Not strictly DIY, but anyway....

A friend of mine has an office, in that office there is quite a lot of
halogen lighting, and probably 20 PCs, and 4 servers.
They are soon to get aircon in the "Computer Room" (Basement!)
The electricity meter is rated at only 40A (Single Phase) - The little disk
inside is spinning at quite a high rate! (I think it was about twice per
second, or thereabouts when I looked)
They seem to have two consumer units, each about 20 way - both have a 100A
isolator
I have a clamp meter, so will test the load on it when I am next there.
Should this be uprated, as I know my house supply is 80A!
Would this usually be done free of charge by the electricity company?

I was also going to suggest looking into getting Economy 7, so the
electricity used at night (Servers and A/C and people who leave their PC's
on!) would be on cheaper electricity.

Sparks...

On Mon, 27 Sep 2004 19:52:50 +0100, Sparks wrote:

Not strictly DIY, but anyway....

A friend of mine has an office, in that office there is quite a lot of
halogen lighting, and probably 20 PCs, and 4 servers.
They are soon to get aircon in the "Computer Room" (Basement!)
The electricity meter is rated at only 40A (Single Phase) - The little disk
inside is spinning at quite a high rate! (I think it was about twice per
second, or thereabouts when I looked)
They seem to have two consumer units, each about 20 way - both have a 100A
isolator
I have a clamp meter, so will test the load on it when I am next there.
Should this be uprated, as I know my house supply is 80A!
Would this usually be done free of charge by the electricity company?

I was also going to suggest looking into getting Economy 7, so the
electricity used at night (Servers and A/C and people who leave their PC's
on!) would be on cheaper electricity.

Sparks...

If the actual rating says 40amps then yes. If the name plate actually
says 40LR then it's good for 80amps. As to E7, I can't remember the
actual break-even point, but I seem to recollect that something like 23%
or 27% of energy useage should be in the night period before it becomes
cheaper to switch to E7.

--
wanderer at tesco dot net

"Sparks" wrote
| Should this be uprated, as I know my house supply is 80A!
| Would this usually be done free of charge by the electricity company?

I don't think they do anything free. If this 40A meter is at the end of a
rather elderly main, the main might need upgrading. Possibly costly.

20 PCs at 100W is only 2kW. Changing to LCD screens will cut power
consumption and also reduce the thermal load on the aircon. Low energy
lighting would also reduce the thermal load compared to halogens. As this is
a workplace, Electricity at Work Regulations will apply and the installation
should be periodically inspected, with particular attention to the earth
leakage of 20 PCs and screens which might be on one 32A ring circuit.

| I was also going to suggest looking into getting Economy 7, so
| the electricity used at night (Servers and A/C and people who
| leave their PC's on!) would be on cheaper electricity.

This would cost *more*, as E7 has a higher *daytime* rate. E7 only saves
money if heavy consumption can be moved *off* daytime or 24-hour use and
into the cheap rate period (hence storage heaters and stored water heating).

In an office, PCs, lights, electric kettle, handwash water heaters in the
loos, non-stored electric heating, etc, will be used mostly during the day
with very little night time use.

Owain

o Economy 7 is quite a bit more expensive during the day than night
---- enough that it may actually work out more expensive overall
o The meter is insufficient for the existing load
---- it could well be very old too - and miss-reading isn't unheard of

Economy 7 is typically favoured for storage heaters and such like.

You have 20 PCs & 4 Servers...
o Hopefully distributed across more than 1 RCD
---- ie, RCBOs would be good here - Memshield look attractive (as RCBOs go :-)
o Yes, earth leakage is relatively low per modern PC
---- however on 24 machines that could add up to sizeable total leakage
---- a 30ma RCD will trip at around 15-30ma

So the whole wiring installation beyond meter could do with checking,
and usual check on Earth bonding for any office kitchen & services etc.

I prefer HVAC for people & a good heat removal system for the machine room,
since 4 servers is hardly a particularly oversized load (unless they plan on more).
--
Dorothy Bradbury

I was also going to suggest looking into getting Economy 7, so the
electricity used at night (Servers and A/C and people who leave their PC's
on!) would be on cheaper electricity.

