Discuss Zs on ring main high in the UK Electrical Forum area at ElectriciansForums.net
A bit more info as requested by @timhoward would help.Circuit too long according to OSG…resistance’s on conductors high due to length… how many RM are going to be over the length OSG…suggest’s….
ze 0.34 R1 1.12 Rn 1.13 R1+ R2 0.76zs1.00…r2 1.96Was it a circuit you completely installed or did you extend it?
We're trying to work out if it is high due to sub-optimal design (and everything terminated correctly etc.) or high due to mis-adventure and the DIY pixies having played.
If you tell us the breakdown of the tests, Ze, r1, rn, r2, R1+R2 it would help.
There are 3 RM in the house… this RM travels a distance from the DB before looping into the power points….in most cases being RCD protected this would not be flagged upA bit more info as requested by @timhoward would help.
Dropping the OCPD to 25A is a "fix" only in the sense the Zs, and (probably) VD figure allowed, become consistent with the circuit implemented. But it is not really satisfactory as such a long RFC suggests it is something like a whole house on one circuit, and so total load would be high and might make 25A trip-prone.
Is there any point where you could break the RFC and link up two more cables as legs to make two RFCs? Taking great care of course not to have them cross-linked!
soz r2 1.96 R1+R2 0.76What is your r2?
I think the Zs is well under the permitted 1667 ohms as it isWhat are people's thoughts on adding a parallel 4mm separate CPC to the first point in each direction? Mathematically that would probably get the Zs under the bar. Do regs allow that?
I know what you mean, but this is NICEIC.....we can't expect them to know that.I think the Zs is well under the permitted 1667 ohms as it is
r2 ever-so slightly high, although not by much really. Otherwise too long for theoretical voltage drop limits then. What is this circuit likely to power? Table lights, TV, Chargers normal house equipment
Exactly the inspector actually calculated the length by the resistances…we can all do that…under normal circumstancesI know what you mean, but this is NICEIC.....we can't expect them to know that.
I'm so glad I'm not registered, I don't have to go through any of thisI know what you mean, but this is NICEIC.....we can't expect them to know that.
Not really possible now… not too sure on the outcome on this one… waiting for Niceic responseWhat are people's thoughts on adding a parallel 4mm separate CPC to the first point in each direction? Mathematically that would probably get the Zs under the bar. Do regs allow that?
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