So what's the odds?

[Duncan A]

How much is your time, or your electrician's time worth?
Check the phases beforehand:
https://www.test-meter.co.uk/phase-rotation-testers/
Or tell the electrician to obtain such a device!
Duncan

 

[Bm101]

:shock:

What did you do Chris? What did you do!?!

The actual answer is 14.

I know this because I am not intelligent enough to work out the practical statistical probabilities of 21 3-phase prewired machines working on start up. I am wise enough not to spend too much of my Bear of Little BrainPower worrying about it though. They are not even my machines. So I guessed it.


(I mean no absolutely no disrespect to anyone of course so please don't be offended if you are intelligent enough to enjoy a puzzle and remember that I often get up to walk to the kitchen, get there and wonder what the hell I am doing in the kitchen.)
It reminded me a bit of this thing I saw on the net once of some Sherlock Holmes fans trying to solve an door code entry problem.

 

[Chrispy]

How much is your time, or your electrician's time worth?
Check the phases beforehand:
https://www.test-meter.co.uk/phase-rotation-testers/
Or tell the electrician to obtain such a device!
Duncan

Sorry but there is no electric to test rotation. And even if there were how do you connect three red wires to three red wires?

 

[Chrispy]

Even though there has been an attempt at bribary by an unnamed person who thinks 14 is the answer, I will try and be honest and fair when I find out, hopefully soon just waiting for the meter to be fitted now. By the way the lines man / jointer who came today and fitted the fuse head to the end of the supply cable says that it is of unstandard rotation and we must correct it when conecting the distribution board.

 

[Bm101]

Even though there has been an attempt at bribary by an unnamed person who thinks 14 is the answer, I will try and be honest and fair when I find out, hopefully soon just waiting for the meter to be fitted now. By the way the lines man / jointer who came today and fitted the fuse head to the end of the supply cable says that it is of unstandard rotation and we must correct it when conecting the distribution board.

I'm shocked. Horrified even. What sort of cad would stoop to such depths?!? Some people can be so dastardly. Monstrous behaviour. etc etc etc

 

[sunnybob]

"By the way the lines man / jointer who came today and fitted the fuse head to the end of the supply cable says that it is of unstandard rotation and we must correct it when conecting the distribution board."

HUH???????????

 

[Chrispy]

"By the way the lines man / jointer who came today and fitted the fuse head to the end of the supply cable says that it is of unstandard rotation and we must correct it when conecting the distribution board."

HUH???????????

Well it means that SSE has mixed up their wires so my machines will all run backwards if wired correctly.

 

[n0legs]

Rotation should still be clockwise at the cutout anyway. The SSE craftsman should have proven this with his rotation meter.
Example
Correct/standard
Brown. Black. Grey. N/E
L1. L2. L3

Out of phase/unstandard
Shift this one phase clockwise and it becomes
Grey. Brown. Black. N/E
L3. L1. L2

As long as the installation is wired in the correct rotation the machines (and if you've been uber lucky with the guesswork) will all rotate the right way.

I need to ask, why wasn't a note of the machines "colours" made before disconnection at the old workshop?

 

[chaoticbob]

You have three live, it only needs one to be wrong to make it go backwards, so the odds arent 50/50, theyre 33%

with odds of 1 in 3 being wrong, you would be very unlucky to score a maximum, so taking a third of a third and rounding, i go with 4.

I'm sending my banking details for you to pay the million quid into under a seperate email.

Arf! If anyone's actually interested in the maths...

6 ways to attach 3 wires to 3 terminals, columns are the terminals, numbers the wires:

1 2 3
3 1 2
2 3 1

1 3 2
2 1 3
3 2 1

Observant readers will have noticed that the members of each group of three are are related by cyclic permutation, which can't affect the direction of rotation, so the odds are 50:50. Therefore 10 machines will turn one way, 10 the other, and the 21st will find itself in a probabilistic quandry and explode. You have been warned.
Rob.

 

[Chrispy]

So finally we have the result, still no mains connection but through a mobile generater, the answer is 9 that is 9 needed rewiring including one that the the electrician had mixed up the wires in the distribution board.

 

[marcros]

I am going to claim victory on that then with my guess of 10