DIY Chatroom Home Improvement Forum

DIY Chatroom Home Improvement Forum (http://www.diychatroom.com/)
-   Electrical (http://www.diychatroom.com/f18/)
-   -   Need Help wiring 24VAC Sprinkler System (http://www.diychatroom.com/f18/need-help-wiring-24vac-sprinkler-system-55970/)

fazlis85 10-26-2009 10:45 AM

Need Help wiring 24VAC Sprinkler System
 
Background Info: I have just expanded my already huge sprinkler system (16+ zones). The old timer only controlled 12 zones so I added an additional timer to control the new valves/solenoid. Each timer needs to output 24VAC to the main valve solenoid and one respective valve (without the main valve turned on, there will be no water reaching my other valves). So the old timer controls 12 zones (from before) + Main Valve & the new timer controls 4 (new zones) + Main Valve. The main valve must be turned on to let water flow to the manifold where the other valves are.

With one timer, life was simple. 2 leads (24VAC polarity doesn't matter) went to the main valve and the timer would turn it on at the beginning of the watering cycle (it would also turn on each zone one at a time to cover all of the backyard).

Now with two timers, both timers will need to turn on this main valve solenoid. At most times (ideally), only one timer will be supplying power to the main valve. However I want to play it safe (in case both timers decide to turn on at the same time) and feed 24V to the same main valve. I need to isolate the two sources.

Soo...I have two 24VAC sources and need one output to the solenoid of the main valve. If either one of the sources is active/triggered by any of the timers, output should shoot 24VAC. Sprinkler Valve Solenoid shouldn't take more than 2 amps

Now I was thinking of using a couple of diodes but remembering back from college, I think they are effective for DC circuits (and only half way block AC current). Please help me create a diode/relay schematic to put this together or if there are any other suggestions.

nap 10-26-2009 10:52 AM

first, as long as the 24 vdc is from the same source for each of the sections, there is no problem with both feeding the main solenoid at the same time.

presuming there was no backfeed from one zone solenoid to another zone solenoid in the original set up, there should be no problem with that now either.

If you want to get real fancy, all you have to do is have either section (old or new) operate a relay (2 relays total in parallel) that control a common 24 vdc source that is then used to operate the main solenoid.

fazlis85 10-26-2009 11:07 AM

24VAC is from two sources...(two timers). If both are turned on feeding the main solenoid, wont they back-feed the other timer?

I dont know much about wiring AC relay, but willing to try. I do know 12V DC relays (85,86,37 etc).

teamo 10-26-2009 02:52 PM

If it was me I would just get a new timer that can handle all of the zones. If you want to stay with the two timers I would think that you could just program them with some lag time between programs. I am assuming that you are worried about overlapping the programs. Couldn't you just program the second timer to come on a few minutes after the last zone on the first timer stops.

fazlis85 10-26-2009 03:21 PM

Even though I would program the two so that there are no overlaps...I wanted it to be idiot proof in case one of the kids decided to fiddle around.

Can someone point me in the direction as to how I can wire some 24V AC relays? I would want each to be triggered by timers and both to switch on the solenoid as I am assuming back-feeding the relay wont be an issue (since its a diff relay coil circuit).

Yoyizit 10-26-2009 03:57 PM

If I understand what you want, there is no problem with two identical 'formers feeding the same valve at times, provided they are phased correctly.

Power both 'former #1 and 'former #2 primaries and arbitrarily label secondary leads A1, B1, A2 and B2. Tie a knot in A1. Hook A1 to A2.
If you read ~48v to 56v across B1 and B2 then tie a knot in B2.
If you read ~8v or less then tie a knot in A2.

The 'formers should then be wired across the valve so the knotted wires connect together when both timers are on. When both are on check that you have ~24v across the valve.
If you mess with the primary wiring you need to do the phasing again.

Non-identical 'formers are a little more difficult. You need to do some calculations and measurements and add resistors.

BTW, depending on the price of a 'former
vs. the price of a fuse with holder,
you may want to fuse both 'formers.

fazlis85 10-26-2009 04:40 PM

Quote:

Originally Posted by Yoyizit (Post 345672)
If I understand what you want, there is no problem with two identical 'formers feeding the same valve at times, provided they are phased correctly.

Power both 'former #1 and 'former #2 primaries and arbitrarily label secondary leads A1, B1, A2 and B2. Tie a knot in A1. Hook A1 to A2.
If you read ~48v to 56v across B1 and B2 then tie a knot in B2.
If you read ~8v or less then tie a knot in A2.

The 'formers should then be wired across the valve so the knotted wires connect together when both timers are on. When both are on check that you have ~24v across the valve.
If you mess with the primary wiring you need to do the phasing again.

Non-identical 'formers are a little more difficult. You need to do some calculations and measurements and add resistors.

BTW, depending on the price of a 'former
vs. the price of a fuse with holder,
you may want to fuse both 'formers.

1) Just to confirm by "former", you mean transformer right (as in my 24VAC power source)?

2) Also A1 & B1 would be pos/neg from the first source? and A2 & B2 would be from the second source?

3) What do you mean by tie a knot? Does this simply mean connect the wires together?

Sorry for the noob questions! Btw, the transformers are nearly identical.

Yoyizit 10-26-2009 09:27 PM

Quote:

Originally Posted by fazlis85 (Post 345688)
1) Just to confirm by "former", you mean transformer right (as in my 24VAC power source)?
Yes

2) Also A1 & B1 would be pos/neg from the first source? and A2 & B2 would be from the second source?
Yes. Source #1 is one transformer, #2 is the other. I don't use pos/neg 'cause it's AC.

3) What do you mean by tie a knot? Does this simply mean connect the wires together?
Identify that wire somehow, either with a knot in it or a band of tape around it or a spot of paint on it.

Sorry for the noob questions! Btw, the transformers are nearly identical.

Good.
Once it's hooked up and working, confirm that when both transformers are powering the same load, the current in each secondary is less than its amp rating.
E.g., the amp rating of a 24v 40 VA transformer would be 40/24 = 1.7 A.


All times are GMT -5. The time now is 11:12 AM.