Kitchens and Part P

[ban-all-sheds]

IS NOT ( a OR b ) is the same as IS NOT a AND IS NOT b

Yup.

so my brain automatically went to
IS NOT ( a OR b OR c ) but the regs write it as IS NOT ( a OR b ) AND IS NOT c

Yup.

so AND IS NOT = OR ???
it's late and my brain hurts now...

IS NOT ( a OR b ) AND IS NOT c ≡ IS NOT a AND IS NOT b AND IS NOT c ≡ IS NOT ( a OR b OR c )

There are probably old and grizzled guys here with PLC experience who can have a good guess at your maximum age...

 

[Stoday]

The problem arises because of the multiple negatives. Consider this analogy, which I think is more apt than the original:

My wife says I don't have to mow the lawn if it's not cloudy or raining and the lawnmower's not working.

Do I have to fix the lawnmower and start mowing? Or can I take it easy? Can I do so if the sun's shining or if it rains, can I sit around with a beer? See? It's not easy to understand what's what.

 

[mikhailfaradayski]

get the cheeky mooo to go and mow the lawn herself. Leaves you free to go to the pub for a few hours. Hopefully, when you return, you'll have a nice lawn and maybe she'll have cooked dinner aswell

 

[LoveRocket]

Yes, work on a special installation is notifiable no matter where it is.

OK.

In that case if you link [is it not in a kitchen or special location] and [is it not a special installation] with or, then as you pointed out, it only needs one of them to be true for it to be not notifiable.

So work which is a special installation, i.e. work which is not [not a special installation] (as you also pointed out, the two nots cancel each other out, so "is not not" ≡ "is") becomes non-notifiable if the other of the two alternatives is true.

So a special installation which is not in a kitchen or special location becomes non-notifiable.

please read my edited post above..

OK

do you not see the flaw in that remark?
you are saying then that ONLY work in a kitchen or special location on a special installation is notifiable? meaning that if it's NOT work on a special installation ( ie adding sockets to existing circuits etc ), then work in a kitchen is NOT notifiable..

No - you've got 2B around the wrong way again.

2B is not a list of conditions which if false make the work notifiable, it is a list of conditions which if true make it non-notifiable.

And the difference is crucial, because of the way that AND, OR and NOT interact.

As I said above, (NOT (x OR y)) is not the same as ((NOT x) OR (NOT y)).

For the work to be not notifiable via Para 2 of Schedule 2B is has to be

(a) Work which is not in a kitchen or special location

AND it has to be

(b) Work which is not a special installation

AND it has to be

(c) Work which consists of adding light fittings and switches to an existing circuit etc.

It's only by having AND (b) that you don't end up with a special installation being non-notifiable when it's not in a kitchen or special location.

The way that Schedule 2B works is that you stop, and exit with a "non-notifiable" answer as soon as you get a match.

So if you have it saying "It's not notifiable if it's not in a kitchen or special location OR <a list of other conditions>" then you stop if it's not in a kitchen or special location, because the things that come after the OR are irrelevant. You've answered "Yes", or "True" to one of them, i.e. the "not in a kitchen or special location", so you don't need to consider the others, you've come out with a TRUE from your (a) OR (b) OR (c)..

lets look at this another way..

"tomorrow I will mow the lawn if it is not cold and not cloudy" <- your structure

this means that you will ONLY mow the lawn if it is both sunny and warm
but not if it's cold but sunny, or warm but cloudy.

"tomorrow I will mow the lawn if it is not cold or not cloudy" <- my structure

this means that you will mow the lawn if is sunny but cold, or if it's warm but overcast, or if it is sunny and warm..

In this example "mowing the lawn if" is analogous to "becomes non-notifiable if".

I can't stress often enough what 2B is about. 2B is a list of things which if any are true make the work non-notifiable, not a list of things which if any are false make it notifiable.

Sorry if this is a bit large - it might be a struggle to get the right balance between size and legibility.

The shaded square is, I think, what we are both agreed on regarding notifiablity of kitchens, special locations and special installations, and the highlighted parts in the bottom middle square show where your structure breaks down.

It shows hiw, when you reject my structure and adopt yours you end up with a result equivalent to saying that if the work is not a special installation but is in a kitchen or special location, it's non-notifiable, and if it's not in a kitchen or special location but is a special installation, it's non-notifiable.

And that's not the case, and it's not what you know to be the case.

You are quite right about what is and is not notifiable - where you are wrong is thinking that the SI has got it wrong. It has not, and neither has AD P which explicitly puts the implied "and" from the SI into

"Work that is not in a kitchen or special location and does not involve a special installation (e) and consists of:"

Jesus H Christ on a bike


Tipper (that's the OP), I refer you to my earlier response.

Have you used your nice new cooker yet?

 

[mikhailfaradayski]

wow, i bet he's a scream at parties

 

[ban-all-sheds]

Jesus H Christ on a bike

Don't exaggerate - I know I'm impressive, but not that much.

 

[LoveRocket]

Jesus H Christ on a bike

Don't exaggerate - I know I'm impressive, but not that much.

You keep on rockin'. if lawnmower based boolean logic and truth tables are how you enjoy your weekends, then don't let anyone stop you.

 

[ban-all-sheds]

The problem arises because of the multiple negatives.

Those aren't too bad - you just start with the last one, establish whether that condition is true or false, and then work backwards.

And the rules for Boolean operators aren't complicated - anyone who knows that 2 + 3 x 4 is 14 and not 20 can grasp them, it's just that they aren't taught to everyone in school like arithmetic is.

Consider this analogy, which I think is more apt than the original:

My wife says I don't have to mow the lawn if it's not cloudy or raining and the lawnmower's not working.

So thats mowlawn is FALSE if (NOT (cloudy OR raining) and NOT lawnmowerworking) is TRUE.

As FALSE = NOT TRUE

mowlawn = NOT (NOT (cloudy OR raining) and NOT lawnmowerworking)

mowlawn = NOT ( (NOT cloudy) AND (NOT raining) AND (NOT lawnmowerworking)

mowlawn = cloudy OR raining OR lawnmowerworking

Do I have to fix the lawnmower and start mowing?

If it's cloudy or raining you have to mow the lawn, so yes, you would have to fix the lawnmower. (Or find another way to mow the lawn)

Or can I take it easy? Can I do so if the sun's shining or if it rains, can I sit around with a beer?

If it is cloudy, or raining, or the mower is working you have to mow the lawn

See? It's not easy to understand what's what.

Don't be daft - it's incredibly easy to understand. Your wife wants you to mow the lawn, so I suggest you get on with it, and that any attempt to explain to her that you didn't mow it because that's what she said she wanted will come with a serious health warning.

But you're right - in casual speech it's often clear what people mean even when what they actually say is the opposite.

For example I refer you to the question I asked earlier - let's see what your answer would be.


If had been raining and then stopped, and you said "let's go out for a walk", and someone said "Oh, is it not raining any more?", what one-word answer would you give?

 

[holmslaw]

..

 

[Tipper]

No, not used the cooker yet 'cos it ain't installed yet. Still reading if you know what I mean!

In any event I will DIY........

or perhaps I'll get the leccy back......

or then again maybe I'll get my wife to do it ..............seeing as it's her cooker anyway!

Think I'll draw a 'Mind Map', they're good for setting out all the possibilities.