I have been looking at these boxes. Am I right to think that they only have holes around the circumference? I was hoping to mount the box on the external wall and use only one entry: have the SWA enter at the bottom and the T&E to exit through the back, through the wall. Is this possible? Do they come with blanks to close off unused entries?
Thanks, Stephen.
It is funny you should mention that. Where the SWA leaves the house, another wire runs with it. It is uninsulated and is braided (it looks silver in colour; I thought it might be steel). I thought it was some sort of ancient earth wire.
Whilst doing more digging I have found what looks like the other end of this braided wire, connected to nothing! I guess like the SWA, it was not long enough to reach the garage and presumably it's joint broke and got lost long ago. There is no "other half" entering the garage; that just relies on the SWA for earthing.
I'll have to look into this further. I don't know what the previous owner did in there; would you need a better earth for welding or something? I'll only be using it for lights and a socket for the lawn mower. Though I am hoping to have the whole garage replaced when I have the time and money.
Thanks, Stephen.
I bought one of the dedicated SWA cutters a few years ago from TLC. It made life so much easier than using a hac ksaw. I wish I'd had one years ago/ I've had the pyro tools for years, but SWA is sometimes needed.
IME for occasional use, a Monument screw adjusted pipe cutter works well on SWA. Mine is >40yrs old, has never had a new wheel and works on up to 30mm diameter.
If in doubt wind a bit of insulating tape round it first, and then hacksaw along the edge.
You need the g clamp style...
Indeed - although as someone else suggested you can use it to just mark the steel, then cut with a hacksaw or side cutters once marked rather than doing the whole job with a pipe cutter.
For a one off I would be tempted to just use a stanley knife to ring the cable in required place, and use the score line to trim to with side cutters. Rather like as shown:
If all you need it an earth connection, then the armour (for any domestically sized SWA) is larger than adequate to act as one. The only complication comes on systems that have TN-C-S (PME) earthing at the head end, and you are exporting that earth to an outbuilding. You then need to make sure the outbuilding is also included in the main systems equipotential zone - which may require a substantial main bonding conductor, and the SWA armour alone may not add up to enough copper equivalent metal to do that.
(If that were the case, then personally I would make the garage a TT install, and not couple the SWA earth at the far end).
See
(Just thinking "out loud" here, so if this is stupid, tell me so nicely.)
It seems to me that if you live on a TN-S or TN-C-S street, all the houses would be in the same equipotential zone because they all share the same earthing system. Is that right? If so, is that OK primarily because of the size of the earth or earth/neutral conductor between each house & the main cable under the street? (I guess if it's PME, the repeated earth electrodes along the cable run help too.)
In the case of a TN-S install you might argue that they would all share a common earth potential - but even that might drift a bit between properties depending on how much earth leakage there is from each property, and how far you are from the substation.
The effect with TN-C-S may be more pronounced since the PEN conductor will be carrying significant current and hence may see more voltage rise over the length. (it depends on how many times it is reconnected to a "real" earth along the route).
However the supply of an earth alone does not create an equipotential zone. For that you need to ensure that all other ways a potential can be introduced into the house are tied into one equipotential zone. Inside a house that is usually doable and also controllable, since you can identify the things that can bring a potential into the zone (including the main earth), and bond them. Under fault conditions the supplied earth may rise to (say) 100V above "true" earth, but you don't care so long as anything you can make contact with is lifted to near enough the same potential.
Once you venture out of the house it gets harder - partly due to the distance - since unlike with separate properties, which can each have their own equipotential zone - bits of your property need joining to the same one when you export a TN-C-S earth). Also depending on the nature of the outbuilding itself it may have easy access to multiple local earth potentials that could in theory (under fault conditions) be dramatically different from that of the suppliers earth. (think of something like a greenhouse with a mud floor).
Its more a case of keeping clear in your mind that earthing and equipotential bonding work in different ways. The former is designed to limit the duration of a shock (by allowing adequate flow of current to trip a protective device), the later to reduce its magnitude (by electrically clamping isolated bits together).
While the two systems have fortuitous effects that can benefit each other, its possible to have one that functions well within design tolerance, and the other than does not.
Interesting, thanks.
To answer my own questions: from what I can tell, they do not come with blanks for unused entries and the version with a cut out and the back is called a foundation box; the problem is, where to find one.
It isn't DIY as such (other than the fact I'm doing it myself!)
I've been brewing commercially part-time for over a year on a small 300 litre kit I put together myself. From January I'll be brewing full-time on a 16 hectolitre kit which I've again mostly put together myself. It's still small scale on the grand scheme of things but I'll be brewing once a week so that's about 3380 pints per week!
The SWA stripping was wiring up 2 x 9kw and 1 x 18kw 3-phase immersion elements that will be used to boil the wort prior to fermentation.
Sounds like err, Fun!...
No gas there then?.
JOOI Where do you get the water from, a well or surely not tap or mains water?....
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