Verification of volt drop

[greeny]

Hi,
I know how to calculate volt drops on radial ccts, As a ring main is a loop and you ignore any spurs is there a voltage drop or is it considered to perfect or near perfect mains voltage regulation!.
How do you,or dont you verfiy votage regulation on a ring main when certifing that you have checked volt drops.
Perhaps you just have to accept the max length and Zs rules for a ring main

If I am missing something please excuse me for wasting your time.
Greeny

 

[WayneL]

Hi,
I know how to calculate volt drops on radial ccts, As a ring main is a loop and you ignore any spurs is there a voltage drop or is it considered to perfect or near perfect mains voltage regulation!.
How do you,or dont you verfiy votage regulation on a ring main when certifing that you have checked volt drops.
Perhaps you just have to accept the max length and Zs rules for a ring main

If I am missing something please excuse me for wasting your time.
Greeny

It's near enough impossible to calculate volt drop at any particular point on a ring.

This is why they quote max. circuit lengths in BRB.

Calculating volt drop on a lighting circuit is pretty much impossible as well

The only circuits that you can accurately calculate are single load radial circuits e.g. cooker, shower,

immersion etc.

 

[Guest123]

You're right the calc for VD on a ring final is different to a radial type circuit.....

As long as the maximum circuit lengths specified in BS 7671 are adhered to (checked when end to end resistances are measured) then your VD will be well within limits as the maximum circuit lengths are calculated primarily using the VD constraint.

 

[acat]

If you need the formula its Max Length = Voltage Drop x 1000
--------------------------------------------------mva/m x Design Current


Chris

dashes for correct layout only

 

[Guest123]

If you need the formula its Max Length = Voltage Drop x 1000
--------------------------------------------------mva/m x Design Current


Chris

dashes for correct layout only

Not quite correct for a Ring Final mate.....

Lvd =

______4 x max permitted vd x 1000_
_________Ib x (mV/A/m) x Ct______

Which gives....4 x 11.5 x 1000 / 26 / 18 / 1 = 98.3M.

 

[acat]

Thanks Lenny Im trying the Mrs tells me very very TRYING


Chris

 

[Guest123]

the Mrs tells me very very TRYING


Chris

Theres a lot of that about.....

 

[Sintra]

Hi,
I know how to calculate volt drops on radial ccts, As a ring main is a loop and you ignore any spurs is there a voltage drop or is it considered to perfect or near perfect mains voltage regulation!.
How do you,or dont you verfiy votage regulation on a ring main when certifing that you have checked volt drops.
Perhaps you just have to accept the max length and Zs rules for a ring main

If I am missing something please excuse me for wasting your time.
Greeny

Voltage drop may be evaluated by measurement or by calculation and is not normally required during the initial verification of an installation. 612.14

This is another confusing reg so when has it to be verified on an EIC if it is not normally required to be verified. Reading that reg you could put non applicable in the relevant box.

Anybody any ideas on this?

 

[Guest123]

We were having this very conversation only the other day.

If it doesn't have to be verified on initial verification then when does it????

Yet another contradiction in ol' red.....cant wait for the ammendments....

 

[cr0ft]

Fresh off my exams today and our lecturer told us it would normally only be calculated on periodic inspection. I am super green though, but that's what we were told.