No wonder global warming is getting to be a problem. Are these the same
people who'd object to a wind farm in their back yard too;?....

Sparks...



--
Tony Sayer

On Mon, 27 Sep 2004 21:12:57 +0100, Owain wrote:

20 PCs at 100W is only 2kW. Changing to LCD screens will cut power
consumption ...

But not by as much as one might expect. This 17" CRT consumes 60W,
similar sized LCDs are 40 to 50W...

Low energy lighting would also reduce the thermal load compared to
halogens.

And probably make a bigger saving in the power consumption than
switching displays to LCD... 6 x 40W to 6 x 9W, 186W saved or
1.5kWHr/8 hr day.

This would cost *more*, as E7 has a higher *daytime* rate. E7 only
saves money if heavy consumption can be moved *off* daytime or
24-hour use and into the cheap rate period (hence storage heaters
and stored water heating).

It might it depends on the night load obviously the more you use at
night rate the more you save but to break even you don't need to use
*that* much at the night rate.

Based on (old) Norweb E7 and Domestic tarrifs with standing charges.
20 units at day rate requires 5.68 units at night rate to break even,
thats a base night load of just over 800W.

On the same figures, once above 20 units/day total around 22% of that
total needed to be used in the 7hr off peak period. 7hrs is 29% of the
day...

--
Cheers
Dave. pam is missing e-mail

On Tue, 28 Sep 2004 12:01:04 +0100, Steve Firth wrote:

I think you're blagging a bit here, since the 15" Trinitrons I use
are rated at 240W and the 19" is rated at 350W.

What the plate on the back says and what a unit takes are two
different things. The plate on this monitor says:

100-240v AC
2.5A

So could be anywhere from 250W to 600W... Plugging the monitor via a
little power monitor it takes 55W, OK it probably has a switched mode
PSU which can confuse such power meters but looking at the UPS logs
that indicates just over 100W, still somewhat short of the lower of
the two figures above but admitedly more than 55W... The empirical
"hand on box" would be nearer the 100W mark than 250W.

--
Cheers
Dave. pam is missing e-mail

In article ,
(Steve Firth) writes:
Dave Liquorice wrote:

But not by as much as one might expect. This 17" CRT consumes 60W,
similar sized LCDs are 40 to 50W...

Switching to LCDs saved having to install uprated aircon at a
call-handling centre where I do work on the network and software. I
think you're blagging a bit here, since the 15" Trinitrons I use are
rated at 240W and the 19" is rated at 350W. 40W for an LCD sounds about
right.

Saving 200W/monitor is on line with the calculations for the call
centre. 60W for your monitor sounds about right for standby.

I measure monitors for AirCon loading, and they're nothing like
the figures you have here. 20" monitors are just over 100W, and
they scale down proportionally. You can get around 15% variation
based on scan rate and image brightness too. Standby mode is
typically maximum of 10W, although some have multi-stage standby
and can go lower.

I haven't measured a flat panel display's power consumption so
I can't comment on those. I could measure one when I get my
true power meter back (currently loaned out).

--
Andrew Gabriel

I haven't measured a flat panel display's power consumption so
I can't comment on those. I could measure one when I get my
true power meter back (currently loaned out).

I think that would be a good idea Andrew just to see how the relative
efficiencies stack up.

I presume that your meter copes with switch mode power supplies OK?.....
--
Tony Sayer

Okay, I checked it today and the maximum I saw on the meter (I didn't watch
it all day!) was 58A
I expect when the kettle, fridge, the three water coolers/heaters, all the
lights and all the PC's are on this figure would be greater.

The Meter does state Max 40A

There doesn't seem to be any RCD's on the main (2) consumer units, just
MCB's and a 100A isolator on each CU.
There is a third very small CU with a main switch and two fuses, this is
marked "Top Floor"
No idea if this then connects to a newer CU or not - didn't get time to
check!
All the CU's connect to the meter via a Henley block

At lockup time, with most of the lights off, there was about 10A being
consumed.

During the day I put my clamp meter around the main earth (the cable that
comes from an earthing block where all the earths from the CU, Gas pipe, etc
connect to, to the main incoming supply cable)
This was showing between 800mA and 1A - should we evacuate the building!

Sparks...