V2L

SimonH2 said:

So then you are into a situation where the supply isn't floating, it's earthed at some point. So now it's a "single fault creates a hazard" situation - and the touch voltage is 110V. User picks up a drill that's got a bit damp, has other hand on scaffolding, zap

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As you rightly say a "single fault creates a hazard",

When asked to comment on this the official answer ( such as from pen pushers in a office ) is that the single fault will be detected and the equipment taken out of service.

Have you ever handled live 55V ac circuits, by that I mean stripping cables and terminating them live?


Read more: https://www.diynot.com/diy/threads/v2l.582087/page-4#ixzz7E6S33UWt

I don't work live at any voltage. A friend of mine lost an eye when he shorted a car battery and he was hit by the arc. Hard lesson learned.

scousespark said:

Have you ever handled live 55V ac circuits, by that I mean stripping cables and terminating them live?


Read more: https://www.diynot.com/diy/threads/v2l.582087/page-4#ixzz7E6S33UWt

I don't work live at any voltage. A friend of mine lost an eye when he shorted a car battery and he was hit by the arc. Hard lesson learned.

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No it's something I try to not make a habit of doing, however it's very difficult to fault find with the power off! When working in control panels, working on he ELV sections live can be very hard to avoid. They're usually fused at quite a low current, even if its a massive transformer, like 1KVA @ 24V, requiring a 40A OCD this is usually fused down further to say 6A as most relay contacts are around that figure and allows for thinner wiring. Arcs at 24V on a 6A MCB are virtually not existant unless extremely reactive circuits are being switched.

scousespark said:

Hi John. I think 'black sheep' is a bit strong, implying that there is malice in play when a mistake is made. I never stated, nor implied, that everybody involved in the electrical installation industry was perfect.

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Hi there, we can argue about semantics as much as you wish, but, as you imply, in every trade/profession there is an entire spectrum between 'excellent'/'perfect' and "shouldn't really be doing the job" - and I think that the great majority of people (both within and outside of the trades/professions concerned) would refer to extreme examples of the latter as "black sheep" (not just incompetent, but "likely to bring the trade/profession into disrepute").

However, I would say that, even at that 'bottom extreme' of the spectrum, true malice is extremely rare. In context, I would think that there are incredibly few, if any, electricians (or 'electricians') who have true 'malice', in the sense that they deliberately, or even knowingly, set out to create danger or to do harm.

scousespark said:

Maybe I have been lucky when I've met members of the IET, HSE, NICEIC but I have found they actually know a bit about electrical installation.

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I would say 'typical', rather than 'lucky', since the people 'at the bottom of the spectrum' are, fortunately, a small minority, so one would expect that most of the people that anyone 'met' would be at least "OK", often better.

However, as always, we only really hear about the exceptions (the "black sheep") - just as we don't switch on the 6 o'clock news and hear about all the planes that haven't crashed, all the people who haven't been murdered, all the police officers who have done their jobs impeccably etc. etc. The fact that we don't usually hear about, or discuss, any of the 'good' things in the world (like excellent electricians) in no way alters the fact that the great majority of things (including electricians) are 'good'.

Having said that, I do agree with bernard that it seems that in many trades/professions (including those we are discussing), there seems to be an increasing tendency for people not to know/understand (maybe because they haven't been taught) the basic/fundamental principles and concepts underlying the discipline in which they are practising.

That tends to create a "Jobsworth" situation, with people (sometimes 'blindly') learning and applying sets of rules/regulations, without an ideal degree of understanding of why those rules/regs exist, or necessarily an ability to apply discretion and common sense or to be able to deal with situations which are 'out of the ordinary' (a common example being that of people who think that various things 'are not allowed' because they do not appear in the (non-exhaustive) examples shown in Appendix 15 of BS7671).

From the viewpoint of the individuals concerned, this will also make life more difficult for them, since it's much easier to learn about things when one understands their basis that if one has to learn them as one would a poem!

Kind Regards, John

JohnW2 said:

Hi there, we can argue about semantics as much as you wish, but, as you imply, in every trade/profession there is an entire spectrum between 'excellent'/'perfect' and "shouldn't really be doing the job" - and I think that the great majority of people (both within and outside of the trades/professions concerned) would refer to extreme examples of the latter as "black sheep" (not just incompetent, but "likely to bring the trade/profession into disrepute").

However, I would say that, even at that 'bottom extreme' of the spectrum, true malice is extremely rare. In context, I would think that there are incredibly few, if any, electricians (or 'electricians') who have true 'malice', in the sense that they deliberately, or even knowingly, set out to create danger or to do harm.
I would say 'typical', rather than 'lucky', since the people 'at the bottom of the spectrum' are, fortunately, a small minority, so one would expect that most of the people that anyone 'met' would be at least "OK", often better.

