On 10/08/2013 10:29, wrote:

Shouldn't there be some certification from an approval body to
support

that?..


Read John Rumm's link to the article by Fluke. There's a body that
sets the Class I-IV standard, but it's up to the manufacturer to
self-certify compliance.

If they also stick an external standards body stamp on the case, then
IIUC they are also supposed to submit the device to said body for proper
testing.

Those photos do not really inspire any confidence it would actually
perform up to the claimed standards.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 10/08/2013 14:19, wrote:

Thanks for the heads up. I will whip the lid off when it arrives
and will be having serious words with Maplin if it turns out so.

I own a UNI-T multitester ( http://www.uni-trend.com/UT526.html ) and
for the price I'm quite happy with it. In all the ways I've been able
to test it, it seems to perform to it's stated spec. But I'm using it
either as an insulation tester or low-ohm meter. That has safety
implications, but less so than probing into a live high-energy
system.

Maybe they've found a way to make your meter Class III without
requiring HRC fuses. Realistically, Maplin isn't in a position to
check every claim on every product they sell, and has to trust its
suppliers.

Yup, I doubt Maplin do much if any evaluation of the actual technical
specs.

I see both sides of the arguments advanced here. As John Rumm says,
for serious work, it's a real safety concern. As others say, for very
occasionally probing inside a CU - you would be phenomenally unlucky
to come to grief.

I actually agree with you on the odds - most of the time.

It does help to have a feeling for how "stiff" the supply is in any
given circumstance though. And there is one of the chicken and egg
situations, where having proper test equipment that you can plug in and
get a quick indication of the supply impedance and PFC from the off is
rather useful.

Secondly, even if you are only moderately keen on DIY there is a good
argument for having adequate test gear to be able to carry out a full
range of tests, something that a multimeter is not going to let you do.
£100 - £150 on ebay will most likely get you some professional grade kit
second hand which will not only let you do all the tests, but also in
the knowledge that its likely to fare better if things go pear shaped as
a result of events beyond your control.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

If they also stick an external standards body stamp on the case, then

IIUC they are also supposed to submit the device to said body for proper

testing.


Ok, I've just had another look at my UNI-T UT526.

The manual says "Designed and manufactured strictly in accordance with IEC61010 safety standard, the instrument meets with Over Voltage Standard (CATIII600V)..."

And there's no approvals marked on the instrument itself (other than CE which is self-certified)

So it's all self-certified.

On 10/08/2013 11:06, Archibald wrote:
On Fri, 09 Aug 2013 15:59:41 +0100, John Rumm

Given a working knowledge of ohms law, you should be able to work that
out for yourself.

Sadly, no. Perhaps you caqn enlighten?

A consumer unit does not stop transients (although you will get a slight
snubbing effect from the magnetic coil in the MCB). Hence it is possible
to drive your test equipment into a failure inducing overvolt by
connecting it at any point in a system.

What does change the further you move from the origin of the supply in a
building, is the prospective short circuit current and the prospective
fault current. Both fall as a result of the increasing loop and supply
impedance (also the temperature rise introduced when small CSA wiring is
driven into adiabatic heating under fault conditions, adds additional
resistance). These factors conspire to make arc flash very much less
likely in the first place, and far less damaging should it actually happen.

I'm afraid the difference of a few mOhms due to heating effects would
not really change my approach or assesment of the risks involved.

And neither should it. As always, you size upon the less salient point
and ignore the important bit. I presume this is by intention since you
feel the need to "win" the argument?

The key factor in reducing PSCC, is the length of 2.5mm^2 cable (or
whatever) between the point of contact and the socket. Even if you are
on a very stiff supply, by the time you are 20m down a circuit, or
inside an appliance on the end of a plug and flex you have the comfort
of knowing that there will be 500A or less of fault current to play with
regardless of what is available at the incomer.

A DMM has an input impedance of 10MOhm or thereabouts. I'm sure the
spike produced by the introduction of such a load would have world
changing repercussions!

Who mentioned the meter itself introducing a spike?

The spikes come from a lightening strikes, or motor switching, inductive
back EMFs, or your neighbour welding something etc. i.e. not things you
have much control over.

Will your meter maintain that 10MOhm impedance in the presence of an
8000V transient as required in the CAT III tests? Are the track spacings
adequate to not suffer breakdown? (they may well be, have you looked
inside at the construction?)

Someone carrying out DIY work can do it without the aid of a £100-00
DMM.

Of course. A DMM at any price range can't even do all the required tests
anyway.

I have yet to find a job that my Wickes DMM wasn't suitable for
and that includes for professional use. In fact the only problem I
might have on a site is the use of a "not calibrated for indication
only" label. Apart from this it is an acceptable tool!

So how do you do an insulation resistance test with it?

A RCD ramp test?

How do you time the RCD trip time?

A Non tripping ELI measurement?

How about accurate low ohms measurements of R1+R2 loops etc?

As I stated
before, any idiot can spend a fortune on test equipment, but that does
not mean they can use it correctly.

Did anyone claim otherwise? You need the prerequisite knowledge to use
any test equipment safely. Hopefully that would also include the
knowledge of the limitations of that equipment.

There are a few little rules your flight of fancy does not take into

Flights of fancy? These would be the same flights of fancy that have
killed people, and also result in injuries each year I take it?

account incidentally. No one should work live if it's avoidable. There

Agreed.

are none contact measures available to indicate voltage and anyone
sticking both hands inside a piece of live apparatus even with the
fingerproof terminals in current use would need a serious amount of
reprogramming.

