Show us your Conduit!

[Guest 004]

Though i agree with you in the use of a separate CPCs in conduits, conduit installed correctly and professionally can and will give you a very good earth return. This was always proved by testing with a 25A ductor test. One of the last projects i was involved in, in the UK was a large shopping centre that totally relied on the steel conduit, throughout the whole building. Never saw a bad reading on any of the final tests i witnessed!!!

What year was that Grandad?

 

[Engineer54]

What year was that Grandad?

89/90 as far as i remember, ....and OY, ...Not so much of the grandad!! ...lol!!!

 

[Knobhead]

MrEnigma, I wonder how many of our compatriates on the board would recognise a “Ductor”?

 

[bugsy]

Dont forget the galveroid!

 

[netblindpaul]

Me!
I'm looking for a reasonably priced used one at the moment!!!

 

[Engineer54]

Some of those Ductor testers were almost works of art in there wooden cases, ...One that comes to mind was the ''Claire'' instrument... Those bits of kit, seemed to last for years and years, unlike some of today's stuff!! lol!!!

 

[Knobhead]

Some of those Ductor testers were almost works of art in there wooden cases, ...One that comes to mind was the ''Claire'' instrument... Those bits of kit, seemed to last for years and years, unlike some of today's stuff!! lol!!!

Where I served my time we had two dating from the 1950’s. Used daily for M&Q statutory testing, the mate kept them polished. As you say “works of art”. They were still in use in the 90’s when I left the company.

 

[Steve1412]

Nah mate hospital saddles areView attachment 4980 wider to the wall and thiner to the conduit end.

Aint seen them in years...peeps never believe you when you say there is a difference between distance and hospital......25mm hospital sadddles where also used to knock out unruly elephants!!!!!!lololol

 

[sparkiegaz]

looks ok to me ,,seen worse feller,,

 

[somersetsparks]

Company I work for still has a ductor although I believe there is no longer a requirement to use one.
I still use the conduit as cpc most of the time unless they spec otherwise, I always use lockrings behind knockouts etc to give a better surface area put a light smear of silicone grease on threads and scratch paint of any boxes behind the bush/lockring.

I do find it odd that people are happy to rely on a piece of squashed 1mm but unhappy with 80 sq mm of galv steel!
Obviously there are circumstances where i would run an earth but not to many.

In answer to davelerave - Most submains I work on are still in 4 core, usually with seperate cpc.

I would probably have used an inspection elbow on that corner, but as the OP says its what you get told to do by the gaffer and what is in the stores. (which in these tight times doesn't seem to be a great deal!)

 

[somersetsparks]

oh.. one other thing, the prob with distance saddles is they mean if you have any besa boxes they space them off the wall a little , and you have to be very careful when fixing them as there is no adjustment.

I always use them if I am dropping down from trunking into accessories as they space it nicely for knockouts removing the need for sets.

 

[High Tower]

MrEnigma, I wonder how many of our compatriates on the board would recognise a “Ductor”?

High current, milliohmmeter, used for measuring low resistance, see were not all as thick as you are smug

 

[Engineer54]

They can also come in micro ohm sets, used for measuring contact resistance of say bus bar joints and larger breaker contacts etc, etc... Some of those models can deliver in excess of a 100A test current...

 

[JD6400]

Also know as a flash tester isn't it ?

 

[Engineer54]

Flash tester?? .....No!!

 

[High Tower]

Are you thinking of pat testing ???

 

[somersetsparks]

Flash testing is used to test enclosures. They test an enclosures ability to handle an arc flash, I know that they were testing panels at 2.5kv on the last petrochem job i was on.

 

[JD6400]

I was involved on a large hotel build a few years ago and one Friday evening got asked to check why the power was going up and down erratically on one part of the build .
To cut along story short i found that one of the 1200 kva ( i think it was this size but it was a few years ago and we do not tend to deal with this size normally ) incomers fed into a floor standing panel the size of a large mini bus , had got a loose bus bar which had all but melted away .
The switch gear supplier would not take responsibility for it so our old timer Foreman asked for the flash test results to prove continuity at the factory and they backed down .
From memory he said the test involved firing 10000 volts with high current through it to bring out any loose joints but nobody does it any more because i quote " it tends to blow the s""t out of what you wanted to test in the first place "
I would love to know more about this and if it was indeed true , as of yet i have not come across anything like again .
Many thanks Dave

 

[somersetsparks]

Like I say the last petrochem job I went on, all enclosures were flash tested to 2.5kv on site as part of commissioning.

