3ph to Single Phase

[JohnW2]

It seems much more common now, than I think it used to be. I think standards in manufacturing of both sockets and plugs have declined - they might meet spec., but do they meet spec. long term?

Who knows? It's difficult for a standard to impose requirements in relation to performance after long periods in service under unknown conditions.

I think the 13amp fuse only helps by blowing when there is a short, rather than a bit of overload, even then - more often than not in the case of a short, it's the MCB which trips rather than the 13amp fuse.

Up to a point but, over the years, I have on a few occasions come across instances of a 3A or 6A fuse blow when (inappropriately) put into a plug supplying a 2kW or 3kW load.

In any event, this doesn't alter my belief that, since a 13A fuse may allow ~22A to flow for long periods, the Standard should require the plug/socket to be able to cope with that (at least initially) -which is not the case with BS1363.

Kind Regards, John

 

[SimonH2]

TOne of the offices I visited had the unmistakeable smell of 'warm cable', they had 9 blocks of 3 desks, each with a 6way lead powering 3 pc/monitor. However all 37 positions were powered from a single 13A socket and they were very aware they had to power each station one by one to avoid blowing the fuse. There was only the one 20A radial in the room.

I've had the reverse of that at my last job. The offices were built in the 80s when there were few demands for sockets - so there were few sockets, and what there were were in horrible metal skirting trunking. When we tooko over another room, we had to power about 5 desks from one socket - and while I'm carefully arranging extensions (aware of the limitations) I had people asking "I thought you weren't supposed to daisy chain extensions ?", so I had to carefully explain about loads and adding them up etc. The laser printer went directly into one of the wall sockets.

Who knows? It's difficult for a standard to impose requirements in relation to performance after long periods in service under unknown conditions.

Agreed, but when it's for something that is mostly going to be used by unskilled persons, under unknown conditions, with little (if any) inspection or maintenance - then it really needs to cater for that even if not explicitly. I'm inclined to agree that a standard which only requires "carry 10A for half an hour" (or whatever the numbers are) is of questionable suitability for something that may well be asked to carry 22A for many hours when misused by unskilled persons.

 

[JohnW2]

Agreed, but when it's for something that is mostly going to be used by unskilled persons, under unknown conditions, with little (if any) inspection or maintenance - then it really needs to cater for that even if not explicitly.

Agreed, up to a point. However, it would probably be unrealistic to have a standard which took into account the "worst conceivably imaginable scenarios' and/or 'the most imaginably stupid users'! However...

I'm inclined to agree that a standard which only requires "carry 10A for half an hour" (or whatever the numbers are) is of questionable suitability for something that may well be asked to carry 22A for many hours when misused by unskilled persons.

I totally agree. I really don't believe it has even occurred to the vast majority of the general public that a "double 13A socket" cannot safely serve 2 x 13A loads 'indefinitely', so I really think the standard should require the products to be capable of that.

Historically, I imagine that BS1363 was initially written at a time when very few households/users would have even one 3kW load to plug in, let alone two - so the problem seems to have been a failure to keep the Standard up-to-date with an evolving world. Mind you, if the Standard were to be 'updated' (along the lines I have suggested) 'tomorrow', it would then presumably leave goodness-knows how many (hundreds of) millions of 'non-compliant' sockets in service for many years/decades to come -so the impact of such a change would be extremely slow in showing itself.

Kind Regards, John

 

[Harry Bloomfield]

I totally agree. I really don't believe it has even occurred to the vast majority of the general public that a "double 13A socket" cannot safely serve 2 x 13A loads 'indefinitely', so I really think the standard should require the products to be capable of that.

Historically, I imagine that BS1363 was initially written at a time when very few households/users would have even one 3kW load to plug in, let alone two - so the problem seems to have been a failure to keep the Standard up-to-date with an evolving world. Mind you, if the Standard were to be 'updated' (along the lines I have suggested) 'tomorrow', it would then presumably leave goodness-knows how many (hundreds of) millions of 'non-compliant' sockets in service for many years/decades to come -so the impact of such a change would be extremely slow in showing itself.

I think it very unlikely that two 13 amp loads would need to be applied simultaineously, from one twin socket. 13amps would normally mean a heating load, who would need to have two 3kw heaters running within feet of each other - who could even afford such a load?

 

[JohnW2]

I think it very unlikely that two 13 amp loads would need to be applied simultaineously, from one twin socket. 13amps would normally mean a heating load, who would need to have two 3kw heaters running within feet of each other - who could even afford such a load?

I agree - but since nearly all of the general public will assume that 2 x 13A loads (if they had them, and needed to use them simultaneously in close proximity) would be OK, I would probably have expected the standard to have addressed that possibility.

In any event, although I can't say I've experienced the problem myself, we hear plenty of reports of problems arising when two 'credible' loads (e.g. a WM plus Dryer) are plugged into the same double socket - so one would hope that the minimum requirement of the standard would at least 'ensure' that such problems should not arise, wouldn't one?

Kind Regards, John

 

[Harry Bloomfield]

In any event, although I can't say I've experienced the problem myself, we hear plenty of reports of problems arising when two 'credible' loads (e.g. a WM plus Dryer) are plugged into the same double socket - so one would hope that the minimum requirement of the standard would at least 'ensure' that such problems should not arise, wouldn't one?

