very high r1 result!

[HappyHippyDad]

Afternoon all..

I have just been testing a ring final circuit and got r1 = 107Ω

It is TNCS, rN is 0.4Ω

I'm sorry I haven't got anymore results for you, I'm nowhere near home at the moment and those are the only 2 results I can remember.

This is on a kitchen ring and the Kitchen is being ripped out over the next week and I shall be reinstalling a ring in the new kitchen. This will be a good time to find any fault but...

My question is what could give this kind or result? 107 is huge! I initially thought loose connection, but even if the conductor was just brushing the socket terminal I would have thought it would be far lower than that?

Thanks..

 

[telectrix]

loose connection been arcing and gone high resistance?

 

[HandySparks]

Were all appliances on the circuit unplugged or switched off?

 

[HappyHippyDad]

Were all appliances on the circuit unplugged or switched off?

No..

 

[telectrix]

Were all appliances on the circuit unplugged or switched off?

how could appliances affect the r1?

 

[ImpededLoop]

loose connection been arcing and gone high resistance?

About all it could be or a screw through the live conductor.

What was rn?

 

[HappyHippyDad]

About all it could be or a screw through the live conductor.

What was rn?

Sorry.. Have corrected the OP rN=0.4Ω

 

[ImpededLoop]

Sorry.. Have corrected the OP rN=0.4Ω

I'm still sticking with Tel's suggestion.

 

[7029 dave]

HR/ loose connection I bet.

 

[telectrix]

has DIY Dave changed a socket or 3?

 

[HandySparks]

how could appliances affect the r1?

Usually, for an intact ring, appliances connected wouldn't affect the result by enough to matter. However, if the line is broken, the measurement could well be via two (or more) appliances, if left plugged in and switched on. Part of the neutral conductor would be 'bypassing' the break in the line conductor, using the appliances to bridge line to neutral. Given the measurement of 107ohms for r1, this seems quite possible.

So the path could be: line (part) - load 1 - neutral (part) - load 2 - line (part)

Obviously, the measurement value would depend on the resistances of the loads in circuit.

 

[SJD]

My guess is the same as HandySparks, the L is broken somewhere, and you are measuring connected loads.

 

[telectrix]

so how would the load resistance get from the load neutral back to the other L leg of the rfc? (always assuming that the N legs are dissed from the DB as they should be when measuring r1,rN, r2).

 

[PEG]

Usually, for an intact ring, appliances connected wouldn't affect the result by enough to matter. However, if the line is broken, the measurement could well be via two (or more) appliances, if left plugged in and switched on. Part of the neutral conductor would be 'bypassing' the break in the line conductor, using the appliances to bridge line to neutral. Given the measurement of 107ohms for r1, this seems quite possible.

So the path could be: line (part) - load 1 - neutral (part) - load 2 - line (part)

Obviously, the measurement value would depend on the resistances of the loads in circuit.

Yep,same test,loads disconnected,will answer that :icon12:

 

[TJ Anderson]

so how would the load resistance get from the load neutral back to the other L leg of the rfc? (always assuming that the N legs are dissed from the DB as they should be when measuring r1,rN, r2).

It would put the 2 appliances (at least) in series across L-L to bridge the open circuit. It would require at least one appliance plugged in and switched on at either side of the break / High res termination

 

[HandySparks]

so how would the load resistance get from the load neutral back to the other L leg of the rfc? (always assuming that the N legs are dissed from the DB as they should be when measuring r1,rN, r2).

As I said, two or more appliances. At least one each side of the break, obviously.

 

[marc8]

Why not just split it down until you find the high resistance joint or damaged cable

 

[Englishman]

Come across a few like that and the problem has been at the mcb, where one of the two cables has been put the wrong side of the little termination clamp.

 

[campo]

Could it be a screw is on the insulation not the wire?

 

[telectrix]

Come across a few like that and the problem has been at the mcb, where one of the two cables has been put the wrong side of the little termination clamp.

cable ends would be out of the mcb for testing r1. nice try though.