If it's a ring final circuit, this is a non-standard circuit arrangement, and the designer is therefore responsible for determining that overcurrent (overload and fault current protection) is addressed correctly for all possible combinations of current sharing. would it be easier to split into 2 no. 16 A or 20 A 50 m radials ?

When you ask about C32, is that for ADS or overcurrent?

What is the arrangement of the circuit (is it TN or RLVS)?

It would also be "unusual" to have 32A overcurrent protection for 16A sockets for unfused plugs -  conventionally 16A or sometimes 20A would be expected.

100m is quite long for a 110V circuit - (not sure if that's the circumference of the ring or the distance to the furthest point, but either way) v.d. might be quite a limiting factor. If it's fed from a transformer from a 230V part of the installation, you'd have to consider v.d. in not only the 110V part but the 230V part and the effect of the transformer as well. A 230V circuit and local transformers might start to look more attractive.

   - Andy.

32A breaker feeding any  16A sockets for unknown use without fusing down would be unusual, as there is very little to stop overload of any one socket. Two is not unknown in theatrical practice, but in that case the loads are well defined and the loading hopefully understood by the installer.
What drives you to this layout and not say two radials protected at 20A or less instead ? It seems an odd choice, so I presume there is a good reason. 

The 4mm will be fine with the 32A interms of rating, assuming its not in thermal insulation,  and two paths of 4mm feeding each socket seems quite chunky - is the 100m to the far point of the ring - so 200m ring-round, or is the 100m the ring round distance so that the far point is 50m from the origin, and fed by the equivalent of 8mm ? VD may be an issue -transformers droop too.

Also H07 - are you thinking flex then, or is this a fixed installation ?
mike

First, why are there so many sockets please? If it is to enable machinery or tools to be used at different workstations (OR), it may be fine; but if it is to enable multiple machines to be used (AND), will you not overload the circuit?

Second, a domestic ring depends upon the BS1362 fuse in every plug. How will you replicate that?

Thank you you for the answers guys. To be more precise with the case. There will be about 8 or 9 110V sockets 16A (internally fused I guess). The furthest socket is about 50m away from Transformer. All this will be fitted in PRR or modular switchgear enclosure if you like. The customer is not providing any details about LVAC (transformer) unit but asking for this amount of sockets to be fitted and in this particular arrangement which is ring arrangement. Those sockets are going to be using mostly for power tools etc and they would like to have at least one socket available in each room/section. I hope this make more sense now and 4mm2 cable and 32A MCB sound more understandable.

"Internally fused " 110 volt 16 amp sockets are most unusual and would probably be custom made. 16 amp sockets of any voltage should not in my view be installed on an OCPD . larger than 20 amps, Fuses would be needed in BOTH poles of a circuit supplied from an isolating transformer with an earthed center tap. Or two pole MCBs

The customer is not providing any details about LVAC (transformer) unit

If you are responsible for the choice of breaker and cable, then you need to check then if this is the normal "110V  centre tapped" i.e. two 55 wolt windings in series with an earth point in the middle, or one side is earthed, so there is a definite live and neutral it affects the fusing arrangement and if breakers are double pole.

If the customer is responsible for the design, and you are 'only' the wireman as it were, then  it needs to be crystal clear that you accept no responsibility for the design and it is up to them as design authority  to ensure that the ADS operates safely to their design.
You should be very wary of accidentally acquiring the  responsibility for a design that is not yours, and you do not have full visibility or control over  - what if the transformer they chose cannot operate a 32A breaker but catches fire above 20A instead for example - is that your fault ? It could be...

It all sounds very odd as described.

Mike.

sockets 16A (internally fused I guess).

Are we talking about sockets with interval overcurrent protection - something like this: https://www.cef.co.uk/catalogue/products/1150765-16a-2p-e-110v-unswitched-socket-with-25a-rcd-ip44 (but with an MCB or RCBO instead of an RCCB).

The furthest socket is about 50m away from Transformer.

for voltage drop - 4mm² has a v.d. of around 11mV/A/m so 16A (for one leg of the ring) over 50m would give a v.d. of 8.8V - whereas 5% of 110V is 5.5V - so that looks like a problem even before you consider v.d. in the 230V circuit supplying the transformer.

I suppose that you might be able to arrange the transformer (e.g. via taps) to boost the secondary voltage somewhat, undoing the voltage drop on the 230V side and perhaps increasing the starting voltage on the 110V side, but that wouldn't undo the power losses, so maybe not an ideal solution.

   - Andy.

you do get unfused things like this in theatre and events/ concert land, an unfused 32 to 16A split, but the assumption is that the person using them is at least part skilled and installs things in a way that the load at the far end is well defined and limits the potential for overload. Generally 16A sockets on a 32A supply for unskilled use is not wise.



Mike.

I don't understand that bit about voltage drop. Ok, on one leg of the ring which is 50m there is 8.8V drop but this is a ring arrangement so this will be compensate with additional 50m 4mm2 cable to the furthest socket so we should ended up with about half of this amount so 4.4V sounds better now. Current me if I am wrong.

I have also found VD formula like this but have no idea if this is correct and where is that 4 comes from