The other point you may care to consider is that many " professional"
meters The Flukes I used included, do not have a fuse for the higher
current ranges. Although different sockets and interlocks are
available, this does not allow for operator error. I'm not sure what
would make the most effective fuse at that point, the shunt or the
test leads.

I can't see much scope for measurement of current during DIY wiring
work. If you do need to measure mains current draw then you are much
better off with a clamp meter in the first place.

However I bet even your entry level Fluke will contain at least some
input protection, have shielded compartments round the probe sockets and
MOVs on the board etc, so if you accidentally stick it on mA or Ohms and
then connect it across your main incomer terminals, its less likely to
blow up in your face. The moral here is you get what you pay for,

On a final note, I consider one of the most serious ommissions from
any meter now is the crock clip. I never ever did work two handed and
do not feel comfortable doing so now, it seems strange however with
todays safety culture you are forced into chinese restaurant mode to
measure aross a couple of terminals.

On a final note do you actually connect equipment up to this
phenomenally unstable supply the Electricity board provides?

Two final notes?

I find it amazing that entire streets are not going down due to these
"transients".

Do you sell extension sockets or UPS for a living BTW?

Not generally. However looking at the logs from a UPS can be quite
enlightening. I have seen some (in a domestic, rural installation) where
transients in excess of 1kV occur several times every day, along with
other disruptions such as sags and brownouts. (the UPS was installed
after transients killed pretty much every major component in their computer)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Saturday, 10 August 2013 15:34:03 UTC+2, Tim Streater wrote:

Could ye learn to snip d'ye think?



I do apologise. It's Google's fault but I'm working on it.

On Sat, 10 Aug 2013 16:31:04 +0100, John Rumm
wrote:

On 10/08/2013 11:06, Archibald wrote:
On Fri, 09 Aug 2013 15:59:41 +0100, John Rumm

Given a working knowledge of ohms law, you should be able to work that
out for yourself.

Sadly, no. Perhaps you caqn enlighten?

A consumer unit does not stop transients (although you will get a slight
snubbing effect from the magnetic coil in the MCB). Hence it is possible
to drive your test equipment into a failure inducing overvolt by
connecting it at any point in a system.

What does change the further you move from the origin of the supply in a
building, is the prospective short circuit current and the prospective
fault current. Both fall as a result of the increasing loop and supply
impedance (also the temperature rise introduced when small CSA wiring is
driven into adiabatic heating under fault conditions, adds additional
resistance). These factors conspire to make arc flash very much less
likely in the first place, and far less damaging should it actually happen.

I'm afraid the difference of a few mOhms due to heating effects would
not really change my approach or assesment of the risks involved.

And neither should it. As always, you size upon the less salient point
and ignore the important bit. I presume this is by intention since you
feel the need to "win" the argument?

The key factor in reducing PSCC, is the length of 2.5mm^2 cable (or
whatever) between the point of contact and the socket. Even if you are
on a very stiff supply, by the time you are 20m down a circuit, or
inside an appliance on the end of a plug and flex you have the comfort
of knowing that there will be 500A or less of fault current to play with
regardless of what is available at the incomer.

A DMM has an input impedance of 10MOhm or thereabouts. I'm sure the
spike produced by the introduction of such a load would have world
changing repercussions!

Who mentioned the meter itself introducing a spike?

The spikes come from a lightening strikes, or motor switching, inductive
back EMFs, or your neighbour welding something etc. i.e. not things you
have much control over.

Will your meter maintain that 10MOhm impedance in the presence of an
8000V transient as required in the CAT III tests? Are the track spacings
adequate to not suffer breakdown? (they may well be, have you looked
inside at the construction?)

Someone carrying out DIY work can do it without the aid of a £100-00
DMM.

Of course. A DMM at any price range can't even do all the required tests
anyway.

I have yet to find a job that my Wickes DMM wasn't suitable for
and that includes for professional use. In fact the only problem I
might have on a site is the use of a "not calibrated for indication
only" label. Apart from this it is an acceptable tool!

So how do you do an insulation resistance test with it?

A RCD ramp test?

How do you time the RCD trip time?

A Non tripping ELI measurement?

How about accurate low ohms measurements of R1+R2 loops etc?

All the above are beyond the scope of normal DIY work. The original
post referred to a Megger and earth testing. Both these tests can be
completed with a DMM and a few additional "off the shelf" items.

For DIY work I would think a DMM is the best approach. Personally I
have never felt the need to do an insulation check using high voltage
anyway. I tend to trust the cable manufacturer and then there is a
breaker that would trip. Earth loop impedance wouldn't be a problem
either.

RCD testing is taking things to ridiculous levels. If I had access to
the equipment to test the things, I wouldn't bother anyway. I couldn't
certify the tests so there wouldn't be a lot of point doing more than
a button press.

As I stated
before, any idiot can spend a fortune on test equipment, but that does
not mean they can use it correctly.

Did anyone claim otherwise? You need the prerequisite knowledge to use
any test equipment safely. Hopefully that would also include the
knowledge of the limitations of that equipment.

There are a few little rules your flight of fancy does not take into

Flights of fancy? These would be the same flights of fancy that have
killed people, and also result in injuries each year I take it?

account incidentally. No one should work live if it's avoidable. There

Agreed.

are none contact measures available to indicate voltage and anyone
sticking both hands inside a piece of live apparatus even with the
fingerproof terminals in current use would need a serious amount of
reprogramming.

