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SMS

wrote:
My pool, like most of the pools I've seen, use an Intermatic
mechanical timer to turn the pool pump on and off. It does not seem
that there are any low cost digital timers available.

Is there any reason I could not use an irrigation timer and relay like
those used on sprinkler pumps? The only drawback I can see is that
its a bit more complicated to simply turn the pump on whenever you
wish using the digital timers vs throwing a mechanical switch.

Orbit makes a relay specifically for this purpose,
"http://www.orbitonline.com/products/Accessories/02/04/04/615/". It's
$39, "http://www.amazon.com/gp/product/B000I19I5E".

It's rated at 25 amps which is more than enough for even a 3HP pump
running at 208-230V (but not enough for a 2HP pump running at 115V).

Remember that the sprinkler valves are 24 VAC. Buying a new 24VAC 25A
relay will cost almost as much as the Orbit relay. Unless you can find
some appropriate relays on the surplus market, go with the Orbit
product. This relay looks like it would work (but I don't know the coil
current that the sprinkler timer can supply):

"http://www.electronicsurplus.com/commerce/catalog/product.jsp?product_id=71570"
"http://www.tycoelectronics.com/catalog/bin/TE.Connect?C=1&M=BYPN&TCPN=1393212-4&RQPN=T92S7A22-24"

If you have spare zones on an existing electronic sprinkler timer then
you don't even need to buy a new timer. I may do exactly this since I
have a 9 zone Orbit timer with three free zones.

The timer I have does allow you to turn zones on manually, and it's kind
of nice because you can specify the times for manual operation (up to 99
minutes).

The only thing you may have an issue with is that the sprinkler timers
limit the number of minutes per zone. I.e. my Orbit timer limits you to
99 minutes. But since I can program up to four start times per zone per
day, this would give me 396 minutes or over six hours, which is
sufficient, even for hot summer days where the pump is run for 3 hours,
twice a day. It's also a hell of a lot easier than switching the trips
on an Intermatic when you want to change times.

I've been having trouble with my Intermatic mechanical timer where the
trips loosen over time, then rather than tripping, they just slide until
they hit another trip thingee. I guess some Loctite would solve this,
but I like the idea of controlling it with my sprinkler timer, which is
inside the house.