[PLUG-TALK] [PLUG] Line conditioners

Keith Lofstrom keithl at gate.kl-ic.com
Thu Nov 13 12:52:55 PST 2014


Moving to plug-talk

On Wed, Nov 12, 2014 at 09:45:07PM -0800, John Jason Jordan wrote:
> The problem is that I am going to do it on the cheap. That means:
> 
> 	* a 7200 watt portable tri-fuel generator (about $1000)
> 	* no transfer switch
> 
> Instead of the transfer switch (over $1000, plus permit), I plan to
> install an outside plug near the generator that will pass through the
> wall into the basement where I will connect it to three regular 120
> volt outlets upstairs. These outlets will be dead unless the generator
> is running, never connected to the regular house wiring. When the power
> goes out I will just manually unplug selected appliances from their
> normal outlets and plug them into the generator outlets. I called the
> city and they admitted that I do not need a permit for this wiring. It
> is essentially nothing more than permanent extension cords. 

Surprising that they say no permit required.  Electrical inspectors
in Washington County are in charge of any wire that goes in the walls,
even ethernet - wire insulation can carry a flame, and their principal
goal is fire safety.  I suspect that if you put these wires in, and
you don't get them inspected, you will have a hard time collecting on
an insurance claim in case of a fire.  Check with your insurance agent.
You may also have a hard time with building inspectors when you sell.

All the usual code requirements apply - proper grounding, nail plates
where the wires pass through studs, etc.  Even if you skip the 
inspection, try to meet the latest National Electrical Code.

> The problem is that few generators advertise that they are safe for
> electronic/computer equipment, and those that do are outrageously
> expensive. The model that I am most seriously considering says:
> 
> 	This generator is not intended to power sensitive electronic
> 	equipment such as TVs, DVD players, stereos, desktop computers
> 	or laptop computers without the use of an appropriate line
> 	conditioner and/or surge protector (both not included).
> 	Sensitive electronic equipment should be operated on approved
> 	inverter type generators or pure sine wave generators.

Cheap generator/inverter systems produce square waves, not sine waves,
and are poorly regulated for frequency and voltage.  I have a little
1kW Honda with an inverter and a power-save option.  For low loads it
dials back the gas motor while still producing regulated sine wave AC. 
Good for electronics, not so good for starting a motor in a furnace
or refrigerator, which requires a brief burst of high current to start.

The big cheap generators are intended for motor loads, like concrete
saws at construction sites.  Again, these draw bursts of current to
start, or when they stall during a cut.  These big induction motors
tolerate crap power.  The generator flywheel helps provide the burst
of current needed.

Transfer switch - in my generator subpanel, I have a pair of breakers
with a little mechanical gizmo that only allows one of the pair to
be active at one time.  A little iffy, but installed with the help
of an electrician, and the electrical inspector allowed it.

> The only such electronic equipment that I want to run from the
> generator are a laptop computer, desktop computer, a cable modem,
> router and a couple of switches, and an older stereo. Both computers,
> the modem, router and switches are powered from a UPS. The UPS, in
> turn, has a cheap Free Geek surge protector between it and the wall
> outlet. The surge protector is one of the devices that I will move to
> its nearby generator outlet in the event of a power failure. As
> for the stereo, it has been run in the past without issue from an
> ancient spark-spitting Generac (now deceased).

Most cheap UPS's are passthrough - they pass wall current through
unmodified, then switch over to the inverter when the power goes
out (with a switching delay).  These do not turn crap power into
regulated sine waves, and the isolating UPS's may be just 
vulnerable to crap power as the rest of your electronics.

Surge protectors ... don't always.  They are more suited to
tripping a breaker when lightning hits, not keeping a steady
stream of crap power out of your electronics. 

> Do I need to be concerned? If so, what kind of line conditioning
> equipment shuld I use?

You should be very concerned.  If you are running separate wires,
you should consider two separate circuits and generators, one for
electronics and one for refrigerators/furnace/aircon, stuff with
big motors.  Not sure how new appliances with lots of electronic
controls fare against crap power.

----

Of course, the real problem is educating your "green" neighbors
about electrical reliability, so they don't demand generators that
makes the grid fail.  Alternative energy is typically intermittent
and the opposite of reliable.  See http://www.keithl.com/wind4.png
Alternative energy that reliably integrates into the power grid is
expensive, and most advocates are impressed by big peak generation
numbers rather than by 24x7 availability and exact balancing of
generation to load.

I suspect the grid will need to get bad enough to prevent the
delivery of media nonsense before people stop paying attention
to the ignorant technological opinions of moron reporters.  

Keith

-- 
Keith Lofstrom          keithl at keithl.com



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