Low Voltage from the Central Air Crashes My Computer

When our A/C comes on, it pulls a lot of power. The lights dim
momentarily, but all the computers in the house weather it fine, except
one: my homemade Asus 2.67 GHz dual-proc system.

I purchased a Belkin UPS and an APC Line-R voltage regulator. I can see
the indicator light on the APC regulator show low voltage on occasion
when the AC is on. But bottom line is that the APC device cannot make
up for the problem.

Does anyone think the problem is in the power supply on this computer?
If so, is there a model or type that could withstand the voltage drops
better? I can't recall the output of my current model, but I do recall
searching for a quiet one with adequate margin. Would a very much
oversized model do any better?

Any advice is much appreciated.

In article . com,
"JRoughgarden" wrote:

When our A/C comes on, it pulls a lot of power. The lights dim
momentarily, but all the computers in the house weather it fine, except
one: my homemade Asus 2.67 GHz dual-proc system.

I purchased a Belkin UPS and an APC Line-R voltage regulator. I can see
the indicator light on the APC regulator show low voltage on occasion
when the AC is on. But bottom line is that the APC device cannot make
up for the problem.

Does anyone think the problem is in the power supply on this computer?
If so, is there a model or type that could withstand the voltage drops
better? I can't recall the output of my current model, but I do recall
searching for a quiet one with adequate margin. Would a very much
oversized model do any better?

Any advice is much appreciated.

Looking at the installation manual for one of the Line-R products,
it mentions a selector switch. The 110V setting is the lowest one:

80 - 130V (Selector Switch set to 110V)

Now, if your line voltage drops below 80V, even the Line-R is
not going to be able to help.

The power supply by itself, will probably drop out at 90V
or so. Power supplies have a "hold-up time" spec (maybe
17 milliseconds), and usually the hold-up time is sufficient
to withstand the startup transient of a motor starting
elsewhere in the house. But it sounds like your problem is
sustained voltage is not right.

You should be aware, that power companies have been known to
share too many customers with one pole transformer. If the
power company is not applying brown out conditions (reduced
line voltage) on purpose, as part of summer load shedding,
it could be that the transformer on the pole is undersized.

Also, since many devices in a household, will draw extra
current to compensate for reduced voltage, you should
realize that the situation in your house is doing
neither the power company, nor you, any good. Even small
voltage reductions have been known to damage small electric
motors (electric weed whacker brush assemblies). The
motors in your air conditioner could be drawing way
more current than they are supposed to - sure, they
probably have a thermal cutout, but still elevated
temperature is not good for them.

If you own a multimeter and know how to use it safely,
you could measure the line voltage as a function of
time. Try measuring your house voltage when your AC
is off and when it is on. Perhaps if your neighbours
have AC, listen for when their unit goes off, and
make another measurement. Or simply complain to your
utility, and let them figure it out. (Maybe they'll
explain that they have been using brownout in your
area, to fix their summer loading problems.)

If you can demonstrate to the utility, that the fault is
an undersized pole transformer, they should be only too
happy to install a beefier one.

But get it fixed! Trying to hide the problem, could
result in an expensive repair when something else breaks.

Paul

On 7 Aug 2006 21:41:31 -0700, "JRoughgarden"
wrote:

When our A/C comes on, it pulls a lot of power. The lights dim
momentarily, but all the computers in the house weather it fine, except
one: my homemade Asus 2.67 GHz dual-proc system.

What power supply is it using; make, model, rated wattage
and current per rail?




I purchased a Belkin UPS and an APC Line-R voltage regulator. I can see
the indicator light on the APC regulator show low voltage on occasion
when the AC is on. But bottom line is that the APC device cannot make
up for the problem.

You need another circuit for the AC, there are more devices
than just that one system that shouldn't have such low AC.


Does anyone think the problem is in the power supply on this computer?

It's all shades of grey. Yes, if the system load was less
on that PSU, or if another PSU was capable, that would be
somewhat of a countermeasure for what is still an ongoing
problem with your home wiring.


If so, is there a model or type that could withstand the voltage drops
better? I can't recall the output of my current model, but I do recall
searching for a quiet one with adequate margin. Would a very much
oversized model do any better?


I would have thought you bought a pretty beefy PSU for a
dual 2.7GHz system... a beefier one might help, possibly
even more helpful is one with active PFC but we don't even
know just how low the voltage is getting. I was only
assuming above that all the parts are on the same circuit,
the AC in addition to multiple other systems? Or are the
other systems which survive this problem, not on the same
circuit?

For the light to dim (voltage reduction) when the A/cndx comes on is
due to the initail surge taken by the A/cndx motor... the usual cause
is either the wiring or a 'resistive' joint...

this could be a fuse with bad contacts the connection from the outside
mains etc etc all not capable of passing that initial surge current
as the motor starts up from a stall or stopped position.

The wiring and anything in between such as fuses, switches etc should
be able to handle this load at start up.... abit like using thin wire
on a starter motor in a car... you'll eitther get voltage drop or the
wire will 'blow' ~ abit like a fuse would.

This problem is usually related from the outside connection to the
fuse or distributer box in the house.