However, as always, we only really hear about the exceptions (the "black sheep") - just as we don't switch on the 6 o'clock news and hear about all the planes that haven't crashed, all the people who haven't been murdered, all the police officers who have done their jobs impeccably etc. etc. The fact that we don't usually hear about, or discuss, any of the 'good' things in the world (like excellent electricians) in no way alters the fact that the great majority of things (including electricians) are 'good'.

Having said that, I do agree with bernard that it seems that in many trades/professions (including those we are discussing), there seems to be an increasing tendency for people not to know/understand (maybe because they haven't been taught) the basic/fundamental principles and concepts underlying the discipline in which they are practising.

That tends to create a "Jobsworth" situation, with people (sometimes 'blindly') learning and applying sets of rules/regulations, without an ideal degree of understanding of why those rules/regs exist, or necessarily an ability to apply discretion and common sense or to be able to deal with situations which are 'out of the ordinary' (a common example being that of people who think that various things 'are not allowed' because they do not appear in the (non-exhaustive) examples shown in Appendix 15 of BS7671).

From the viewpoint of the individuals concerned, this will also make life more difficult for them, since it's much easier to learn about things when one understands their basis that if one has to learn them as one would a poem!

Kind Regards, John

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Yeah... I've worked with the good'ns and I've worked with the s++t. I find that on big building sites there is usually a high proportion of those at the lower end of the scale in the main M&E contract, whereas those in small crews tend to be at the higher end. On that basis ones perspective could easily be totally biased by where they work and hence their standards are likely to match.
On big sites it's sometimes hard to find fitters capable of some relatively simple circuits, as an example (apologies if I've mentioned before) installing about a dozen intermediates in a corridor, I was not allowed into the various rooms due to lack of working lighting. The 'electrician' had run 2of 3C&E between each switch and after 2 days of his attempts at wiring knocked off at 3pm having wired only a few. I complained yet again to the site manager and stuck in a RFI note stating we would be contracharging for wasted time if we didn't have access into the rooms first thing in the morning. I was informed the 'electrician' was one of the best on site and as there were so many switches it was complicated. I offered to wire the switches for a days pay (my direct rate being maybe half that of agency staff). Manager accepted the offer and by 5pm I'd wired all, including redoing those already done.
Of the 6 wires running between the switches he'd made a random selection and judging by the ends of the unused wires he'd obviously tried other combinations. Lucky for me a grey and a white drum of cable had been used for the pull in so the job really was a POP. I never did find out whether the 'electrician' was taking the spis or simply incapable but if he was one of the best I hate to think what the rest were like.

Oh and YΔ motor wiring... less than 50% success rate, some even manage to run a neutral wire too... and find somewhere to terminate it!

My opinion...
Far too many 'qualified' electricians these days are taught to pass their exams/tests and simply don't get any training. Then far too many of these 'losers' think they know it all and think they're Gods gift (kind of reminds me of someone). Some of them may not be bad at house bashing but certainly not in commercial work.

One guy had been in the Army and elected to train as an electrician at de-mob, it was a 4 week course with a string of tickets at the end. Guess how good he was?

Oh and far too many spend all day on their phone complaining about the headache while boasting how many pints of lager they'd drunk the night before. Yeah this bit is a bit flippant but I didn't make it up.

bernardgreen said:

When asked to comment on this the official answer ( such as from pen pushers in a office ) is that the single fault will be detected and the equipment taken out of service.

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At a previous job we had air conditioning installed - each unit having hot and chilled water supplies, and two control valves. We had 4 port valves, the plumbing being two pipes (flow & return) from either the hot or chilled water system, and twp pipes to the coil in the unit.
The guy doing the plumbing was a really nice guy, but he just couldn't get his head around this even when given a sketch showing how the pipes went relatuve to the arrow on the valve. I think the only reason he didn't get every combination of wrong connections is because we didn't have that many units

SimonH2 said:

At a previous job we had air conditioning installed - each unit having hot and chilled water supplies, and two control valves. We had 4 port valves, the plumbing being two pipes (flow & return) from either the hot or chilled water system, and twp pipes to the coil in the unit.
The guy doing the plumbing was a really nice guy, but he just couldn't get his head around this even when given a sketch showing how the pipes went relatuve to the arrow on the valve. I think the only reason he didn't get every combination of wrong connections is because we didn't have that many units

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I have those T-Shirts too.
One in particular we were the controls company called in to get an AHU heating properly after modification.
Originally there was one heating and one cooling coil, each with a swept 3 port 3" valve:

Someone had suggested adding a second heating coil and that had been done, it was an exact copy of the first. My job was to fit the actuator to the new valve, run the control cables and modify the panel. As soon as I took my first look I spotted 2 errors, in fact 4 as both heating coils were the same

I made my concerns known but not being a wet boy my comment went unheeded.

