Strange Socket In Hospital

[JohnW2]

Hospitals had some odd things, including plugs with no fuses, so over 13 amp could be used. So anyone's guess.

I suspect that no enough thought went into that. The usual claim was not that it enabled more than 13A to be supplied but that it avoided a situation in which 'crucial medical equipment' stopped functioning because a fuse in its plug had blown.

That argument always seemed to me to overlook the fact that if a fuse in the plug of a piece of equipment blows, it's almost always going to be because the equipment has already stopped working (properly or at all)!

 

[JohnW2]

It certainly seems there was a period when unfused 13A plugs were used on mobile x-ray machines.

Wayback Machine

Fair enough - and that's talking about eric's 'fuseless fuses', hence relying on the sub-circuit's OPD.

That document refers to the "30A sockets" that some machines needed - so maybe my dusty memory is remembering 30/32A single-phase ones, and thinking that they were all 3-phase. Mind you, the Indian document I've just posted does specify 3-pase (although it's not clear what they mean by 230V 3-phase)

 

[ericmark]

Maybe I was wrong to mention the red plugs with no fuse, most of us know how to make a plug not need a fuse, but think to detail how it is done could make our electrical as dangerous as the USA 120–0–120 volt system, so saying no more about that.

 

[JohnW2]

Maybe I was wrong to mention the red plugs with no fuse, most of us know how to make a plug not need a fuse, but think to detail how it is done could make our electrical as dangerous as the USA 120–0–120 volt system, so saying no more about that.

I agree that it would be inappropriate to talk about "how it is done" here (even though it will be fairly obvious to most people).

However, I think you may have a little more faith in fuses than you should have - or, to put it another way, I'm not sure that "our electrical" would be a lot more dangerous is the plugs did not have fuses.. Don't forget that (at the worst end of their performance spec) a 13A fuse may allow nearly 30 A to flow indefinitely, and around 50 A for 1 minute.

There would undeniably be some theoretical additional risk to cables and equipment downstream of the plug if it did not have a fuse, but I suspect that this 'additional risk' is, in practice, a lot less than we might imagine.

 

[blup]

Saw this in my local hospital and wondered...

How...?
Why...?

Is it a special socket with two separate feeds?


View attachment 372142

Its just ring fencing the socket so it is permanently available for x rays. It would be awkward to have to unplug a life support machine because there weren't any other sockets available for x rays

 

[Harry Bloomfield]

How would they split the earth

Separate wire, all the way back to source?

Remember when they used to add special dedicated circuits, just for PC's.

 

[Risteard]

Non-standard socket-outlets should really be used in this application.

 

[JohnW2]

Non-standard socket-outlets should really be used in this application.

... and they are (in hospitals) - which is why I'm not convinced by some of the suggestions we're hearing.

 

[sparkwright]

It certainly seems there was a period when unfused 13A plugs were used on mobile x-ray machines.

Wayback Machine

WAS there a 13 amp unfused plug?

 

[JohnW2]

WAS there a 13 amp unfused plug?

Yes, the red 'unfused' plugs certainly were used in hospitals,and maybe still are. As I wrote yesterday,the argument for them that i often heard never seemed very convincing to me- since the blowing of a plug fuse almost always means that something has gone fundamentally wrong with the connected load (which has therefore probably already stopped working.

 

[JohnW2]

Its just ring fencing the socket so it is permanently available for x rays. It would be awkward to have to unplug a life support machine because there weren't any other sockets available for x rays

That would indeed be 'awkward', but I think that every hospital ward I've ever seen has had a vast number of socket outlets - at least one double socket by every bed, for a start, but countless others as well - so I don't think it would ever be difficult to find a 'free' one pretty close

 

[JohnD]

I seem to remember that X ray equipment used D- type MCBs.

And that a lot of hospital sockets are on 10 mA RCDs.

You may remember the old story about the hospital cleaner's hoover.

 

[JohnW2]

I seem to remember that X ray equipment used D- type MCBs.

That would make sense. As I wrote above ...

..... I think it also could have a very high 'start-up' current, hence presumably needing a very forgiving OPD!.

.... although most of my recollections are so old that it may well have been fuses back then,even in hospitals. As I've said, I recall the very big plugs (and matching sockets all over the place, and the cable drums on the sides of the machines which had lots of hefty cable (probably more than half an inch in diameter), which I thought was 3-phase, butmay have been just high-current single-phase. However, as I've also said, the kit around today is much less power=hungry.

And that a lot of hospital sockets are on 10 mA RCDs.

I have no idea about the modern gear, but it wouldn't surprise me if X-ray equipment were too 'leaky' (particularly in relation to its filtering) for a 10 mA RCD to be usable.

You may remember the old story about the hospital cleaner's hoover.

"hoover" ? - we need more popcorn

 

[Notch7]

Shouldn’t the sign say “left hand socket” not “left hand plug”

 

[JohnW2]

Shouldn’t the sign say “left hand socket” not “left hand plug”

Of course it should - but that point was made in the very first response to the OP (i.e. in post #2)