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Gib Bogle 11-23-2003 08:49 PM

Leave computers on?
 
For years I've been leaving my computers on all the time. A throwaway
comment about the power used by a P4 has prompted me to revisit this
policy. My reasoning always was that the startup and shutdown cycle is
what has most effect on the lifetime of many components. I wonder if
there is any definitive information on this. The main issue, of course,
is the survival of my disk drives.

Gib


Bruce Simpson 11-23-2003 09:37 PM

Re: Leave computers on?
 
On Mon, 24 Nov 2003 09:49:18 +1300, Gib Bogle
<bogle@too.much.spam.ihug.co.nz> wrote:

>For years I've been leaving my computers on all the time. A throwaway
>comment about the power used by a P4 has prompted me to revisit this
>policy. My reasoning always was that the startup and shutdown cycle is
>what has most effect on the lifetime of many components. I wonder if
>there is any definitive information on this. The main issue, of course,
>is the survival of my disk drives.


Different parts of your computer are affected in different ways by
their operating cycles.

One of the real killers is thermal cycling. Each time you turn your
PC on, all the bits inside warm up, and in doing so, they physically
expand slightly.

This thermal expansion (and the contraction that occurs as things cool
down after it's turned off) produce significant mechanical stresses
inside some components and those stresses can produce failures after
many cycle.s

At the moment of turn-on, some parts of your system (especially the
power-supply and CRT monitor) are subjected to surge currents and
voltages that may be significantly higher than those experienced when
the system is left running. A well-designed system should have no
problem coping with these surges -- but each one represnts the chance
for a highly-stressed and slightly sub-spec'd component to fail.

On the other hand however -- a constant exposure to high temperatures
(such as the core of a CPU left running continuously) produces a
gradual decay of the semiconductors to the point where they will
eventually fail..

Every time you increase the temperature, you hasten this decay -- and
it's far from a linear relationship -- which is why a cool computer is
a happy computer.

Components that have moving parts (such as fans, hard drives, etc)
tend to wear out and the more hours they're run, the more worn (and
likely to fail) they become.

But to answer your question -- is it better to turn off or leave
running... well the answer dependson your specific circumstances.

With the price of electricity now hitting over 13-cents a unit in some
parts of the country and the average PC chewing about 100W even when
the monitor is turned off, a machine left on permanently will consume
its own value in power in 10,000 hours of operation. Surprisingly
htat's less than 18 months of full-time running -- that's less than
the warranty period of most machines!

Economically speaking it makes sense therefore to turn your machine
off and on as required -- allowing the warranty to pay for any bits
that might fail due to the increased amount of thermal cycling this
produces. Sure, leaving it on full-time may result in a reduced
likelihood of failure occuring -- but the power you'll save by turning
it off and on will have paid for two new machines by the time the
warranty expires anyway.

Of course, having said that, I leave my CPUs on 24/7 -- mainly because
they get used abuot 12-18 hours a day anyway.

--
you can contact me via http://aardvark.co.nz/contact/

harry 11-23-2003 10:54 PM

Re: Leave computers on?
 


Bruce Simpson wrote:
> On Mon, 24 Nov 2003 09:49:18 +1300, Gib Bogle
> <bogle@too.much.spam.ihug.co.nz> wrote:
>
>> For years I've been leaving my computers on all the time. A
>> throwaway comment about the power used by a P4 has prompted me to
>> revisit this policy. My reasoning always was that the startup and
>> shutdown cycle is what has most effect on the lifetime of many
>> components. I wonder if there is any definitive information on
>> this. The main issue, of course, is the survival of my disk drives.

>
> Different parts of your computer are affected in different ways by
> their operating cycles.
>
> One of the real killers is thermal cycling. Each time you turn your
> PC on, all the bits inside warm up, and in doing so, they physically
> expand slightly.
>
> This thermal expansion (and the contraction that occurs as things cool
> down after it's turned off) produce significant mechanical stresses
> inside some components and those stresses can produce failures after
> many cycle.s
>
> At the moment of turn-on, some parts of your system (especially the
> power-supply and CRT monitor) are subjected to surge currents and
> voltages that may be significantly higher than those experienced when
> the system is left running. A well-designed system should have no
> problem coping with these surges -- but each one represnts the chance
> for a highly-stressed and slightly sub-spec'd component to fail.
>
> On the other hand however -- a constant exposure to high temperatures
> (such as the core of a CPU left running continuously) produces a
> gradual decay of the semiconductors to the point where they will
> eventually fail..


If you stay within the safe operating area of a semiconductor, there is no
process of depletion or decay.
Components such as power supplies also have startup voltage and current
limited by design.
There aren't really any parts apart from the cooling fans that will
experience significant attrition through off/on cycles
CRT monitor phosphors have a fixed attrition, as do the electron gun
assemblies due to the filament evaporation, so they should be turned off.
Disk drives deteriorate over time through evaporation of grease on the
spindle shaft which is accellerated by temperature
The mtbf for modern drives is ~300,000 hrs or more, whats that, about 35 yrs
LOL
The start stops is specified as 50,000 so it might only last 12 years if you
turn it on and off 10 times per day

I'd have to agree with Bruce that its more economical to power off or let
the power management features take care of powering off as much as possible
as manufacturers seem to have engineered out any potential increased wear
and tear due to power cycling to the point that they are insignificant.



Craig Shore 11-23-2003 11:25 PM

Re: Leave computers on?
 
