AC POWER & GROUND
All the electronic stuff we put in runs off AC power
coming from the wall outlet. We assume the power is OK but assuming anything
when trying to fix a problem can make you chase your tail for a long time.
While we're making assumptions the third world engineers
designing this stuff also assume your AC power is OK. They usually only
design and test the equipment with good power.
On the good side modern power supplies (regulated
switching electronic power supplies) are much more dependable and much less
susceptible to power problems than older power supplies (non-regulated linear
power supplies using a transformer). High or low voltage will often damage the
older linear power supplies. Modern switching power supplies handle low or high
power more gracefully.
There are various problems that can occur with AC power
that aren't obvious. You really don't know if the voltage is high or low, going
high or low intermittently, or if there's an occasional spike or dropout that's
causing problems (like when something that uses a lot of power starts up in the
building or even at a nearby building).
You don't know if there's noise on the power line that
your equipment doesn't like.
You don't even know if the power outlet is wired
correctly, or if electricians wired the electrical panel and ground correctly.
If your problem isn't intermittent, you're
lucky. Check the voltage with a meter.
Put in a UPS with charged batteries and pull the plug from
the wall. If your problems go away, it has something to do with power.
The first thing to do is use this
3 Prong AC Line Test Plug
which is a quick check to see if the outlet is wired correctly (I use it every
time I install something to prevent future service calls):
This cheap little tester will tell you if the hot and
neutral are on the correct blades and if the ground is connected properly. But
it won't tell you if the ground is actually connected to a ground rod outside,
or if the ground is good. You've got to go look at that yourself.
If the problems are still there after pulling the UPS from
the wall you could still have a no ground or a bad ground problem. After
verifying that the ground rod is connected outside you could try running a wire
from the electrical panel along the floor to a ground connection on your
Sometimes you can get a ground from the metal conduit
coming from the electrical panel. But, since conduit pieces are joined together
with connectors that have to be tightened properly you can't count on there
being a good electrical connection between pieces of conduit.
To try running your equipment without a ground
(to see if the problem goes away) carry a
3 Prong to 2 Prong Adapter
to run the equipment without the ground on the power plug:
Having a spare Battery Backup to use for troubleshooting
makes a lot of sense. If the equipment works OK on the Battery Backup with the
power plug pulled from the wall, and doesn't when it's plugged into the wall,
you're pretty close to fixing the problem.
A more expensive
Battery Backup / UPS with good regulation, or a commercial power regulator
(without battery backup capability) may be necessary. Especially in a factory
environment where when certain machines are running it degrades the power in the
You may need to
leave a laptop running the Battery Backup utility software to log power
anomalies. Without logging them you'll probably never find an intermittent AC
power problem. We use CyberPower Battery Backups (we don't sell them), which do
have voltage regulation in addition to being a backup. Their 1500VA (900W) is a
good size for most phone systems and smaller servers / computers, and is fairly
light to carry around (well, kind of).
CP1500AVRLCD is a
good diagnostic tool. It connects to the PC or laptop via USB. Here's what the
Backup and utility screen looks like:
APC and other backup manufacturers have similar control
panels. We've had the worst luck with Minuteman Backups, which are truly
Besides "normal" power problems I've seen an employee
purposely go and flick the circuit breaker for the phone system on and off
rapidly (after hours), which caused a service call first thing in the morning
(the CPU can only handle so much!). There was no battery backup on the system.
It turns out the guy was quite literally crazy causing all kinds of damage at