Sign in with
Sign up | Sign in
Your question

Power over Ethernet Environmental Requirements

Last response: in Networking
Share
Anonymous
June 28, 2005 4:20:59 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Hi all,

Voice over IP (VoIP) is a technology being considered where I work (a
University). We have a very large network with Cat5 outlets for data
and voice, but the voice is patched back to a regular telephone system.

It would be nice to be able to connect all Cat5 outlets into an
PoE-capable Ethernet switch, then simply configure each port to the
voice or data VLAN. However, there are some issues that I'd like your
opinions on. If a typical wiring closet has 192 outlets (and our
network has LOTS of closets), and these are all patched into a PoE
switch stack, then that equates to about 6KW of power requirements
(rough figures from various sites). Does this mean
- I need to route a major power supply to the wiring closet?
- I need a colossal UPS to provide a decent amount of runtime? (By the
way, regular phone systems are protected by UPSes. Anyone know how
long they are meant to run in the UK? I'm assuming there's some kind of
regulation)
- That much power is going to generate a lot of heat. Do I need air
conditioning, which itself must be protected by the UPS?
- That much power represents a fire risk(?) - do I need a fire
suppression system?

Suddenly a humble wiring closet needs the kind of very expensive
environment previously reserved for server rooms.

Any opinions greatly appreciated.

Kind regards,

Anwar
Anonymous
June 28, 2005 11:57:11 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

amahmood5@uclan.ac.uk wrote:

> Hi all,
>
> Voice over IP (VoIP) is a technology being considered where I work (a
> University). We have a very large network with Cat5 outlets for data
> and voice, but the voice is patched back to a regular telephone system.
>
> It would be nice to be able to connect all Cat5 outlets into an
> PoE-capable Ethernet switch, then simply configure each port to the
> voice or data VLAN. However, there are some issues that I'd like your
> opinions on. If a typical wiring closet has 192 outlets (and our
> network has LOTS of closets), and these are all patched into a PoE
> switch stack, then that equates to about 6KW of power requirements
> (rough figures from various sites). Does this mean
> - I need to route a major power supply to the wiring closet?
> - I need a colossal UPS to provide a decent amount of runtime? (By the
> way, regular phone systems are protected by UPSes. Anyone know how
> long they are meant to run in the UK? I'm assuming there's some kind of
> regulation)
> - That much power is going to generate a lot of heat. Do I need air
> conditioning, which itself must be protected by the UPS?
> - That much power represents a fire risk(?) - do I need a fire
> suppression system?
>
> Suddenly a humble wiring closet needs the kind of very expensive
> environment previously reserved for server rooms.
>
> Any opinions greatly appreciated.

Take a step back and look at things a bit clearer. That "6 KW" is a bit
higher than the maximum amount of power permitted under the spec. You have
to determine how many ports will be connected to a PoE device and also how
much power each requires. Once you've done that, you'll have a better idea
of power requirements. Incidentally, to give you an idea for comparison.
I used to do planning for a large telecommunications company. In my
office, there were over 2000 bays of equipment. The total 48V plant ran
about 7,000 amps or 336 KW. Somehow I doubt you'll get your phone system
drawing anywhere near that 6 KW of power.

Now, once you've determined that, you'll have to decide how to best power
the equipment. You may want to follow standard telecom practice and have
one or more 48V battery banks, with sufficient capacity to carry the
system. Don't forget, you'll have to power everything that the phone
system passes through. There shouldn't be much of a fire hazard with
properly installed and maintained equipment. As for site power, fire
protection etc., you'd better talk to someone qualified and not rely on
what people here say. Doesn't the university have a facilities department,
whose job it is to worry about such things?
Anonymous
June 28, 2005 2:44:33 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

amahmood5@uclan.ac.uk wrote:
>Suddenly a humble wiring closet needs the kind of very expensive
>environment previously reserved for server rooms.

Suddenly your infrastructure is being asked to do something it never
did before (or being asked to do it in a way it wasn't before). Sure,
it's conceptually simple, but why should implementing a brand new
phone system be cheap or easy?
June 29, 2005 12:35:51 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

<amahmood5@uclan.ac.uk> wrote in message
news:1119943259.471152.176800@o13g2000cwo.googlegroups.com...
> Hi all,
>
> Voice over IP (VoIP) is a technology being considered where I work (a
> University). We have a very large network with Cat5 outlets for data
> and voice, but the voice is patched back to a regular telephone system.
>
> It would be nice to be able to connect all Cat5 outlets into an
> PoE-capable Ethernet switch, then simply configure each port to the
> voice or data VLAN.

note - this means you get a phone OR a PC on each connection - so you are
probably doubling the number of ethernet connected outlets. you can do that
and make a manufacturer very happy, or you can use some of the phone / PC
daisy chaining arrangements and roughly halve the number of ports.

However, there are some issues that I'd like your
> opinions on. If a typical wiring closet has 192 outlets (and our
> network has LOTS of closets), and these are all patched into a PoE
> switch stack, then that equates to about 6KW of power requirements
> (rough figures from various sites).

192 * 15.4w = 3 kW or so. Add in the power draw for the switch internals as
well.

maybe 6 kW if you have dual supplies - but the max draw is only 3 kW

Does this mean
> - I need to route a major power supply to the wiring closet?

if you provision to that then yes.

but only 1/2 your ports will feed phones? - only build to what you need with
some headroom.

just remember most IP phones draw much less than the 13+ W available at the
end of a Cat5 cable - around 2W for a nortel IP phone last time i asked.

> - I need a colossal UPS to provide a decent amount of runtime? (By the
> way, regular phone systems are protected by UPSes. Anyone know how
> long they are meant to run in the UK? I'm assuming there's some kind of
> regulation)

depends on your power arrangements - "real" high uptime sites have a jenny
to take the load and the UPS is just there for paranoia and switchover time.

i work for a Telco and our high paranoia / "nonstop" availability CPE with
battery backup is set up for 4 hours.

probably more a safety / legal issue than a technical one.

> - That much power is going to generate a lot of heat. Do I need air
> conditioning, which itself must be protected by the UPS?

No (or not as much as you are expecting) - you have to remember with PoE
that the PoE power dissipation takes place in the cabling (the difference
between the 15.4W worst case supply and the 13.whatever worst case device),
and in the PoE device - which will be in offices rather than the wiring
closet.

the closet power will go up some as those new switches will generate more
heat due to the PoE add ons - manufacturer data sheet should give the heat
numbers (or you insist your supplier works it all out and underwrites it).

> - That much power represents a fire risk(?) - do I need a fire
> suppression system?

this is where you need to talk to the Uni fire officer.....
>
> Suddenly a humble wiring closet needs the kind of very expensive
> environment previously reserved for server rooms.

just remember this is now part of a distributed PBX - and the one you are
replacing probably eats a fair amount of power and money.

And distributed systems usually cost more to build and run just because they
are distributed.....
>
> Any opinions greatly appreciated.
>
> Kind regards,
>
> Anwar
--
Regards

Stephen Hope - return address needs fewer xxs
!