split load board zs on cert

[darren bergin]

what do you put for maximum zs value on a split load board ring circuit protected by 30ma rcd
do you look at tables in regs book or is it just 1667 thanks

 

[ericmark]

Looking on the IET forms the question is not asked. Although the max Ze is considered as not greater than 200 ohms as above that it is likely to be unstable.

I will agree there seems to be some questions which are not asked which I would like to see. At incomer we are asked for PFC but not on any circuit and since volt drop is the main constraint to cable length it would have seemed prudent to measure PFC at furthest point in a circuit.

230/PFC = R2 + Rn resistance or R1 + R2 resistance which ever PFC is higher not really interested in second but first measurement giving R2 + Rn can be used to calculate volt drop.

So I can see that some firms may print their own forms asking for extra information but as to what should be entered that would be up to firm who has commissioned the modified forms.

 

[Spark123]

Or just put 1666 ohms

 

[GaryMo]

I put the maximum Zs value for the overcurrent protective device in use, for example, 1.44ohms for a B32 MCB.

 

[Spark123]

Even for TT systems

You are allowed up to the Zs max for the RCD, however anyone worth their salt won't pass a circuit which has an R1+R2 resistance much higher than expected.

 

[GaryMo]

Even for TT systems

Just TN

 

[Adam_151]

I put the maximum Zs value for the overcurrent protective device in use, for example, 1.44ohms for a B32 MCB.

I prefer to do this, whenever I can, but if its out of spec I use 1666

Unfortunatly we only seem to get RCBOs in C type... I don't like doing it, but its compliant

 

[sparkypete1]

hi o/p is 1600+ a bit much, i may be reading your post wrong and i do applogise if so , but i thought for value zs on a 32amp type B mcb/rcbo is 1,44. again sorry if iam reading your post wrong.

 

[RF Lighting]

If the circuit is RCD protected, then theoretically anything upto 1666Ω would be an acceptable Zs. It's not really good practice to rely soley on an RCD though IMO.

 

[sparkypete1]

so why are all 17th edition mains boards that we at gateshead council fit all have to be full rcbo boards.

 

[RF Lighting]

Presumably because of regulation 522.6.6

 

[ricicle]

so why are all 17th edition mains boards that we at gateshead council fit all have to be full rcbo boards.

If you are working as an Electrician are you sure you want to be asking that ?

 

[GaryMo]

Come on, you know a council rewire consists of bundles of mini trunking!

 

[sparkypete1]

sorry when i said council i mean i work for a company that dose council repairs, but ultimitly they are our paymasters.

 

[GaryMo]

I assumed so. My comment above was in jest.