The other point you may care to consider is that many " professional"
meters The Flukes I used included, do not have a fuse for the higher
current ranges. Although different sockets and interlocks are
available, this does not allow for operator error. I'm not sure what
would make the most effective fuse at that point, the shunt or the
test leads.

I can't see much scope for measurement of current during DIY wiring
work. If you do need to measure mains current draw then you are much
better off with a clamp meter in the first place.

Read the "operator error" bit.

However I bet even your entry level Fluke will contain at least some
input protection, have shielded compartments round the probe sockets and
MOVs on the board etc, so if you accidentally stick it on mA or Ohms and
then connect it across your main incomer terminals, its less likely to
blow up in your face. The moral here is you get what you pay for,

I dont recollect ever needing to check incomer Volts. A quick jab on
the RCD test button saves getting the meter out.

On a final note, I consider one of the most serious ommissions from
any meter now is the crock clip. I never ever did work two handed and
do not feel comfortable doing so now, it seems strange however with
todays safety culture you are forced into chinese restaurant mode to
measure aross a couple of terminals.

On a final note do you actually connect equipment up to this
phenomenally unstable supply the Electricity board provides?

Two final notes?

Yep Interruptions I'm afraid. No rest for the wicked!

I find it amazing that entire streets are not going down due to these
"transients".

Do you sell extension sockets or UPS for a living BTW?

Not generally. However looking at the logs from a UPS can be quite
enlightening. I have seen some (in a domestic, rural installation) where
transients in excess of 1kV occur several times every day, along with
other disruptions such as sags and brownouts. (the UPS was installed
after transients killed pretty much every major component in their computer)

:-)

Domestic rural! Long cable runs and a few farmers adding their unique
"footprints" to the supply, not too surprising I suppose.

I would have thought a PC power supply was fairly immune though, lots
of ferrite in the thing and a fully wound transformer to produce the
very much lower Voltage. I suppose there can be more than the one
obvious route into the thing though.

AB

On Sat, 10 Aug 2013 23:42:59 +0100, Archibald
wrote:

lots snipped

All the above are beyond the scope of normal DIY work.

Which rather suggests that consumer units etc. are outside the scope
of DIY... (be careful here!)

The original
post referred to a Megger and earth testing. Both these tests can be
completed with a DMM and a few additional "off the shelf" items.

For DIY work I would think a DMM is the best approach.

Only if the user is aware of possibly misleading indications of a high
input-impedance meter :-)

Personally I
have never felt the need to do an insulation check using high voltage
anyway. I tend to trust the cable manufacturer and then there is a
breaker that would trip. Earth loop impedance wouldn't be a problem
either.

Except under fault conditions, which is exactly what you're looking
for...


--
Frank Erskine

On Sun, 11 Aug 2013 00:29:33 +0100, Frank Erskine
wrote:

On Sat, 10 Aug 2013 23:42:59 +0100, Archibald
wrote:

lots snipped

All the above are beyond the scope of normal DIY work.

Which rather suggests that consumer units etc. are outside the scope
of DIY... (be careful here!)


They are at the input side. Anyone disconnecting the device or
working on the input would have a live set of meter tails to deal
with.

Diagnosis of problems within the unit is straightforward and wouldn't
normally call for test equipment anyway.
The original

post referred to a Megger and earth testing. Both these tests can be
completed with a DMM and a few additional "off the shelf" items.

For DIY work I would think a DMM is the best approach.

Only if the user is aware of possibly misleading indications of a high
input-impedance meter :-)

Let the user beware! Avo sevens went out the window years back, so
very few meters now present much of a load. Seriously though I got
caught out on this one myself using a two cable LED "prodder" bought
from CEF. I stuck the thing on a known "dead" cable just to be sure
that I could get stuck in with the screwdriver and to my surprise it
was live. After stripping back the trunking and cursing the moron that
had numbered the cables I found it was simply open circuit at both
ends. Capacative pick up from an adjacent cable had lit the
appropriate number of LEDs up.

I never associated a "prodder" with sensitivity, but now I know!

A second little snag [reading 100V on a 110V supply derived from the
55V and center tap of a transformer] saw the thing consigned to the
bin! My fault, the next LED up from 50V was 100V, this wiring error
was a first for me, so I wasted a lot of time looking for obscure
instrumentation problems! The electrician must have had an off day on
that project as we had turned out hundreds with the correct supply!

Personally I
have never felt the need to do an insulation check using high voltage
anyway. I tend to trust the cable manufacturer and then there is a
breaker that would trip. Earth loop impedance wouldn't be a problem
either.

Except under fault conditions, which is exactly what you're looking
for...

The most common fault is a tripping breaker supplying a heating
element. The most simple diagnostic tool is the breaker itself.
Disconnection removes the fault and stops the tripping. Even with a
Megger disconnection of the element would have to be carried out at
some point.

More obscure faults can also be found in the same fashion, just
disconnect until the tripping stops. Then mop up the puddle!

Earth loop impedance would need a little more than a DMM if you didn't
want to superglue the breakers :-), but I have more than enough
confidence in a few more basic checks to ensure that my earting is
safe and the RCD picks up the problem.

AB

On 10/08/2013 23:42, Archibald wrote:
On Sat, 10 Aug 2013 16:31:04 +0100, John Rumm

I have yet to find a job that my Wickes DMM wasn't suitable for
and that includes for professional use. In fact the only problem I
might have on a site is the use of a "not calibrated for indication
only" label. Apart from this it is an acceptable tool!

So how do you do an insulation resistance test with it?

