Consumer unit upgrade TT system

[monkeyhanger]

Appreciate a bit of advice regarding this that I'm doing in the morning-

Consumer unit upgrade in house with 6mm gas & water bonding existing (leaving bonding as it is). Existing rod in house with 6mm up to CU.

(Existing install) From a TT system in the house there is a 2.5/1.0 T&E running to a detached outhouse (perhaps, four meters from the back of the house) feeding an existing fuseboard in there with BS3036 fuses for 15A sockets radial and 5A one light.

The outhouse has a copper water pipe supplying a washing machine. This isn't bonded where it rises from the concrete floor in the outbuilding and there isn't a seperate rod in there. The only earthing of anything in there is the 1.0mm CPC of the T&E submain & CPCs of light/sockets.

Am I right in thinking that the CPC in the T&E won't suffice in the requirements for equipotential bonding in the outbuilding (it appears that the T&E is ran under the concrete back yard in plastic conduit.. many years ago). If I install a rod & earth conductor to the existing BS3036 unit in the outbuilding and bonding between this unit & the copper pipework in the outbuilding, should I insulate the 1.0mm CPC in the T&E submain from the outbuilding installation (at the outbuilding end)? Or leave it connected at both ends- in the house and the outbuilding. If either is acceptable would it be best practice to leave it connected both ends?

I am quite aware of requirements when exporting TNS and TNCS but I've never came across TT in the main building with an outbuilding where bonding is required.

This is hopefully obvious to one of you who may read this before tomorrow

 

[davesparks]

Frigging hell Dave, we're not in the Arctic Tundra!

I don't know where he is, it could easily be the frozen north. They have icebergs and polar bears everywhere north of Watford don't they?

 

[PEG]

I don't know where he is, it could easily be the frozen north. They have icebergs and polar bears everywhere north of Watford don't they?

...The day before yesterday,i was running back and forth,outdoors,taking readings with an AC/DC clamp ammeter,alternating between loads,(see what i did,there...)...and get thrashed with the hail storm...

...Me tee-shirt was soaked :joker:

 

[Engineer54]

Frigging hell Dave, we're not in the Arctic Tundra!

The ground doesn't have to be frozen for the whole 4' to make a considerable difference to the Ra value, which is why stability over the seasons is an important factor in any TT system....

 

[monkeyhanger]

Afternoon everyone, just to update the thread with regards to the job to help anyone who reads this in the future in a similar situation. I installed a 4ft rod to the outbuilding, 80 Ohms. Bonded the water. Phoned NAPIT technical support who advised me that it was acceptable to leave the CPC in the submain T&E connected, however if I wished I could disconnect it. I left it connected.

I left the existing rod in the house as I found it, tested & reconnected it to the earth bar in the new CU.

Now lets not have any bickering, enjoy the bank holiday weekend!

 

[monkeyhanger]

Incidentally, personally, if it was above about 80 ohms I would have coupled another rod on

 

[trev]

Why is 80 ohms the magic figure? So 81 you'd have drove another but 80 is tickety boo

 

[monkeyhanger]

I'm not sure why, just a preference!

 

[Knobhead]

My preference would be <1Ω

So where does 80Ω come from?
Would it be that it just happens to be 80Ω on this installation and you can grab the money and run without any real work?

 

[trev]

My preference is also for <1 ohm. I've done it dozens of times, my record is still the same. I've not beaten 0.29 yet. Did one last week and got 0.58 which I was pretty happy with.

 

[Deleted member 9648]

Incidentally, personally, if it was above about 80 ohms I would have coupled another rod on

Why is 80 ohms the magic figure? So 81 you'd have drove another but 80 is tickety boo

I'm not sure why, just a preference!

Priceless!

 

[Silly Sausage]

My preference is also for <1 ohm. I've done it dozens of times, my record is still the same. I've not beaten 0.29 yet. Did one last week and got 0.58 which I was pretty happy with.

You've got the rare knack of hitting underground cables Trev!

 

[trev]

And water supplies and sewerage pipes mate

 

[richy3333]

And water supplies and sewerage pipes mate

And I'm guessing Australia to get a reading that low.

 

[trev]

And I'm guessing Australia to get a reading that low.

Nah. Big, fat rods and cables mate

 

[Leesparkykent]

Chill out mate, earth rods have always been a touchy subject on here lol. ^^

 

[Marvo]

Okay, I realise TT earth impedance topics are always emotional events but please stay on topic and play the ball, not the man. Take a deep breath.....in through the nose .....and.......out through the mouth.....and repeat once more. See, you're feeling better already and just read the advice in my sig now before posting.

Seriously, keep it civil!!

 

[Engineer54]

I see our friend has once again come along and arbitrarily decided off his own back what's constructive and what isn't. What a waste of time contributing, it's now a meaningless dead as a doornail thread!!

