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Forum Index : Other Stuff : Rain water tank+pump+solenoids+sensors

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domwild
Guru

Joined: 16/12/2005
Location: Australia
Posts: 873
Posted: 01:04pm 26 Aug 2015
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Hi,

Just got a 22,500l rain water tank and pump and have a few questions:

1. The irrigation station controllers Bunnings and others are selling, they all seem to drive the solenoids for sprinklers. Assuming it is a four-station controller, does one station then gets used to deliver 24VAC to a 24VAC/240VAC relay to switch on the single-phase pump? I know if it is a three-phase pump the controller then connects to a contactor. Or do I have to ask the non-existing Bunnings staff member (see senior knowledgeable ones only during ads!) if that particular controller has provision to also start my pump or is this never the case anyway or only with dearer ones Google brings up from US shops?

2. My above-ground tank is connected to the pump via the obligatory gate valve. I take it all solenoids are NC (normally closed) as the tank would simply empty through the pump otherwise. For programming does the pump get started and then at the same time the solenoid(s) get opened as the solenoids need pressure to open?

3. My pump is a cheeep Indian-built pump with a gland seal consisting of, most likely graphite powdered rope, i.e., not a mechanical seal, so this pump should not run dry as the shaft then heats up and messes up the seal. So as this pump should never run dry, so what sort of a pressure sensor (24VAC) should be part of the line from controller to the starting relay in series? Should it be at the inlet side to the pump or after? Can those things be set to a pressure value? A near empty tank would have, let's say, a few tens of millimeters of head; too little? Or does it have to be on the outlet side of the pump, where pressure then would drop to zero on an empty tank?

4. Similarly, are there 24VAC rain sensors available and similarly wired in in series with the pump circuit to stop the irrigation from running during rain?

5. It is a 2HP pump or 1.5kW; the "compliance plate (?)" claims 12.5A but has an Aussie 10A three-pin plug installed? Would this be starting Amps or "locked rotor Amps"? Do I have to ask the electrician to install a 15A socket to plug it into or can I get away with 10A? If it is a 15A system, then I have more problems as the Bunnings seven-day 240VAC timers (would add a 240VAC to 24VAC transformer) come only for 10Amps max. as the simplest solution without a controller. I am no too sure at the moment if I can drive the entire system with heaps of sprinklers and trickle pipes and horse trough with just a single solenoid linked in series to the pump with possible rain and pressure sensors.

So many questions, so little time! Thanks.
Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up.

Winston Churchill
 
rustyrod

Senior Member

Joined: 08/11/2014
Location: Australia
Posts: 121
Posted: 06:38pm 26 Aug 2015
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I AM assuming that your pump is not a "pressure pump" with inbuilt switching to cut out at a certain pressure

1 One of my irrigation controllers has a dedicated pump control so the pump runs for the complete multi station sequence.

connect your relay and the water valve in parallel, one sequence only!

2 install the solenoid valve after the pump, as when it's solenoid closes the water pressure in the tank plus the spring inside will stop the flow

3 water level monitor on tank possibly more reliable (washing machine level sensor works through thin plastic hose on a few tens of millimeters of head)

4 I have seen rain sensors but can't remember where, Radio and Hobbies? Big W?

5 It has a 10 amp plug so plug it in and cross your fingers.(Mr General Public would not even consider that it may overload the circuit)

5a (would add a 240VAC to 24VAC transformer) come only for 10Amps max. If it burns out 10 or 15 amps is not going to make much difference to the volume of smoke
Always Thinking
 
domwild
Guru

Joined: 16/12/2005
Location: Australia
Posts: 873
Posted: 07:19pm 26 Aug 2015
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Thanks for help, rustyrod. It is not a home pressure pump. Must go!
Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up.

Winston Churchill
 
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