 

[JD6400]

Thanks Somersetsparks but the test i referred to was to check continuity and not if would contain a arc flash over , unless i have got the wrong end of the stick and you are saying the test is for your instance and not mine ?
Thanks for the reply anyway but could you clarify please .

 

[Engineer54]

That's what he's saying dpelctricalltd, Ductor testing is basically injecting high current accross a joint or contact test area, measuring the resistance. Flash testing involves injecting high voltage, 2.5 to 4KV, for testing insulation properties of panels and the like, and measures any weaknesses in mA....

 

[Engineer54]

I was involved on a large hotel build a few years ago and one Friday evening got asked to check why the power was going up and down erratically on one part of the build .
To cut along story short i found that one of the 1200 kva ( i think it was this size but it was a few years ago and we do not tend to deal with this size normally ) incomers fed into a floor standing panel the size of a large mini bus , had got a loose bus bar which had all but melted away .
The switch gear supplier would not take responsibility for it so our old timer Foreman asked for the flash test results to prove continuity at the factory and they backed down .
From memory he said the test involved firing 10000 volts with high current through it to bring out any loose joints but nobody does it any more because i quote " it tends to blow the s""t out of what you wanted to test in the first place "
I would love to know more about this and if it was indeed true , as of yet i have not come across anything like again .
Many thanks Dave

Tests of this type carried out at the factory, normally in the presence of a representative of the client, would in all likelihood be a high-pot test. There are many different test voltage formulas for this test, but generally if testing with DC voltage it's 3x rated voltage plus a 1000. (11KV tested at 34kv) This testing is normally only conducted after verification tests with a 5KV insulation test kit that can measure in the Tg ohm range. These High-Pot tests, in AC or DC are classified as destructive tests, so initial factory testing is quite often limited to 1 to 3 minutes, whereas final commissioning testing prior to be putting into service can be upto 15 minutes, and sometimes at an increased voltage.
Leakage levels are measured and recorded in mA....

Obviously there's an awful lot more to these tests than i've outlined, but should give a general idea...

EDIT....

By the way, Ductor tests would have also been applied to the Bus Bar joints and connections, sometimes these are conducted in the presence of the clients representative, but normally only as a sample on maybe 2 or 3 of the them, and readings compared with the factory test report. Also remember that these panels are then split down for transportation to site, so any bus bar joints connecting the panel sections together at site is the responsibility of the installer, ...Not the manufacturer!!! These bus bar joints will then require Ductor testing before sealing/closing the bus bar chambers to each panel section....

 

[Knobhead]

The tests that can do major damage are short circuit withstand. They are usually done on a sample panel for type approval. I for one wouldn’t be happy to take delivery of a new panel knowing some loony has shoved 50KA for 3 seconds through it.
Years ago I saw a film by GEC showing a withstand test failure. I don’t know about the purchaser witnessing the test, I wouldn’t want to be in the same county.

HiPot testing is fun, I’ve only done them up to 5000V myself. But have had to be the company representative during testing of 11KV gear. It wasn’t new stuff so the tests were down rated to 17KV to earth.

The highlight of testing was the interfering manager. I’d set up barriers warning, notices, etc. while I was doing 1 minute 2.5KV tests to earth on a 1.7KV cable. I was quite happily sat in the sub watching the figures rising in to gig ohms when suddenly the reading flicked down accompanied by a squeal from outside. Turned the test off and went to investigate. The idiot had climbed over the barrier to have a look at the termination I’d done and of course he couldn’t resist touching J Pity he didn’t arrive later when I was doing the 5KV phase – phase tests.
He’s nursing a sore arm while I’m nursing sore ribs from laughing.

 

[rocker]

What a bloody idiot! Don't you just wish we could put all the managers on a big old boat and send them off to sea to see how they 'manage'?

 

[Engineer54]

HiPot testing is fun, I’ve only done them up to 5000V myself. But have had to be the company representative during testing of 11KV gear. It wasn’t new stuff so the tests were down rated to 17KV to earth.

Very true, rarely if ever will you test at those higher levels, after the initial putting into service testing has been conducted. Which is why it's very important to keep up to date records of all such tests on cables and equipments. This especially in the case of multi cored cables, where both KV and times will need to be reduced quite significantly depending on age and length of cable runs (joints etc) Though i've never tested at quite so low a figure as 17KV normally the lower figures would be around 2 X rated voltage, but times would be around 5 to 8 minutes max, again depending on charging up times of long cables....