Complex Installations demand calc

[Andy78]

Thanks for taking the time to explain that SC
Really is a struggle for someone like me who has to relearn everything every few years when it comes to maths. I'm hoping to refresh myself on basic transposition of formulae soon as that never sunk in to a permanent state either.

 

[Ian1981]

In my copy it is definitely 66.44 + 0.22 (8 - 1) 66.44.

Which is as I've described. 66.44 + (0.22 x (8 - 1) x 66.44)

Perhaps I’ve actually got a dud copy?
Does yours have the mistakes I described earlier such as using old reference method numbers and on the same page using 1.44 ohms max zs for type b 32 amp mcb then using the correct 1.37 ohms?
Think it’s when it’s describing max lengths of a ring circuit I’d have to dig it out to check the page number for where it’s at?

 

[Andy78]

Perhaps I’ve actually got a dud copy?
Does yours have the mistakes I described earlier such as using old reference method numbers and on the same page using 1.44 ohms max zs for type b 32 amp mcb then using the correct 1.37 ohms?
Think it’s when it’s describing max lengths of a ring circuit I’d have to dig it out to check the page number for where it’s at?

I have a counterfeit copy of GN3, got it from Amazon. It was explained to me that small errors like that and spelling mistakes occur through the counterfeiters using scanners to "read" the pages of the original and reprint it. These scanners, or the software that interprets the scan, are prone to mistakes.

 

[SparkyChick]

Andy is correct and it is a misprint as I have the same book.
In fact there’s several mistakes in it such as giving the max zs of a type b 32 amp mcb as 1.44 ohms then directly underneath or above this example it gives the correct figure of 1.37 ohms.
Also uses old reference methods such as reference method 1 and reference method 3 etc.
Still a decent book tho.

Yes, it has those values on page 25.

 

[Ian1981]

I have a counterfeit copy of GN3, got it from Amazon. It was explained to me that small errors like that and spelling mistakes occur through the counterfeiters using scanners to "read" the pages of the original and reprint it. These scanners, or the software that interprets the scan, are prone to mistakes.

MY design guide was bought through amazon cant remember if it has the iet hologram on or if that’s just bs 7671 and on site guide publications.

 

[SparkyChick]

Thanks for taking the time to explain that SC
Really is a struggle for someone like me who has to relearn everything every few years when it comes to maths. I'm hoping to refresh myself on basic transposition of formulae soon as that never sunk in to a permanent state either.

You're probably already doing it without realising... use Ohm's law much?

 

[SparkyChick]

MY design guide was bought through amazon

Same as mine, but I have to admit the thought of it being counterfeit didn't enter my mind... I just put it down to typos in the updates. My OSG has a table I had to stick in regarding maximum Zs as I recall.

I've just looked at the IET site and unfortunately they don't hologram everything... just the BYB, OSG and GN3.

 

[telectrix]

way back in the days of short pants and when a £1 was worth £1 (soon not, thanks to harold wilson), i recall being taught BODMAS... brackets,of, divide, multiply,add, subtract. where did orders come from ( except from a rupert).

 

[Andy78]

You're probably already doing it without realising... use Ohm's law much?

Yes, I'm not that bad, lol. Tried to transpose the adiabatic the other night and failed miserably though.

 

[telectrix]

Yes, I'm not that bad, lol. Tried to transpose the adiabatic the other night and failed miserably though.

fret not. i tried to transpose aluminium into gold. thaat was a failure also.

 

[SparkyChick]

Yes, I'm not that bad, lol. Tried to transpose the adiabatic the other night and failed miserably though.

If you would like me to take a look at your workings and give you some pointers, feel free to PM a picture of them (the workings out before any you dirty booggers having a beer - or wine - on a Sunday get any funny ideas) I'll gladly take a look.

 

[telectrix]

If you would like me to take a look at your workings and give you some pointers, feel free to PM a picture of them (the workings out before any you dirty booggers having a beer - or wine - on a Sunday get any funny ideas) I'll gladly take a look.

you mean you'll take a look at my funny ideas? oops. brackets first as in bodmas.

 

[SparkyChick]

way back in the days of short pants and when a £1 was worth £1 (soon not, thanks to harold wilson), i recall being taught BODMAS... brackets,of, divide, multiply,add, subtract. where did orders come from ( except from a rupert).

I'm guessing if you're being serious (it's sometimes hard to tell ), of = "the square root of", "the square of" which are the orders/indices.

Although I'm not actually sure orders is the right term to use. Powers and Indices is what you would normally call them.

A ^ B = A to the power of B

2 ^ 2 = 4 (the square of)
4 ^ 0.5 = 2 (the square root of) - this is derived from (A ^ (1/B))

So for the cube of and the cube root of:-

3 ^ 3 = 27 (the cube of 3)
27 ^ 0.333333 (or more accurately 1/3) = 3 (the cube root of 27)

 

[telectrix]

as i remember, "of" was similar to multiply. as in 1/2 of 10 = 5.

 

[SparkyChick]

as i remember, "of" was similar to multiply. as in 1/2 of 10 = 5.

Interesting. I wouldn't have thought of that.

I see that as a multiplication.