Re: Central Vac overload

["John Gilmer" <jlgilmer@xxxxxxxxxxxx>]

"Robert Green" <robert_green1963@xxxxxxxxx> wrote in message
news:hosmv1$fp7$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Some of you might remember my question about building a silencing cabinet
> for a central vac.  Well, it worked, but too well.  The problem is now
> that
> if something gets stuck in the hose, we can no longer hear the immediate
> increase in the motor load the way we used to.  On occasion, the unit's
> motor even shuts down from the overload.

Believe it or not, the "motor load" is usually at a minimum when the vac is
completely blocked off.

If you want to monotor for a blocked inlet you might want to check flow in
the exhaust (after the bag).   Most central vacs exhaust through a tube
which can be connected outside if your don't want to "re-cycle" the dirt the
filter bag misses.


>
> Does anyone have any ideas how to detect the "laboring" of the motor so I
> can sound a chime or some other alarm when something clogs the pope - I
> mean
> pipe - the Pope has enough problems of his own.  (-:
>
> I am going to try a test today with my Kill-0-Watt meter to see if there's
> a
> substantial increase in current draw.  I might be able to use a current
> sensor to detect the upswing and sound a chime or some other kind of
> warning.  I don't want to shorten the life of the motor by letting the
> thermal overload shut it down after it has overheated.

In many/most central vacs (and even some "shop vacs") the cooling air for
the motor is separate from the air used to suck up dirt.    If your's isn't
separate then a blockage would definitely cause it to overheat.  Otherwise,
you may find that it actually runs slightly cooler when the inlet is
blocked.

Frankly, sensing overheat isn't a bad way of seeing if something has gone
wrong.

Modern motors "run hot" so don't worry about overheating shortening the life
of the motor.

If anything, the life limiting is as likely to be the motor bearings as the
windings.

If you like to worry about blockage, you can quickly check to see whether it
still "picks up" a piece of pocket litter.

>