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Power - Earth-RCD's- ISO/TX's and workshops.

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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Red to black » Wed Feb 20, 2013 2:52 am

The Thing is refugee,

The regs are convoluted, and often refer to another reg somewhere else, and this can give conflicting information at times.
It is important that one section of the regs are not taken in isolation (pun not intended), they are co-dependent on other regs elsewhere in the big book.

You could ask 10 good sparks the same question and get 10 different answers. :omg:

The subjects at hand are quite complicated, and another thing that does not help is that this particular (latest) subject is way off the beaten track, and is highly specialised, and it is rarely taught in electrical courses, it is merely touched upon and briefly skimmed past. A lot of good electricians don't understand it either, certainly your average domestic/commercial spark won't, and unless you have either experience and/or good guidance in this field, then it is so easy to get this wrong.(I don't profess to know all of it either)
This is about as far away from normal electrical practices as it is just about possible to get.
It is hardly a typical everyday electrical installation.

As I said earlier, some of the things implemented goes against conventional teachings, wisdom and experience, and can be highly counter intuitive, certain parts of it can go against the very grain of everything most technical people think as normal.

Don't forget an electronics repair workshop is one of the few places that exposed live parts are the norm, rather than the exception.

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Refugee » Wed Feb 20, 2013 3:33 am

I fully agree that the regulations are written so that you have to shuttle back and forth in order to make use of them. A good browser with loads of bookmarks is needed.
Single isolating transformer workshops need a lot of space for the guard zones around the benches and so on. This requires a big building and a big budget for the specialists.
Larger companies will set them up as they look impressive and they are prepared to give the extra training for the engineers.
Single transformer benches are more practical for small workshops and home set ups and do not require a great deal of training to use them.
In the place where I worked the management were aware that TV engineers required isolating transformers and scopes and otherwise had no electrical training.
It was set up in the 1970s.
They had good intentions but did not know how specialised the task was.

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Terrykc » Wed Feb 20, 2013 12:24 pm

Murphyv310 wrote:... There actually was diagrams on the HSE website (2001) on how various different TV workshops should be wired from a one man business to large workshops with many benches run from one isolating TX. Perhaps someone good at Googling could find them and post it here.


I found this: http://www.hse.gov.uk/pubns/eis36.pdf

No diagrams but it does say this:

This leaflet contains notes on good practice which are not compulsory but which you may find helpful in considering what you need to do.

Note the 'not compulsory' ...!

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Mark Hennessy » Wed Feb 20, 2013 1:05 pm

Hi Terry,

As your post arrived, I was simultaneously reading through EIS36 as well. Great minds :=D

But, nothing in there that really helps...

I've spent a fair amount of time searching for information about earth-free environments, and so-far have found surprisingly little. I don't know if this lack of information is in some way indicative of the current attitude to it?

I've been thinking about this a lot, and simply can't reconcile the practice. For example, here is a really simple question:

If you are working in an earth-free environment, with insulated floors, benches and equipment that has been designed to work safely this way, then why do you need an isolation transformer at all? Especially if you are sharing it between multiple benches?

The advice I've quoted is very clear and extremely easy to understand and implement; it doesn't require special test equipment or unsafe practices like lifting earth connections of Class 1 equipment. Whereas the idea of sharing a large isolation transformer between many benches, even if they are "earth free" and out of reach of each other, makes no obvious sense to me so far. Are there economies of scale with the purchasing of the transformer - even when the additional cost of making the workstations and equipment earth-free are considered? What happens when you need to use a specialised piece of test gear that isn't available in an earth-free version? What am I missing with this?

All the best,

Mark

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Red to black » Wed Feb 20, 2013 2:20 pm

Hi Mark,
Where earth free and non conducting locations are concerned then electrical seperation becomes an additional protective measure, not the sole protective measure.

Non conducting locations is one specific term

Earth free local equipotential bonding is the other.

Nowhere in the regs suggests not connecting the earth (more correctly the cpc) on a class 1 piece of equipment with the proviso.

i) it is earthed on normal mains.
ii) it is still connected but not actually earthed when using an isolated supply, to supply the test equipment in both 413 and 418 regs, in the case of the 418 it specifically states it has to be present and is used as a bonding conductor but not earthed.