A RCD ramp test?

How do you time the RCD trip time?

A Non tripping ELI measurement?

How about accurate low ohms measurements of R1+R2 loops etc?

All the above are beyond the scope of normal DIY work.

For the complete bodge artist, perhaps. For those who want to see jobs
done to a proper standard, they are certainly not beyond the scope.

The original
post referred to a Megger and earth testing. Both these tests can be
completed with a DMM and a few additional "off the shelf" items.

Off the shelf 500V sources? What did you have in mind, a microwave oven?

For DIY work I would think a DMM is the best approach. Personally I
have never felt the need to do an insulation check using high voltage
anyway. I tend to trust the cable manufacturer and then there is a
breaker that would trip. Earth loop impedance wouldn't be a problem
either.

That is an enlightening paragraph. Not sure there is much I can say really.

RCD testing is taking things to ridiculous levels. If I had access to

RCD testing is a *requirement* of the wiring regs. If you are installing
one, or checking the operation of one, you need the right test gear.
RCDs can and do fail.

Have you not read the multitude of nuisance trip posts on this group?

Do you not suppose having the kit to test the thing might actually
prove rather useful to the DIYer? It will cost less than getting an
electrician in to play hunt the fault.

the equipment to test the things, I wouldn't bother anyway. I couldn't
certify the tests so there wouldn't be a lot of point doing more than
a button press.

Yea sorry, I was coming at this from the engineering perspective that
the purpose of testing is to make sure that the stuff actually works
correctly and is safe, not from the pointy capped perspective of making
sure all the paperwork lines up.

Your standards may well be different to mine.

I can't see much scope for measurement of current during DIY wiring
work. If you do need to measure mains current draw then you are much
better off with a clamp meter in the first place.

Read the "operator error" bit.

However I bet even your entry level Fluke will contain at least some
input protection, have shielded compartments round the probe sockets and
MOVs on the board etc, so if you accidentally stick it on mA or Ohms and
then connect it across your main incomer terminals, its less likely to
blow up in your face. The moral here is you get what you pay for,

I dont recollect ever needing to check incomer Volts. A quick jab on
the RCD test button saves getting the meter out.

A moment ago you said you could do ELI checks with a DMM. How were you
proposing to do those without also measuring the supply voltage?

I find it amazing that entire streets are not going down due to these
"transients".

Do you sell extension sockets or UPS for a living BTW?

Not generally. However looking at the logs from a UPS can be quite
enlightening. I have seen some (in a domestic, rural installation) where
transients in excess of 1kV occur several times every day, along with
other disruptions such as sags and brownouts. (the UPS was installed
after transients killed pretty much every major component in their computer)

:-)

Domestic rural! Long cable runs and a few farmers adding their unique
"footprints" to the supply, not too surprising I suppose.

I would have thought a PC power supply was fairly immune though, lots
of ferrite in the thing and a fully wound transformer to produce the
very much lower Voltage. I suppose there can be more than the one
obvious route into the thing though.

Indeed - it had suffer several serial failures of different bits, before
on one occasion suffering a dead PSU, mobo, and optical drive in one
hit. Fortunately the only surviving bits included the HDD (which I
cloned and replaced anyway).



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sun, 11 Aug 2013 15:01:10 +0100, John Rumm
wrote:

On 10/08/2013 23:42, Archibald wrote:
On Sat, 10 Aug 2013 16:31:04 +0100, John Rumm

I have yet to find a job that my Wickes DMM wasn't suitable for
and that includes for professional use. In fact the only problem I
might have on a site is the use of a "not calibrated for indication
only" label. Apart from this it is an acceptable tool!

So how do you do an insulation resistance test with it?

A RCD ramp test?

How do you time the RCD trip time?

A Non tripping ELI measurement?

How about accurate low ohms measurements of R1+R2 loops etc?

All the above are beyond the scope of normal DIY work.

For the complete bodge artist, perhaps. For those who want to see jobs
done to a proper standard, they are certainly not beyond the scope.

Rubbish, get real! I doubt even a lot of professionals would test at
this level if they didn't have to certify their work.

The original
post referred to a Megger and earth testing. Both these tests can be
completed with a DMM and a few additional "off the shelf" items.

Off the shelf 500V sources? What did you have in mind, a microwave oven?

Oh dear! we're not too good at lateral thinking are we?


For DIY work I would think a DMM is the best approach. Personally I
have never felt the need to do an insulation check using high voltage
anyway. I tend to trust the cable manufacturer and then there is a
breaker that would trip. Earth loop impedance wouldn't be a problem
either.

That is an enlightening paragraph. Not sure there is much I can say really.

RCD testing is taking things to ridiculous levels. If I had access to

RCD testing is a *requirement* of the wiring regs. If you are installing
one, or checking the operation of one, you need the right test gear.
RCDs can and do fail.



Er there is a test button, or hadn't you noticed?

Have you not read the multitude of nuisance trip posts on this group?

Yes, are you suggesting they all rush out and buy the kit to test the
things? Get with it!

Do you not suppose having the kit to test the thing might actually
prove rather useful to the DIYer? It will cost less than getting an
electrician in to play hunt the fault.

Er let me see, what does an RCD cost, how long to replace? I would
imagine the electricians first visit would involve a brief appraisal
of the load, the likely cable route, followed by a swop of the RCD to
see what happens.

Anyway testing for a tripping RCD wouldn't need any form of equipment
in most cases. What happens when the intermittent RCD is due to an
internal DJ or some temperature related parameter?

