Re: Central Vac overload

["Existential Angst" <UNfitcat@xxxxxxxxxxxxxxx>]

"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.
>
> 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.
>
> Thanks in advance

I think what you'll find is that your killawatt will show a substantial
DECREASE in current.  The motor is not laboring, but actually speeding up,
as there is no air to load it.  Almost counter-intuitive, that as a vacuum
clogs, it works less!

What is likely happening is that the motor is going out on temperature
overload, not from current, but from lack of airflow, that cools the motor.

Still, you could use a current alarm like what Mike did, or an air flow
switch (Graingers) in the exhaust, or even a thermostat switch somewhere in
the exhaust, around the motor, before the motor temp overload kicks in.

Probably an airflow switch in the exhaust would be the cheapest, most
straightforward.
You could even build this yourself with a piece of a soda can and a
microswitch from radio shack or someplace.

What I would do is connect a NO relay to the power switch (the coil of the
relay).  Then, in series with the relay contacts, I would put a NC
microswitch operated by the soda can flapper.
This way, the alarm will sound if air flow stops, but not when the unit is
off.

--
EA


>
> --
> Bobby G.
>
> Crossposted to alt.home.repair;comp.home.automation, follow up in AHR,
> please!
>
>