I will post the Earth free local equipotential bonding regs in a bit.

I think you are mixing this up, possibly with the old service engineers bodge when they did not have an iso tx. :thumbl:

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Mark Hennessy » Wed Feb 20, 2013 2:46 pm

Hi R2B,

You're obviously across the wiring regs - I don't claim to be - but I'm just trying to think things through from first principles...

All of this is a "layer" sitting on top of the wiring regs. The regs get me some nice standard RCD-protected outlets in my workshop; now I need to install supplementary equipment to provide the facilities I need. I think of the bench as an appliance; perhaps I'm wrong, but it explains why the regs appear to be pretty vague about this specific topic.

The shocking (sorry!) idea of lifting the Earth connections of Class 1 test equipment was not raised by me; it appears to be the practice when people are sharing large isolation transformers in earth-free environments. If the earth was left in place, then large fault currents could flow between different pieces of test equipment on different benches, depending on what each engineer was doing.

We all know that the Earth connection on an item of Class 1 equipment is to protect the end user in the event of an internal fault that puts mains Live in contact with the case. With a nice low earth impedance, a large current will flow and take out the fuse - with the case of the item staying at a nice and safe potential. With a moderate earth impedance - e.g. a TT supply - the mandatory RCD provides the protection. Of course, now that RCDs are pretty universal, the RCD normally opens before the fuse.

So, supplying a Class 1 item of test equipment via an isolation transformer might mitigate the risk of a Live-case fault in the test gear. But...

1. That's not what seems to happening in these setups, based on the data posted here.
2. If you're doing that, why not just use the isolation transformer for the DUT?

And that takes me back to square 1, collecting another £200 as I go :=D

Cheers,

Mark

PS: Thanks for posting the extracts - they are very interesting :thumbl:

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Michael Watterson » Wed Feb 20, 2013 3:00 pm

I think for people at home or working in a small way we need the KISS principle.

1) If test equipment has a 3 core cable or metal work connected to the "signal" common it should connect to the mains earth.

2a) Each device under test that doesn't have built in isolation should have its own isolation transformer. The secondary should not be earthed on either wire, but there ideally can be a mains earth terminal post to connect to the part of the DUT that will be regarded as "signal" earth for the test gear.

2b) If equipment normally isolated by a SMPSU is having work done on the PSU unit / section is should be treated as "2a". If the SMPSU is exposed (like Set top box or DVD player, not like PC with SMPSU in a separate cabinet) then also an isolation transformer is recommended.

isolation_mistake.png
isolation_mistake.png (6.33 KiB) Viewed 3679 times


In the example EVEN if the scope is isolated you will destroy the bridge.
You don't need a 1KVA transformer.
One for the highest wattage device and one maybe smaller. Are you likely to ever be working on more than two "live" circuits at once?

Stick to ONE isolation transformer per device under test(DUT).
Optionally earth the point on the DUT that will be "signal Common" before connecting test gear.
Never use test gear with an earth lifted (or on an isolation transformer unless you really understand why you would do this).
Treat EVERYTHING with more than 40V as potentially lethal, Treat Isolated by transformer "DUT" like any 500V circuit.
Remember even a 220V HT radio with its own transformer has easily over 700V peak to peak across a centre tapped winding for dual rectifier fullwave.

With sweaty hands 50V can kill.

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Terrykc » Wed Feb 20, 2013 3:08 pm

I'm very puzzled by the constant references in this thread to isolating transformers feeding multiple bench positions.

As soon as two (or more) items are connected to it, it is no longer an isolated supply!

Worse still, unlike the mains supply where the neutral is bonded to earth, either side of the transformer secondary can be earthed by the connection of test equipment and the side of this supply which is earthed can vary from time to time as different people connect and disconnect test gear.

I cannot conceive of a more lethal arrangement, especially as we are talking, in general, about the days before ELCBs were widely used - I'm not even sure they'd been invented, to be honest.

I can check with a meter that the chassis of a live chassis receiver is connected to earth, via the neutral main and, barring sets with non-polarised connectors, know for certain that whatever I do, the chassis is connected to earth and nothing can alter that fact.