If you care to ask anyone that does engage in faultfinding, I think
you will find that the answer to most intermittents does not lie in
the ability to test the items characteristics at any given time. The
clue is in the words "nuisance tripping".


the equipment to test the things, I wouldn't bother anyway. I couldn't
certify the tests so there wouldn't be a lot of point doing more than
a button press.

Yea sorry, I was coming at this from the engineering perspective that
the purpose of testing is to make sure that the stuff actually works
correctly and is safe, not from the pointy capped perspective of making
sure all the paperwork lines up.

That is the reason for most testing. Have a look around a few new
industrial installations sometime and see how far the rules are
followed, yet every one has all the documentation signed off and
catalogued before I'm let loose on it!


Your standards may well be different to mine.

No! Apart from the odd PAT test I certify nothing. Anything I do
certify is "by the book" and also safe to use.


I can't see much scope for measurement of current during DIY wiring
work. If you do need to measure mains current draw then you are much
better off with a clamp meter in the first place.

Read the "operator error" bit.

However I bet even your entry level Fluke will contain at least some
input protection, have shielded compartments round the probe sockets and
MOVs on the board etc, so if you accidentally stick it on mA or Ohms and
then connect it across your main incomer terminals, its less likely to
blow up in your face. The moral here is you get what you pay for,

I dont recollect ever needing to check incomer Volts. A quick jab on
the RCD test button saves getting the meter out.

A moment ago you said you could do ELI checks with a DMM. How were you
proposing to do those without also measuring the supply voltage?

If you know the current, and know the resistance.... It's called Ohms
Law.

I didn't say I could do the checks with a DMM, read the post!


I find it amazing that entire streets are not going down due to these
"transients".

Do you sell extension sockets or UPS for a living BTW?

Not generally. However looking at the logs from a UPS can be quite
enlightening. I have seen some (in a domestic, rural installation) where
transients in excess of 1kV occur several times every day, along with
other disruptions such as sags and brownouts. (the UPS was installed
after transients killed pretty much every major component in their computer)

:-)

Domestic rural! Long cable runs and a few farmers adding their unique
"footprints" to the supply, not too surprising I suppose.

I would have thought a PC power supply was fairly immune though, lots
of ferrite in the thing and a fully wound transformer to produce the
very much lower Voltage. I suppose there can be more than the one
obvious route into the thing though.

Indeed - it had suffer several serial failures of different bits, before
on one occasion suffering a dead PSU, mobo, and optical drive in one
hit. Fortunately the only surviving bits included the HDD (which I
cloned and replaced anyway).


A wise decision. I like the thought of a logger, though.

I recently had a problem with an instrumentation feed. 110V and the
Voltage was spot on every time I measured it. Clients supply, so it
was outside my hands to investigate.
All the 110V stuff and a lot of the 24V stuff, HMI, CPU, I/O
cards and metering equipment had failed over the years. All I could do
was replace the duff equipment which was most of what was on the PLC
rack this time and fit a mains conditioner from RS. I did think about
going for a UPS, but at one time it was difficult getting the client
to appreciate there was a site problem.


Incidentally I remember commissioning the job a number of years back,
and it was a constant fight with the electricians to cable the signal
wiring properly, they had no concept of grounding and in desperation
once, I went to B&Q to get some TV coax downlead just to demonstrate
that my bits worked and their wiring wasn,t fit for puprpose. They
never did wire it properly, when I last looked at the field wiring
they had used twisted pairs to replace the original multicore SWA.

I know for a fact that these people must have had every bit of test
documentation in place before departing or the project would not be in
the hands of the current owners!

AB

On Sunday, 11 August 2013 16:01:10 UTC+2, John Rumm wrote:

A moment ago you said you could do ELI checks with a DMM. How were you

proposing to do those without also measuring the supply voltage?

Excuse me butting in here, gentlemen, but i've been trying to follow this argument with some difficulty as a non electrician. What do you mean by "ELI"?
To me that refers to the phase difference between voltage and current in an inductor which cannot be measured by a mere multimeter AFAIK. Clarification please!

On 11/08/2013 16:05, wrote:
On Sunday, 11 August 2013 16:01:10 UTC+2, John Rumm wrote:

A moment ago you said you could do ELI checks with a DMM. How were
you

proposing to do those without also measuring the supply voltage?

Excuse me butting in here, gentlemen, but i've been trying to follow
this argument with some difficulty as a non electrician. What do you
mean by "ELI"? To me that refers to the phase difference between
voltage and current in an inductor which cannot be measured by a mere
multimeter AFAIK. Clarification please!

Apologies, I thought it had been spelled out earlier in the thread, but
it may not have been.

ELI = Earth Loop Impedance (aka Earth Fault Loop Impedance, and Zs)

When you have a fault to earth (i.e. a short circuit between line and
earth), the current that will flow (the Fault Current or Earth Fault
Current) will be limited only by the ELI.

This will be the sum of the impedance of the supply itself as presented
at your house, the external impedance of the earth connection provided
(Ze), plus the resistance of all the wiring between your consumer unit
and the location of the fault.

The ELI is a fundamental metric that you need to know when carrying out
circuit modifications / installations. You can estimate it by
calculation, but this may constrain your design somewhat since you may
have to assume a much larger Ze than is actually present. So its better
to actually measure it with a loop impedance meter.

If the ELI rises too high, then you may not get sufficient fault current
to open the protective device quickly enough[1] to give adequate shock
protection, or adequate fire protection. If the ELI is very low at the
fault, then you may need to consider if the fault current actually
exceeds the breaking capacity of the circuit protective device itself.


