Board Change

[Andy™]

30A will melt the cable... you also use L&N for VD, not L&E

where did you get the 14.82 from? 4D1B (singles) is 18 mv/a/m, so 18x24x60/1000 (24A being the max for singles in conduit) give a VD of 25.92V

at 32A (cable melting temp) you will get 34.56v

 

[m4tty]

Thanks Andy

I got the 14.82 from OSG p166 (resistance of copper conductors) is this not the right table then. I have got BRB so ill use that instead in future cheers.

Thanks again for your help on this one.

Cheers

 

[m4tty]

To check the voltage with the load on in the garage, would I start the compressor up and check the voltage at the old cu thats in the garage. If I held the meter on checking the voltage on cu and started welding would the voltage drop as more is being drawn

Thanks

 

[Andy™]

To check the voltage with the load on in the garage, would I start the compressor up and check the voltage at the old cu thats in the garage. If I held the meter on checking the voltage on cu and started welding would the voltage drop as more is being drawnThanks

thats pretty much it. let us know what you get. also a voltage with no-load will be needed (most likely same as the reading you already have)

 

[m4tty]

Thanks will let you know the results cheers

 

[m4tty]

Sorry to keep on but if you measured (R1 plus Rn) at the end of a radial circuit then you can work out VD from them results. Is that how VD is normally worked out??

Cheers

 

[Andy™]

vd is worked out by mv/a/m / 1000

mv from 7671 tables

a - design current

m - length in m

you can work back form R1R2 to get length of cable

 

[spinlondon]

I did not use the word 'safer' that was spinlondons statement, the words I used were 'improved' and '17th edition'.Puzzled as to why he edited his post with the last two lines and started referring to the Zs of fuses and MCB's when the OP had made no indication that they were borderline for MCB's. I could only conclude he was referring back to my post as an after thought and taking it out of context, could be wrong but that

 

[PC Electrics]

Presently BS3036 Rewirable with 2.5mm singles run under garden path in plastic conduit. Garage about 200ft away from house. Been like it since 1970. In garage is Lathe, Medium sized Compressor, Welder & Lighting. When compressor starts up lights dim. Bad but 'works' lol

Been like it since 1970 - that'll be okay then!

In my opinion, this isn't just a small deviation that you can note on your IEC. This is a whopper. To get the vd down to acceptable limits for lighting you'd probably have to put a 10A mcb on this circuit, which would trip every time he tried to start his compressor (and prob the welder too).

You also said he's got a lathe. Has he got HF florries? No? Oooh, dangerous. (there is a reg about avoiding strobe effects but don't know the number just now).

You should be telling the client you cannot reconnect this circuit to a new board. They should have at least a 6mm swa (and preferably 10mm) submain installed to the workshop.

Your legal responsibilities are that the reconnected circuits should be 'adequate' - this one is nowhere near.

If they don't want to do that, then the only other course of action I can see is to henley the supply and fit your new board next to the existing. Transfer the house circuits to the new board and leave the workshop circuit exactly where it is, untouched. And note this on your cert.

Why not ring your scheme tech help and ask their opinion and report back?

 

[ian932]

OMG FFS how ott can you go

IMHO if you are going to make statements about what is stated in the Regulations, you should quote the regulations verbatim, or ensure that your statement is unamigous.

Firstly unamigous is spelt unambiguous, but no one is perfect

Check your own lack of concise statements, http://www.talk.electricianforum.co.uk/showthread.php?p=94283#post94283 you must have the regs to hand to compile this rant so why did you not use it for that post. glass houses and all that!!!

Most people on here comment from memory and may word stuff slightly wrong but if they do others will post corrections NICELY and not try to make someone look stupid.

My last posts were based on reading your two lines

 

[spinlondon]

Sorry you feel my post is over the top.

Thanks for the spelling correction.

I think stating "It always used to be reference method 1." is quite concise. How would you make it more concise? As for having the Regs. to hand, no I don't.

Sorry, I thought I had posted nicely.

I think I have remembered why I edited that post. I think you posted whilst I was writing my post. I then noticed your comment about how installing a 17th edition board would improve the installation, I then thought I'd better add the line about the Zs, as an explanation.

My apologies, I was mistaken. I don't believe it was you who stated that defects should be placed under deviations. Not particuarly inclined to go looking for errors. However, if I'm responding to someones request for information, and I notice someone has posted something that is incorrect, I will point it out. Although, I doubt if I'll bother with spelling mistakes.