If I am using a so called isolated supply that anybody else has access to, all bets are off ...

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Mark Hennessy » Wed Feb 20, 2013 3:17 pm

Hi Jeffrey,

ppppenguin wrote:It does make you wonder why so much testgear was (still is?) Class 1.


I think it's partly performance (noise pickup) and simplicity (as adding extra measures to make it qualify as Class 2, then getting it certified as such, obviously costs)



There's no problem with metal cases and exposed metal parts on Class 2 kit provided that the mains bits are adequately insulated from anything accessible to the user.

Am I right in thinking that Class 2 kit is not allowed to to have an earth connection via the mains cable? Obviously you can locally bond the case of Class 2 kit to anything you like, that happens willy nilly if you plug (say) a Class 2 freeview box into a Class 1 amplifier.


The difference between Class 1 and Class 2 is simply that Class 1 must be earthed to prevent the case becoming live in fault conditions. Class 2 gear has (or should have!) measures such that a single failure can't cause the case to become live.

I don't see a problem with earthing Class 2 gear - as you say, it often happens when you connect items together. It's just that it's not required for safety reasons.

When I first joined the BBC, engineers used to convert domestic gear (e.g. office hi-fi systems) from Class 2 to Class 1 by adding 3-core mains leads, and install sheets of Paxolin between PCBs and casework to guarantee safety. Probably a little overboard, and caused the occasional hum-loop with audio gear. Not done any more to my knowledge.



When we are naughty and lift the earth on a scope (hands up all those who have never done it - didn't see many raised) we are treating that scope as if it were class 2. The risk of an insulation failure in the mains transformer of a decent quality scope is pretty slim so we get away with it.


I've never done it. Back in my childhood workshop, I was aware that the half-mains chassis of a Philips K30 (the set that cost me my A-levels!) had quite a bite. My 'scope - a Telequipment DM63 - is largely metal in construction. The knobs were plastic, but had metal grub screws. When you press the buttons, it's easy to touch the front panel at the same time. Even at that age, I knew not to go there...

And that's the problem. The 'scope might be quite happy, and the risk of a failure from inside the 'scope itself is probably pretty low, but the metalwork of the 'scope is now at some arbitrary and indeterminate voltage above mains Earth because in the scenarios that Trevor is describing (at Sony and Brands), you're sharing the secondary of the isolating transformer with your colleagues. And while you might be in an earth-free environment, would you trust it? Bench tops get damaged, painted metal gets scratched, floors might be damp, basement workshops can be very humid, contractors doing work might not understand the system. All fairly minimal risks, sure, but for the sake of a single isolating transformer per bench, I simply can't see why anyone would risk it.

All the best,

Mark

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Red to black » Wed Feb 20, 2013 3:19 pm

ppppenguin wrote:.

Am I right in thinking that Class 2 kit is not allowed to to have an earth connection via the mains cable? Obviously you can locally bond the case of Class 2 kit to anything you like, that happens willy nilly if you plug (say) a Class 2 freeview box into a Class 1 amplifier.

When we are naughty and lift the earth on a scope (hands up all those who have never done it - didn't see many raised) we are treating that scope as if it were class 2. The risk of an insulation failure in the mains transformer of a decent quality scope is pretty slim so we get away with it.


Hi Jeffery,
The regs don't specifically say that class 2 equipment cannot have a CPC, but why would it ? unless it was a functional Earth.

Mark,
Under the 17th
Supplementary bonding may be ommitted (in domestic) where ALL of the following applies:

i) All final circuits of the location comply with the requirements for ADS (Automatic disconnection of Supply),[ which is normally a fuse/MCB and or RCD etc.,IOW it is the normal method of fault protection in domestic]
ii) all final circuits of the location have additional protection by means of an RCD [30mA]
iii) all oil/gas,water, services, structural steel are bonded as per regs [usually at the main earth terminal at the origin]
What is meant by this, is if the location complies with the latest regs, then supplementary bonding can be ommited, if it is an older install say 16th ed then supplementary bonding may need to be applied

I have simplified the above, but that is the jist of it for domestic. :thumbl:
This is another poorly understood subject and an aspect of things where myths abound. :thumbl:

Outside of domestic supplementary bonding is still a valid protective measure, and is mandatory for certain types of install, hospital operating theatres for one.

