Monday 20 December 2021

Station grounding.


 

There's an interesting piece, partly about station earthing, over on PE4BAS' blog at the moment.

Whilst I commented on the dangers of misunderstanding earthing, which is widespread, it doesn't seem to have appeared. Bas later said he didn't see the comment.

Well, these things happen.  Given Bas' response, I think it's important to underscore the dangers even more than I had already, so I've updated this blog a little as a result.

What I will place here is a clear warning to anyone who is thinking of attaching (or already has) wires to the earth system of a house.  

UPDATE: this post unexpectedly became even more relevant, as the ARRL merrily published (21/12/2021) a graphic on their FB page that shows a grounding system that would not be acceptable or legal where PME systems exist.  They should know better, not least as PME is used in some parts of the US, and widely outside of the US.  ARRL publications are widely sold outside the US, which only highlights the failure of the ARRL to consider the potential consequences.

Firstly, there are laws about modifying the electrical supply systems, including the earth, in most countries.  These can carry criminal punishments if you don't adhere to them.  Having a radio licence does not make you qualified, nor does it give you consent to start fiddling with the electrical supply, even in your own house.  You may resent being told that, but that doesn't make it any less true.

One, very good reason why these rules exist is because, if you do get things wrong, that error might well appear on the lines outside, putting people working on them in danger.  

Secondly, an RF earth is not the same thing as an electrical safety earth - although under certain fail conditions, they can become the same thing - and run the very real risk of starting a fire. 

In PME systems, for example, the earth is connected at the input to your house at the neutral; one wire serves two functions.  If the neutral breaks, say, in a storm, then you could find your entire neighbourhood's circuit trying to complete to earth via your radio equipment.  It won't take it, by a very long margin, and will catch fire.  Neutral breaks are not exactly rare.  You might be lucky and find there's a drop to ground from the line outside which happens to be in the right place to stop this situation from arising.  But you can never know where any break will be, so you can't sensibly take a gamble on the PME arrangement outside.

A PME system, as widely found in the UK.  If you install RF earths, it is a legal requirement - and, strictly, requires a qualified installer - to connect every one with its own 10sq mm minimum cable back to the 'incoming' earth (which would be at the chocolate block connector in practical terms here).  No advice is given - seek a qualified installer and talk to your network. A point of weakness may remain, even then, because the earth cable that runs from the input fuse to the distribution box is often not of a high enough cross-sectional area.  You can't change this wire (at least, not legally), and so a network engineer will need to do it.

Your electrical supply may be very different in nature, especially in relation to the earthing system, to the person writing about what they've done in the shack.  It's as well to remember this. 

This is a typical 'recommended' earthing system for radio shacks you can find online, often originating in the USA.  In a large part of the UK, this WOULD NOT conform to regulations, and represents a SERIOUS FIRE RISK - which includes burning your house down. A heavy-duty earth cable from the rod, directly back to the supply input earth/neutral is required in common PME systems.  Screw-type connections to the rod should be avoided - they tend to corrode and make bad connections.

Just remember that your house may well burn down if you connect things up wrongly and contrary to electrical rules.  If that happens, an insurance company is almost certain to refuse - quite rightly - to pay out.  That is a very serious and ruinous outcome.  If Bas, or anyone else, is qualified to do such work, then all well and good; my post wasn't aimed at such people, rather obviously, and they shouldn't be offended.  But others should be very careful indeed.

I urge anyone who is thinking about station grounding to consult their network supplier, and seek such information and consent as may be required.  Connecting wires up to copper rods is easy.  Recovering from an uninsured, burned-down house is not.


2 comments:

PE4BAS, Bas said...

Should I write a warning on top of my blogpost as well John? I really don't about any insurance issues if electricity wiring is modified according the rules. I have to write that I'm originally a electrician. Although some rules have changed of course. But basically I understand what is safe and what is not. However, you can ask any electrician about the combination RF-ground and safety earthing. I don't think you will get equal answers about it. Station grounding is complex. Although in my opinion it is important that everything grounded/earthed in the shack should have equal potential, no matter what! You can bond station ground (separate earthrod) and the house safety earth together or you can use either station ground and disconnect house safety ground or use house safety ground and forget about a separate station ground.
When I read your warning I think you would prefer to forget the house safety earthing and use only the separate station ground. If I think it over I think that is the best way to do it. Just like I wrote, my mind is a bit blurred at the moment. 73, Bas

Photon said...

I think you've taken it far too personally, to be honest.

It's a warning to other people to be careful; you may understand electricity supply and be qualified to modify things, but others mostly aren't (in the UK, it's actually been illegal to do most domestic wiring unless fully qualified for some years now).

The RSGB happily printed an article that was dangerously wrong in what it told operators was OK to install; it didn't show any understanding of protective multiple earth systems, which are widespread in the UK. I should say the RSGB accepted it got it wrong, though I never saw the promised correction. I've seen similar errors in letters of other magazines more recently.

I had the regional network manager discuss this with me, and whilst I am not in any way qualified in electricity supply, I was told my understanding of the situation with RF/electrical earth was correct. In fact, it was something the network manager hadn't thought about before I raised it.

I've been reminded before by you, Bas, that each is free to write what they want on our blogs. That goes for me, too. I won't take any lessons in what I think people should be careful about, not least as many of them don't even understand what and why they are earthing in the first place!