[1] For example, a B32 MCB will require a fault current of 160A to
operate in the "instant" part of its trip curve.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sun, 11 Aug 2013 16:49:17 +0100, John Rumm
wrote:

On 11/08/2013 16:05, wrote:
On Sunday, 11 August 2013 16:01:10 UTC+2, John Rumm wrote:

A moment ago you said you could do ELI checks with a DMM. How were
you

proposing to do those without also measuring the supply voltage?

Excuse me butting in here, gentlemen, but i've been trying to follow
this argument with some difficulty as a non electrician. What do you
mean by "ELI"? To me that refers to the phase difference between
voltage and current in an inductor which cannot be measured by a mere
multimeter AFAIK. Clarification please!

Apologies, I thought it had been spelled out earlier in the thread, but
it may not have been.

ELI = Earth Loop Impedance (aka Earth Fault Loop Impedance, and Zs)

When you have a fault to earth (i.e. a short circuit between line and
earth), the current that will flow (the Fault Current or Earth Fault
Current) will be limited only by the ELI.

This will be the sum of the impedance of the supply itself as presented
at your house, the external impedance of the earth connection provided
(Ze), plus the resistance of all the wiring between your consumer unit
and the location of the fault.

The ELI is a fundamental metric that you need to know when carrying out
circuit modifications / installations. You can estimate it by
calculation, but this may constrain your design somewhat since you may
have to assume a much larger Ze than is actually present. So its better
to actually measure it with a loop impedance meter.

If the ELI rises too high, then you may not get sufficient fault current
to open the protective device quickly enough[1] to give adequate shock
protection, or adequate fire protection. If the ELI is very low at the
fault, then you may need to consider if the fault current actually
exceeds the breaking capacity of the circuit protective device itself.


[1] For example, a B32 MCB will require a fault current of 160A to
operate in the "instant" part of its trip curve.

And taking things to their logical conclusion, all those companies
selling extention reels without the appropriate test equipment and
safety notices should be prosecuted for negligence :-)

AB

Archibald wrote:
On Sun, 11 Aug 2013 16:49:17 +0100, John Rumm
wrote:

On 11/08/2013 16:05, wrote:
On Sunday, 11 August 2013 16:01:10 UTC+2, John Rumm wrote:

A moment ago you said you could do ELI checks with a DMM. How were
you

proposing to do those without also measuring the supply voltage?

Excuse me butting in here, gentlemen, but i've been trying to follow
this argument with some difficulty as a non electrician. What do you
mean by "ELI"? To me that refers to the phase difference between
voltage and current in an inductor which cannot be measured by a
mere multimeter AFAIK. Clarification please!

Apologies, I thought it had been spelled out earlier in the thread,
but it may not have been.

ELI = Earth Loop Impedance (aka Earth Fault Loop Impedance, and Zs)

When you have a fault to earth (i.e. a short circuit between line and
earth), the current that will flow (the Fault Current or Earth Fault
Current) will be limited only by the ELI.

This will be the sum of the impedance of the supply itself as
presented at your house, the external impedance of the earth
connection provided (Ze), plus the resistance of all the wiring
between your consumer unit and the location of the fault.

The ELI is a fundamental metric that you need to know when carrying
out circuit modifications / installations. You can estimate it by
calculation, but this may constrain your design somewhat since you
may have to assume a much larger Ze than is actually present. So its
better to actually measure it with a loop impedance meter.

If the ELI rises too high, then you may not get sufficient fault
current to open the protective device quickly enough[1] to give
adequate shock protection, or adequate fire protection. If the ELI
is very low at the fault, then you may need to consider if the fault
current actually exceeds the breaking capacity of the circuit
protective device itself.


[1] For example, a B32 MCB will require a fault current of 160A to
operate in the "instant" part of its trip curve.

And taking things to their logical conclusion, all those companies
selling extention reels without the appropriate test equipment and
safety notices should be prosecuted for negligence :-)

No:-) Because the extention lead (in most cases) is protected by a BS1362
13A fuse and not a 32A MCB.

--
Adam

On Sunday, 11 August 2013 17:49:17 UTC+2, John Rumm wrote:
[...]

Thanks, John. In the electronics universe which I spend a good deal of time inhabiting, there is a mneumonic "ELI the ICE man" which prompted my query.

Take a butcher's: http://www.electronicstheory.com/html/e101-31.htm

On 11/08/2013 18:12, Archibald wrote:
On Sun, 11 Aug 2013 16:49:17 +0100, John Rumm
wrote:

If the ELI rises too high, then you may not get sufficient fault current
to open the protective device quickly enough[1] to give adequate shock
protection, or adequate fire protection. If the ELI is very low at the
fault, then you may need to consider if the fault current actually
exceeds the breaking capacity of the circuit protective device itself.


[1] For example, a B32 MCB will require a fault current of 160A to
operate in the "instant" part of its trip curve.

And taking things to their logical conclusion, all those companies
selling extention reels without the appropriate test equipment and
safety notices should be prosecuted for negligence :-)

Not if the lead has a BS1361 fused plug on the end... but it is one of
the reasons you should not go daisy chaining multiple leads.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sun, 11 Aug 2013 18:21:57 +0100, "ARW"
wrote:

Archibald wrote:
Snip

And taking things to their logical conclusion, all those companies
selling extention reels without the appropriate test equipment and
safety notices should be prosecuted for negligence :-)

No:-) Because the extention lead (in most cases) is protected by a BS1362
13A fuse and not a 32A MCB.