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Red to black » Wed Feb 20, 2013 3:41 pm

Yes agree Jeffrey,

I worded that badly :oops: , iii) in the above was meant to refer to the main bonding being up to current regs.

Electricians to this day still argue over aspects of this poorly understood subject. :thumbl:

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Mark Hennessy » Wed Feb 20, 2013 4:29 pm

Hi R2B,

Thanks for the info - all makes senses. I'm not immediately sure how it applies to the specific conversation here - regarding Earth-free workstations sharing a single secondary - but very useful nonetheless.

Thanks also to Michael and Terry. With all due respect to what the HSE recommended at Brands and Sony and no-doubt others, are we in a position to agree that the advice posted by Michael, myself and others is the correct advice that our members should follow?

1. One DUT per transformer secondary.
2. All Class 1 test equipment to be connected to mains earth - earths cannot be lifted.
3. The mains earth should NOT be carried through to the isolated socket.


And that operating multiple DUTs from a single transformer requires complex setup (Earth-free environment, Class 2 test gear) that is unlikely to be practical for a typical enthusiast or small business? And unless someone can explain otherwise, it seems to be in inferior in every regard (apart perhaps from current delivery?) to the simple model.

Don't forget that all other sockets need to have RCD protection that's separate to the lighting circuits (especially if you have a workshop in a cellar - I really must get around to fitting those emergency light fittings!).

All the best,

Mark

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Red to black » Wed Feb 20, 2013 4:52 pm

Right Mark this for you :=D ,
writing in [ ] is mine.
This is not for use in domestic.

418.2 Protection by earth-free local equipotential bonding

This method of protection shall be only used in special circumstances [A professional workshop is one]
Note: Earth-free local equipotential bonding is intended to prevent the appearance of a dangerous touch voltage

418.2.1 All electrical equipment shall comply with one of the provisions for basic protection described in section 416 [ basic insulation of cables, live conductors and enclosures preventing access to live parts]

418.2.2 protective bonding shall interconnect every simultaneously accessible conductive part and extraneous-conductive parts [ think of a Faraday cage]

418.2.3 The local protective bonding shall neither be in electrical contact with Earth directly, nor through exposed-conductive parts, nor through extraneous-conductive parts.
Note: where this cannot be fulfilled, protection by automatic disconnection of supply [ADS] is applicable (see section 411) [ this is a series of regs relating to ADS and trip times etc.]

418.2.4 Precautions shall be taken to ensure that persons entering the equipotential location cannot be exposed to a dangerous potential difference, in particular, where a conductive floor insulated from earth is connected to the earth-free bonding conductors.

418.2.5 Where this measure is applied, a warning notice complying with 514.13.2 [ the protective bonding conductors associated with the electrical installation in this location MUST NOT BE CONNECTED TO EARTH,
Equipment having exposed conductive parts connected to earth must not be brought into this location] shall be fixed in a prominent position adjacent to every point of access to the location concerned.

-----------------------------------------
As you can see when this measure is used in conjunction with the electrical seperation regs, it is a complex setup, usually only large workshops implement this type of scheme, it is to be monitored and under supervision at all times.

This is a vast subject, and is not your normal everyday installation.
I have only added these parts to aid learning and discussion, which is a good thing ;) IMO.
I am not trying to overcomplicate things, it is an interesting subject in it's own right.

Ps. Mark, I only added the supplementary bonding, as you referred to it in one of your earlier posts, and thought you may like the info. :thumbl:

Phew! "£"

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Mark Hennessy » Wed Feb 20, 2013 5:09 pm

Wow - thanks for that R2B :thumbl:

I wonder how commonplace Earth-free working remains today, given the obvious complexity? I can perhaps envisage this being viable in certain scenarios - perhaps test/calibration on a production line, where you only use the same test gear day-in, day-out? Viable, not necessarily better. I wonder how this fits in with anti-static requirements? Not sure I'd want my wrist connected to an "earth" that could be at any potential, even if it comes via a 1M resistor.