Davy

JRoughgarden wrote:
When our A/C comes on, it pulls a lot of power. The lights dim
momentarily, but all the computers in the house weather it fine, except
one: my homemade Asus 2.67 GHz dual-proc system.

I purchased a Belkin UPS and an APC Line-R voltage regulator. I can see
the indicator light on the APC regulator show low voltage on occasion
when the AC is on. But bottom line is that the APC device cannot make
up for the problem.

Does anyone think the problem is in the power supply on this computer?
If so, is there a model or type that could withstand the voltage drops
better? I can't recall the output of my current model, but I do recall
searching for a quiet one with adequate margin. Would a very much
oversized model do any better?

Any advice is much appreciated.

As Kony says there are several partial causes, any of which might
account for it alone, or one may be the whole problem. Thankfully
though there is a simple solution in many cases. First, if your pc is
on the same electrical circuit as the ac, move it to another one. Now
if necessary open the psu, discharge the mains reservoir cap, and
connect a 2nd much larger mains reservoir cap to it. This will carry
the psu through brownout for a very limited time. By very I mean a
fraction of a second, but that will generally be enough to get past the
initial surge of the ac compressor.

If you dont want to open the psu, you could use a separate unit that
rectifies the mains plus a big capacitor, and feed the pc off the
resulting dc.

There is a final time-honoured bodge if all else fails: an
autotransformer to add 10% to the Vsupply. Not recommended, not good
practice, but if you really get stuck it does work.

There are also several other approaches, all of which are not as easy
to implement, such as running the pc off a motor generator, using a
brownout detector to momentarily drop cpu freq right down, cut 12v
drive feeds and so on - dont go there, just waffling.


NT

Paul, Kony, etc define why that problem may exist. IOW computer
power supply should work just fine even when an incandescent lamp on
that same circuit dims to less than 40% intensity. This power supply
resiliency is even required by industry specs. What voltage - how low
- is that electricity dropping during air conditioner startup?

For example, that wire from wall receptacle probably makes many
connections through other wall receptacles to breaker box. If wire to
each receptacle is pushed into rear, then the connection is often poor
- insufficient. Sufficient for human safety and not a problem for
incandescent bulbs. But insufficient for computer and air conditioner.
Then when air conditioner starts, line voltage drops too low due to
wires not wrapped tight around wall receptacle's side screws.

You can inspect for this quickly by only removing each cover plate.
Is that wire wrapped around side screws on receptacle? If not, then
voltage may drop excessively during air conditioner startup. Therefore
computer might shutdown AND excessive strain is put on air conditioner.

Clearly your one power supply is not as resilient. However is it in
violation of industry standard specs? Learn by lowering voltage until
computer shuts down, then measure that voltage with a meter. A variac
is used to adjust voltage. You probably don't have a variac and may
not have that 3.5 digit multimeter. Numbers from that test are
necessary to properly answer your question. Better is to start with
wall receptacle inspections.

Your symptoms imply a larger problem that may also cause pre-mature
air conditioner failure. Inspect how wires are connected to each wall
receptacle on that circuit. Maybe also verify that wire is firmly
connected to its circuit breaker and that circuit breaker is properly
seated in breaker box - or get someone who knows how to inspect this.
A first and simple inspection that may eliminate the problem and avoid
future failures.

Computer power supply should work just fine even when AC voltage
drops to 90 volts, as Paul noted. Some inferior power supplies (that
sell only on price and watts) don't do this when marketing to people
who then fix a defective power supply with a UPS.

Computer should work just fine even when air conditioner starts and
without a UPS. If not, find reason for that failure before damage
occurs even to air conditioner. Start with easiest first step; wall
receptacle inspection.

JRoughgarden wrote:
When our A/C comes on, it pulls a lot of power. The lights dim
momentarily, but all the computers in the house weather it fine, except
one: my homemade Asus 2.67 GHz dual-proc system.

I purchased a Belkin UPS and an APC Line-R voltage regulator. I can see
the indicator light on the APC regulator show low voltage on occasion
when the AC is on. But bottom line is that the APC device cannot make
up for the problem.

Does anyone think the problem is in the power supply on this computer?
If so, is there a model or type that could withstand the voltage drops
better? I can't recall the output of my current model, but I do recall
searching for a quiet one with adequate margin. Would a very much
oversized model do any better?

Any advice is much appreciated.

w_tom wrote:
Paul, Kony, etc define why that problem may exist. IOW computer
power supply should work just fine even when an incandescent lamp on
that same circuit dims to less than 40% intensity.

Then as I posted this, I realized this is a central air conditioner.
IOW it should not share power with anything else; should be on its own
separate circuit. Therefore the loose connection may be inside breaker
box. Those main wires to mains circuit breaker must be tight. If some
incandescent bulbs dim, and others get bright, then problem may be a
loose neutral.

Also this may be a symptom of a loose or failing wire from utility or
its transformer. After confirming no obvious problems on your side (ie
inside breaker box), then utility may put a monitor on your line to
identify their equipment is OK. IOW that utility testing might find a
failure before failure happens; such as an exploding transformer or a
failed service wire.