Deep joy & happiness, all is well with the world :-)

http://wiki.diyfaq.org.uk/index.php?title=Fuse

In my opinion cable drums present a far more tangible risk of danger,
yet they are freely on sale with only scant regard to warning people
of the hazards.

A fuse has a response delay also. Methinks there is an argument for
ensuring that the protective device on these things undergos a
functional check at the point of sale. The storage system should be
changed also. Optimum safety will only ensue when cables are sold in
rectangular boxes of length equalling that of the required extention,
with ventilation slots of course :-)


Seriously I have seen an"Asda special" after it was used to power a
2KW heater. It wasn't a nice sight.

AB

On Sat, 10 Aug 2013 11:06:59 +0100, Archibald wrote:

The other point you may care to consider is that many " professional"
meters The Flukes I used included, do not have a fuse for the higher
current ranges.

Care to name the model number?

On a final note, I consider one of the most serious ommissions from
any meter now is the crock clip.

There are plenty of croc clips available that meet the requirements of IEC 61010
at various levels

For instance these are CAT III 1000V and CAT IV 600V rated

http://uk.farnell.com/fluke/ac175/set-crocodile-clip-threaded-1kv/dp/2310392
http://www.farnell.com/datasheets/1720308.pdf


--

On Thursday, 8 August 2013 15:19:35 UTC+1, dennis@home wrote:
On 08/08/2013 11:40, tony sayer wrote:



Anyway i'm just being practical. The spec on a Wickes meter is more

than adequate for my work. I could destroy it, or a Fluke for that

matter in an instant. Whats wrong with the cable on a Wickes meter

incidentally? What was wrong with the insulation on a two for four

quid Maplin DMM by the way. What is so critical about the rating of

the cables and what do I look for when buying same?

Well we need a meter for field use that can handle measurement of very

small currents and voltages and at the same time can check the incoming

mains supplies which are very "stiff" and I wouldn't like to trust a 10

quid or otherwise device across that sort of power!. Its quite easy to

forget to take the leads of the amps measurement range when your

checking three phase supplies;!.



I expect this will be fine for most DIY use.



http://www.lidl.co.uk/cps/rde/SID-AF...l&id=4807&ar=3



"Reads voltage, electricity and resistance"


Oh look it reads electricity ????? always wanted to read that.

On Mon, 12 Aug 2013 13:14:20 +0100, The Other Mike
wrote:

On Sat, 10 Aug 2013 11:06:59 +0100, Archibald wrote:

The other point you may care to consider is that many " professional"
meters The Flukes I used included, do not have a fuse for the higher
current ranges.

Care to name the model number?

Sorry I bought my last Fluke around fifteen years back, I don't
remember the model number. I know for a fact that the thing wasn't
fused on the higher current range, because it didn't have one. I would
have bought it from Farnell with only a scant bit of attention to the
specs.. Well a DMM is a DMM and for £70-00 or thereabouts One expects
a current range. The pile of junk didn't have one. It went in the bin,
it wasn't worth the space in my toolbox. Prior to this I have had
models that needed the fuse replacing and I know they were less than
10.0 A

The only meters I owned that I could name were the Avo 7 and Avo 8,
none of the others were quite so notable!

On a final note, I consider one of the most serious ommissions from
any meter now is the crock clip.

There are plenty of croc clips available that meet the requirements of IEC 61010
at various levels

For instance these are CAT III 1000V and CAT IV 600V rated

http://uk.farnell.com/fluke/ac175/set-crocodile-clip-threaded-1kv/dp/2310392
http://www.farnell.com/datasheets/1720308.pdf

Crock clips were invariably supplied with meters once, they were not
extras that you find you need halfway through a job.

IMHO holding a pair of probes in contact with two conductors of
considerable potential difference should be discouraged to the point
where two hand held prods are to be ordered as an extra, not the crock
clip! Better still make them half a meter long and incorporate a
resistor chain in each for those who insist on prodding bus bars & the
like.

AB

On 12/08/2013 02:46, Archibald wrote:
On Sun, 11 Aug 2013 18:21:57 +0100, "ARW"
wrote:

Archibald wrote:
Snip

And taking things to their logical conclusion, all those companies
selling extention reels without the appropriate test equipment and
safety notices should be prosecuted for negligence :-)

No:-) Because the extention lead (in most cases) is protected by a BS1362
13A fuse and not a 32A MCB.

Deep joy & happiness, all is well with the world :-)

http://wiki.diyfaq.org.uk/index.php?title=Fuse

In my opinion cable drums present a far more tangible risk of danger,
yet they are freely on sale with only scant regard to warning people
of the hazards.

A fuse has a response delay also. Methinks there is an argument for
ensuring that the protective device on these things undergos a
functional check at the point of sale. The storage system should be
changed also. Optimum safety will only ensue when cables are sold in
rectangular boxes of length equalling that of the required extention,
with ventilation slots of course :-)


Seriously I have seen an"Asda special" after it was used to power a
2KW heater. It wasn't a nice sight.

It needs a label: "instructions written on other end of the flex".


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Mon, 12 Aug 2013 05:52:54 -0700 (PDT), whisky-dave
wrote:

On Thursday, 8 August 2013 15:19:35 UTC+1, dennis@home wrote:

http://www.lidl.co.uk/cps/rde/SID-AF...l&id=4807&ar=3



"Reads voltage, electricity and resistance"


Oh look it reads electricity ????? always wanted to read that.