For a general workshop, even in a large company, it sounds like a total nightmare.

Thanks again - it's my round "£"

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Red to black » Wed Feb 20, 2013 5:54 pm

In actual fact very few workshops fully implement that level of 'earth free', some Laboratotories might, and maybe huge workshops.

Much more usual is combination of partially earthfree and electrical seperation used together (if that makes sense).

In one small shop that I set up (more or less a single bench), the H&S mush wanted:

any pipe work/radiators to be boxed in and made innaccessable
the aerial to be earth free
All containment and electrical accessories (switches and fixed lighting) in the area to be plastic (including pattress screws).
A thick rubber mat for the area (had to be specially ordered)
it's own earth free supply.
One iso TX for the DUT (seperate from everything else)
and another iso tx for the test equipment, I used a 4-way socket block to be used as the bonding 'strip' so I could plug more than one piece of testing equipment in at a time.

Oh! and a piece of black and yellow demarcation tape across the floor in the workshop doorway.

This was in the early 90's, and so prior to the 17th.

Now I am not saying he is right or wrong, as when these people say "jump" we say how high ? :=D

The previous shop (a few years earlier) was only required to get one iso tx for one DUT, and that was it!

They are a law unto themselves, and what they want is anyones guess, I suppose it depends on what they class it as, or, more likely they don't understand it either ! :O

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Mark Hennessy » Wed Feb 20, 2013 5:55 pm

ppppenguin wrote:Mark's comment about antistatic needs some thought. If I'm conencted via 1M to what is meant to be earth but turns out to be mains it needs 1000V to put 1mA through me. That's both unlikely and harmless. I don't think I'm worried.


I agree that 1mA, or even a quarter of that is probably harmless, but you'd feel it. If nothing else, it might be awfully distracting. As it happens, 0.25mA is the highest "touch current" permissible for Class 2 and hand-held Class 1 devices.

Luckily, static is rarely an issue in my cellar :=D


For vintage work we don't generally need to worry about antistatic. I'm pretty cavalier about it even with modern kit but my bench top is hardboard. This is definitely not a conductor but it's a pretty mediocre insulator that doesn't suffer from static buildup. Recommended as a cheap, confortable and easily replaced work surface.


I thought about hardboard for much the same reason. The trouble was getting a sheet of it down the cellar stairs (bench is 7' by 3'). In the end, I went for solid oak flooring, laid over chipboard "loftboards", which are in turn screwed to four lengths of 4" by 2" joists. The idea of solid wood that would outlast me appeals. I was a bit worried about the chipboard being hygroscopic, but offcuts that have been down here for years seem to be OK. But that's another thread...

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Red to black » Wed Feb 20, 2013 6:03 pm

Having read Jeffrey's and Trevor's replies after I posted,

I agree with both, a single Iso Tx for the one DUT, and everything else as normal, with maybe the supplies to the W/shop RCD'd

This is all you really need for day to day tinkering.

Summed up with such few words, and as Trevor said anything else is madness (and probably not allowed) for a home workshop., also as Jeffrey pointed out the anti static mat is for use in normal circumstances.

Thanks though for a fascinating thread :thumbl:
Last edited by Red to black on Wed Feb 20, 2013 6:06 pm, edited 1 time in total.

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Refugee » Wed Feb 20, 2013 6:06 pm

Red to black wrote:As you can see when this measure is used in conjunction with the electrical seperation regs, it is a complex setup, usually only large workshops implement this type of scheme, it is to be monitored and under supervision at all times.

This is a vast subject, and is not your normal everyday installation.
I have only added these parts to aid learning and discussion, which is a good thing ;) IMO.
I am not trying to overcomplicate things, it is an interesting subject in it's own right.

Ps. Mark, I only added the supplementary bonding, as you referred to it in one of your earlier posts, and thought you may like the info. :thumbl:

Phew! "£"


The "supervision at all times" issue is interesting.
It can be put to the test by simply carrying an extension lead into the workshop. Since this could reach between two work stations. You should be stopped by the supervisor immediately :!:

The static is also interesting too.
If audio equipment is being worked on it may tend to pick up static buzz from the ground plane being floated.
The single transformer setups rely on floating the supply and not the ground plane.

