32A to 2x 16A

[DrySand]

I am currently looking at installing some equipment in a small IT comms room and am looking for some advice on the current setup and how to proceed, I am not an electrician myself.



1: Currently there is a 32A supply being fed directly into PDU with 13A sockets, same as the the link below, my first thought is that this is unsafe, but as each plug would be fused am I wrong?
https://cpc.farnell.com/lms-data/pdu-12ws-v-32cmdo/12-way-vert-13a-sw-pdu-32a-plug/dp/EN84502



2: I would prefer to introduce two UPSes for redundancy as per standard practice. The UPSes are 16A devices, I believe that these shouldn't be plugged directly into the 32A supply and that a splitter with 16A protection should be used as per the below, is that correct?
32 Amp Commando Splitter to 2x16 Amp Sockets - https://www.dcdi.co.uk/shop/05m-32-amp-comm-plug-to-2x-16a-comm-skt-mcbs

 

[Strima]

What UPS are you considering using?

 

[DrySand]

What UPS are you considering using?

These are the ones:
SmartUPS 2200VA RM 230V

APC Smart-UPS, Line Interactive, 2200VA, Rackmount 2U, 230V, 8x IEC C13+1x IEC C19 outlets, SmartSlot, AVR, LCD - SMT2200RMI2U | APC UK

SMT2200RMI2U - APC Smart-UPS, Line Interactive, 2200VA, Rackmount 2U, 230V, 8x IEC C13+1x IEC C19 outlets, SmartSlot, AVR, LCD | APC UK

www.apc.com

 

[pc1966]

1: Currently there is a 32A supply being fed directly into PDU with 13A sockets, same as the the link below, my first thought is that this is unsafe, but as each plug would be fused am I wrong?

No it is perfectly safe due to the fused UK style of plugs.

The normal UK ring final circuit has a 32A breaker (or older 30A fuse) for protection due to this.

2: I would prefer to introduce two UPSes for redundancy as per standard practice. The UPSes are 16A devices, I believe that these shouldn't be plugged directly into the 32A supply and that a splitter with 16A protection should be used as per the below, is that correct?

Those UPS show a 16A plug as the power input so they should be protected by a 16A (or maybe at most 20A) breaker.

Your best solution is to get an electrician in to arrange two separate supplies for the two UPS, each with a 16A MCB. I would use a a C-curve for better tolerance of any switch-on surges.

If this is a non-domestic installation and you have other precautions in place (e.g. separate earth wire to the equipment racks) then you might be better to have the supplies on only a MCB, and not RCD-protected. This will give you less risk of spurious tripping on leakage currents.

But it should be part of a doccumented risk assessment to detemine that the supplies are not going to be used for general purpose equipment (doh!) and that the risk of high leakage currents or a fault-to-ground has been considered and precautions taken (e.g. the additional "high integrity" earthing arrangements).
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Just to add, if you have dual PSU servers and want to save some money then you can have one feed from the UPS and the other direct from mains. If a UPS goes bang (sadly more common than you might expect) then you keep going.

But if doing that, and maybe more generally if you are looking at the power arrangements anyway, there is a strong case for having a surge protection device fitted at the distribution board (CU / fusebox, if not already fitted). This is becoming more common now it is in the 18th edition wiring regulations.

 

[DrySand]

Your best solution is to get an electrician in to arrange two separate supplies for the two UPS, each with a 16A MCB. I would use a a C-curve for better tolerance of any switch-on surges.

Thanks very much for your answer, lots of detail and I now have a better understanding. I'll inform the client and see what they say.

On the quoted section, does that effectively give me the same result as using the splitter linked in my original post? As that splits it into two curcuits each protected by a 16A C-Curve MCB.

Also, would I be able to install that splitter without being an electrician myself?

 

[pc1966]

Thanks very much for your answer, lots of detail and I now have a better understanding. I'll inform the client and see what they say.

On the quoted section, does that effectively give me the same result as using the splitter linked in my original post? As that splits it into two curcuits each protected by a 16A C-Curve MCB.

Also, would I be able to install that splitter without being an electrician myself?

If you want to split a 32A circuit safely and easily then you can also look at something like this:

32A to 2x 16A splitter

However, the primary reason for having two separate circuits is for reliability - if one UPS takes out the supply on a fault the other is still OK.

If you use a splitter then you will not achieve any real selectivity (the ability for a fault to be contained to only the effected circuit) on a high current fault due to the way that MCB operate. You can get selectivity with a 16A and 32A fuse in series though, but not with an upstream MCB due to the behaviour of the "instantaneous" magnetic trip.
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Also other Olsen stuff might be netter in your case, such as:

32A Rated Rack Mounted IEC C19 Sockets

Same idea as the one you linked to.

 

[davesparks]

On the quoted section, does that effectively give me the same result as using the splitter linked in my original post? As that splits it into two curcuits each protected by a 16A C-Curve MCB.

Using the device you linked earlier will allow you to connect both UPS safely, but it will still all be powered by one circuit, so a single fault can take out the supply to the whole rack, which would defeat the object of having dual power supplies in my opinion.

 

[DrySand]

If you want to split a 32A circuit safely and easily then you can look at something like this:

32A to 2x 16A splitter

However, the primary reason for having two separate circuits is for reliability - if one UPS takes out the supply on a fault the other is still OK.

If you use a splitter then you will not achieve any real selectivity (the ability for a fault to be contained to only the effected circuit) on a high current fault due to the way that MCB operate. You can get selectivity with a 16A and 32A fuse in series though, but not with an upstream MCB due to the behaviour of the "instantaneous" magnetic trip.

Thanks for that, makes a lot of sense.

I actually simplified my question in the first instance, there are actually 2x 32A supplies (Lets call them A and B) which we would to split into 4x 16A.

There will be two racks, each with 2 UPS, in each rack there will be one UPS supplied by 32A socket A and one supplied by 32A socket B, so that we can have that level or redundancy.

I was trying to find the difference between the splitter from my original post and the one you linked? Is it the type of curcuit breaker?

 

[pc1966]

I actually simplified my question in the first instance, there are actually 2x 32A supplies (Lets call them A and B) which we would to split into 4x 16A.

There will be two racks, each with 2 UPS, in each rack there will be one UPS supplied by 32A socket A and one supplied by 32A socket B, so that we can have that level or redundancy.

OK so you would still have some redundancy if the 32A breaker went.

I was trying to find the difference between the splitter from my original post and the one you linked? Is it the type of curcuit breaker?

No, mostly the Olsen ones are robust rack-mounted kit so I would prefer to use them (but a bit more expensive).

Also when bonded to the rack (electrically) you get a higher integrity earth from the 32A "commando" connectors than the IEC style of plugs & sockets which helps if considering no RCD protection (which might already be how your setup is configured).

 

[davesparks]

I was trying to find the difference between the splitter from my original post and the one you linked? Is it the type of curcuit breaker?

The one Pc1966 linked to is designed for server racks and appears to built from good quality components.

The one you linked to is more of a cheap and cheerful unit designed for use in outdoor temporary installations. They are often found being used by food vendors, burgers vans, market stalls etc at events