the WiFi.
I won't bother using/trying Ethernet over mains.
Thanks for your help and advice :thumbl:
Best regards
Jon

Jon
BVWS Member

 
Posted : 01/02/2013 12:13 am
Anonymous
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I do have a pipe, but it's full. So there are coax and Screened Cat5e going around the base of the wall and up the back of a drain pipe.

Here we have MMDS which is 2.5GHz. The older discarded ones have a N connector for downconverter and dipole. The current ones have the downconverter built into the stalk. A pair of those gives about 1km at full speed (8km at low speed)

Sticking ordinary Bridge Wifi on window sills gives easily 30m. (more at lower speed).

 
Posted : 01/02/2013 12:59 am
crustytv
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Please run Cat5e.

The Powerline Ethernet are horrible RF wise. Worse than any SMPSU, CFl or TV by up to 20dB :sad:

I install extra Cat5e and can run "IR" Remote, DC, Audio and even HDMI on it.

Well that's that dismissed then! :|

If I had followed that advice I would have missed the opportunity of a solution that worked and suited my needs.

The last 3 houses I installed a dedicated hardwired CAT5e network over the entire house to all rooms and the workshop. This time I could not be arsed with all the hassle of routing wires, crimping plugs etc so installed this solution. The proof is in the pudding it works and I suffer no issues. Perhaps you should let people decide by using and having their own experience. At £20 it's worth a try and you can always take it back if you find it's not for you.

Just my attempt to offer a balanced opinion.

Chris

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Posted : 01/02/2013 8:15 am
GlowingAnode
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Red to Black is correct about cascaded RCDs and the hassle of having an RCD trip at the house. However there is still the thorny problem of whether to export the earth from the house to the shed or run the shed as its own TT system with an earth rod.

If you use the exported earth ie a continuation of a TNS/TNC-S, then you run the risk of a voltage difference between mains earth and local "true" earth, either induced or through IR voltage drop. This can cause a nuisance in the form of interference to radio reception amongst other problems.
Under fault conditions this voltage could be several tens of volts.
If you intend to bring external aerials and/or RF earths into your workshop, then TT (local earth rod) is to be advised.
By creating a local equipotential zone, this will minimise any voltage difference (and hence induced loop currents) between mains earth and true (RF) earth.
A double pole mains filter is also highly recommended, especially if you're operating a transmitting station.
The downside being the design of the installation requires careful consideration, and periodic testing of the earth is required.
Rob.

Thursday night is shed night.

 
Posted : 04/02/2013 12:50 am
Red_to_Black
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I was thinking of problems more on the lines of if it was TNC-S and extraneous metal parts, mainly water or gas pipes being present in the shed/outbuilding.
As then these pipes need bonding with at least 10mm^ back to the main earth terminal (MET) in the house.

It is possible to use an Earth Marshalling Terminal (EMT) at the shed end, but then the supply cable earth has to have enough current carrying capacity (CCC) for both the expected Earth fault current and the bonding combined, and this leads to rather large supply cabling cross sectional area (csa), or a seperate bonding cable, which can be very expensive on long runs.

In this case it is sometimes better to segregate (insulate) the incoming earth at the shed and TT (earth rod) the shed supply, if armoured cable is used the armourings still have to earthed from the supply end but seperated/insulated from the shed earthing system.

The supply cable sizes are then more reasonably sized (and cheaper) for the TT at the shed end.

There is not usually as much of a problem with the TNS system as with the TNC-S system in this scenario, as again any bonding can be done with smaller csa cables.

 
Posted : 04/02/2013 1:08 am
GlowingAnode
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Yes, ok Baz good point.
Looks like another reason to favour a local TT installation, especially if it's a remote building.
Rob.

Thursday night is shed night.

 
Posted : 04/02/2013 11:19 am
Terrykc
(@terrykc)
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There is a lot of useful information on earthing here:

http://wiki.diyfaq.org.uk/index.php?tit ... hing_Types
http://wiki.diyfaq.org.uk/index.php?tit ... ty_outside
http://wiki.diyfaq.org.uk/index.php?title=TT_Earthing
http://wiki.diyfaq.org.uk/index.php?tit ... nd_Bonding

Note that there is a link to an IEE Wiring Matters article in the first one, which is broken. The article in question is included in this:

http://electrical.theiet.org/wiring-mat ... mplete.cfm

When all else fails, read the instructions

 
Posted : 04/02/2013 11:59 am
crustytv
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Posts: 11869
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Split the developing discussion about power/earth/RCD etc off from my workshop construction thread. It was starting to dominate and It warrants a discussion thread of its own really.

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Posted : 04/02/2013 12:13 pm
GlowingAnode
(@glowinganode)
Posts: 463
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Red to Black is correct about cascaded RCDs and the hassle of having an RCD trip at the house. However there is still the thorny problem of whether to export the earth from the house to the shed or run the shed as its own TT system with an earth rod.

If you use the exported earth ie a continuation of a TNS/TNC-S, then you run the risk of a voltage difference between mains earth and local "true" earth, either induced or through IR voltage drop. This can cause a nuisance in the form of interference to radio reception amongst other problems.
Under fault conditions this voltage could be several tens of volts.
If you intend to bring external aerials and/or RF earths into your workshop, then TT (local earth rod) is to be advised.
By creating a local equipotential zone, this will minimise any voltage difference (and hence induced loop currents) between mains earth and true (RF) earth.
A double pole mains filter is also highly recommended, especially if you're operating a transmitting station.
The downside being the design of the installation requires careful consideration, and periodic testing of the earth is required.
Rob.

See here; http://wiki.diyfaq.org.uk/index.php?tit ... g_an_earth
(taken from one of Terry's links above)
Cheers.

Thursday night is shed night.

 
Posted : 04/02/2013 12:28 pm
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