That is perhaps the one exception, in a domestic load.

 

[SimonH2]

I think it very unlikely that two 13 amp loads would need to be applied simultaineously, from one twin socket. 13amps would normally mean a heating load, who would need to have two 3kw heaters running within feet of each other - who could even afford such a load?

Visit to doctor a while ago - heating system down in health centre so portable heaters in use. I see two fan heaters in one extension and mention it to reception. Next time I go, both heaters still there, but at least using two sockets.

Our church a couple of years ago when our boiler was broken so using a couple of fan heaters to take the chill off (one directed towards organists stool so she could feel her fingers to play). Some sockets stopped working - 15A rewirable fuse blown. Person responsible said "but I used two different sockets" - before expressing wonder as to how I was able to figure which fuse had blown I suppose this is understandable as few people will be used to such low capacity socket circuits. My guess is that the fusing was based on having a local earth electrode of questionable performance in the past - the (radial) wiring is imperial and equivalent to about 4.5mm² so I imagine fusing was limited by fault current considerations rather than cable current carrying capacity. We're now TN-C-S, though still with a higher than average Ze.

 

[JohnW2]

That is perhaps the one exception, in a domestic load.

Probably true - but it's the one 'exception' which we keep hearing about, and the reason why some poeple take every opportunity to strongly advise people not to connect two such loads via the same double socket. In my opinion, that should not really be necessary in relation to something called, and almost universally perceived as, "a double 13A socket".

Kind Regards, John

 

[JohnW2]

.... 15A rewirable fuse blown .... I suppose this is understandable as few people will be used to such low capacity socket circuits. My guess is that the fusing was based on having a local earth electrode of questionable performance in the past - the (radial) wiring is imperial and equivalent to about 4.5mm² so I imagine fusing was limited by fault current considerations rather than cable current carrying capacity.

I would very much doubt that 'explanation', since I doubt that even a 'local earth electrode of UNquestionable performance' would have a low enough Re/Ze to facilitate ADS with a 15A BS3036 fuse - which, even if the R1+R2 of the final circuit was zero, would require a maximum Ze of 2.43Ω (more than an order of magnitude lower than anything likely to be seen with a typical domestic-like TT electrode). In fact, the same would usually also be true even with a 5A BS3036 fuse (max Zs = 9.1Ω).

Kind Regards, John

 

[SUNRAY]

I really don't believe it has even occurred to the vast majority of the general public that a "double 13A socket" cannot safely serve 2 x 13A loads 'indefinitely', so I really think the standard should require the products to be capable of that.
Kind Regards, John

Sadly there are far too many in non domestic situations, who should know, who are also oblivious to the limitations of a DSSO.
I am able to quote a council owned theatre bringing in their own electricians to put in temporary supplies for a touring show and ran 4 extension leads from 2 DSSO's to supply 4x 3KW follow spots and of course the first this that happened was the 30A mcb Tripped, his solution was to move one end of the ring circuit to a spare 15A MCB

The same venue where I discovered the 30A feed to Strand Junior 8 dimmer board running 8x 1KW lights was via a BS546 15A socket and plug.

 

[scousespark]

Sadly there are far too many in non domestic situations, who should know, who are also oblivious to the limitations of a DSSO.
I am able to quote a council owned theatre bringing in their own electricians to put in temporary supplies for a touring show and ran 4 extension leads from 2 DSSO's to supply 4x 3KW follow spots and of course the first this that happened was the 30A mcb Tripped, his solution was to move one end of the ring circuit to a spare 15A MCB

The same venue where I discovered the 30A feed to Strand Junior 8 dimmer board running 8x 1KW lights was via a BS546 15A socket and plug.

which council owned theatre was this?

 

[AdrianUK]

Sadly there are far too many in non domestic situations, who should know, who are also oblivious to the limitations of a DSSO.
I am able to quote a council owned theatre bringing in their own electricians to put in temporary supplies for a touring show and ran 4 extension leads from 2 DSSO's to supply 4x 3KW follow spots and of course the first this that happened was the 30A mcb Tripped, his solution was to move one end of the ring circuit to a spare 15A MCB

The same venue where I discovered the 30A feed to Strand Junior 8 dimmer board running 8x 1KW lights was via a BS546 15A socket and plug.

Ah yes.... its also my experience that "Theatres", indeed any entertainment venue that needs to cope with varying temporary supplies, & 'Council Electricians' don't go well together. It always goes wrong!

To be fair to the good old BS546 standard, the old 15A plug was so well engineered that I'm sure it didn't even get warm at 30A, even for hours on end!

 

[JohnW2]

To be fair to the good old BS546 standard, the old 15A plug was so well engineered that I'm sure it didn't even get warm at 30A, even for hours on end!

Indeed - I almost made that point myself. The same might even be true of a 5A BS5436!

Kind Regards, John

 

[SUNRAY]

To be fair to the good old BS546 standard, the old 15A plug was so well engineered that I'm sure it didn't even get warm at 30A, even for hours on end!

Indeed - I almost made that point myself. The same might even be true of a 5A BS5436!

Kind Regards, John

I couldn't agree more... Which is precisely why the entertainment sector never fell into the trap of adopting the terrible design of 13A connectors as a standard where they are avoidable.

 

[SUNRAY]

which council owned theatre was this?

Does it make a difference which Medway theatre?