llile@SALTONUSA.COM wrote:
> Now one or the other damper *must* be open at all times, and one of my
> jobs was to build the interlock that made this happen.  My stuff worked
> fine, but the contractor put tiny little motors on the dampers.  I was
> *inside* the air handler when the inevitable occurred.  The 200 HP fan
> kicked on, and both dampers remained closed.  The walls began buckling,
> and the whole wall of dampers began to move toward me with a noise like a
> bulldozer was coming through them. .  I had to hit the door (which opened
> OUT) with my shoulder a few times to get out of there alive.  I ran is
> slow motion like one of those dream sequences in the movies to slam the
> panic switch on the motor controls and shut the whole system down.

That's an amazing story, but I have to ask:

1. Why wasn't the interlock *mechanical*, so that it would be impossible
   to close both dampers at once?

2. Why weren't there switches to detect the both-closed condition and
   disable the fan?

-- Dave Tweed

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