Isolating automation

Isolating automation

Post by James W. Brow » Fri, 08 Sep 2000 23:51:53



I have a poolhouse about 600 feet from the main house, and each has its own
separate electrical service, meter and panel (obviously, grounds are not
bonded together).  A 2 inch PVC conduit containing low voltage wiring runs
between the two.  I need contact closures in the automation controller in
the main house to control 110v loads in the pool house, either through
relays or remote controllable breakers.  What is the best way to isolate
these circuits from each other?  I would prefer to buy some little "black
boxes" with optical or other isolation, as opposed to cobbling together my
own components.  Thank you.
 
 
 

Isolating automation

Post by Karl Denning » Sat, 09 Sep 2000 01:08:37




Quote:>I have a poolhouse about 600 feet from the main house, and each has its own
>separate electrical service, meter and panel (obviously, grounds are not
>bonded together).  A 2 inch PVC conduit containing low voltage wiring runs
>between the two.  I need contact closures in the automation controller in
>the main house to control 110v loads in the pool house, either through
>relays or remote controllable breakers.  What is the best way to isolate
>these circuits from each other?  I would prefer to buy some little "black
>boxes" with optical or other isolation, as opposed to cobbling together my
>own components.  Thank you.

Run a RLY8-XA over there (Applied Digital), put the transformer for the
valves and contactors over THERE, and run just the signal for communications
to it from the main house.  Add in a SECUI16 to get sensor input from the
other end.

This is what I do.

Sample configuration files (from my WORKING system here, at my home, that
does exactly this) for HomeDaemon (available for free from the first link
below) are available on request.

BTW, an awful lot of pool loads (like pumps, etc) are 220VAC.  If your pump
is (and if its more than 3/4 horse or so it almost certainly is) you
need to make sure you use 220VAC rated contactors and such.  They're
readily available.

Jandy makes valve actuators that run on either 12 or 24VAC for actually
turning pool and spa valves.  If you get the 24VAC ones you'll find that

relatively inexpensively in wet-location-approved enclosures.  These work
great for virtually all residential pool installations.

Tap the PVC water lines and insert some LM34 temperature sensors, and you
can completely automate the pool and spa hardware.  Go a bit further with
pressure sensors and the like and you can build in all kinds of safety
(both life and property) stuff that is usually missing from residential
pool equipment - anti-entrapment control specifically, along with protection
from low water level air ingestion into the pump (which will rather quickly
trash the seals on the pump if it happens and you don't detect it.)

If you know the normal output pressure levels on your system you can set
up the controls so that both low and high output pressure trips off the pump
and other hardware.  Low pressure corresponds to either a blockage of the
suction (entrapment), a broken pipe on the output side (no head restriction)
or sucking air (low water level.)  High pressure corresponds to either a
valve stuck/broken in the wrong place ("deadheading" the pump) or a blockage
of some kind (filter clogged, output blocked, etc)  Any auto parts store
can sell you an analog oil pressure sensor which just happens to have a
range of operation quite suitable for this type of use.

With a control system that works off hard-wired sensors detecting this and
shutting down on these kinds of problems can be done in a fraction of a
second - in the case of entrapment, this is a very important thing indeed!

(There are "anti-entrapment" devices that work to break suction alone, but
the problem is that without a pump pressure sentry as well you'll destroy
the pump in short order if they trip.  The best system would involve both,
but just monitoring output pressure would provide *most* - but not all - of
the protection of a suction-pressure-break system)

--
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