We left off last time
while checking the standby generator.
Specifically, is the engine block warm from the block heater? These heaters often fail, and many diesel gensets have trouble starting if completely cold.
It’s always a good
idea to exercise the generator periodically, and although it’s tempting to run
it without its load (no interruptions and surges for the transmitter to cope
with), that really doesn’t test much except the starter motor and battery
unless the load is connected. In fact,
it is best if the generator is fully loaded up.
The best way to test,
though possibly not the most convenient, is to turn off the main hydro
breaker. This after all is your best
simulation of a complete hydro outage.
The generator should start up, the load should transfer, and the
generator should fairly quickly settle at 60 Hz. Don’t worry too much if the frequency is one
or two Hz off frequency, but pay particular attention if the generator
continues “seeking,” or changing speed.
In excessive cases the engine looks like it’s ready to leap off its
motor mounts. Problems of this nature
may indicate adjustments to the governor are necessary. Time to call in the generator
specialists: some of the newer
electronic governors have as many as six or seven controls, all interdependent,
for frequency, damping, response rate, sensitivity, etc., etc. Proceed with caution!
A good load test will
run the generator for an hour or so.
Most of those I informally polled liked to see a load test every two to
four weeks.
STUFF TO THINK ABOUT:
A three-phase system
should have full three-phase failure sensing… while this seems like a
no-brainer, it’s surprising what some genset
suppliers will provide in lieu of the full-meal deal… usually one or two
sensors. If you think about it for a
while, you’ll realize that you shouldn’t accept anything less than three
sensors. A single sensor, say between
phase A and B, works unless phase C is lost.
A second sensor, between B and C, will sense the failure of C, but what
if instead a tree, leaning against your power line, shorts lines A and C
together, blowing the in-line fuse for C?
The two-sensor system will not detect this fault, and the genset will not start.
Been there, done that… best to check that you’re sensing voltages
between all three legs of the line!
Delay on neutral is a deliberate hesitation of a few seconds, between hydro
on load and generator on load. Normally
it’s an extra-cost option—it can become important if there are large motors,
particularly single-phase units, on-site, and if the transfer switch operates
quickly. The still-rotating motor stores
energy (mechanically—the “flywheel” effect) from before the transfer action—if
the genset’s applied energy is out-of-phase with the
stored energy, the resulting surge as the two power sources rush to synchronize
may be large enough to intermittently pop circuit breakers
or generator exciter diodes. O joy! Delay on neutral can be added to avoid this
problem. Some modern advanced transfer
switches contain synchronizers, which add complexity but permit a very rapid
(<100mS) hot transfer without requiring delay on neutral, and without these
surges.
Unlike diesel fuel,
gasoline spontaneously breaks down over time, with the more volatile components
evapourating, and the heavier compounds depositing
out, varnishing
in the carburetor. The gummy deposits
ruin engine performance. Gasoline
generators should be exercised frequently to prevent this, and really stale
gasoline should be replaced. Diesel fuel
will not break down this way, but fungus-like critters can actually live at the
margin between the fuel and any water that’s gotten into the fuel tank. They will plug up fuel injectors if they get
past the fuel filters. Recent practice
has been to add extra, more efficient filters in the fuel line, and to
occasionally have the fuel sampled and tested.
All that rust and crud that accumulates in outside tanks means it’s a
good idea to refill once the tank’s half empty.
There’s less condensation in the tank that way, too.
Incidentally, if,
ahem, your diesel generator ever runs out of fuel, it may take a surprising bit
of effort to get it running smoothly again.
There’s often a little hand-pump located under the injectors—the correct
procedure is to crack open the injectors, and pump the little manual plunger
until fuel squirts from them. Depending
on the length of your fuel lines, this may take a while. Then re-tighten the injectors and try to
start without the load connected. You
may have to crack open the injectors again to bleed them while the engine
coughs a bit. Once you get the engine
running smoothly, you can apply the load and you’re back in business! We’ll leave the maintenance of belts, hoses,
radiators, coolants, lubricants and batteries to your imagination. Rest assured that, as with any mechanical
device, something’s always ready to fail just as soon as you let down your
guard!