3-phase MCB rating
 

Slightly OT as this is not really DIY, and certainly doesn't involve me
me making any wiring changes (burning down a fire HQ might not be
appreciated)

I need to use a 3-phase supply, which is presented on a red commando
socket, and is protected via a type-D 32A MCB occupying 3-DIN ways of
the distribution board (SquareD KQ+) can I check my understanding that
this will supply 32A *per* phase?

3-phase MCB rating
 

Andy Burns wrote:
Slightly OT as this is not really DIY, and certainly doesn't involve me
me making any wiring changes (burning down a fire HQ might not be
appreciated)

I need to use a 3-phase supply, which is presented on a red commando
socket, and is protected via a type-D 32A MCB occupying 3-DIN ways of
the distribution board (SquareD KQ+) can I check my understanding that
this will supply 32A *per* phase?

Yes it will be 32A per phase. This means that you can apply a total load
of upto 230V x 32A x 3 = 22kW.

Note that if your commando socket only has 4 pins then you have no neutral!

Type D means that the magnetic trip will operate at between 10x and 20x
the nominal rating (i.e. instantaneous trip at 320 to 640A on any of the
three phases).

HTH

3-phase MCB rating
 

On 27/11/2007 23:18, Rumble wrote:

Yes it will be 32A per phase. This means that you can apply a total load
of upto 230V x 32A x 3 = 22kW.

Thanks, maximum required is 18A per phase (10kVA UPS)

Type D means that the magnetic trip will operate at between 10x and 20x
the nominal rating (i.e. instantaneous trip at 320 to 640A on any of the
three phases).

Yep thanks, I gleaned that from the specs on Voltimum's web site.

For MCBs (single phase in this case) supplying IT equipment with SMPSUs
with inrush current ranging from 30A/3ms to 80A/20ms is a type B MCB
asking for trouble at times when several (say 10) servers are powered up
simultaneously (e.g before/after a generator test)

3-phase MCB rating
 

In article ,
Rumble writes:
Andy Burns wrote:
Slightly OT as this is not really DIY, and certainly doesn't involve me
me making any wiring changes (burning down a fire HQ might not be
appreciated)

I need to use a 3-phase supply, which is presented on a red commando
socket, and is protected via a type-D 32A MCB occupying 3-DIN ways of
the distribution board (SquareD KQ+) can I check my understanding that
this will supply 32A *per* phase?

Yes it will be 32A per phase. This means that you can apply a total load
of upto 230V x 32A x 3 = 22kW.

Note that if your commando socket only has 4 pins then you have no neutral!

Type D means that the magnetic trip will operate at between 10x and 20x
the nominal rating (i.e. instantaneous trip at 320 to 640A on any of the
three phases).

You need to watch the earth fault loop impedance carefully with a
Type D breaker. You may need an RCD to ensure compliance with the
required trip time on a short to earth if you have a long cable or
a greater than ideal earth fault loop impedance. Type D breakers
are normally used only for loads with a large initial surge (e.g.
some motors).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

3-phase MCB rating
 

On 28/11/2007 00:27, Andrew Gabriel wrote:

You need to watch the earth fault loop impedance carefully with a
Type D breaker.

I was surprised it was a type D, the written sheet inside the case
actually states a type C is fitted, but when I checked, I found it is
actually a type D that is fitted.

You may need an RCD to ensure compliance with the
required trip time on a short to earth if you have a long cable or
a greater than ideal earth fault loop impedance. Type D breakers
are normally used only for loads with a large initial surge (e.g.
some motors).

Thanks, I'll raise that with the electrical contractors.

3-phase MCB rating
 

Andy Burns wrote:
On 27/11/2007 23:18, Rumble wrote:

Yes it will be 32A per phase. This means that you can apply a total
load of upto 230V x 32A x 3 = 22kW.

Thanks, maximum required is 18A per phase (10kVA UPS)

Type D means that the magnetic trip will operate at between 10x and
20x the nominal rating (i.e. instantaneous trip at 320 to 640A on any
of the three phases).

Yep thanks, I gleaned that from the specs on Voltimum's web site.

For MCBs (single phase in this case) supplying IT equipment with SMPSUs
with inrush current ranging from 30A/3ms to 80A/20ms is a type B MCB
asking for trouble at times when several (say 10) servers are powered up
simultaneously (e.g before/after a generator test)

Yes, a type B may well be asking for trouble. Type C is probably the
best compromise.

3-phase MCB rating
 

On 27/11/2007 23:18, Rumble wrote:

Note that if your commando socket only has 4 pins then you have no neutral!

It's 5 pin, wired in 5 core SWA 4mm^2 to the commando socket; then wired
in "semi-flexible" cable with transparent plastic outer over a tinned
braid woven over the cores from commando plug to UPS, total length about
15m.

3-phase MCB rating
 

Andy Burns wrote:
On 27/11/2007 23:18, Rumble wrote:

Note that if your commando socket only has 4 pins then you have no
neutral!

It's 5 pin, wired in 5 core SWA 4mm^2 to the commando socket; then wired
in "semi-flexible" cable with transparent plastic outer over a tinned
braid woven over the cores from commando plug to UPS, total length about
15m.


Cool. FYI That's called "SY flex".