"Brian Lawson" wrote in message
...
Hey Harold,

I'd be surprised if there isn't a short delay in the transfer from
generator to utility, and not just an inter-lock. Except on very
expensive systems that do phase monitoring. In fact, even from
utility to generator during routine test. Actually, part of this is
occurs naturally as the switch gear is "centre-off" and not
centre-shorted. Common "timing" on emergency power is 13 seconds from
loss of utility, and at least two cycles for strictly resisitive
loads, but we required a 15 second advance warning of transfer to
shut-down to keep from damaging our MG sets.

They are pretty much gone now-a-days in favour of Robonic transfer
switches, but there were lots of fair size systems that had emergency
(called "auxiliary" today) systems where individual circuits were
hand-switched with three-pole-double-throw disconnect, where Up was
ON, Centred was OFF, and Down was ON. I've seen them from as small as
60 Amp up to 500 Amp. Mind you, I would not be too hasty to have to
throw the 500 myself!! With this system, the "load" is connected to
the "centre" or moving poles, and the "up" was normal or utility, and
"down" was the auxiliary. I even recall quite an elaborate system of
chains and pulleys, connected to various of these disconnects, to
"force" the operator to "do" the switching in a required sequence.

Take care.

Brian Lawson,


Hey Brian,

I probably should have been a little more specific when I talked about my
panel. We have just a small (5 Kw) single phase generator that we can use
in an emergency, enough to power our boiler and a few other things. I've
wired enough things through the panel that I can, by selective switching,
run our well, heat, alarm system, freezer, refrigerator, and water heater,
just not all at the same time. While we've not been through it yet, I've
been told that power is known to be off for a few days in our area when we
have severs freezing rain storms. So far we've dodged that bullet, including
last January when Portland got slammed. It started out freezing here, but
about an hour later it changed. We were high enough that the inversion held
the cold air at a lower level. Very lucky, at least that time.

The panel of which I spoke is a real simple device, must be switched
manually, and I even have to plug in the generator, although it would be
left plugged in and in position if desired. It has a couple breakers
mounted back to back with a slide that doesn't permit both the generator and
the line to be connected to the structure at the same time. That way it
can't back feed into the entire grid system.

By the way, you're making me drool with the idea of having a large one that
switches as you describe, especially if it was 3 phase. I came very close
to buying a 15 Kw 3 phase generator while I was still in Utah. There are
times when I wish I had. It was a surplus military unit with sound
proofing enclosure, diesel powered. Appeared to be in excellent condition.

Harold