 

[Silly Sausage]

I see our friend has once again come along and arbitrarily decided off his own back what's constructive and what isn't. What a waste of time contributing, it's now a meaningless dead as a doornail thread!!

I've never seen so much censorship.
Marv's missed his true vocation in life, 20 odd years too late, as an Eastern European civil servant! :smilielol5:

 

[Geordie Spark]

My preference is also for <1 ohm. I've done it dozens of times, my record is still the same. I've not beaten 0.29 yet. Did one last week and got 0.58 which I was pretty happy with.

Tell the truth .. ye belted it through a cast iron gas pipe didn't ye!!

 

[Knobhead]

Tell the truth .. ye belted it through a cast iron gas pipe didn't ye!!

I've added a redundant gas pipe to an earth nest. Seemed a shame to waste it.

 

[Geordie Spark]

I've added a redundant gas pipe to an earth nest. Seemed a shame to waste it.

I would say that's good thinking.

 

[ferg]

Give the guy a break, He's moderating some of the best educated trolls in the field.

 

[Knobhead]

That’s the day job. The shops been quiet for the last five days, not much to get my teeth in to. But I’m expecting business to pick at the end of the month.

 

[Geordie Spark]

Give the guy a break, He's moderating some of the best educated trolls in the field.

Which reminds me ,,,, Where's Biff??

 

[Silly Sausage]

Which reminds me ,,,, Where's Biff??

Yer man left by choice, if the mulch between the ears remembers rightly.
I think he's Guest55 now.

 

[Knobhead]

I've added a redundant gas pipe to an earth nest. Seemed a shame to waste it.

I would say that's good thinking.

I got the idea from the first substation I was involved with. Four 8” dia 120’ long continuous welded pipes took the 11KV cables under 2 railway lines and three roads. Where they protruded in to the cable chamber we welded studs on and connected them to the MET.

 

[Geordie Spark]

I got the idea from the first substation I was involved with. Four 8” dia 120’ long continuous welded pipes took the 11KV cables under 2 railway lines and three roads. Where they protruded in to the cable chamber we welded studs on and connected them to the MET.

Just an off the wall thing for you here Guru; Do you know anything about instumentation with the ABP logo on it?

I'm talking about 20" dials with pointers driven by a Selsyn? unit and had bugin lamps arranged around the circumference of the dial. and Cam switches which were Honeywell micro switches operated by cams driven through> a reduction gearbox.

Another one was a Drum Indicator which was an aluminium cylinder about 4" diameter x maybe 20" long. It was mounted vertically behind a panel which had a vertical slot about half inch wide cut through from top to bottom so you could see part of the drum.

There was a helical line drawn around the drum from top to bottom and one side of the line the drum was painted black and the other was painted red (from memory) as the drum turned - again driven by a selyn - the slot in the front plate would fill from top to bottom either red or black. I believe this was indicating the level of something somewher in the plant.

I used to make these damned things from start to finish including the engraving which was sometimes in Spanish but never knew what the were for.

I think these things were used in the iron & steel making industry.

 

[bigbaddave]

My best recorded reading was 0.13, earth rod bang outside the front door. Got upstairs and it was also a tns and tncs. Had to chuckle.. I'm sure I've got the pic someone. Bare with and I'll post it

 

[trev]

Got upstairs and it was also a tns and tncs.

How was that mate? One or the other surely? What I've noticed a lot recently is that a PME conversion has been done but they've left the old cable to the sheath of the incomer.

 

[Knobhead]

Just an off the wall thing for you here Guru; Do you know anything about instumentation with the ABP logo on it?

I'm talking about 20" dials with pointers driven by a Selsyn? unit and had bugin lamps arranged around the circumference of the dial. and Cam switches which were Honeywell micro switches operated by cams driven through> a reduction gearbox.

Another one was a Drum Indicator which was an aluminium cylinder about 4" diameter x maybe 20" long. It was mounted vertically behind a panel which had a vertical slot about half inch wide cut through from top to bottom so you could see part of the drum.

There was a helical line drawn around the drum from top to bottom and one side of the line the drum was painted black and the other was painted red (from memory) as the drum turned - again driven by a selyn - the slot in the front plate would fill from top to bottom either red or black. I believe this was indicating the level of something somewher in the plant.

I used to make these damned things from start to finish including the engraving which was sometimes in Spanish but never knew what the were for.

I think these things were used in the iron & steel making industry.

The first gauge you mention rings a bell. They were used on Canadian Calcamatic kilns. They were towards the centre of the panel which means they must have been part of the combustion control. What for I can’t remember. All the burner control was by Honeywell and GE. Selsyn were part of GE.


The second “thing” I haven’t a clue. but I'm sure I've seen them.