There must be specialist devices that can manage the static effect and it would be interesting if a web site can be found that shows how this is done.

If the floating ground system is used and all work stations are correctly isolated from each other it does raise the question of an isolating transformer being required for anything more than peace of mind.

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Michael Watterson » Wed Feb 20, 2013 6:08 pm

Yes, I have always preferred hardboard laid on worktop. it's Anti static in the Irish / UK climate.

Trevor.
My point is not that someone would deliberately do that, but unless you 100% have the rule that EACH DUT NEVER shares an isolation transformer it will happen inadvertently*. No matter what might have been acceptable in the past or in large companies, the absolute best practice is that each potentially live "common signal" rail Device Under Test (DUT) gets its own isolation transformer.

(* perhaps SMPSU on DVD player / Freeview box and then immediately working on a live chassis 1/2 wave rectified TV, or mains side of a +5v SMPSU for modulator and then a DAC90, it inherently defeats isolation to use transformer with more than one device. )

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Red to black » Wed Feb 20, 2013 6:15 pm

Michael Watterson wrote:Yes, I have always preferred hardboard laid on worktop. it's Anti static in the Irish / UK climate.

Trevor.
My point is not that someone would deliberately do that, but unless you 100% have the rule that EACH DUT NEVER shares an isolation transformer it will happen inadvertently*. No matter what might have been acceptable in the past or in large companies, the absolute best practice is that each potentially live "common signal" rail Device Under Test (DUT) gets its own isolation transformer.

(* perhaps SMPSU on DVD player / Freeview box and then immediately working on a live chassis 1/2 wave rectified TV, or mains side of a +5v SMPSU for modulator and then a DAC90, it inherently defeats isolation to use transformer with more than one device. )

Michael,
Trevor was referring to a professional set up, can I just point you to this bit which refers to exactly what you are asking/pointing out.

This is for more than one item used on a iso Tx

418.3.7 It shall be ensured that if two faults affecting two exposed conductive parts occur and these are fed by conductors of different polarity, a protective device shall disconnect the supply in a disconnection time conforming with table 41.1 [ generally 0.4 seconds for this application]


:thumbl:

 
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Re: Workshop Isolation Transformers & RCD's

Post by GlowingAnode » Wed Feb 20, 2013 6:26 pm

GlowingAnode wrote:Hi Guys, I've joined a little late here, but if I may add a few points.

Section 418.3.7 covers the two fault situation.
However particular importance must be paid to insulation resistance (and impedance!) if any earth fault current is to be limited to a safe value. Mains filters can cause the separated supply to assume a 115-0-115 bias, so it important to use double pole switching on all outlets.

To summarise, you can run more than one device from a separated supply, but this has no real advantage and in some cases may cause a disadvantage.

Rob.


I did mention the two fault situation last night.

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Red to black » Wed Feb 20, 2013 6:29 pm

You did indeed Rob, :thumbl:

You also mentioned the earth free local equipotential bonding too :thumbl:
Which as you correctly pointed out, is to tie everthing together so that there are no potential differences.

I could have done with your help earlier. :O

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by GlowingAnode » Wed Feb 20, 2013 7:16 pm

Ok, thanks Baz.
Nobody's mentioned insulation monitoring devices (pulls pin and runs away!)
Rob.

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Red to black » Wed Feb 20, 2013 7:17 pm

GlowingAnode wrote:Ok, thanks Baz.
Nobody's mentioned insulation monitoring devices (pulls pin and runs away!)
Rob.

Aaaaargh! ;)

 
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Re: Power - Earth-RCD's- ISO/TX's and workshops.

Post by Refugee » Wed Feb 20, 2013 10:42 pm

It was only at the weekend I turned someone away whom wanted a pair of hair tongs repaired.
They cause too many house fires and I will have nothing to do with the things bhbg
It was worse than that if it ever could be.
They were in bits in a plastic carrier bag with parts ripped out of the PCB ::::)

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