back too the books instead of trying to keep up with yous.

[i=p/u]

i can do all calcs for designing a circuit as in Ib,In ,It etc. heres my wonder. how can you work out whats the max distance you can run a circuit without being caught on VD and max Zs. easy way maybe im missing.

i know IxR=V and you can just keep rechecking till you get within values.

or maybe im asking isit nearly always vd to watch iut for more than zs when designing, so effectively if you within Vd max values youl be within max Zs..

straigten me up soldiers im tyoing myself in knots ha hee

 

[i=p/u]

Re: back too the books instead of tryoing to keep up with yous.

i know thats way of the mark what i said. ok say i have 10A mcb which is 3.71 ohm, max Ze on tn-c-s is 0.35 ohms that leaves me with nearly 3.35 ohms for length which is a massive length if you work it out but vd limits this . so how do you tie the two together for max length???? think this is it

 

[i=p/u]

Re: back too the books instead of tryoing to keep up with yous.

another example tn-c-s system 2.5/1.5 R1+ R2 = per meter19.51
type b mcb 20A max Zs 1.85 ohms
Ze 0.35 ohms that leaves 1.5 ohms divided by 0.019 = 78 meters so how you tie the max length of circuit in with Vd.

at present im getting 30 V as vd. im getting there.

so my max vd is 11.5 v so how do i conver that into meters is what im asking

 

[i=p/u]

Re: back too the books instead of tryoing to keep up with yous.

isit divide it by 3 just which would equal 26 meters and still be max allowed vd..

is there an easier way

 

[i=p/u]

Re: back too the books instead of tryoing to keep up with yous.

<<<<<<<<<<<<< bonkers

 

[i=p/u]

Re: back too the books instead of tryoing to keep up with yous.

im just exploring here ....

 

[i=p/u]

Re: back too the books instead of tryoing to keep up with yous.

beyone my wildest dreams

 

[i=p/u]

Re: back too the books instead of tryoing to keep up with yous.

isit just playing about with Ix R till you get within limits

 

[Knobhead]

Re: back too the books instead of tryoing to keep up with yous.

Don’t worry lad the men in the nice clean white coats will be coming soon.

They’re coming to take me away HaHaHeHe
They’re coming to take me away HaHaHeHe
To the funny farm, where happy people go
They’re coming to take me away HaHaHeHe

 

[i=p/u]

Re: back too the books instead of tryoing to keep up with yous.

enough for one day, light fire and burn these books out back and just stick getting Ib right

 

[thekingiam]

Re: back too the books instead of tryoing to keep up with yous.

Don’t worry lad the men in the nice clean white coats will be coming soon.

They’re coming to take me away HaHaHeHe
They’re coming to take me away HaHaHeHe
To the funny farm, where happy people go
They’re coming to take me away HaHaHeHe

love that song!!

 

[Knobhead]

Re: back too the books instead of tryoing to keep up with yous.

Saw Mike and the Mechanics perform it at Nottingham’s arboretum park the place went mental!

 

[Silly Sausage]

Re: back too the books instead of tryoing to keep up with yous.

Here, i=p/u,

try this program out for your cable calcs...

Castline Systems - CableCalc BS7671 Level P

Haven't tried it myself, let us know what you think.

 

[Mr Mike]

Re: back too the books instead of tryoing to keep up with yous.

Hi i=p/u, please do not burn any books. Keep them, use them and as you go through them, things will fall into place.

Keep going and don't give up.

Regards Mike.

 

[Knobhead]

Re: back too the books instead of tryoing to keep up with yous.

Here, i=p/u,

try this program out for your cable calcs...

Castline Systems - CableCalc BS7671 Level P

Haven't tried it myself, let us know what you think.

You haven’t downloaded it then Archy? I had a look at the site and got as far as them wanting an e-mail, postal address, phone No……… I always get cold feet at that point, I just don’t like giving it out.

 

[pushrod]

I=P/U have alook at table 7.1 in the OSG . when you are designing circuits the length is not usually something that you can change.

 

[i=p/u]

so what your saying is you need to know the length and then design to that.. its like when the current goes up the zs value comes away down.

is that where distribution circuits come in then???? ps i ask myself more questions than i need to probably thanks.

 

[Silly Sausage]

Re: back too the books instead of tryoing to keep up with yous.

You haven’t downloaded it then Archy? I had a look at the site and got as far as them wanting an e-mail, postal address, phone No……… I always get cold feet at that point, I just don’t like giving it out.

Tony, Downloaded it late last night.
Free version limited to SP Radials & Rings, flat 2 & 3 core PVC.

On first playing with it for about 30mins it seemed quite good, but, trying it again it doesn't seem consistent, it might, stress might, have bugs.
I've neither the time nor inclination to investigate further...

2nd time I've d/led stuff from Castline, never had email etc hassle from them.

 

[pushrod]

so what your saying is you need to know the length and then design to that.. .

You are putting a circuit in- You have worked out the likely max load and circuit breaker and cable size. Then you check the length of cable you are putting in against table 7.1 and if it it is less than the max length shown for the conditions you are using you then you should be ok for volt drop. If it wasn't ok you would think about changing the design, eg increasing the cable size or maybe dividing the circuit up etc

is that where distribution circuits come in then???? ps i ask myself more questions than i need to probably thanks.
If you are putting your new circuit in from a sub main you would have to calculate what size Vd you were getting from the main CU to there and take that figure from your 5% or 3% figure. You could not use table 7.1 for a circuit from a sub main. As the distribution circuit to the sub main will use some of your allowable volt drop.

Hope that helps a bit.

 

[i=p/u]

it does. ty . i think what i left out and confused my swlf with my questions was, the bigger the cable = less resistance..