Is there something missing from the diagram as I can only see one error - the valve is the wrong way round, and I bet that's one of the permutations we had.

Did they eventually figure out why it wasn't working ?

Edit: IIRC we were using something like this - the 4 port version makes the plumbing easier (the two ports opposite the actuator are a though pipe, so the tee in the return line is incorporated into the valve body). Actually, looking closely at the image, the non-actuator end of the valve is the flow, and the actuator end is the return - valve is in the return side. But I definitely spent some time explaining to the plumber how it had to be installed, and did him a diagram.
And I've recently used some of the 2 and 3 port versions in my heating at home.

SimonH2 said:

Is there something missing from the diagram as I can only see one error - the valve is the wrong way round, and I bet that's one of the permutations we had.

Did they eventually figure out why it wasn't working ?

Edit: IIRC we were using something like this - the 4 port version makes the plumbing easier (the two ports opposite the actuator are a though pipe, so the tee in the return line is incorporated into the valve body). Actually, looking closely at the image, the non-actuator end of the valve is the flow, and the actuator end is the return - valve is in the return side. But I definitely spent some time explaining to the plumber how it had to be installed, and did him a diagram.
And I've recently used some of the 2 and 3 port versions in my heating at home.

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God ol' trend/honeywell etc 4 port valves, I've install hundreds of actuators on those, 24Vac, 12V dc, 230V ac motorised and 24V wax. In fact I put a dozen of these bodies:
with wax actuators on Ebay back in the summer. Yes I agree they they do make things easy when using ½" pipe but the AHU was 3", I can just imagine the the reaction from the plumber pipe fitter if presented with one of those in 3"

Indeed the swept valve is the wrong way round but additionally the hot water feeds into the bottom of the heating coil, the second coil when fitted was installed in an identical way. They tried getting us back as the systen still didn't work as well as the designer predicted. What I didn't show on the sketch is temp sensors in inlet and outlet pockets:
The cooling worked perfectly with a really decent temp rise across the coil but the heating showed almost no temp drop as any hot water running through the coil went straight out of the top rather than cooling before it left the bottom.
The job was in 2008 but I suspect it was still wrong when the building was decomissioned in 2012. Such a shame as their 'emergency fix' was to position a row of electric fan heaters inside the duct. The really annoying thing is it was right beside another similar AHU for another area which worked as it should and it was so easy to compare them.

SUNRAY said:

I made my concerns known but not being a wet boy my comment went unheeded.

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Yeah, I've met that "I'm the expert, how could you possibly know anything about it when it's not your field" type as well.

SUNRAY said:

God ol' trend/honeywell etc 4 port valves, I've install hundreds of actuators on those, 24Vac, 12V dc, 230V ac motorised and 24V wax.
...
Yes I agree they they do make things easy when using ½" pipe but the AHU was 3", I can just imagine the the reaction from the plumber pipe fitter if presented with one of those in 3"

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Well if they are any good, they'll just get on and fit it It's only a problem if it needs a chainblock to lift it and there's nothing to hang a chainblock off

Indeed the swept valve is the wrong way round but additionally the hot water feeds into the bottom of the heating coil ...

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Ah, it wasn't clear that the drawing also implied physical layout. The fan coil units we had didn't care as the pipe snaked it's way back and forth through the fins. But on a bigger panel I can see you'd just end up with most of the panel cold.

The really annoying thing is it was right beside another similar AHU for another area which worked as it should and it was so easy to compare them.

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Ah, but that was for a different area, so obviously just because the other one is plumbed differently doesn't mean it would be right for the two that weren't I've seen that sort of response from people.

SimonH2 said:

Yeah, I've met that "I'm the expert, how could you possibly know anything about it when it's not your field" type as well.


Well if they are any good, they'll just get on and fit it It's only a problem if it needs a chainblock to lift it and there's nothing to hang a chainblock off


Ah, it wasn't clear that the drawing also implied physical layout. The fan coil units we had didn't care as the pipe snaked it's way back and forth through the fins. But on a bigger panel I can see you'd just end up with most of the panel cold.


Ah, but that was for a different area, so obviously just because the other one is plumbed differently doesn't mean it would be right for the two that weren't I've seen that sort of response from people.

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The really annoying thing is if the new valve had been installed the correct way round it would have been successfully, This is roughly the layout and as they added into existing pipework there were loads of unions. This area was isolated for the alteration and to do the same again should have been just as easy. Red = VT Flow, Black = Return. Coils were vertical pipes with added fins in header and footer akin to a car radiator but much heavier duty.