2 Ring Circuits combined in series

[McKenna32]

or did you just see my screenshots of it?
Kind Regards, John

Yup, just the screenshots, so I can't quote it, but:

Thanks for confirming the MCB is obsolete and the magnetic trip levels - they're in the crosshairs. Why not just switch it for a B32? Well, it's just aesthetically nasty to have it looping around the house twice when everything could be much shorter.

Probably makes me twice as vulnerable to an EMP attack too right? I really need to finish the bunker now...

I'm planning to do an EICR in any case, as there have been a few odd issues with this place I'm certain there are a couple I haven't found and don't have the time to find!

Will plan to get the rings on separate breakers and upgrade to B's at the same time.

perhaps they disagree with you and thought that was better than four wires in an MCB.
.

Well I am right now discovering just how easier said than done that is...

 

[JohnW2]

Thanks for confirming the MCB is obsolete and the magnetic trip levels - they're in the crosshairs. Why not just switch it for a B32? Well, it's just aesthetically nasty to have it looping around the house twice when everything could be much shorter.

Well, it's obviously entirely up to you. However, from the point-of-view of Zs (hence BS7671-compliance in that respect) it would seem that the Zs of what you have is plenty low enough for a B32. If it were me, I think the only reason why I would consider splitting it into two rings (as well as changing to a B32) would be if I did not feel that 32A was enough to service all anticipated 'socket loads' in the whole house.

Kind Regards, John

 

[AndyPRK]

and if there was a fault on one circuit.

Ensure the rings aren’t joined elsewhere

 

[JohnW2]

and if there was a fault on one circuit. Ensure the rings aren’t joined elsewhere

As we've discussed before, introducing 'cross-connections' within a ring final (e.g. turning it into a 'figure-of-8') theoretically makes the circuit 'safer' (less likely that any part of the cable will ever become overloaded). The only downside of which I am aware is that it can represent a bit of a nightmare in terms of testing - particularly for the unwary!

Kind Regards, John

 

[AndyPRK]

What I meant was , ensure you aren’t powering a ring or circuit with two 32A

 

[JohnW2]

What I meant was , ensure you aren’t powering a ring or circuit with two 32A

Oh, fair enough.

I would have thought from everything the OP has said that there is not any other 32A MCB which could possibly be ('also') powering this circuit (as you wrote yourself, one possible reason for it having been done as it apparently has is that the electrician doing it "didn't have another 32A MCB") - but only the OP can tell us for sure.

Kind Regards, John

 

[chivers67]

Hi @chivers67


Two - one end of the upstairs ring, and one end of the downstairs ring


None directly, into the MCB is the other end of the upstairs ring and the other end of the downstairs ring

Have you measured the R1+R2 of both Rings individually? I just wonder if someone was fault finding at some point and left it like this. For the price of another 32A MCB it makes no sense! Has someone used another 32A MCB for another "newer" circuit?

 

[EFLImpudence]

At some point in the past my two ring final circuits in my house (up/down) have been combined in to one, in series, so it’s effectively one ring doing two laps of the house and the R1+R2 reading is rather high – 0.519 ohms

I suppose that actually is R1+R2,

as you continue to write:

This ties up with a previous EIC that was done in 2011 so didn’t make me worry so much but it’s been nagging me as it seemed unduly high.

So it would seem it is, but then you write:

and checked R1, Rn and R2 separately

Could you confirm that those readings were r1/4 etc.?





==================================================
All- FYI: Posts with external quotes are often spammy, so they require "moderator approval".
So they don't appear until one of us has ticked the box.
That's probably what happened earlier in this thread.
Not our design...
Mod
=================================================

 

[JohnW2]

==================================================
All- FYI: Posts with external quotes are often spammy, so they require "moderator approval".
So they don't appear until one of us has ticked the box.
That's probably what happened earlier in this thread.
Not our design...
Mod
=================================================

I'm not sure what you mean by 'external quotes', but my message which triggered the problem just contained quotes of the message I was responding to -= which is the case with virtually all the messages I post, and a high proportion of those posted here by others. I therefore presume that there must be some 'very specific' reason why that particular message of mine got intercepted by the software!

Kind Regards, John

 

[JohnW2]

Could you confirm that those readings were r1/4 etc.?

That question occurred to me but, on reflection, I concluded that they probably had to be - since, otherwise, the figures would have been ridiculously low for a 'whole house ring'. However, I suppose I really should have asked for confirmation of what the figures actually 'were'!

Kin Regards, John

 

[McKenna32]

Thanks for the assistance on this one. Just to tie it off.

If it were me, I think the only reason why I would consider splitting it into two rings (as well as changing to a B32) would be if I did not feel that 32A was enough to service all anticipated 'socket loads' in the whole house.Kind Regards, John

Yeah I think this will be the case in a few years. Since I'm fiddling around with it now and it's a trivial replacement I'll sort it now

Ensure the rings aren’t joined elsewhere

Thanks, no they weren't

I would have thought from everything the OP has said that there is not any other 32A MCB which could possibly be ('also') powering this circuit
Kind Regards, John

There was not - still a couple of mystery cables in there still but nothing else powering the rings

Has someone used another 32A MCB for another "newer" circuit?

Possibly yes! The garage is on another 32A-er. I don't have an EIC for that though so no idea how that was installed. That's probably where one of the rings was originally attached though. Also a cooker on a 32A, equally likely to be that I suppose.

Could you confirm that those readings were r1/4 etc.?

R1 up = 0.95ohm down= 0.40ohm
R2 up = 1.46ohm down = 0.68ohm
Rn up = 0.90ohm down = 0.40ohm

R1+Rn down @ worst case = 0.55ohm (on a spur in the kitchen)
R1+R2 down @ worst case = 0.65ohm
(didn't do R1 + * upstairs, as I haven't modified that circuit, just prodded around in the CU out of interest)

So it's still pretty dicey, if Ze is high, but as advised B32s will remove the chance of any fails if Ze is towards the upper end of the allowed figure.
Cheers

 

[JohnW2]

Yeah I think this will be the case in a few years. Since I'm fiddling around with it now and it's a trivial replacement I'll sort it now

Fair enough - only you know what your present or future requirements will be. 32A is quite a lot (aroind £1.20 per hour, so around £438 per year if you drew that much for just one hour each day) but, if that includes major kitchen appliances, I suppose it might not always be enough

R1 up = 0.95ohm down= 0.40ohm
R2 up = 1.46ohm down = 0.68ohm
Rn up = 0.90ohm down = 0.40ohm

I'm not sure that necessarily answers the question that EFLI posed (and which, as I said, was also in my mind). I doubt that there's any problem, but could you perhaps clarify exactly what those R1 & R2 figures represent (i.e. how you measured them)?

Kind Regards, John

 

[securespark]

I think the forum software is having a 'senior moment'

At my age, I'm beginning to understand this phrase!

 

[JohnW2]

At my age, I'm beginning to understand this phrase!

Probably more so for me - I had a 'significant' birthday last week

Kind Regards, John

 

[securespark]

21 again, 21 again.....he's got the key to the door, never been 21 before (ahem).......