Central air starting should not cause lights to dim significantly
which is also why a central air has its own dedicated circuit in
breaker box. That low voltage on startup would be symptoms of another
(possibly more serious) future failure. You don't want to learn
about that failure during a winter blizzard or during a weekend night.

w_tom wrote:

Paul, Kony, etc define why that problem may exist. IOW computer
power supply should work just fine even when an incandescent lamp
on that same circuit dims to less than 40% intensity. This power
supply resiliency is even required by industry specs.

Post that bit in the ATX specs, you cant, it doesnt exist.

What voltage - how low - is that electricity
dropping during air conditioner startup?

Unlikely he has got what is necessary to measure that properly.

For example, that wire from wall receptacle probably makes many
connections through other wall receptacles to breaker box. If wire to
each receptacle is pushed into rear, then the connection is often poor
- insufficient. Sufficient for human safety and not a problem for
incandescent bulbs. But insufficient for computer and air conditioner.

Mindless silly stuff.

Then when air conditioner starts, line voltage drops too low due
to wires not wrapped tight around wall receptacle's side screws.

Have fun explaining why it affects the lights.

You can inspect for this quickly by only removing each cover plate.
Is that wire wrapped around side screws on receptacle? If not,
then voltage may drop excessively during air conditioner startup.

Not a clue, as always.

Therefore computer might shutdown AND
excessive strain is put on air conditioner.

Not a clue, as always.

Clearly your one power supply is not as resilient.
However is it in violation of industry standard specs?

Which 'industry standard specs' are these ?

Learn by lowering voltage until computer shuts down,
then measure that voltage with a meter. A variac is
used to adjust voltage. You probably don't have a variac

Yeah, tad of a problem there. Or even know what one is either.

and may not have that 3.5 digit multimeter.

Dont need one of those for that particular test.

Numbers from that test are necessary
to properly answer your question.

Nope.

Better is to start with wall receptacle inspections.

Good way to get him electochuted.

Your symptoms imply a larger problem that may also cause
pre-mature air conditioner failure. Inspect how wires are
connected to each wall receptacle on that circuit. Maybe
also verify that wire is firmly connected to its circuit breaker
and that circuit breaker is properly seated in breaker box

Good way to get him electochuted.

- or get someone who knows how to inspect this.
A first and simple inspection that may eliminate
the problem and avoid future failures.

Unlikely that the problem is that easily fixed.

Computer power supply should work just fine even when AC voltage
drops to 90 volts, as Paul noted. Some inferior power supplies (that
sell only on price and watts) don't do this when marketing to people
who then fix a defective power supply with a UPS.

Computer should work just fine even when air conditioner
starts and without a UPS. If not, find reason for that failure
before damage occurs even to air conditioner. Start with
easiest first step; wall receptacle inspection.

Just ignore this fool's ****.


JRoughgarden wrote:
When our A/C comes on, it pulls a lot of power. The lights dim
momentarily, but all the computers in the house weather it fine,
except one: my homemade Asus 2.67 GHz dual-proc system.

I purchased a Belkin UPS and an APC Line-R voltage regulator. I can
see the indicator light on the APC regulator show low voltage on
occasion when the AC is on. But bottom line is that the APC device
cannot make up for the problem.

Does anyone think the problem is in the power supply on this
computer? If so, is there a model or type that could withstand the
voltage drops better? I can't recall the output of my current model,
but I do recall searching for a quiet one with adequate margin.
Would a very much oversized model do any better?

Any advice is much appreciated.

Rod Speed wrote:
wrote:
JRoughgarden wrote:

When our A/C comes on, it pulls a lot of power. The lights dim
momentarily, but all the computers in the house weather it fine,
except one: my homemade Asus 2.67 GHz dual-proc system.

I purchased a Belkin UPS and an APC Line-R voltage regulator. I can
see the indicator light on the APC regulator show low voltage on
occasion when the AC is on. But bottom line is that the APC device
cannot make up for the problem.

Does anyone think the problem is in the power supply on this
computer? If so, is there a model or type that could withstand the
voltage drops better? I can't recall the output of my current model,
but I do recall searching for a quiet one with adequate margin.
Would a very much oversized model do any better?

Any advice is much appreciated.

As Kony says there are several partial causes, any of which might
account for it alone, or one may be the whole problem. Thankfully
though there is a simple solution in many cases. First, if your pc is
on the same electrical circuit as the ac, move it to another one. Now
if necessary open the psu, discharge the mains reservoir cap, and
connect a 2nd much larger mains reservoir cap to it. This will carry
the psu through brownout for a very limited time. By very I mean a
fraction of a second, but that will generally be enough to get past
the initial surge of the ac compressor.

If you dont want to open the psu, you could use a separate unit that
rectifies the mains plus a big capacitor, and feed the pc off the
resulting dc.

snip

A decent full time UPS would make more sense if a second circuit isnt feasible
and the electrical supply authority cant be monstered into fixing the sag.

Why do you say that? A capacitor is far cheaper and simpler.


NT

Rod Speed wrote:

Mindless silly stuff.

not again


NT