I suspect it lost something in the translation from Chinese to German to English


--

On Mon, 12 Aug 2013 19:35:25 +0100, John Rumm
wrote:

On 12/08/2013 02:46, Archibald wrote:
On Sun, 11 Aug 2013 18:21:57 +0100, "ARW"
wrote:

Archibald wrote:
Snip

And taking things to their logical conclusion, all those companies
selling extention reels without the appropriate test equipment and
safety notices should be prosecuted for negligence :-)

No:-) Because the extention lead (in most cases) is protected by a BS1362
13A fuse and not a 32A MCB.

Deep joy & happiness, all is well with the world :-)

http://wiki.diyfaq.org.uk/index.php?title=Fuse

In my opinion cable drums present a far more tangible risk of danger,
yet they are freely on sale with only scant regard to warning people
of the hazards.

A fuse has a response delay also. Methinks there is an argument for
ensuring that the protective device on these things undergos a
functional check at the point of sale. The storage system should be
changed also. Optimum safety will only ensue when cables are sold in
rectangular boxes of length equalling that of the required extention,
with ventilation slots of course :-)


Seriously I have seen an"Asda special" after it was used to power a
2KW heater. It wasn't a nice sight.

It needs a label: "instructions written on other end of the flex".

:-)

Nice One! LOL


AB

On Monday, 12 August 2013 14:52:54 UTC+2, whisky-dave wrote:
On Thursday, 8 August 2013 15:19:35 UTC+1, dennis@home wrote:

On 08/08/2013 11:40, tony sayer wrote:







Anyway i'm just being practical. The spec on a Wickes meter is more



than adequate for my work. I could destroy it, or a Fluke for that



matter in an instant. Whats wrong with the cable on a Wickes meter



incidentally? What was wrong with the insulation on a two for four



quid Maplin DMM by the way. What is so critical about the rating of



the cables and what do I look for when buying same?



Well we need a meter for field use that can handle measurement of very



small currents and voltages and at the same time can check the incoming



mains supplies which are very "stiff" and I wouldn't like to trust a 10



quid or otherwise device across that sort of power!. Its quite easy to



forget to take the leads of the amps measurement range when your



checking three phase supplies;!.







I expect this will be fine for most DIY use.







http://www.lidl.co.uk/cps/rde/SID-AF...l&id=4807&ar=3







"Reads voltage, electricity and resistance"





Oh look it reads electricity ????? always wanted to read that.

Yeah, it reads the meter and tells you what you're electricity bill is going to be. A "smart meter" indeed.

On Mon, 12 Aug 2013 19:25:17 +0100, Archibald wrote:

On Mon, 12 Aug 2013 13:14:20 +0100, The Other Mike
wrote:

On Sat, 10 Aug 2013 11:06:59 +0100, Archibald wrote:

The other point you may care to consider is that many " professional"
meters The Flukes I used included, do not have a fuse for the higher
current ranges.

Care to name the model number?

Sorry I bought my last Fluke around fifteen years back, I don't
remember the model number. I know for a fact that the thing wasn't
fused on the higher current range, because it didn't have one. I would
have bought it from Farnell with only a scant bit of attention to the
specs.. Well a DMM is a DMM and for £70-00 or thereabouts One expects
a current range. The pile of junk didn't have one. It went in the bin,
it wasn't worth the space in my toolbox. Prior to this I have had
models that needed the fuse replacing and I know they were less than
10.0 A

So a meter without a current range didn't have a fuse so you binned it.

Staggering.


--

In article , The Other Mike
scribeth thus
On Mon, 12 Aug 2013 19:25:17 +0100, Archibald wrote:

On Mon, 12 Aug 2013 13:14:20 +0100, The Other Mike
wrote:

On Sat, 10 Aug 2013 11:06:59 +0100, Archibald wrote:

The other point you may care to consider is that many " professional"
meters The Flukes I used included, do not have a fuse for the higher
current ranges.

Care to name the model number?

Sorry I bought my last Fluke around fifteen years back, I don't
remember the model number. I know for a fact that the thing wasn't
fused on the higher current range, because it didn't have one. I would
have bought it from Farnell with only a scant bit of attention to the
specs.. Well a DMM is a DMM and for £70-00 or thereabouts One expects
a current range. The pile of junk didn't have one. It went in the bin,
it wasn't worth the space in my toolbox. Prior to this I have had
models that needed the fuse replacing and I know they were less than
10.0 A

So a meter without a current range didn't have a fuse so you binned it.

Staggering.



Indeed. Very wasteful .... Must have money to burn..
--
Tony Sayer

On Monday, 12 August 2013 20:35:25 UTC+2, John Rumm wrote:

It needs a label: "instructions written on other end of the flex".





--

Cheers,



John.





Clever!

On Sat, 10 Aug 2013 23:42:59 +0100, Archibald
wrote:

Not generally. However looking at the logs from a UPS can be quite
enlightening. I have seen some (in a domestic, rural installation) where
transients in excess of 1kV occur several times every day, along with
other disruptions such as sags and brownouts. (the UPS was installed
after transients killed pretty much every major component in their computer)

:-)

Domestic rural! Long cable runs and a few farmers adding their unique
"footprints" to the supply, not too surprising I suppose.

I would have thought a PC power supply was fairly immune though, lots
of ferrite in the thing and a fully wound transformer to produce the
very much lower Voltage. I suppose there can be more than the one
obvious route into the thing though.

You'd be wrong.