On Mon, 24 Nov 2003 10:37:22 +1300, Bruce Simpson
<checksigformyre@l.address> wrote:

>With the price of electricity now hitting over 13-cents a unit in some
>parts of the country and the average PC chewing about 100W even when
>the monitor is turned off, a machine left on permanently will consume
>its own value in power in 10,000 hours of operation. Surprisingly
>htat's less than 18 months of full-time running -- that's less than
>the warranty period of most machines!


I think you're out on the maths a bit there. You've considered it at
1000w haven't you? :-)

at 13c/kwh, 100w/hr = .013c/hr

10,000 hours x .013 = $130

10,000 hours is 1 year and 52 days



steve 11-24-2003 12:46 AM

Re: Leave computers on?
 
Gib Bogle allegedly said:

> For years I've been leaving my computers on all the time. A throwaway
> comment about the power used by a P4 has prompted me to revisit this
> policy. My reasoning always was that the startup and shutdown cycle is
> what has most effect on the lifetime of many components. I wonder if
> there is any definitive information on this. The main issue, of course,
> is the survival of my disk drives.
>
> Gib


I've been told it is the changes in temperature that can wreck the PC. If
you turn it off and on and it is in a rom that is more of less stable in
temperature throughout the year, that's probably Ok.

Many people consign the PC to the "study".....an often small room, typically
not heated if no one is in it....and the temperatures can vary hugely
through out the year.

The resulting expansion and contraction can - over time - create
micro-stresses in the traces that electricity flows through.

I leave mine on all the time, too. I also replace parts when they get
old....not when they break. As a result, I have few system failures and
have lost only one hard disk in active use in 14 years.

When a hard drive is 3 years old, I buy a new one...and downgrade the old
one to a "who cares" box....which I seem to always give away to some
computerless person before any parts fail.

--
Best Regards,
Steve Withers
defenestrate: The act of throwing Windows out the window and replacing it on
your PC with some other operating system.



steve 11-24-2003 12:49 AM

Re: Leave computers on?
 
steve allegedly said:

> I've been told it is the changes in temperature that can wreck the PC. If
> you turn it off and on and it is in a rom that is more of less stable in
> temperature throughout the year, that's probably Ok.


I should have added: 'and the room temperature is rarely below 20 degrees".

> Many people consign the PC to the "study".....an often small room,
> typically not heated if no one is in it....and the temperatures can vary
> hugely through out the year.


I should have made clear: between being off and being warmed up and turned
on. On a Winter day, the PC might go from 5 degrees to 45 degrees - and
back - several times if used intermittently.

> The resulting expansion and contraction can - over time - create
> micro-stresses in the traces that electricity flows through.




--
Best Regards,
Steve Withers
defenestrate: The act of throwing Windows out the window and replacing it on
your PC with some other operating system.



Gordon 11-24-2003 04:35 AM

Re: Leave computers on?
 
On Sun, 23 Nov 2003 23:25:15 +0000, Craig Shore wrote:

> On Mon, 24 Nov 2003 10:37:22 +1300, Bruce Simpson
> <checksigformyre@l.address> wrote:
>
>>With the price of electricity now hitting over 13-cents a unit in some
>>parts of the country and the average PC chewing about 100W even when
>>the monitor is turned off, a machine left on permanently will consume
>>its own value in power in 10,000 hours of operation. Surprisingly
>>htat's less than 18 months of full-time running -- that's less than
>>the warranty period of most machines!

>
> I think you're out on the maths a bit there. You've considered it at
> 1000w haven't you? :-)
>
> at 13c/kwh, 100w/hr = .013c/hr


Lets try 13c/Kwh, at 100W we hace 0.013$/hr ;-)

>
> 10,000 hours x .013 = $130


Okay here ;-)

>
> 10,000 hours is 1 year and 52 days


Leap years? ;-)



--
Fairy stories exist so children get used to real life



T.N.O. 11-24-2003 07:59 AM

Re: Leave computers on?
 
Steve Robertson wrote:
> Perhaps some dry joints in monitors?? but who ever leaves monitors on??


Well, mine stays on for four hours, then goes into standby... it remains
on, and is warm in the morning, so I assume doesnt cool down.

Steve Robertson 11-24-2003 08:12 AM

Re: Leave computers on?
 
In article <bpr6h3$p83$1@lust.ihug.co.nz>, Gib Bogle <bogle@too.much.spam.ihug.co.nz> wrote:
>For years I've been leaving my computers on all the time. A throwaway
>comment about the power used by a P4 has prompted me to revisit this
>policy. My reasoning always was that the startup and shutdown cycle is


Simple answer: do you leave your car running all night
Do you leave your TV on all night.
Why not, the same arguements apply to them.

Heat & bearing failure is what can kill PC's parts during their useful life (and
caps that arent up to the job)

Steve Robertson 11-24-2003 08:17 AM

Re: Leave computers on?
 
In article <wRawb.9267$ws.828519@news02.tsnz.net>, "harry" <aa@bb.cc> wrote:

>If you stay within the safe operating area of a semiconductor, there is no
>process of depletion or decay.
>Components such as power supplies also have startup voltage and current
>limited by design.
>There aren't really any parts apart from the cooling fans that will
>experience significant attrition through off/on cycles
>CRT monitor phosphors have a fixed attrition, as do the electron gun
>assemblies due to the filament evaporation, so they should be turned off.
>Disk drives deteriorate over time through evaporation of grease on the
>spindle shaft which is accellerated by temperature
>The mtbf for modern drives is ~300,000 hrs or more, whats that, about 35 yrs
>LOL
>The start stops is specified as 50,000 so it might only last 12 years if you
>turn it on and off 10 times per day
>


At last some facts rather than old wives tales


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