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Simple Design Questions

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GJGerson

New Member

Posts: 2

1

Thursday, August 13th 2009, 4:50pm

Simple Design Questions

Greetings,

I'm a newbie, first timer at design/installation of sprinkler systems. I thought I would take a stab at trying to do a system for my house since I am having all of the sod replaced and now is the perfect time to install a system.

The good folks at sprinkler warehouse have been very helpful, but I have a few questions that they suggested I post here.

Before I start, here is a quick run down of my situation:

- I have 11-12GPM and 110PSI.
- My yard is broken up into several sections (see diagram) and has a lot of funky angles.
- I'm not looking for an absolute flawless system; I won't lose sleep if every square inch is not covered.
- I think I have a pretty good understanding of system design - I read everything on this website in the sprinkler school section.

Here is my main question:
How do I really determine how many sprinklers I can put in a single zone? I understand that I only have 11-12GPM to work with at any given time and I understand that you have to subtract the GPM each sprinkler uses, but I'm not sure how to determine what a sprinkler uses. I know it's based on the distance and the PSI, but how do you determine PSI at each sprinkler head?

For Example: The Rain Bird 5004 sprinkler says it uses 1.5GPM at 25PSI and throws the water 33 feet. If I have 11-12GPM to use in a zone, then I would think that I could use 7 of those sprinkler heads (7 x 1.5GPM = 10.5GPM); but if I use 7 sprinkler heads and I divide my 110PSI by 7 then it appears that I will only have 15.71PSI at each sprinkler head. So I'm kind of lost.

Can anyone help me figure that part out?

Really, if I just knew how many sprinklers I can put in each zone I think I could do this. Digging the trenches, assembling the pipe, wiring the valves, I've got all of that covered.



Thanks in advance. P.S. I have a nice drawing that I could provide, but the upload size here is 20KB and it won't take my file.

Wet_Boots

Supreme Member

Posts: 4,102

Location: Metro NYC

2

Thursday, August 13th 2009, 7:09pm

You don't divide pressure by the number of heads. Start over.

GJGerson

New Member

Posts: 2

3

Thursday, August 13th 2009, 8:21pm

I didn't think that sounded right. By any chance could you point me in the right direction where I can find the information I need to figure out how to calculate the right number of sprinklers per zone?

worachj

Advanced Member

Posts: 63

Location: Eagan, Mn

4

Friday, August 14th 2009, 9:29am

Here's a link to a good design tutorial, I found it very helpful. It will help you with figuring out how many heads per zone you can have. Also find and look at the nozzle performance charts for your rainbird heads.

http://www.irrigationtutorials.com/sprinkler00.htm

HooKooDooKu

Supreme Member

Posts: 683

5

Friday, August 14th 2009, 11:04am

Ditto on the irrigation tutorials. It's going to be a lot of reading and a lot of material to take in all at once. So I would suggest that you simply read through it all the way once, the print out a copy of the pages and take additional time to reread it from the beginning again.

But one thing to realize is that designing a system isn't going to be an exact science. Because your dealing with so many interconnected variables (the pressure at the sprinkler head determines the GPM the sprinkler will use, but GMP affect the pressure losses in the pipe, etc). Generally, you have to work out a design based on a few assumptions, then run the calculations and see if they came out ok.

Of course there are a couple of things you can (and need) to do.

For starters, 100+ psi is going to be too much pressure... you'll risk damaging components of the irrigation system. Per the recomendations at irrigation tutorials, if your pressure in 80+, you need to first install a pressure regulator where you've tapped in off the main line.

The other thing is that if your system can handle 11 to 12 GPM max, then you need to target the design for something less. If I was you, I would not design for anything more than about 9 GPM or so.

