Gallery, Projects and General > Project Logs
New Tractor Shed
vintageandclassicrepairs:
Hi All,
--- Quote --- Perhaps this is why a lot of sparkies are using an extra core as earth, and not trusting the SWA to have good continuity
--- End quote ---
The use of the SWA screen as the sole earth conductor has not been allowed (in Ireland anyway)
for years :scratch:
When I had a "real" job, it often included work on SWA cabling installed in the 70's
All these cables had separate earth conductors
Really glad to be out of that game now :D
Recently I was asked to change out the cable to a foot pedal on a press brake
I could not believe how skimpy the shielding and insulation is on the "new" sylflex compared to the old???
John
awemawson:
Although the wire armour is being used as an earth in this run there is also an earth rod as an auxiliary earth as it is quite a long run.
It's four core cable, neutral and three phases, as five core was not available as far as I or my supplier could determine at the time. However I have subsequently found a source :bang:
The regulations do allow the use of the armour as a CPC and I used this rather good link as a guide:
https://gadsolutions.biz/regulations/swa-as-the-cpc
The relevant paragraphs of that article are:
The use of SWA as a Protective Conductor BS7671
The permitted types of protective conductor are listed in 543.2.1 and SWA is identified in sub section (v) as:
A metal covering, for example, the sheath, screen, or armouring of a cable.
It can therefore be verified that the SWA can be used as a protective conductor in compliance with BS7671.
However there are conditions on the use of SWA as a protective conductor defined in
BS7671.
1. It must be adequately sized to meet the requirements of section 543.2.1.
2. If the armour is used as a CPC then any accessories have to be connected to the associated enclosure's earth terminal by a separate CPC (flying lead) to comply with 543.2.7.
3. If the SWA is used as a main equipotential conductor other than on a PME system it must have a copper equivalent CSA, for CSAs over 25mm˛, of not less than half the cross sectional area of the associated earthing conductor and not less than
6mm˛ to comply with 544.1.1. If the installation is PME then the copper equivalent CSA of the SWA must comply with table 54.8.
4. Where a number of installations have separate earthing arrangements any protective conductors common to these have to be suitably sized to carry the maximum current likely to flow through them OR insulated from the other installation at one end to comply with 542.1.3.3
5. If the SWA is to be used as a combined CPC and main bonding conductor it must meet the requirements of both 544.1.1 and 543.1.1
6. Regulation 521.5.1 permits the use of a separate protective conductor to be run in parallel with an SWA cable.
There are tables in that link (above) giving CSA copper equivalent of various SWA cables and mine is very adequately over sized.
awemawson:
Today's task is to commission the new water feed having removed the temporary feed that was necessary to avoid pipes being damaged as the tractor shed was built.
I had tapped the temporary feed off a tap in the field, trenched across a gateway, crossed the stream by just draping the pipe from bank to bank, and brought it into a chicken shed where the original pipe had supplied water. This allowed the chicken and pigs to still have water while the build progressed. The original feed being cut and stopped off in the manhole that I'm using as a marshalling point.
However, as the afternoons job is to slice the bacon, and the flitches need to be rinsed off and dried and left to form a pellicule before chilling and slicing this had to be done first.
Then it was a simple case of isolating the water supply, blanking off the two Tee's where the two water systems were joined, then opening up a few taps and checking for leaks. However first to decide which of the three stopcocks on my distribution manifold was the right one. OK now I've labelled them :clap:
Then open up the manhole, and mop out the seepage water so when the tap is turned on I can see if there are any leaks.
Then cross fingers and start opening up the feed taps on the new distribution system that runs from the Woodwork Shed underground into the Tractor Shed. Then under the Tractor Shed to the man hole.
Obviously my lucky day - no leaks :ddb:
awemawson:
Then it was just a case of recovering the temporary pipe and returning it to the 'pipe store' for future use.
I've left the bit that I trenched across a gate way in situ as it may well prove useful for a cattle trough in future.
OK those flitches are probably ready to pop into the freezer for a bit to stiffen up before slicing so I'd better go and do it ....
Biggles:
Is that your handy work on the bacon Andrew? :drool:
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