Then the final thing, since you've got plenty of pressure to play with, plan on getting control valves with flow control. That way if you design everything assuming a working pressure of 40psi at the heads, but you wind up with 60psi at the heads, then you can effectively tweet the pressure to the zone by adjusting the flow control.

phoenixx

Unregistered

6

Sunday, August 16th 2009, 7:44am

AC or DC to the valves

Im not certain where to post this question so I posted in a few places.. i apologize if thats inappropriate..



I have an irritrol rd600 system in my house with 3 zones.



Zone 1 (front yard) stopped functioning but the other zones worked.. i used a multimeter to check the output of the controller / timer and I get the same output on each of the zones.. approximately 20 - 24vAC when the timer tells each zone to turn on (this is relative to the vc (common) terminal.



I checked at the valve and it was a little low so i changed wire connections and it improved ( zone comes on most of the time...



My question is - is the system SUPPOSE to be outputting AC or DC to the valves...

The valves chatter - this is likely because they are getting AC from the controller...



Im guessing the controller should be outputting DC?



Can anyone tell me what their system does on these terminals..



My email address is phoenixx@oiptonline.net

phoenixx

Unregistered

7

Sunday, August 16th 2009, 8:05am

RE: AC or DC to the valves

Quoted from "phoenixx"


Im not certain where to post this question so I posted in a few places.. i apologize if thats inappropriate..



I have an irritrol rd600 system in my house with 3 zones.



Zone 1 (front yard) stopped functioning but the other zones worked.. i used a multimeter to check the output of the controller / timer and I get the same output on each of the zones.. approximately 20 - 24vAC when the timer tells each zone to turn on (this is relative to the vc (common) terminal.



I checked at the valve and it was a little low so i changed wire connections and it improved ( zone comes on most of the time...



My question is - is the system SUPPOSE to be outputting AC or DC to the valves...

The valves chatter - this is likely because they are getting AC from the controller...



Im guessing the controller should be outputting DC?



Can anyone tell me what their system does on these terminals..



My email address is phoenixx@oiptonline.net



i made a Mistake on the email address.. its phoenixx@optonline.net


Skyglider

New Member

Posts: 2

8

Monday, August 17th 2009, 11:38am

RE: RE: AC or DC to the valves

Quoted from "phoenixx"

My question is - is the system SUPPOSE to be outputting AC or DC to the valves...
The valves chatter - this is likely because they are getting AC from the controller...
Im guessing the controller should be outputting DC?
Can anyone tell me what their system does on these terminals..
phoenixx,

I'm just a beginner that's doing a lot of research. I've learned that there are battery operated controllers and a/c operated controllers. So it appears to me that there must be DC operated valves and 24 v a/c operated valves. Would you happen to have DC valves for a battery timer, but using an a/c controller?

Sky

HooKooDooKu

Supreme Member

Posts: 683

9

Tuesday, August 18th 2009, 8:23am

The "industry standard" for valves is 24 VAC 50/60 cycle.

While I'm not familer with the details of battery operated controllers... just because it's battery operated doesn't mean it can not provide an AC output. One obvious example (different industry), the UPS for computers.

However, I just did some quick googling on the subject, and it looks like most instances where a battery operated controler is used, the selenoid has to be replaced by a DC powered latching selenoid. Basically, to provide long battery life, the selenoid is designed such that lots of battery power is only needed to initially open it. But once open, a minimum amount of power (if any) is needed to keep it on.

Here's at least one example:

http://www.hunterindustries.com/Resources/PDFs/Product_Guides/Domestic/lit344w.pdf

This post has been edited 1 times, last edit by "HooKooDooKu" (Aug 18th 2009, 8:31am)

debo

Active Member

Posts: 44

10

Thursday, September 24th 2009, 3:23pm

Quoted from "worachj"

Here's a link to a good design tutorial, I found it very helpful. It will help you with figuring out how many heads per zone you can have. Also find and look at the nozzle performance charts for your rainbird heads.

http://www.irrigationtutorials.com/sprinkler00.htm
good site and the pros will still complain that it is more complex to justify there high-priced rates.

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